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UE implementing ICS function functional architecture The SCC AS entity combines the SIP signaling arising from the mobile (via the Gm interface) and from the MSC server entity (via the I2 interface) and acts as a back-to-back user agent (B2BUA), providing an anchor point for incoming and outgoing calls: - in the case of an outgoing call, it ends the dialogue with the mobile and the MSC server entity and initiates a new dialogue with the downstream entity. The SCC AS entity is the first application server invoked by the serving call session control function (S-CSCF). - in the case of an incoming call, it ends the dialogue with the upstream entity and initiates a dialogue with the MSC server entity and the mobile. The SCC AS entity is the latest application server invoked by the S-CSCF entity. The SCC AS entity provided the terminating access domain selection (T-ADS) that can route an incoming call to the appropriate mobile network: 2G or 3G network in CS mode, 3G or 4G network in PS mode (Figure 9.2). The SCC AS entity queries the home subscriber server (HSS) to obtain the address of the mobility management entity (MME) and the service GPRS support node (SGSN). The HSS entity asks the SGSN and MME entities to recover network and mobile capacities. Service Centralization and Continuity - NAS (ESM) S6a (DIAMETER) T-ADS (DIAMETER) NAS (SM) (MAP) S6d (DIAMETER) (DIAMETER) NAS (CM) I2 (SIP) Mx / Mi (SIP) Server Figure 9.2. Functional architecture for TADS The MSC server entity ensures registering the mobile from the SCC AS and S-CSCF entities. The MSC server entity provides the translation of the telephone signaling for the establishment of a communication: - call management (CM), a part of non-access stratum (NAS), at CS side; - SIP signaling, at IMS side via the I2 interface. The MSC server entity provides the control of the MSC GW entity for the establishment of the CS bearer, on one side, and the real-time transport protocol (RTP) stream on the side of the IP network. The functional architecture of the ICS functio

n is described in Figure 9.3 in the case where the MSC server entity and the mobile do not implement the ICS service. When the MSC server entity receives the call for the establishment of the communication, it recovers from the SCC AS entity, via camel application part (CAP), the IP multimedia routing number (IMRN). The MSC server entity routes the call to the media gateway control function (MGCF) using the IMRN number to reach the SCC AS entity. The MGCF entity translates the telephone signaling: - ISDN user part (ISUP) at CS network side; - SIP at IMS network side. VoLTE and ViLTE Ut (XCAP) (DIAMETER) (CAP) (DIAMETER) (ISUP) Mg (SIP) Mx / Mi (SIP) Server NAS (CM) H.248 (CS flow) Mb (RTP flow) Figure 9.3. MSC server and UE not implementing ICS function functional architecture The MGCF entity provides the control of the IMS GW entity for the establishment of the CS bearer on one side and the RTP stream on the IP network side. The B2BUA function of the SCC AS entity allows to end the dialogue with the MGCF entity and to start a new dialogue with the called party. 9.1.2. Procedures 9.1.2.1. Registration The registration of the mobile to the IMS network deploys the general procedure if the mobile implements the ICS function. In the case where the mobile and the MSC server entity do not implement the ICS function, the mobile is not registered to the IMS network. The registration procedure of the mobile to the IMS network is described in Figure 9.4, where: - the MSC server entity implements ICS function; - the mobile does not implement ICS function. 1) After the attachment of the mobile, the MSC server entity transmits the SIP REGISTER request to the I-CSCF (interrogating-CSCF) entity. Service Centralization and Continuity 247 The SIP URI (Uniform Resource Identifier) of the REGISTER request is derived from the mobile country code (MCC) and the mobile network code (MNC). The temporary public identity of the headers From and To is derived from the international mobile subscriber identity (IMSI). The private identity in

the Authorization header is also derived from the IMSI private identity. The Contact header contains the parameter + g.3gpp.ics indicating that the MSC server entity implements the ICS service. REGISTER sip:ics.mnc01.mcc208.3gppnetwork.org SIP/2.0 From: <sip:20810999999999@ics.mnc01.mcc208.3gppnetwork.org>; tag=4fa3 <sip:20810999999999@ics.mnc01.mcc208.3gppnetwork.org: Contact: <sip:[5555::aaa:bbb:ccc:ddd]>;expires=600000; +g.3gpp.ics="server" Authorization: Digest username=" 20810999999999@ics.mnc01.mcc208.3gppnetwork.org ", realm=" ics.mnc01.mcc208.3gppnetwork.org ", nonce="", integrity-protected="auth-done", uri="sip: ics.mnc01.mcc208.3gppnetwork.org ", response="" 2) The I-CSCF entity sends to the HSS entity the message DIAMETER user-authorization-request (UAR) to retrieve the list of the S-CSCF entities that can be assigned to the UA entity. 3) The I-CSCF entity performs the selection of an S-CSCF entity to which it forwards the REGISTER request, from the list of the S-CSCF entities received in the message DIAMETER user-authorization-answer (UAA). 4) The I-CSCF entity replaces the initial URI identity (sip: ics.mnc01.mcc208.3gppnetwork.org) by that of the S-CSCF entity (sip:scscf.HomeA.net or sip:scscf.HomeB.net) and transmits the SIP REGISTER request to the selected S-CSCF entity. VoLTE and ViLTE I-CSCF S-CSCF Server Attachment procedure SIP REGISTER DIAMETER UAR DIAMETER UAA SIP REGISTER DIAMETER SAR DIAMETER SAA SIP 200 OK SIP 200 OK SIP REGISTER SIP 200 OK Subscription Subscription Figure 9.4. Mobile registration to IMS network with ICS function 5) As the mobile has been authenticated by the MSC server entity, the S-CSCF entity sends to the HSS entity the message DIAMETER server- assignment-request (SAR) to retrieve the mobile profile. 6) The HSS entity transmits the profile of the mobile in the message DIAMETER server-assignment-answer (SAA). 7), 8) The SIP 200 OK response follows the reverse route taken by the REGISTER request. 9) The S-CSCF entity registers the mobile to the SCC AS entity. 10) The SC

C AS entity responds with SIP 200 OK message to the SIP REGISTER request. After the registration procedure, the MSC server and SCC AS entities deploy the general procedure for subscription to the mobile registration events. Service Centralization and Continuity 9.1.2.2. Session establishment at originating side The procedure to establish the session for the outgoing call is described in Figure 9.5, in the case where the MSC server entity and the mobile implement ICS function. HomeB net Server SIP INVITE SIP 100 Trying SIP INVITE SIP 100 Trying SIP 183 Session Progress SIP 183 Session Progress SIP PRACK SIP PRACK SIP 200 OK SIP 200 OK SETUP CALL PROCEEDING SIP INVITE SIP 100 Trying SIP INVITE SIP 100 Trying SIP INVITE SIP 100 Trying SIP INVITE SIP 100 Trying SIP 180 Ringing SIP 180 Ringing SIP 180 Ringing SIP 180 Ringing SIP 200 OK SIP 200 OK SIP 200 OK CONNECT SIP 200 OK CONNECT ACK SIP ACK SIP ACK SIP 200 OK SIP 200 OK SIP ACK SIP ACK SIP ACK SIP ACK Figure 9.5. Session establishment at originating side MSC server and UE implementing ICS function 250 VoLTE and ViLTE 1), 3) Alice's UA entity initializes the service control by sending the SIP INVITE message to the SCC AS entity. The URI identity of the request is the SIP URI or TEL URI identity of the called party (Bob). SDP (Session Description Protocol) messages associated with the SIP INVITE request indicates that the session is established from a CS-mode network. INVITE tel: +1-212-555-2222 SIP/2.0 C=PSTN - m=audio 9 PSTN - a=setup:active a=connection:nev a=cs-correlation:callerid:+358504821437 2), 4) Each entity responds with the SIP 100 Trying response that allows blocking the retransmission timer of the SIP INVITE request. 5), 6) The response SIP 183 Session in Progress received from the SCC AS entity provides a SDP response that contains the public service identity (PSI). C=PSTN E164 +12125556666 7), 8) Alice's UA entity sends the subsequent SIP PRACK request to acknowledge the provisional response SIP 183 Session in Progress. 9), 10) The SIP 200 OK messag

e is the response to the PRACK request. Alice's mobile proceeds with the establishment of the bearer in the CS- mode network (SETUP) indicating the PSI identity as destination. 11), 13) The MSC server entity generates the SIP INVITE request to the identity PSI. Service Centralization and Continuity 251 The header P-Asserted-Identity contains the phone number of the caller. The header Accept-Contact indicates that the MSC server entity supports supplementary telephone services. INVITE tel : +1-212-555-6666 SIP/2.0 P-Asserted-Identity: <tel:+358-50-4821437> Accept-Contact: *; +g.3gpp.icsi-ref="urn%3Aurn-7%3gpp service.ims.icsi.mmtel" The SIP INVITE request contains an SDP offer that contains the characteristics of the audio stream provided by the MSC GW entity. 12), 14) Each entity responds with the SIP 100 Trying response that allows for blocking the retransmission timer of the SIP INVITE request. 15), 17) The SCC AS entity generates the SIP INVITE request to Bob located in the domain HomeB.net. The SCC AS entity replaces the PSI identity by the TEL URI identity of Bob that was recorded during the first SIP INVITE message. INVITE tel: +1-212-555-2222 SIP/2.0 16), 18) Each entity responds with the SIP 100 Trying response that allows for blocking the retransmission timer of the SIP INVITE request. 19), 20) The SCC AS entity receives from the domain HomeB. net the SIP 180 Ringing message indicating that Bob's phone is ringing. 21), 22) The SCC AS entity responds with the SIP 180 Ringing message to the INVITE request received from Alice's UA entity. 23), 24) The SCC AS entity receives from the domain HomeB. net the SIP 200 OK message indicating that Bob picked up the phone. The SIP 200 OK message contains the SDP message with the characteristics of the audio stream. VoLTE and ViLTE 25), 26) The SCC AS entity responds to the SIP INVITE request of the MSC server entity with the SIP 200 OK message in which the SCC AS entity forwards the SDP message received from the domain HomeB.net. Upon receipt of the SIP 200 OK messag

SIP 100 Trying SIP 183 Session Progress SIP 183 Session Progress SETUP CALL PROCEEDING SIP INVITE SIP 100 Trying SIP INVITE SIP 100 Trying SIP 200 OK SIP 200 OK CONNECT CONNECT ACK SIP ACK SIP ACK SIP 180 Ringing SIP 180 Ringing SIP 180 Ringing SIP 180 Ringing SIP 200 OK SIP 200 OK SIP 200 OK SIP 200 OK SIP ACK SIP ACK SIP ACK SIP ACK Figure 9.6. Session establishment at terminating side MSC server and UE implementing ICS function 7) The S-CSCF entity replaces the SIP URI identity by Bob's telephone number associated with the identity of the MSC Server which recorded Bob. 254 VoLTE and ViLTE INVITE sip: 12125552222@msc.HomeB.net SIP/2.0 6), 8) Each entity responds with SIP 100 Trying response that allows for blocking the retransmission timer of the SIP INVITE request. 9), 10) Bob's UA entity responds with SIP 183 Session Progress message containing the SDP message indicating that the CS bearer is used. Bob's mobile proceeds with the establishment of the bearer in the CS network (SETUP), indicating the PSI identity as destination. 11), 13) The MSC Server entity generates a SIP INVITE request to the PSI identity. The SIP INVITE request contains an SDP offer that contains the characteristics of the audio stream provided by the MSC GW entity. 12), 14) Each entity responds with SIP 100 Trying response that allows for blocking the retransmission timer of the SIP INVITE request. The MSC server entity indicates to Bob's mobile that the media in the CS network has been established (CONNECT) and forwards the SDP message to the MSC GW entity. 15), 16) The SCC AS entity responds to the MSC server entity with SIP 200 OK message containing the SDP message received from the domain HomeA.net. 17), 18) The MSC server entity acknowledges the SIP 200 OK response with the subsequent SIP ACK request. 19), 20) Bob's UA entity responds to the SIP INVITE request received from the SCC AS entity with the SIP 180 Ringing message to indicate that Bob's phone is ringing. 23), 24) Bob's UA entity responds to the SIP INVITE request received fr

om the SCC AS entity with SIP 200 OK message to indicate that Bob picked up the phone. Service Centralization and Continuity 25), 26) The SCC AS entity responds to the SIP INVITE request received from the domain HomeA. net with the SIP 200 OK message to indicate that Bob picked up the phone. 27), 28) The domain HomeA. net acknowledges the SIP 200 OK response with the subsequent SIP ACK request. 29), 30) The SCC AS entity acknowledges the SIP 200 OK response with the subsequent SIP ACK request. 9.2. e-SRVCC function 9.2.1. Functional architecture 9.2.1.1. Architecture for basic call When the mobile has established a call on the 4G evolved packet system (EPS), it is necessary to be able to transfer to the 3G universal mobile telecommunications system (UMTS) or 2G global system for mobile (GSM), if loss of coverage occurs on the 4G EPS network. The enhanced single radio voice call continuity (e-SRVCC) ensures continuity of service when the mobile moves from one network in PS mode to a network in CS mode. The functional architecture of the e-SRVCC function is described in Figure 9.7, for the SIP flow and in Figure 9.8 for the RTP stream. To ensure continuity of service, e-SRVCC function introduces two anchor points in the IMS network: - access transfer control function (ATCF) which provides the anchor point for SIP signaling. The ATCF entity is inserted into the path of SIP signaling between control session CSCF entities, on one hand, the P-CSCF (Proxy-CSCF) entity while, on the other hand, the I-CSCF or the S-CSCF entity; - access gateway transfer (ATGW) that provides the anchor point for the RTP stream. The ATCF entity is located in the visited IMS network in the case of roaming to hide to the nominal IMS network and to the interconnected IMS VoLTE and ViLTE network that the SIP flow has changed IP address, given the move from the PS mode to the CS mode. GERAN DIAMETER UTRAN 2G/3G DIAMETER SIP flow Interconnection interface S / I Server Roaming interface GTPv2-C Sv interface S1-AP GTPv2-C Radio Bearer Bearer Bearer

Figure 9.7. Functional architecture for basic call control plane GERAN UTRAN Interconnection interface BSSAP H.248 RANAP Server GTPCv2-C H.248 Sv interface S1-AP GTPv2-C Radio Bearer Bearer Bearer Figure 9.8. Functional architecture for basic call traffic plane Service Centralization and Continuity The ATGW entity is located in the visited IMS network too in the case of roaming to hide from the interconnected IMS network that the RTP stream has changed its IP address, given the move from the PS mode to the CS mode. The ATGW entity is controlled by the ATCF entity via the H.248 protocol. The ATGW entity may also perform the transcoding of voice if the codecs used, firstly, in the EPS network and, secondly, in GSM or UMTS networks, are different. Figure 9.9 provides an example of the constitution of the RTP stream between Alice's UA in the domain HomeA net, Bob's UA in the domain HomeB. net and ATGW entities. domain HomeA net domain HomeB net RTP flow RTP/flow RTP flow Alice @IP 192.1.1.1 @IP 200.1.1.1 @IP 200.1.1.2 @IP 200.2.2.2 @IP 200.2.2.1 @IP 192.2.2.1 N° port 3456 N° port 11234 N° port 8899 N° port 6544 N° port 10124 N° port 4528 Figure 9.9. RTP flow characteristics for service continuity Figure 9.10 provides an example of the constitution of the RTP stream between MSC GW entity in the domain HomeA net, Bob's UA in the domain HomeB net ATGW entities, after the PS-CS inter-system handover for Alice's mobile. domain HomeA. net domain HomeB net Alice CS flow RTP flow RTP flow RTP flow @IP 196.1.1.1 @IP 200.1.1.1 @IP 200.1.1.2 @IP 200.2.2.2 @IP 200.2.2.1 @IP 192.2.2.1 N° port 7236 N° port 5238 N° port 8899 N° port 6544 N° port 10124 N° port 4528 Figure 9.10. RTP flow characteristics at the end of PS-CS inter-system handover The SCC AS entity implements the mechanisms for the control of the registration of the e-SRVCC function and for the transfer of the session at the PS-CS inter-system handover. VoLTE and ViLTE The MME entity of the EPS network is affected by the e-SRVCC function by performing the following fun

ctions: - it separates the bearer dedicated to the voice from the other media carrying no voice; - it initializes, via the Sv interface, the e-SRVCC procedure for voice handover to the target cell of the GSM or UMTS network; - it coordinates the handover from the PS mode to the CS mode for voice and possibly the handover of the PS mode to the PS mode for the other streams. The MSC server entity of the 2G GSM or 3G UMTS network is also affected by the e-SRVCC function by performing the following functions: - it ensures the availability of resources in the 2G GSM or 3G UMTS network before executing the handover; - it coordinates the execution of the handover and the transfer of the telephone communication. The transfer of the telephone signaling involves transferring, on one hand, SIP signaling exchanged between the mobile and the ATCF entity, while on the other hand, the signaling consisting of call management exchanged between the mobile and the MSC server and SIP exchanged between MSC server and ATCF entity. The voice transfer involves transferring, on one hand, the RTP stream established between the mobile and the ATGW entity, while on the other hand, the CS bearer between the mobile and the MSC GW entity and the RTP stream established between the MSC GW entity and the ATGW entity. 9.2.1.2. Architecture for emergency call The functional architecture of the e-SRVCC function in the case of an emergency call is given in Figure 9.11. The emergency access transfer function (EATF) ensures continuity of service when the mobile performs the PS-CS inter-system handover. The EATF entity constitutes the anchor point of the SIP signaling and acts as a B2BUA entity. Service Centralization and Continuity In the case of roaming, the E-CSCF (Emergency CSCF) and EATF entities are located in the visited network. GERAN UTRAN 2G/3G Server GTPv2-C Sv interface S1-AP GTPv2-C Radio Bearer Bearer Bearer Figure 9.11. Functional architecture for emergency call control plane SIP flow is transmitted to the public safety answering point (P

SAP) via the interconnect border control function (IBCF) in the case of IMS interconnection or via breakout gateway control function (BGCF) and MGCF entity in the case of CS interconnection. The RTP stream is transmitted to the PSAP emergency center via TrGW in the case of IMS interconnection or via IMS GW in the case of CS interconnection. In the case of IMS interconnection, the IBCF entity ensures the anchor point of the SIP stream. In the case of IMS interconnection, the TrGW entity ensures the anchor point of the RTP stream. In the case CS interconnection, the MGCF entity ensures the anchor point of the SIP stream. 260 VoLTE and ViLTE In case of CS interconnection, the entity IMS GW entity ensures the anchor point of the RTP stream. 9.2.2. Procedures 9.2.2.1. Registration The registration procedure implementing the e-SRVCC function is shown in Figure 9.12. 1) The ATCF entity transfers the SIP REGISTER request to the I-CSCF entity by inserting the Path header containing the PATH URI identity and the header Feature - Caps with the following parameters: - +g.3gpp. atcf: this parameter informs the session transfer number for SRVCC (STN-SR); -+g.3gpp.atcf-mgmt: this parameter contains the URI identity of the ATCF entity; - +g.3gpp.atcf-path: this parameter contains the identity PATH URI identity of the ATCF entity; - +g.3gpp.srvcc-alerting: this parameter indicates that the MSC Server entities support the SRVCC function during the ringing phase. REGISTER sip:home1.net SIP/2.0 Feature-Caps: *;+g.3gpp.atcf="<tel:+1-237-888-9999>"; +g.3gpp.atcf-mgmt-uri = <sip:atcf.HomeA.net>" +g.3gpp.atcf-path="<sip:termsdgfdfwe@atcf.HomeA.net>"; +g.3gpp.mid-call; +g.3gpp.srvcc-alerting Path:<sip:termsdgfdfwe@atcf.HomeA.net>,<sip:aga2gfgf@pcs f1.HomeA.net:5070;ob> . . . 2) In the second registration phase, when the mobile has been authenticated, the ATCF entity includes in the message SIP 200 OK, the Header Feature-Caps with the parameter +g.3gpp.atcf containing STN-SR number. SIP/2.0 200 OK Feature-Caps: - *;+g.3gpp.atcf="<tel:+1-2

37-888-9999>" Service Centralization and Continuity P-CSCF I-CSCF S-CSCF SCC AS SIP REGISTER SIP REGISTER SIP REGISTER DIAMETER UAR DIAMETER UAA SIP REGISTER DIAMETER MAR SIP 401 SIP 401 SIP 401 SIP 401 DIAMETER MAA SIP REGISTER SIP REGISTER SIP REGISTER DIAMETER LIR DIAMETER LIA SIP REGISTER DIAMETER SAR SIP 200 SIP 200 DIAMETER SAA SIP 200 SIP 200 SIP REGISTER SIP 200 SIP MESSAGE SIP MESSAGE SIP 200 SIP 200 DIAMETER PUR DIAMETER PUA DIAMETER IDR DIAMETER IDA Figure 9.12. Registration for service continuity 3) At the end of the mobile's registration, the SCC AS entity receives from the S-CSCF entity the SIP REGISTER message containing the following information created by the ATCF entity: - the SIP URI identity of the ATCF entity; - the PATH URI identity for the identification of the mobile while registering; - the STN-SR session transfer number. 4) The SCC AS entity responds with SIP 200 OK message to the SIP REGISTER request. 5) The SCC AS entity communicates to the SIP URI of the ATCF entity, in the SIP MESSAGE request, additional information concerning the PATH URI identity: its own access transfer update - transfer session identifier (ATU-STI) and the mobile subscriber ISDN number (MSISDN). 262 VoLTE and ViLTE MESSAGE sip:atcf.HomeA.net SIP/2.0 <?xml version="1.0" encoding="UTF-8"?> <SRVCC-infos> <SRVCC-info - ATCF-Path- URI="sip: :termsdgfdfwe@atcf.HomeA.net": <ATU-STI>sip:sccas.HomeA.net</ATU-STI: C-MSISDN>tel:+358-50-4821437</C-MSISDN> </SRVCC-info> </SRVCC-infos> 6) The ATCF entity responds with the SIP 200 OK message to the SIP REGISTER request. 7) The SCC AS entity forwards the message DIAMETER profile- update-request (PUR) to the HSS entity to update the STN-SR session number. 8) The message DIAMETER profile-update-answer (PUA) acknowledges the received message DIAMETER PUR. 9) The HSS entity sends the message DIAMETER insert-subscriber-data- request (IDR) to the MME entity for the update of the STN-SR session number. 10) The message DIAMETER insert-subscriber-data-answer (IDA) acknowledges the receiv

ed message DIAMETER IDR. 9.2.2.2. Session establishment at originating side The procedure for establishing the session implementing e-SRVCC function for an outgoing call is given in Figure 9.13. 1) The establishment of the session is started by the SIP INVITE request transmitted by Alice's UA entity to Bob's UA entity. The body of the SDP message contains the characteristics of the RTP stream of the offer of Alice's UA entity: - IPv4 address (192.1.1.1); - port number (3456). Service Centralization and Continuity P-CSCF S-CSCF HomeB.net SIP INVITE SIP 100 SIP INVITE SIP 100 SIP INVITE SIP INVITE SIP 100 SIP 100 SIP INVITE SIP 100 SIP INVITE SIP 100 SIP 183 SIP 183 SIP 183 SIP 183 SIP 183 SIP 183 SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 180 SIP 180 SIP 180 SIP 180 SIP 180 SIP 180 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP ACK SIP ACK SIP ACK SIP ACK SIP ACK SIP ACK Figure 9.13. Session establishment for service continuity originating side VoLTE and ViLTE The Route headers contain the identities of the P-CSCF and S-CSCF entities, Alice's UA entity does not know the identity of the ATCF entity which, however, is located between the P-CSCF and S-CSCF entities. 2) As the SIP 200 OK response to the SIP REGISTER request contains the header Feature - Caps with parameter +g. 3 gpp atcf, the P-CSCF entity forwards the SIP INVITE request to the ATCF entity. 3) Upon receipt of the SIP INVITE message, the ATCF entity reserves the resource with the ATGW entity providing the anchor point for the RTP stream. The ATCF entity transfers to the S-CSCF entity the SIP INVITE request whose associated SDP message, sent to the domain HomeB net, is that of ATGW entity to replace that of Alice's UA entity: - Alice's IP address (192.1.1.1) is replaced by the value communicated by the ATGW entity (200.1.1.2); - the port number (3456) is replaced by th

e value communicated by the ATGW entity (8899). 4) The SIP 183 Session Progress response from the domain HomeB. net contains the characteristics of the RTP stream in the SDP message body: - IPv4 address (200.2.2.2); - port number (6544). 5) Upon receipt of the provisional SIP 183 Session Progress response, the ATCF entity configures the ATGW entity and replaces the SDP message body received from the domain HomeB. net by that received from the ATGW entity: - the IP address (200.2.2.2) is replaced by the ATGW entity address (200.1.1.1); - the port number (6544) is replaced by the value communicated by the ATGW entity (11234). 9.2.2.3. Session establishment at terminating side The procedure for establishing the session implementing e-SRVCC function for an incoming call is illustrated in Figure 9.14. Service Centralization and Continuity P-CSCF SCC AS S-CSCF I-CSCF HomeA net DIAMETER LIR SIP INVITE DIAMETER LIA SIP 100 SIP INVITE SIP 100 SIP INVITE SIP 100 SIP INVITE SIP 100 SIP INVITE SIP 100 SIP INVITE SIP INVITE SIP 100 SIP 100 SIP 183 SIP 183 SIP 183 SIP 183 SIP 183 SIP 183 SIP 183 SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP PRACK SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP UPDATE SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 180 SIP 180 SIP 180 SIP 180 SIP 180 SIP 180 SIP 180 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP 200 SIP ACK SIP ACK SIP ACK SIP ACK SIP ACK SIP ACK Figure 9.14. Session establishment for service continuity terminating side 1) The SIP INVITE request received from the domain HomeA. net by the I-CSCF entity contains the SDP message body with the RTP stream characteristics: - IPv4 address (200.1.1.2); - port number (8899). VoLTE and ViLTE 2) The S-CSCF entity forwards the SIP INVITE request to the SCC AS, ATCF, P-CSCF and Bob's UA entities: - the identity of the SCC AS entity is obtained following the review of the initial filter criteria (iFC); - the identities of the ATCF and P-CSCF entities are retrieved fr

om the Path header of the SIP REGISTER request; - the IP address of Bob's UA entity results from registration. 3) Upon receipt of the SIP INVITE message, the ATCF entity reserves the resource with the ATGW entity providing the anchor point for the RTP stream. The ATCF entity transfers to the P-CSCF entity the SIP INVITE request whose associated SDP message, sent to Bob's UA entity, is that of the ATGW entity to replace the one received from the domain HomeA. net: - the IP address (200.1.1.2) is replaced by that of the ATGW entity (200.2.2.1); - the port number (8899) is replaced by the value communicated by the ATGW entity (10124). 4) The SIP 183 Session Progress response from Bob's UA entity contains the characteristics of the RTP stream in the SDP message body: - IPv4 address (192.2.2.1); - port number (4528). 5) Upon receipt of the provisional response SIP 183 Session Progress, the ATCF entity configures the ATGW entity and replaces the SDP message body received from Bob's UA entity by the one received from the ATGW entity: - the IP address (192.2.2.1) is replaced by that of the ATGW entity (200.2.2.2); - the port number (4528) is replaced by the value communicated by the ATGW entity (6544). Service Centralization and Continuity 9.2.2.4. PS-CS inter-system handover The PS-CS inter-system handover procedure is given in Figure 9.15. Server UTRAN RRC MeasurementReport S1-AP HANDOVER REQUIRED GTPv2-C SRVCC PS-CS REQUEST RELOCATION REQUEST RELOCATION REQUEST ACK GTPv2-C SRVCC PS-CS RESPONSE S1-AP HANDOVER COMMAND RRC ConnectionReconfiguration Handover execution HANDOVER TO UTRAN COMPLETE GTPv2-C SRVCC PS-CS COMPLETE NOTIFICATION GTPv2-C SRVCC PS-CS COMPLETE NOTIFICATION ACK GTPv2-C DELETE SESSION REQUEST GTPv2-C DELETE SESSION RESPONSE S1-AP UE CONTEXT RELEASE COMMAND Figure 9.15. PS-CS inter-system handover 1) The decision to perform a handover from the EPS network in PS mode to the UMTS or GSM network in CS mode is taken by the eNB on which the mobile is connected. This decision is taken based on measurement repo

rts from the mobile in the message RRC MeasurementReport. 2) The eNB entity sends to the MME entity the message S1-AP HANDOVER REQUIRED. The handover request may also relate to the flow transferred to the 3G UMTS network in PS mode. 3) From the quality class index (QCI), the MME entity separates the audio stream (QCI = 1) and possibly video (QCI = 2) from other flows and initializes them to be relocated either to the MSC server entity (RTP stream) or to the SGSN entity. VoLTE and ViLTE The MME entity initiates the procedure of PS-CS inter-system handover by transmitting the message GTPv2-C SRVCC PS-CS REQUEST to the MSC server entity, which contains the STN-SR session number and the MSISDN phone number. The MSC server entity sends a handover request to the UMTS terrestrial radio access network (UTRAN) of the UMTS network or the base station sub-system (BSS) of the GSM network. After reserving the resources, the access network acknowledges the request received from the MSC server entity. The answer carries a container that will be transmitted to the mobile. This container contains the radio characteristics of the 2G or 3G cell, which will optimize the mobile connection time. 4) The MSC server entity responds to the MME entity by indicating that resources are available for the execution of the handover in the message GTPv2-C SRVCC PS-CS RESPONSE. 5) The MME entity triggers the execution of the handover by sending the message S1-AP HANDOVER COMMAND to the eNB entity. 6) The eNB entity transmits to the mobile the message RRC ConnectionReconfiguration, causing the connection establishment of the mobile to the radio station of the BSS or UTRAN access network. 7) When the mobile is connected, the access network notifies the MSC server entity which informs the MME entity to the completion of handover in a message GTPv2 SRVCC C-PS-CS COMPLETE NOTIFICATION. 8) This message is acknowledged by a message GTPv2-C SRVCC PS-CS COMPLETE NOTIFICATION ACK. The MSC server entity assigns a temporary mobile subscriber identity (T-TMSI

) to the mobile and updates the location of the mobile to the HSS entity. 9) The MME entity induces the deletion of the context of audio and video streams at the SGW by sending the message GTPv2-C DELETE SESSION REQUEST, if the PS-PS inter-system handover is not established. Service Centralization and Continuity 10) The SGW and PGW entities carry the message received by the message GTPv2-C DELETE SESSION RESPONSE. 11) The MME entity causes the deletion of the contexts of audio and video streams at the entity eNB by sending the message S1-AP UE CONTEXT RELEASE COMMAND to the eNB entity. After the PS-CS inter-system handover, the CS flow is established between Alice's mobile and the MSC GW entity. The next phase involves the establishment of RTP flows between the MSCGW and ATGW entities. 9.2.2.5. Access transfer The access transfer procedure is described in Figure 8.16. P-CSCF Server SIP INVITE (URI STN-SR, SDP MSC GW) SIP 100 Trying SIP 200 OK (SDP ATGW) SIP ACK SIP INVITE (URI ATU-STI, SDP ATGW) SIP 100 Trying SIP 200 OK (SDP ATGW) SIP ACK SIP BYE SIP BYE SIP 200 OK SIP 200 OK Figure 9.16. Access transfer for service continuity 1) The MSC server entity sends the SIP INVITE request to the ATCF entity. The URI identity of the query contains the STN-SR session number mentioned by the MME in the procedure of the PS-CS inter-system handover. The header Asserted-Identity contains Alice's phone number (MSISDN). INVITE tel +1-237-888-9999 SIP/2.0 P-Asserted-Identity: <tel:+358-50-4821437> 270 VoLTE and ViLTE The body of the SDP message contains the characteristics of the RTP stream provided by the MSC GW entity: - IPv4 address (196.1.1.1); - port number (7236). 2) Upon receipt of the SIP INVITE message, the ATCF entity transfers the SDP message of the MSC GW entity to the ATGW entity and responds with the SIP 200 OK message containing the SDP message with the RTP flow characteristics provided by the ATGW entity: - IPv4 address (200.1.1.1); - port number (5238). The next phase aims at informing the SCC AS entity about the

transfer of Alice's communication to a CS network. 3) The ATCF entity establishes a new dialogue with the SCC AS entity by sending a new SIP INVITE request. The URI identity of the query contains the ATU-STI identity of the entity SCC AS entity recovered during registration. The SIP INVITE message incorporates a Require header with the value tdialog to mean that the header Target-Dialog is required. The header Target-Dialog specifies that the existing dialogue (Call - ID header, tag parameters of the headers From and To) must be connected with the dialogue established by the ATCF entity. The P-Asserted-Identity header contains Alice's phone number (MSISDN). INVITE sip:sccas.HomeA.net SIP/2.0 Require: tdialog Target-Dialog: me03a0s09a2sdfgjk1491777; remote- tag=774321; local-tag=64727891 P-Asserted-Identity: <tel:+358-50-4821437> Service Centralization and Continuity The body of the SDP message contains the characteristics of the RTP stream provided by the ATGW entity of the domain HomeA. net (IPv4 address 200.1.1.2 and port number 8899) while establishing the session. As the SDP message body has not changed, there is no need to make an update for the domain HomeB.net 4) The SIP 200 OK response incorporates the SDP message communicated by ATGW entity of the domain HomeB. net (IPv4 address 200.2.2.2 and port number 6544) that the SCC AS entity had retained. 5) The SCC AS entity sends the SIP BYE request to complete the initial dialogue in the P-CSCF and ATCF entities and possibly in Alice's UA entity if it has carried out for the SIP flow the inter-system PS-PS handover simultaneously with the PS-CS inter-system handover. In the case where Alice's UA entity may not respond with a message SIP 200 OK, the ending of the dialogue takes place at the initiative of the entities concerned network. 9.2.2.6. Emergency call 9.2.2.6.1. Session establishment for an emergency call The procedure for establishing the emergency call by implementing the e-SRVCC function is illustrated in Figure 9.17. P-CSCF E-CSCF SIP INVITE SIP IN

VITE SIP INVITE SIP INVITE SIP INVITE SIP 200 OK SIP 200 OK SIP 200 OK SIP 200 OK SIP 200 OK SIP ACK SIP ACK SIP ACK SIP ACK SIP ACK Figure 9.17. Session establishment for service continuity emergency call 272 VoLTE and ViLTE 9.2.2.6.2. Access transfer for an emergency call The procedure of access transfer for an emergency call is described in Figure 9.18. P-CSCF I-CSCF E-CSCF Server PS-CS inter-system handover SIP INVITE (URI E-STN-SR, SDP MSC GW) SIP reINVITE (URI PSAP, SDP MSC GW) SIP 200 OK SIP 200 OK SIP 200 OK SIP 200 OK SIP ACK SIP ACK SIP ACK SIP ACK SIP BYE SIP BYE SIP BYE SIP 200 OK SIP 200 OK SIP 200 OK Figure 9.18. Access transfer for an emergency call 1) The MSC server entity sends the SIP INVITE request to the EATF entity. The URI identity of the query contains the E-STN-SR number of the EATF entity, configured at the MSC server entity. The body of the SDP message contains the characteristics of the RTP stream provided by the MSC GW entity. 2) The EATF entity transfers the SDP message received to the entity in charge of the interconnection with the emergency center, in a SIP reINVITE message. 3) The EATF entity issues the SIP BYE request to complete the initial dialogue in the P-CSCF entity, and possibly in Alice's UA entity if it has carried out for the SIP stream the PS-PS inter-system handover simultaneously with the PS-CS inter-system handover. Short Message Service 10.1. Message structure A short message service (SMS) over the SGsAP protocol allows for a mobile connected to the 4G network to send and receive an SMS in CS (Circuit-Switched) mode. A short message service over the session initiation protocol (SIP) is a supplementary telephone service offered by the IMS. The SMS message is generated and interpreted by the short message application layer (SM-AL) between the mobile and the SMS service center (SMS-SC) (Figures 10.1 and 10.2). The short message transport layer (SM-TL) ensures reliable transmission of SMS messages between the mobile and the SMS-SC entity (Figures 10.1 and 10.2). The sho

rt message relay layer (SM-RL) ensures reliable transmission of SMS messages between, firstly, the mobile, and, secondly: - the interworking mobile services switching center (SMS-IWMSC) for outgoing SMS messages (Figures 10.1 and 10.2); - the gateway mobile-services switching center (SMS-GMSC) for incoming SMS messages (Figures 10.1 and 10.2); The short message control layer (SM-CL) ensures reliable transmission of SMS messages between the mobile and the MSC server entity (Figure 10.1). VoLTE and ViLTE: Voice and Conversational Video Services over the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2016. Published by ISTE Ltd and John Wiley & Sons, Inc. 274 VoLTE and ViLTE For the architecture of SMS over SGsAP, the mobility management entity (MME) ensures relaying SM-CL messages and the MSC server entity that SM-RL messages (Figure 10.1). For the architecture of SMS over SIP, the IP short message gateway (IP- SM-GW) provides relaying SM-RL messages (Figure 10.1 and 10.2). Mobile SMS-SC SM-AL SMS-IWMSC SM-AL SMS-GMSC SM-TL SM-TL MSC Server SM-RL SM-RL Not defined SM-CL SM-CL SGsAP Figure 10.1. Protocol architecture for SMS over SGsAP Mobile SMS-SC SM-AL SMS-IWMSC SM-AL SMS-GMSC SM-TL SM-TL IP-SM-GW SM-RL SM-RL Not defined Figure 10.2. Protocol architecture for SMS over SIP 10.1.1. SM-TL layer SMS-SUBMIT message carries outgoing SMS messages from the mobile to the SMS-SC entity. SMS-SUBMIT-REPORT message is an acknowledgment on the part of the SMS-SC entity, positive or negative, of the SMS-SUBMIT message. SMS-DELIVER message carries incoming SMS messages from the SMS-SC entity to the mobile. SMS-DELIVER-REPORT message is an acknowledgment on the part of the mobile, positive or negative, of the SMS-DELIVER message or the SMS-STATUS-REPORT message. Short Message Service SMS-STATUS-REPORT is a report sent by the SMS-SC entity to the mobile which transmits the SMS-SUBMIT message, report relating to the delivery of the SMS message to the destination. 10.1.2. SM-RL layer The header of the SM-RL layer contains

the following fields: - Message Type Indicator: this field indicates the type of message (RP-DATA-ACK RP, RP-ERROR); - Message Reference: this field contains a sequence number that associates the RP-DATA message and the RP-ACK or RP-ERROR response; - Originator Address: this field indicates the E.164 phone number of the SMS SC entity issuing the SMS message; - Destination address: this field indicates the E.164 phone number of the SMS SC entity receiving the SMS message. The RTP-DATA header contains SMS-SUBMIT, SMS-DELIVER or SMS-STATUS-REPORT messages from the SM-TL layer. The RP-ACK header is an acknowledgment of the receipt of RP-DATA header and contains the SMS-SUBMIT-REPORT or SMS-DELIVER- REPORT messages from the SM-TL layer. 10.1.3. SM-CL layer The header of the SM-LC layer contains the following fields: - Protocol Discriminator: this field indicates the nature of the data transmitted. It takes the value "SMS message"; - Transaction Identifier: this field identifies the number of the transaction; - Message Type: this field shows the type of message (CP-DATA, CP-ACK, CP-ERROR). 276 VoLTE and ViLTE The CP-DATA header contains the headers RP-DATA or RP-ACK and the associated messages of the SM-TL layer. The CP-ACK header is an acknowledgment of receipt of the message CP-DATA. 10.2. SMS over SGsAP 10.2.1. Functional architecture Short message service over SGsAP is a feature of the circuit-switched fallback (CSFB) mechanism which allows a mobile connected to a 4G network to use the services of the 2G/3G network in CS mode. The functional architecture of the short message service over SGsAP is described in Figure 10.3. Outgoing SMS IWMSC UTRAN Server Incoming SMS Figure 10.3. Functional architecture for SMS over SGsAP When attaching the mobile, the MME entity attaches the mobile to the MSC server entity, selected by the MME entity. The MME entity must perform a conversion of the tracking area identity (TAI) of the mobile on the 4G network in a location area identity (LAI) on the 2G or 3G network. SMS message is

conveyed between the mobile and the MSC server entity, and is supported by the following messages: - non-access stratum (NAS) message between the mobile and the MME entity; - SGsAP message between the MME and MSC server entities. Short Message Service SGs interface is the reference point between the MME and MSC server entities for signaling. This interface supports SGsAP signaling. For an incoming SMS message, the MSC server entity generates a paging to the MME entity. If the mobile is in standby state on the 4G network, the MME entity triggers the paging procedure for establishing the signaling bearer on LTE-Uu and S1-MME interfaces, allowing the transport of NAS messages. 10.2.2. Procedures 10.2.2.1. Originating side The transfer procedure for outgoing SMS messages is given in Figure 10.4. Server IWMSC SMS / SMS-SUBMIT / RP-DATA / CP-DATA NAS UPLINK NAS TRANSPORT SMS / SMS-SUBMIT/RP-DATA / CP-DATA SGsAP UPLINK UNITDATA CP-ACK SGsAP DOWNLINK UNITDATA CP-ACK NAS DOWNLINK NAS TRANSPORT SMS / SMS-SUBMIT / RP-DATA MAP FORWARD SHORT MESSAGE SMS / SMS-SUBMIT SMS-SUBMIT-REPORT SMS-SUBMIT-REPORT / RP-ACK MAP FORWARD SHORT MESSAGE ACK SMS-SUBMIT-REPORT / RP-ACK / CP-DATA SGsAP DOWNLINK UNITDATA SMS-SUBMIT-REPORT / RP-ACK / CP-DATA NAS DOWNLINK NAS TRANSPORT CP-ACK NAS UPLINK NAS TRANSPORT CP-ACK SGsAP UPLINK UNITDATA SGsAP RELEASE REQUEST Figure 10.4. Procedure at originating side for SMS over SGsAP 278 VoLTE and ViLTE 1) The message SMS/SMS-SUBMIT/RP-DATA/CP-DATA is carried by the message NAS UPLINK NAS TRANSPORT between the mobile and the MME entity. 2) The message SMS/SMS-SUBMIT/RP-DATA/CP-DATA is conveyed by the message SGsAP UPLINK UNITDAT between the MME and MSC Server entities. The CP-ACK message is transmitted by the MSC server entity to acknowledge the receipt of the message SMS/SMS-SUBMIT/RP- DATA/CP-DATA. 3) The CP-ACK message is conveyed by the message SGsAP DOWNLINK UNITDATA between the MSC Server and MME entities. 4) The CP-ACK message is conveyed by the message NAS DOWNLINK NAS TRANSPORT between the MME e

ntity and the mobile. 5) The message SMS/SMS-SUBMIT/RP-DATA is carried by the message MAP FORWARD SHORT MESSAGE between the MSC server and SMS-IWMSC entities. 6) The message SMS/ SMS-SUBMIT is transferred to the SMS-SC entity. 7) The SMS SC entity acknowledges receiving the message SMS/SMS- SUBMIT message by sending SMS-SUBMIT-REPORT message to the SMS-IWMSC entity. 8) The message SMS-SUBMIT-REPORT/RP-ACK is carried by the message MAP FORWARD SHORT MESSAGE ACK between the SMS- IWMSC and MSC server entities. 9) The message SMS-SUBMIT-REPORT/RP-ACK/CP-DATA is carried by the message SGsAP DOWNLINK UNITDATA between the MSC server and MME entities. 10) The message SMS-SUBMIT-REPORT/RP-ACK/CP-DATA is carried by the message NAS DOWNLINK NAS TRANSPORT between the MME entity and the mobile. Short Message Service The CP-ACK message is transmitted by the mobile to acknowledge the receipt of the message SMS-SUBMIT-REPORT/RP-ACK/CP-DATA. 11) The CP-ACK message is conveyed by the message NAS UPLINK NAS TRANSPORT between the mobile and the MME entity. 12) The CP-ACK message is conveyed by the message SGsAP UPLINK UNITDATA between the MME and MSC server entities. When the SMS-SC entity has the confirmation that the SMS message was delivered to the destination, it sends to the mobile the SMS-STATUS- REPORT/RP-ACK, whose transport is nothing but reproduced steps 7 to 12. 13) The MSC server entity informs the MME entity that the transfer of the SMS message is done by sending the message SGsAP RELEASE REQUEST. 10.2.2.2. Terminating side The transfer procedure for incoming SMS messages is given in Figure 10.5. 1) The SMS-SC entity sends the message SMS/SMS-DELIVER to the SMS-GMSC entity. 2) The SMS-GMSC entity interrogates the home location register (HLR) via the message MAP SEND ROUTING INFO FOR SM to obtain the identity of the MSC server entity. 3) The HLR entity provides the identity of the MSC server entity to the SMS-GMSC entity in the message MAP SEND ROUTING INFO FOR SM 4) The message SMS/SMS-DELIVER/RP-DATA is transported by

message MAP FORWARD SHORT MESSAGE between the SMS-GMSC and MSC server entities. 5) The message SGsAP PAGING containing the temporary mobile subscriber identity (TMSI) of the mobile, is transmitted to the MME entity. 6) The message S1-AP PAGING, containing the identity shortened TMSI (S-TMSI) is sent to all eNB entities of the TAI area. VoLTE and ViLTE Server SMS / SMS-DELIVER SEND ROUTING INFO FOR SM SEND ROUTING INFO FOR SM ACK SMS / SMS-DELIVER / RP-DATA MAP FORWARD SHORT MESSAGE SGsAP PAGING S1-AP PAGING Paging Service Request SGsAP SERVICE REQUEST SMS / SMS-DELIVER / RP-DATA / CP-DATA SGsAP DOWNLINK UNITDATA SMS / SMS-DELIVER / RP-DATA/CP-DATA NAS DOWNLINK NAS TRANSPORT CP-ACK NAS UPLINK NAS TRANSPORT CP-ACK SGsAP UPLINK UNITDATA SMS-DELIVER-REPORT / RP-ACK / CP-DATA NAS UPLINK NAS TRANSPORT SMS-DELIVER-REPORT / RP-ACK / CP-DATA SGsAP UPLINK UNITDATA SMS-DELIVER-REPORT / RP-ACK MAP FORWARD SHORT MESSAGE ACK SMS-DELIVER-REPORT CP-ACK SGsAP DOWNLINK UNITDATA CP-ACK NAS DOWNLINK NAS TRANSPORT SGsAP RELEASE REQUEST Figure 10.5. Procedure at terminating side for SMS over SGsAP 7) The RRC Paging message is broadcast by the eNB entities belonging to the TAI area. The mobile connects to the eNB entity and performs a service request to the MME entity to establish the signaling bearer. Short Message Service 8) The MME entity sends a service request to the MSC server entity, via the message SGsAP SERVICE REQUEST. 9) The message SMS/SMS-DELIVER/RP-DATA/CP-DATA conveyed by the message SGsAP DOWNLINK UNITDATA between the MSC server and MME entities. 10) The message SMS/SMS-DELIVER/RP-DATA/CP-DATA transported by the message NAS DOWNLINK NAS TRANSPORT between the MME and the mobile. The CP-ACK message is transmitted from the mobile to acknowledge the message SMS/SMS-DELIVER/RP-DATA/CP-DATA. 11) The CP-ACK message is conveyed by the message NAS UPLINK NAS TRANSPORT between the mobile and the MME entity. 12) The CP-ACK message is conveyed by the message SGsAP UPLINK UNITDATA between the MME and MSC server entities. The message

SMS-DELIVER-REPORT/RP-ACK is transmitted from the mobile to acknowledge the message SMS/SMS-DELIVER/RP-DATA. 13) The message SMS-DELIVER-REPORT/RP-ACK/CP-DATA is carried by the message NAS UPLINK NAS TRANSPORT, between the mobile and the MME entity. 14) The message SMS-DELIVER-REPORT/RP-ACK/CP-DATA is transported by the message SGsAP UPLINK UNITDATA between the MME and MSC server entities. 15) The message SMS-DELIVER-REPORT/RP-ACK is transported by the message MAP FORWARD SHORT MESSAGE ACK, between the MSC server and SMS-GMSC entities. 16) The SMS-GMSC entity sends the message SMS-DELIVER- REPORT to the SMS-SC entity. The CP-ACK message is transmitted by the MSC server entity to acknowledge the message SMS-DELIVER-REPORT/RP-ACK/CP-DATA. 282 VoLTE and ViLTE 17) The CP-ACK message is the message conveyed by SGsAP DOWNLINK UNITDATA between the MSC server and MME entities. 18) The CP-ACK message is conveyed by the message NAS UPLINK NAS TRANSPORT between the MME entity and the mobile. 19) The entity MSC server informs the MME entity that the transfer of the SMS messages is done by sending the message SGsAP RELEASE REQUEST. 10.3. SMS over SIP 10.3.1. Functional architecture The functional architecture of the SMS over SIP is given in Figure 10.6. The IP-SM-GW entity is an application server of the IMS network. The IP-SM-GW entity provides the protocol interworking between, firstly, the IMS network and secondly, the SMS-IWMSC entity for outgoing SMS messages or the SMS-GMSC entity for incoming SMS messages. Outgoing SMS IWMSC IP-SM UTRAN Incoming SMS Figure 10.6. Functional architecture for SMS over SIP When the mobile registers with the S-CSCF entity, the S-CSCF entity registers the mobile to the IP-SM-GW entity. To receive incoming SMS messages, the IP-SM-GW entity registers in turn the mobile to the HLR entity and provides also its address. The entities SMS-IWMSC, SMS-GMSC and SMSC are not affected by the architecture of SMS over SIP. Short Message Service 10.3.2. Procedures 10.3.2.1. Originating side The transfer p

rocedure for outgoing SMS messages is shown in Figure 10.7. P-CSCF S-CSCF IP-SM-GW IWMSC SMS / SMS-SUBMIT / RP-DATA SIP MESSAGE SMS / SMS-SUBMIT / RP-DATA SIP MESSAGE SMS / SMS-SUBMIT / RP-DATA SIP MESSAGE SMS / SMS-SUBMIT / RP-DATA MAP FORWARD SHORT MESSAGE SMS / SMS-SUBMIT SMS-SUBMIT-REPORT SMS-SUBMIT-REPORT / RP-ACK MAP FORWARD SHORT MESSAGE ACK SMS-SUBMIT-REPORT / RP-ACK SIP MESSAGE SMS-SUBMIT-REPORT / RP-ACK SIP MESSAGE SMS-SUBMIT-REPORT RP-ACK SIP MESSAGE Figure 10.7. Procedure at originating side for SMS over SIP 1) The message SMS/SMS-SUBMIT/RP-DATA is carried by the SIP MESSAGE message between the mobile and the proxy call session control function (P-CSCF). The identity of the request contains the public service identity (PSI) of the SMS-SC entity. 284 VoLTE and ViLTE The SIP MESSAGE message indicates in the header Content Type that the message body contains an SMS message. MESSAGE sip:sc.homeA.net SIP/2.0 Content-Type: application/vnd.3gpp.sms 2) The message SMS/SMS-SUBMIT/RP-DATA is carried by the SIP MESSAGE message between the P-CSCF and serving CSCF (S-CSCF) entities. The P-CSCF entity inserts in the header P-Asserted-Identity the uniform resource identifier (URI) of the origin of the SMS message. MESSAGE sip:sc.homeA.net SIP/2.0 P-Asserted-Identity:<sip:alice@homeA.net> - Content- - Type: application/vnd.3gpp.sms 3) The S-CSCF entity analyzes the received message and the initial filter criteria (iFC) to determine the destination of the SIP MESSAGE message. The message SMS/SMS-SUBMIT/RP-DATA is carried by the SIP MESSAGE messages between the S-CSCF and IP-SM-GW entities. 4) The answer 202 Accepted acknowledges the SIP MESSAGE message received by the IP-SM-GW entity. 5) to 8) The messages are identical to those exchanged for SMS over SGsAP, the IP-SM-GW entity playing the same role as the MSC server entity. 9) The message SMS-SUBMIT-REPORT/RP-ACK is carried by the SIP MESSAG message between the IP-SM-GW and the S-CSCF entities. The identity of the request contains the URI identity of the mobile origi

nating the SMS message. MESSAGE sip:alice@homeA.net SIP/2.0 Short Message Service 10) The message SMS-SUBMIT-REPORT/RP-ACK is carried by the SIP MESSAGE message between the S-CSCF and the P-CSCF entities. 11) The message SMS-SUBMIT-REPORT/RP-ACK is carried by the SIP MESSAGE message between the P-CSCF entity and the mobile. 12) The 200 OK response acknowledges the SIP MESSAGE message received by the mobile. 10.3.2.2. Terminating side The transfer procedure for incoming SMS messages is given in Figure 10.8. 1) to 4) The messages are identical to those exchanged for SMS over SGsAP, the IP-SM-GW entity playing the same role as the MSC server entity. 5) The message SMS/SMS-DELIVER/RP-DATA is carried by the SIP MESSAGE message between the IP-SM-GW and S-CSCF entities. The identity of the request contains the URI identity of the mobile receiving the SMS. The IP-SM-GW entity inserts in the header P -Asserted-Identity - its own identity. MESSAGE sip bob@homeB.: net SIP/2.0 P-Asserted-Identity: <sip:ipsmgw.homeB.net> 6) The message SMS/SMS-DELIVER/RP-DATA is carried by the SIP MESSAGE message between the S-CSCF and P-CSCF entities. 7) The message SMS/SMS-DELIVER/RP-DATA is carried by the SIP MESSAGE message between the P-CSCF entity and the mobile. 8) The 200 OK response acknowledges the SIP MESSAGE message received by the mobile. 9) The message SMS-DELIVER-REPORT/RP-ACK is carried by the SIP MESSAGE message between the mobile and the P-CSCF entity. 286 VoLTE and ViLTE P-CSCF S-CSCF IP-SM-GW SMS / SMS-DELIVER SEND ROUTING INFO FOR SM SEND ROUTING INFO FOR SM ACK SMS / SMS-DELIVER / RP-DATA MAP FORWARD SHORT MESSAGE SMS / SMS-DELIVER /RP-DATA SIP MESSAGE SMS / SMS-DELIVER / RP-DATA SIP MESSAGE SMS / SMS-DELIVER / RP-DATA SIP MESSAGE 200 OK 200 OK 200 OK SMS-DELIVER-REPORT / RP-ACK SIP MESSAGE SMS-DELIVER-REPORT / RP-ACK SIP MESSAGE SMS-DELIVER-REPORT / RP-ACK SIP MESSAGE SMS-DELIVER-REPORT/RP-ACK MAP FORWARD SHORT MESSAGE ACK SMS-DELIVER-REPORT Figure 10.8. Procedure at terminating side for SMS over SIP The identity of the

request contains the URI identity of the IP-SM-GW entity. MESSAGE sip : ipsmgw homeB. net SIP/2. 0 10) The message SMS-DELIVER-REPORT/RP-ACK is carried by the SIP MESSAGE message between the P-CSCF and S-CSCF entities. 11) The message SMS-DELIVER-REPORT/RP-ACK is carried by the SIP MESSAGE message between the S-CSCF and IP-SM-GW entities. Short Message Service 12) The answer 202 Accepted acknowledges the SIP MESSAGE message received by the IP-SM-GW entity. 13), 14) The messages are identical to those exchanged for SMS over SGsAP with the IP-SM-GW entity playing the same role as the MSC server entity. Bibliography Chapter 1 - Network Architecture [3GPP TS 23.401] General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access [3GPP TS 23.228] IP Multimedia Subsystem (IMS); Stage 2 [3GPP TS 24.229] IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 [3GPP TS 29.212] Policy and Charging Control (PCC); Reference points Chapter 2 - Signaling Protocol [3GPP TS 24.301] Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS): Stage 3 [3GPP TS 36.331] Radio Resource Control (RRC): Protocol specification [3GPP TS 36.413] S1 Application Protocol (S1AP) [3GPP TS 36.423] X2 application protocol (X2AP) [3GPP TS 29.274] Evolved General Packet Radio Service (GPRS) Tunneling Protocol for Control plane (GTPv2-C); Stage 3 [IETF RFC 3261] SIP: Session Initiation Protocol [IETF RFC 4566] SDP: Session Description Protocol [IETF RFC 3428] Session Initiation Protocol (SIP) Extension for Instant Messaging VoLTE and ViLTE: Voice and Conversational Video Services over the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2016. Published by ISTE Ltd and John Wiley & Sons, Inc. 290 VoLTE and ViLTE [IETF RFC 3262] Reliability of Provisional Responses in the Session Initiation Protocol (SIP) [IETF RFC 3515] The Session Initiation Protocol (SIP) Refer Method [IETF RFC 6665] SIP-Specific Event Not

ification [IETF RFC 3311] The Session Initiation Protocol (SIP) UPDATE Method [IETF RFC 3588] Diameter Base Protocol [3GPP TS 29.229] Cx and Dx interfaces based on the Diameter protocol; Protocol details [3GPP TS 29.329] Sh Interface based on the Diameter protocol; Protocol details [3GPP TS 29.272] Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol [3GPP TS 29.212] Policy and Charging Control (PCC); Reference points [3GPP TS 29.214] Policy and Charging Control over Rx reference point [3GPP TS 29.215] Policy and Charging Control (PCC) over S9 reference point; Stage 3 [3GPP TS 32.299] Diameter charging applications Chapter 3 - Basic Procedures [3GPP TS 23.401] General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access [IETF RFC 3665] Session Initiation Protocol (SIP) Basic Call Flow Examples [3GPP TS 24.228] Signaling flows for the IP multimedia call control based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 [3GPP TS 24.930] Signaling flows for the session setup in the IP Multimedia core network Subsystem (IMS) based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 [3GPP TS 23.167] IP Multimedia Subsystem (IMS) emergency sessions Bibliography 291 Chapter 4 - Radio Interface Procedures [3GPP TS 36.300] Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 [3GPP TS 36.213] Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures Chapter 5 - Service Profiles [GSMA PRD IR.92] IMS Profile for Voice and SMS [GSMA PRD IR.94] IMS Profile for Conversational Video Service [3GPP TS 24.604] Communication Diversion (CDIV) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.605] Conference (CONF) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS

24.606] Message Waiting Indication (MWI) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.607] Originating Identification Presentation (OIP) and Originating Identification Restriction (OIR) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.608] Terminating Identification Presentation (TIP) and Terminating Identification Restriction (TIR) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.610] Communication HOLD (HOLD) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.611] Anonymous Communication Rejection (ACR) and Communication Barring (CB) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol specification [3GPP TS 24.615] Communication Waiting (CW) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol Specification [3GPP TS 26.114] Multimedia Telephony; Media handling and interaction 292 VoLTE and ViLTE Chapter 6 - Interconnection [3GPP TS 29.163] Interworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks [3GPP TS 29.165] Interworking between SIP-I based circuit-switched core network and other networks [3GPP TS 23.205] Bearer-independent circuit-switched core network; Stage 2 [3GPP TS 23.231] SIP-I based circuit-switched core network; Stage 2 [3GPP TS 29.165] Inter-IMS Network to Network Interface (NNI) Chapter 7 - Handover [3GPP TS 23.401] General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access Chapter 8 - Roaming [GSMA PRD IR.65] IMS Roaming and Interworking Guidelines [GSMA PRD IR.88] LTE Roaming Guidelines [3GPP TS 29.079] Optimal Media Routing within the IP Multimedia System (IMS); Stage 3 Chapter 9 - Service Centralization and Continuity [GSMA PRD IR.64] IMS Service Centralization and Continuity Guidelines [3GPP TS 23.292] IP Multimedia Subsystem (IMS) Centralized Services; Stage 2 [3GPP TS 24.292] IP Multimedia (IM) Core

Network (CN) subsystem Centralized Services (ICS); Stage 3 [3GPP TS 23.237] IP Multimedia Subsystem (IMS) Service Continuity; Stage 2 [3GPP TS 24.237] IP Multimedia Subsystem (IMS) Service Continuity; Stage 3 [3GPP TS 23.216] Single Radio Voice Call Continuity (SRVCC); Stage 2 Bibliography Chapter 10 - Short Message Service [3GPP TS 23.040] Technical realization of the Short Message Service (SMS) [3GPP TS 24.011] Point-to-Point (PP) Short Message Service (SMS) support on mobile radio interface [3GPP TS 23.272] Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 [3GPP TS 23.204] Support of Short Message Service (SMS) over generic 3GPP Internet Protocol (IP) access; Stage 2 Index 180 Ringing, 58, 88, 94, 95, 98, 154, AMR WB, 167, 168, 169, 170 155, 165, 166, 182, 184-186, 188 ANM, 175, 177, 182, 184-186, 188- 190, 193, 228, 249, 251, 253, 254 181 Call Is Being Forwarded, 58, application server, 12, 15, 16, 20, 63, 152, 153, 155 81, 98, 149, 150, 153, 154, 156, 183 Session Progress, 58, 88, 90, 91, 158-160, 162, 164-167, 243, 244, 93, 95, 97, 101, 102, 158, 183, 196, 197, 228, 231, 232, 234, 235, 241, ARP, 10, 11, 106, 148 242, 249, 253, 254, 256, 266 ARQ, 112, 113, 122, 123, 134, 136- 202 Accepted, 58, 284, 287 141, 143-145, 401 Unauthorized, 14, 59, 79, 80 ASR (DIAMETER), 98 603 Decline, 59, 166, 167 ATCF, 255-258, 260-266, 269, 270, ATGW, 255-258, 263, 264, 266, 269-271 AAA (DIAMETER), 88, 93, 94, 95, ATU-STI, 261, 262, 269, 270 98, 102, 103 authentication code, 29, 71, 79, 80 AAR (DIAMETER), 88, 91, 94, 95, AUTN, 29, 61, 71, 79, 80 98, 102, 103 access point name (APN), 4, 10, 11, 12, 72, 147, 148 ACM, 175, 177, 182, 184, 185, B2BUA, 16, 244 , 246, 258 186188, 189, 190 BCCH, 34, 110, 113, 114 AIA (DIAMETER), 70, 71 BCH, 34, 110, 114, 122, 124-126 AIR (DIAMETER), 70, 71 bearer AMBR, 10, 11, 12 dedicated, 9, 11, 30-32, 43, 44, 51, AMR, 112, 167, 168, 169, 170, 181, 64, 65, 87, 91-94, 97-104, 106, VoLTE and ViLTE: Voice and Conversational Video Services over the 4G Mobile Network, First Edition.

André Perez. C ISTE Ltd 2016. Published by ISTE Ltd and John Wiley & Sons, Inc. VoLTE and ViLTE default, 3, 9, 11, 28, 30, 31, 39, 42, communication barring, 151, 166, 43, 64, 69, 72, 73, 86, 91, 224 radio, 5, 6, 8, 9, 33, 74, 110, 111, compression, 2, 110-112 134, 203, 206, 208, 212, 214, core network (EPS), 2, 149 216, 221, 256, 259 CQI, 130 BGCF, 20, 173, 174, 180-182, 185, C-RNTI, 33, 127-129, 131, 134 190, 192, 194-196, 259 CS (Circuit-Switched), 173, 273 BICC, 175, 176, 181-184, 186, 187, CSFB (CS Fallback), 276 188, 190, 191 CTF, 19, 20 BYE, 54, 55, 88, 89, 98-101, 164, CW, 151, 164, 165, 166 177, 190, 191, 269, 271, 272 data link layer, 109 call forwarding, 85, 166 DCCH, 35, 110, 113, 114, 122, 123, Call Management (CM), 245, 258 124, 126-129, 131-134 camel application part (CAP), 245 DEA, 23, 24 CANCEL, 46, 47, 55, 59, 61, 88, 89, DIAMETER (routing), 24 155, 175, 179 DL-SCH, 34, 35, 110, 114, 123 CCA (DIAMETER), 70, 86, 87, 203, DM-RS, 122 206, 208, 210, 217 DNS (Domain Name System), 24, 77 CCCH, 34, 110, 113, 114 DRA, 23, 24 CCR (DIAMETER), 70, 86, 203, DRB, 2, 6, 8, 9, 33, 38, 39, 74, 111, 206, 208, 210 CDF, 19- 21 DRX, 132, 133, 134 CDIV, 150, 151 DiffServ Code Point (DSCP), 2 CDR, 19, 20, 21 DTCH, 110, 113, 114 Cell-Specific (RS), 121, 124 EATF, 258, 259, 271, 272 CFB, 153, 154 ECGI, 4, 36, 69, 71, 106, 204-206, CFNL, 156 210, 215, 216 CFNR, 154, 155, 166 E-CSCF, 12, 13, 15, 106-108, 174, CFU, 152, 154, 156, 157 259, 271, 272 CGF, 19, 20 emergency center, 15, 259, 272 charging, 5, 13-16, 19-23, 61, 64 EMM, 27-30, 69-75, 85- 87 66, 73, 204, 224 ENUM, 24, 25, 181, 182, 194, 231, Circuit-Switched, 17, 148, 174, 200, 243, 273, 276 EPC, 1, 202, 205, 211, 219, 223, 282 CKNAS, 71, 72 E-RAB, 9, 40, 41, 43, 52, 88, 92, 95, codec, 60, 89, 90, 97, 101, 103, 104, 99, 100-103, 105 167-172, 175, 176, 181, 183, 257 ESM, 27, 28, 30- 32, 70, 74, 75, 86- audio, 167 88, 92, 95, 99, 100-102, 103, 105, video, 171 Index e-SRVCC, 148, 255-258, 260, 262, public, 15, 18, 77, 108, 148-150, 264, 271 157, 160, 173, 247, 250, 25

9, E-UTRAN, 1, 2, 4, 36, 70, 202, 204, 205, 211, 219, 223 temporary, 3, 28, 33, 58, 69, 73, EVS, 167, 169, 170 126, 128, 131, 179, 201, 202, 207-211, 213-218, 220, 221, F, G, H 247, 268, 279 IDR (DIAMETER), 261, 262 FDD, 116, 125, 131, 135, 137, 138, IK, 71, 72, 79, 80, 143 141, 143, 144 IKNAS, 71, 72 GBR, 9-11 IMPI, 18, 148 GGSN, 228 IMPU, 18, 148, 157 GMSC, 273, 274, 276, 279, 280-282, IMRN, 245 IMS-GWF, 20, 98 GPRS, 7, 37, 49, 73, 218, 219, 244 IMSI, 3, 18, 28, 69, 147, 247 GSM, 37, 255, 257, 258, 267, 268 interconnection (IMS), 259 GTP-C, 6, 8, 217 intra-system, 4, 33, 199, 201 GTP-U, 6, 7, 8, 44, 47, 49, 73, 75, 92, IPSec, 13, 75, 77, 78, 79, 80 203, 204, 207, 208, 209, 210, 211, IP-SM-GW, 274, 282-287 212, 213, 214, 216, 217, 219 IPX, 25 GUTI, 3, 28, 30, 69, 73 ISC, 17, 244, 245, 246 H.248, 175-178, 180, 246, 256, 257 ISIM, 80 H.264, 171, 172 IWMSC, 273, 274, 276-278, 282, H.265, 171, 172 handover, 2, 3, 4, 8, 33, 39, 40, 41, 43, 44, 46, 47, 51, 52, 110, 126, HARQ, 113, 122, 123, 134, 136, 137, KASME, 61, 71, 72, 74 138, 139, 140, 141, 144, 145 KeNB, 71, 72, 74 HLR, 279, 280, 282, 286 key, 69, 71, 72, 74, 79, 80, 119 HOLD, 151, 161-163, 170, cipher, 79 H-PCRF, 22, 23, 65, 224 integrity, 2, 29, 30, 33, 38, 71, 72, 74, 78, 79, 110, 247 secret, 71 Ki, 71, 80 IBCF, 192-197, 224-242, 259 LAI, 276 ICB, 166 LIA (DIAMETER), 76, 81, 84, 85, ICS, 145, 223, 244-249, 252, 253 95, 186, 187, 189, 261, 265 IDA (DIAMETER), 261 location area, 3, 4, 30, 36, 45, 72, 276 Identity logical channel, 34, 35, 92, 109, 113, module, 71, 80 presentation, 151, 157, 158 LRF, 12, 15, 108 private, 3, 18, 77, 78, 80, 148, 149, VoLTE and ViLTE LTE, 6, 8, 27, 30, 32, 33, 70, 74, 75, OIR, 151, 157, 158 86, 87, 92, 94, 100, 202, 205, 211, OMR, 226, 228, 235 M, N, o packet-switched, 148, 200, 243 MAA (DIAMETER), 76, 79, 261 paging, 3, 4, 30, 33, 34, 36-38, 40, MAC, 6, 8, 109, 110, 113, 127-129, 41, 51, 52, 113, 114, 277, 279, 280 134, 136 PATH URI, 260-262 MAR (DIAMETER), 76, 79, 261 PBCH, 34, 110, 122, 124-126 MBR, 10-12 PCC, 21-23, 34, 61, 64

, 110, 113, MBSFN RS MCC, 36, 45, 247 PCCH, 34, 110, 113, 114 MCCH, 110-114 PCEF, 5, 21-23, 64-66 MCH, 110, 114, 123 PCFICH, 110, 122, 124, 126 media resource, 12, 162 PCH, 34, 110, 114, 123 MGCF, 20, 66, 173, 174, 175, 176, PSS, 121, 124-126, 201 177, 179, 180, 182, 183, 184, 185, PSTN, 173-175, 180, 181, 250 186, 187, 188, 189, 190, 191, 245, PUA (DIAMETER), 261 246, 259 PUCCH, 110, 122-124, 131, 141- MGW, 173-177, 179-181, 183, 184, 186-188, 190, 191, 246, 285, 286 PUR (DIAMETER), 261, 262 MIB, 113, 114, 122, 125, 126 PUSCH, 34, 35, 110, 122-124, 127- MIMO, 120, 121, 130, 137 129, 131, 132, 135, 138-145 MNC, 36, 45, 247 quality of service, 5, 9, 31, 72 QCI, 2, 4, 5, 10, 11, 21, 31, 69, 91, acknowledgment, 44 102, 106, 130, 131, 148, 267 transparent, 112 QoS, 2, 5, 10, 11, 31, 72, 74, 89, 91, MRFC, 12, 16, 17, 20, 162-164, 174 93, 130, 147, 148 MFRP, 12, 17, 162, 163 RAA (DIAMETER), 88, 93, 95, 99, MSC GW, 244, 245, 251, 252, 254, 101-103, 105 256, 257, 258, 269, 270, 272 RACH, 110, 114, 123, 124, 126-129, MTCH, 110, 113, 114 MWI, 151, 159 radio link control (RLC), 33, 109 NAS (messages), 29, 33, 35, 38, 39, RAND, 29, 61, 71, 79, 80, 113, 114, 41, 69, 72, 109, 277 123, 124, 126-129, 201 NOTIFY, 41, 44, 53, 56, 61, 65, 76, random access, 113, 114, 123, 124, 83-85, 160, 163, 164, 175, 179, 126-129, 201 208, 210, 215, 216 random access response (RAR), 128 OCB, 167 RA-RNTI, 127-129, 131 OCS, 19-23, 66, 67 re-auth-request (RAR), 64-66, 91 OFCS, 19, 20-23, 65, 66 reference signal, 121, 122 OIP, 151, 157, 158 Index retransmission, 89, 90, 94, 96, 112, SIP-I, 175, 177, 184, 185, 188, 189, 113, 128, 130, 131, 134, 136, 137, 190, 191 142, 143, 182, 184, 187, 188, 250- SI-RNTI, 124, 126, 131 252, 254 SISO, 120 release complete (RLC), 41, 41, 86, SLF, 18, 19, 23, 62, 63 87, 176, 208, 216, 217, 221 SM-AL, 273-287 RNC, 218-221 SM-CL, 273-275 roaming, 22-25, 42, 107, 148, 223- SM-RL, 273-275 227, 229, 231, 233, 235, 237, 239, SM-TL, 273-276 241, 255, 257, 259 SMS, 33, 57, 136, 193, 228, 257, ROHC, 110-112 273-287 routeing, 9,

225-229, 232, 233, 235, SMS-SC, 273-275, 278, 279, 281, 236, 240 nominal routeing, 225, 228, 229, SPR, 11, 21-23, 73, 91, 224 232,233 SPS, 131, 134, 135 optimal routeing, 226, 227, 235, SRB, 6, 33-35, 38, 110, 111 236, 240 SRS, 122, 131 SS7, 180 SSS, 121, 124, 125, 126, 201 STA (DIAMETER), 99, 101, 105 SAA (DIAMETER), 76, 81, 84, 85, S-TMSI, 128, 279 STN-SR, 147, 148, 260-262, 268, SAR (DIAMETER), 76, 81, 84, 85, 269, 272 248, 261 STR (DIAMETER), 99, 101, 105 SCC AS, 243, 244, 245, 246, 248- SUBSCRIBE, 3, 4, 18, 24, 28, 56, 61, 255, 261-263, 265, 266, 269-271 63, 64, 69, 71, 76, 82, 83, 128, 147, service centralization, 200, 243 148, 151, 158, 159, 187, 192, 224, service continuity, 257, 261, 263, 244, 247, 261, 262, 268, 279 265, 269, 271 synchronization signal, 121, 201 session description protocol (SDP), system information, 3, 33, 36, 38, 17, 60, 87, 149, 181, 250 113, 114, 122, 124-128 SGsAP, 273, 274, 276-284, 285, 287 SGSN, 218, 219, 220, 221, 244, 245, SIB, 2, 3, 9, 33, 51, 54, 83, 112, 113, TC-RNTI, 127-129, 131 114, 124, 126, 127, 128, 164, 170, TDD, 116-118, 125, 131, 135, 138- 171, 174, 176, 179, 218, 240, 258, 141, 144, 145 267, 271, 272 TDM, 173, 175, 178, 180, 183 SIGTRAN, 180, 183 TEID, 47, 49-52, 73-75, 92, 202, SIMO, 120, 121 204-207, 209-214, 216 SIP (request), 16 TIP, 25, 58, 82, 109, 111-116, 120, SIP (response), 102, 177, 228, 250, 121, 130, 142, 143, 151, 158, 165, 174,178 VoLTE and ViLTE TIR, 151, 158, 159 ULA (DIAMETER), 70 TM, 16, 17, 34, 49, 58, 112, 128, ULR (DIAMETER), 70 150, 175, 268, 279 UL-SCH, 34, 35, 110, 114, 123 TMSI, 128, 268, 279 UMTS, 37, 223, 255, 257, 258, 267, TRF, 226, 227, 236-241 transmission mode, 120, 137-141 URN, 29, 43, 56, 57, 63, 106, 108, transport channel, 34, 35, 109, 110, 144, 150, 166, 175, 191, 251, 282 114, 122, 123, 125 user agent (UA), 13, 16, 53, 54, 77, uplink, 42, 86, 110, 114, 115, 117, 150, 181, 244 118, 122, 123, 126, 130-132, user equipment (UE), 2, 9, 27, 69, 135, 137-141, 143, 144, 200, 109, 243 277-282 USIM, 71 TrGW, 192, 193, 195-197, 225, 22

6- ViLTE, 101-104, 170 235, 237-239, 241, 259 VoHSPA, 200 TTI, 29, 33, 45, 56, 72, 91, 113, 120, VoLTE, 87, 88, 90, 94, 95, 98-102, 130, 143-145, 268 104, 110, 133, 138, 140, 142-145, TTI bundling, 143, 144 150, 170 V-PCRF, 22, 23, 65, 224 UAA (DIAMETER), 76, 248, 261 UAR (DIAMETER), 76, 78, 248, 261 X2-AP, 7, 45, 46, 49, 129, 199, 200, UDA (DIAMETER), 76, 82 202-204, 206, 207 UDR (DIAMETER), 76, 82 XCAP, 17, 244, 246 UE-Specific RS, 121 XML, 17, 82, 83, 164-166, 262 UICC, 71, 80, 107 Other titles from Networks and Telecommunications CHIASSERINI Carla Fabiana, GRIBAUDO Marco, MANINI Daniele Analytical Modeling of Wireless Communication Systems (Stochastic Models in Computer Science and Telecommunication Networks Set - Volume 1) BENSLAMA Malek, KIAMOUCHE Wassila, BATATIA Hadj Connections Management Strategies in Satellite Cellular Networks BENSLAMA Malek, BATATIA Hadj, BOUCENNA Mohamed Lamine Ad Hoc Networks Telecommunications and Game Theory BERTHOU Pascal, BAUDOIN Cédric, GAYRAUD Thierry, GINESTE Matthieu Satellite and Terrestrial Hybrid Networks LE RUYET Didier, PISCHELLA Mylène Digital Communications 1: Source and Channel Coding PEREZ André LTE and LTE Advanced: 4G Network Radio Interface PISCHELLA Mylène, LE RUYET Didier Digital Communications 2: Digital Modulations PUJOLLE Guy Software Networks ANJUM Bushra, PERROS Harry Bandwidth Allocation for Video under Quality of Service Constraints BATTU Daniel New Telecom Networks: Enterprises and Security BEN MAHMOUD Mohamed Slim, GUERBER Christophe, LARRIEU Nicolas, PIROVANO Alain, RADZIK José Aeronautical Air-Ground Data Link Communications BITAM Salim, MELLOUK Abdelhamid Bio-inspired Routing Protocols for Vehicular Ad-Hoc Networks CAMPISTA Miguel Elias Mitre, RUBINSTEIN Marcelo Gonçalves Advanced Routing Protocols for Wireless Networks CHETTO Maryline Real-time Systems Scheduling 1: Fundamentals Real-time Systems Scheduling 2: Focuses EXPOSITO Ernesto, DIOP Codé Smart SOA Platforms in Cloud Computing Architectures MELLOUK Abdelhamid, CUADRA-SANCHEZ Antonio Quality

of Experience Engineering for Customer Added Value Services OTEAFY Sharief M.A., HASSANEIN Hossam S. Dynamic Wireless Sensor Networks PEREZ André Network Security PERRET Etienne Radio Frequency Identification and Sensors: From RFID to Chipless RFID REMY Jean-Gabriel, LETAMENDIA Charlotte LTE Standards LTE Services TANWIR Savera, PERROS Harry VBR Video Traffic Models VAN METER Rodney Quantum Networking XIONG Kaiqi Resource Optimization and Security for Cloud Services ASSING Dominique, CALÉ Stéphane Mobile Access Safety: Beyond BYOD BEN MAHMOUD Mohamed Slim, LARRIEU Nicolas, PIROVANO Alain Risk Propagation Assessment for Network Security: Application to Airport Communication Network Design BEYLOT André-Luc, LABIOD Houda Vehicular Networks: Models and Algorithms BRITO Gabriel M., VELLOSO Pedro Braconnot, MORAES Igor M. Information-Centric Networks: A New Paradigm for the Internet BERTIN Emmanuel, CRESPI Noël Architecture and Governance for Communication Services DEUFF Dominique, COSQUER Mathilde User-Centered Agile Method DUARTE Otto Carlos, PUJOLLE Guy Virtual Networks: Pluralistic Approach for the Next Generation of Internet FOWLER Scott A., MELLOUK Abdelhamid, YAMADA Naomi LTE-Advanced DRX Mechanism for Power Saving JOBERT Sébastien et al. Synchronous Ethernet and IEEE 1588 in Telecoms: Next Generation Synchronization Networks MELLOUK Abdelhamid, HOCEINI Said, TRAN Hai Anh Quality-of-Experience for Multimedia: Application to Content Delivery Network Architecture NAIT-SIDI-MOH Ahmed, BAKHOUYA Mohamed, GABER Jaafar, WACK Maxime Geopositioning and Mobility PEREZ André Voice over LTE: EPS and IMS Networks AL AGHA Khaldoun Network Coding BOUCHET Olivier Wireless Optical Communications DECREUSEFOND Laurent, MOYAL Pascal Stochastic Modeling and Analysis of Telecoms Networks DUFOUR Jean-Yves Intelligent Video Surveillance Systems EXPOSITO Ernesto Advanced Transport Protocols: Designing the Next Generation JUMIRA Oswald, ZEADALLY Sherali Energy Efficiency in Wireless Networks KRIEF Francine Green Networking PEREZ André M

obile Networks Architecture BONALD Thomas, FEUILLET Mathieu Network Performance Analysis CARBOU Romain, DIAZ Michel, EXPOSITO Ernesto, ROMAN Rodrigo Digital Home Networking CHABANNE Hervé, URIEN Pascal, SUSINI Jean-Ferdinand RFID and the Internet of Things GARDUNO David, DIAZ Michel Communicating Systems with UML 2: Modeling and Analysis of Network Protocols LAHEURTE Jean-Marc Compact Antennas for Wireless Communications and Terminals: Theory and Design RÉMY Jean-Gabriel, LETAMENDIA Charlotte Home Area Networks and IPTV PALICOT Jacques Radio Engineering: From Software Radio to Cognitive Radio PEREZ André IP, Ethernet and MPLS Networks: Resource and Fault Management TOUTAIN Laurent, MINABURO Ana Local Networks and the Internet: From Protocols to Interconnection CHAOUCHI Hakima The Internet of Things FRIKHA Mounir Ad Hoc Networks: Routing, QoS and Optimization KRIEF Francine Communicating Embedded Systems / Network Applications CHAOUCHI Hakima, MAKNAVICIUS Maryline Wireless and Mobile Network Security VIVIER Emmanuelle Radio Resources Management in WiMAX CHADUC Jean-Marc, POGOREL Gérard The Radio Spectrum GAITI Dominique Autonomic Networks LABIOD Houda Wireless Ad Hoc and Sensor Networks LECOY Pierre Fiber-optic Communications MELLOUK Abdelhamid End-to-End Quality of Service Engineering in Next Generation Heterogeneous Networks PAGANI Pascal et al. Ultra-wideband Radio Propagation Channel BENSLIMANE Abderrahim Multimedia Multicast on the Internet PUJOLLE Guy Management, Control and Evolution of IP Networks SANCHEZ Javier, THIOUNE Mamadou VIVIER Guillaume Reconfigurable Mobile Radio Systems WILEY END USER LICENSE AGREEMENT Go to www.wiley.com/go/eula to access Wiley's ebook EULA. This book presents the architecture of two networks that make up the backbone of the telephone service VoLTE and video service ViLTE. The 4G mobile network makes it possible to construct bearers through which IP packets, containing either telephone signals (SIP, SDP) or voice or video media (RTP stream), are transported. The IMS network per

forms the processing of the telephone signal to provide VoLTE and ViLTE services, including call routing and the provision of additional services. Different procedures are described: the set-up and termination of a session, interconnection with third-party networks, roaming and intra-system handover. The inter-system handover PS-CS is a special case that occurs when the mobile loses 4G network coverage over the course of a session. The e-SRVCC mechanism enables continuity of the service during the switch of the telephone communication to the 2G or 3G networks. The SMS service for short messages, which is a special telephone service in itself, is provided by two structures, one relying on the IMS network, and a second on the CSFB functionality. André Perez is a consultant and teacher in networks and telecommunications. He works with industrialists and operators regarding architecture studies and leads training on the 4G and IMS networks for NEXCOM SYSTEMS. WILEY www.iste.co.uk 91781848219236 NETWORKS AND TELECOMMUNICATIONS SERIES Wi-Fi Integration to the 4G Mobile Network André Perez WILEY Wi-Fi Integration to the 4G Mobile Network Wi-Fi Integration to the 4G Mobile Network André Perez WILEY First published 2018 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc. Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address: ISTE Ltd John Wiley & Sons, Inc. 27-37 St George's Road 111 River Street London SW19 4EU Hoboken, NJ 07030 www.iste.co.uk www.wiley.com © ISTE Ltd 2018 The rights of André Perez to be identified as the a

4.2. PLCP sub-layer 4.3. PMD sub-layer 4.3.1. Transmission chain 4.3.2. Frequency plan 4.3.3. Frequency multiplexing 4.3.4. Space multiplexing 4.3.5. Modulation and coding scheme Chapter 5. 802.11ac Interface 5.1. MAC layer 5.1.1. Management frame evolution 5.1.2. Control frames 5.1.3. MAC header structure 5.2. PLCP sub-layer Contents 5.3. PMD sub-layer 5.3.1. Transmission chain 5.3.2. Frequency plan 5.3.3. Frequency multiplexing 5.3.4. Spatial multiplexing 5.3.5. Modulation and coding scheme Chapter 6. Mutual Authentication 6.1.802.1 1x mechanism 6.1.1. EAPOL protocol 6.1.2. EAP 6.1.3. RADIUS messages 6.1.4. Authentication procedure 6.2. Key management 6.2.1. Key hierarchy 6.2.2. Four-way handshake procedure 6.2.3. Group Key Handshake procedure 6.3. Application to the 4G mobile network 6.3.1. EAP-AKA method 6.3.2. Mutual authentication procedure 6.3.3. Procedure for rapid renewal of authentication 6.3.4. Application to the MIPv4 FA mechanism Chapter 7. SWu Tunnel Establishment 7.1. IPSec mechanism 7.1.1. Header extensions 7.1.2. IKEv2 protocol 7.1.3. Procedure 7.2. Application to the 4G mobile network 7.2.1. SWu tunnel establishment procedure 7.2.2. Procedure for rapid renewal of authentication Chapter 8. S2a/S2b Tunnel Establishment 8.1. PMIPv6 mechanism 8.1.1. Mobility extension 8.1.2. Procedures 8.1.3. Application to the 4G mobile network 8.2. GTPv2 mechanism 8.2.1. Trusted Wi-Fi access 8.2.2. Untrusted Wi-Fi access Wi-Fi Integration to the 4G Mobile Network 8.3. MIPv4 FA mechanism 8.3.1. Components of mobility 8.3.2. Foreign agent discovery 8.3.3. Registration 8.3.4. Procedure 8.3.5. Application to the 4G mobile network Chapter 9. S2c Tunnel Establishment 9.1. MIPv6 mechanism 9.1.1. IPv6 header extensions 9.1.2. ICMPv6 messages 9.1.3. Procedures 9.2. DSMIPv6 mechanism 9.3. Application to the 4G mobile network 9.3.1. Trusted Wi-Fi access 9.3.2. Untrusted Wi-Fi access 9.3.3. IFOM function Chapter 10. Network Discovery and Selection 10.1. Mechanisms defined by 3GPP organization 10.1.1. ANDSF function 10.1.2. RA

N assistance 10.2. Mechanisms defined by IEEE and WFA organizations 10.2.1. Information elements provided by the beacon 10.2.2. Information elements provided by the ANQP server Chapter 11. Carrier Aggregation 11.1. Functional architecture 11.2. Protocol architecture 11.2.1. LWA 11.2.2. LWIP aggregation 11.2.3. LAA aggregation 11.3. Procedures 11.3.1. LWA 11.3.2. LWIP aggregation 11.3.3. LAA aggregation 11.4. PDCP Contents Chapter 12. MPTCP Aggregation 12.1. Functional architecture 12.2. TCP 12.2.1. TCP header 12.2.2. Opening and closing a connection 12.2.3. Data transfer 12.2.4. Slow Start and Congestion Avoidance mechanisms 12.2.5. Fast Retransmit and Fast Recovery mechanisms 12.2.6. ECN mechanism 12.3. MPTCP 12.3.1. Establishment of MPTCP connection 12.3.2. Adding a TCP connection 12.3.3. Data transfer 12.3.4. Closing an MPTCP connection 12.3.5. Adding and removing an address 12.3.6. Return to the TCP connection Bibliography Index List of Abbreviations 3rd Generation Partnership Project Authentication Authorization Accounting Authenticate and Authorize Answer Additional Authentication Data Authenticate and Authorize Request Access Category Acknowledgment Advanced Encryption Standard Application Function Automatic Control Gain Authentication Header Association Identifier Arbitration Inter-Frame Space Authentication and Key Agreement Acknowledgement Mode A-MPDU Aggregate MAC Protocol Data Unit A-MSDU Aggregate MAC Service Data Unit Access Network Discovery Information ANDSF Access Network Discovery and Selection Function Wi-Fi Integration to the 4G Mobile Network Access Network Query Protocol Access Point Access Point Name Address Resolution Protocol Abort-Session-Answer Abort-Session-Request Authentication Network Binary Convolutional Coding Binding Cache Entry Binding Identifier Binary Phase-Shift Keying Basic Service Set BSSID BSS Identifier Credit-Control-Answer Clear Channel Assessment Complementary Code Keying Counter-mode/CBC-MAC-Protocol Credit-Control-Request Congestion Experienced Challenge Handshake Au

thentication Protocol Cipher Key Correspondent Node Correspondent Node Address Care-of Address Care-of Test Care-of Test Init Cyclic Redundancy Check List of Abbreviations Cyclic Shift Diversity CSMA/CA Carrier Sense Multiple Access/Collision Avoidance Clear To Send Contention Window Congestion Window Reduced Destination Address Duplicate Address Detection Distributed Coordination Function Diameter-EAP-Answer Diameter-EAP-Request Don't Fragment Dynamic Frequency Selection Dynamic Host Configuration Protocol DCF Inter-Frame Space Domain Name System Domain of Interpretation Data Radio Bearer DiffServ Code Point DSMIPv6 Dual-Stack Mobile IP version 6 Data Sequence Signal Direct Sequence Spread Spectrum Extensible Authentication Protocol EAPOL EAP Over LAN ECN-Echo Explicit Congestion Notification ECN-Capable Transport Enhanced Distributed Channel Access Wi-Fi Integration to the 4G Mobile Network Equivalent Home Service Providers Extended Inter-Frame Space Extended Master Session Key evolved Node B station Evolved Packet Core evolved Packet Data Gateway Evolved Packet System E-RAB EPS Radio Access Bearer Extended Rate Physical Encapsulating Security Payload Extended Service Set E-UTRAN Evolved Universal Terrestrial Radio Access Network Foreign Agent Foreign Agent Address Frame-Based Equipment Frame Check Sequence Flow Identifier Fully Qualified Domain Name Generic Advertisement Service Group Encryption Key Guard Interval Group Integrity Key General Packet Radio Service Generic Routing Encapsulation GTP-C GPRS Tunnel Protocol Control GTP-U GPRS Tunnel Protocol User List of Abbreviations Home Agent HESSID Homogeneous Extended Service Set Identifier Home Network Prefix Home Address Home Test Home Test Init High Rate HS2.0 Hotspot 2.0 Home Subscriber Server High Throughput Inter-APN Routing Policy Internet Control Message Protocol Integrity Check Value Inverse Discrete Fourier Transform Information Element Institute of Electrical and Electronics Engineers Internet Engineering Task Force IP Flow Mobility Integrity Key IKE

v2 Internet Key Exchange version 2 International Mobile Subscriber Identity Internet Protocol IPSec IP Security ISAKMP Internet Security Association and Key Management Protocol Industrial, Scientific and Medical Inter-System Mobility Policy Inter-System Routing Policy Initialization Vector Wi-Fi Integration to the 4G Mobile Network Key Confirmation Key Key Encryption Key Licensed Assisted Access Local Area Network Load-Based Equipment Listen Before Talk Logical Channel Identifier Low-Density Parity Check Logical Link Control Local Mobility Anchor LMA Address Local Mobility Domain Long-Term Evolution Long Training Field LTE-Wi-Fi Aggregation LWAAP LWA Adaptation Protocol LTE/WLAN radio level integration with IPsec tunnel LWIPEP LWIP Encapsulation Protocol Multimedia-Authentication-Answer Medium Access Control Message Authentication Code Mobile Access Gateway MAPCON Multiple-Access PDN Connectivity Multimedia-Authentication-Request Mobile Country Code Message Integrity Code Multiple Input Multiple Output Mobile IP Mobility Management Entity List of Abbreviations Mobile Node Mobile Network Code Management Object MPTCP Multi-Path Transmission Control Protocol MAC Service Data Unit MSISDN Mobile Subscriber ISDN Number Master Session Key Maximum Segment Size Multi User Network Access Identifier Non-Access Stratum Network Address Translation Neighbor Discovery Non-Seamless WLAN Offload Online Charging System Offline Charging System Orthogonal Frequency-Division Multiplexing Offload Preference Indication Open System Authentication Peer Authorization Database Proxy Binding Acknowledgement Packet Binary Convolutional Code Proxy Binding Update Policy and Charging Control Phased Coexistence Operation Policy Charging and Rules Function Packet Data Convergence Protocol xviii Wi-Fi Integration to the 4G Mobile Network Packet Data Network PDN Gateway Physical Layer Convergence Protocol Physical Medium Dependent PMIPv6 Proxy Mobile IP version 6 Pairwise Master Key Packet Number Push-Profile-Answer PLCP Protocol Data Unit Push-Pro

file-Request Packet-Switched Power Save PLCP Service Data Unit Preferred Service Provider List Pairwise Transient Key Quadrature Amplitude Modulation Quality of Service Quadrature Phase-Shift Keying Receiver Address Router Advertisement Re-Auth-Answer RADIUS Remote Authentication Dial-In User Service Re-Auth-Request Rivest Cipher Reverse Direction Request For Comments Reduced Inter-Frame Space Radio Link Control Robust Header Compression Radio Resource Control List of Abbreviations Robust Security Network Reference Signal Received Power Received Signal Strength Indication Registration-Termination-Answer Retransmission Time Out Registration-Termination-Request Request To Send Round Trip Time Source Address Security Association Server-Assignment-Answer Selective Acknowledgment Security Association Database Server-Assignment-Request Security Gateway Serving Gateway Short Inter-Frame Space Shared Key Authentication Security Policy Database Security Parameter Index Subscription Profile Repository Service Set Identifier Slot Time Session Termination Answer Space-Time Block Coding Short Training Field Session Termination Request Single User Wi-Fi Integration to the 4G Mobile Network Transmitter Address Tracking Area Identity Traffic Class Transmission Control Protocol Tunnel Endpoint Identifier Traffic Flow Template Traffic Identifier Traffic Indication Map Temporary Key Temporal Key Integrity Protocol Transport Layer Security Type, Length, Value Temporary MIC Key Transmit Power Control TKIP Sequence Counter TKIP-mixed Transmit Address and Key Time To Live Tunneled Transport Layer Security Trusted WLAN Access Gateway Trusted WLAN Access Network Trusted WLAN AAA Proxy Transmission Opportunity User Datagram Protocol User Equipment Universal Integrated Circuit Card U-NII Unlicensed-National Information Infrastructure User Priority Universal Services Identity Module List of Abbreviations V, W, X Very High Throughput VoLTE Voice over LTE Wired Equivalent Privacy Wi-Fi Alliance Wi-Fi Wireless Fidelity Wireless Local Area Netw

ork WLAN Control Plane Wi-Fi Protected Access Weighed Random Early Discard eXtensible Markup Language Introduction The proliferation of mobile applications has increased the amount of data in the 4G mobile network. With the adoption of smartphones and broadband services, such as video streaming, cellular network resources are increasingly constrained. Wi-Fi technology is ideally positioned to add capacity to the cellular network. It is necessary to improve the interworking between the 4G mobile network and the Wi-Fi network in order to offer a global and consistent broadband access to the end-user. In addition to growing traffic, users expect unrestricted access to applications whether at home, in a business or on the road. For this reason, Wi-Fi technology, providing additional coverage, is an appropriate solution for roaming users. The ability to exploit unlicensed frequency bands in addition to the spectrum allocated to cellular networks is of obvious appeal to network operators, who see Wi-Fi as another means of accessing the 4G mobile network. Many mobile phones currently sold include both cellular and Wi-Fi radio access and are capable of simultaneously using both radios. This makes it possible to direct certain services to Wi-Fi access and others to the cellular radio access. xxiv Wi-Fi Integration to the 4G Mobile Network The various standardization bodies, IEEE (Institute of Electrical and Electronics Engineers), WFA (Wi-Fi Alliance) and 3GPP (3rd Generation Partnership Project), paved the way for the integration of Wi-Fi technology into the cellular network, allowing the mobile to access its services through Wi-Fi access. I.1. 4G mobile network I.1.1. Network architecture The 4G mobile network, which is called EPS (Evolved Packet System), consists of an evolved packet core (EPC) and an evolved universal terrestrial radio access network (E-UTRAN) (Figure I.1). The E-UTRAN access network provides the connection of the user equipment (UE). The core network EPC interconnects access networks, provides the in

terface to the packet data network (PDN) and provides mobile attachment and bearer establishment. E-UTRAN Figure I.1. 4G mobile network architecture The evolved node B station (eNB) compresses and encrypts traffic data on the radio interface, as well as encrypts and checks the integrity of signaling data exchanged with the mobile. Introduction The mobility management entity (MME) allows mobile access to the EPS network and controls the establishment of bearers for the transmission of traffic data. The SGW (Serving Gateway) entity is the anchor point for intra-system handover (mobility within the 4G network) and inter-system handover in packet-switched (PS) mode, requiring transfer of mobile traffic to a second- or third-generation mobile network. The PGW (PDN Gateway) entity is the gateway router that connects the EPS network to the PDN. It provides the mobile with its configuration (IP address) and traffic information to the online charging system (OCS) for the prepaid and offline charging system (OFCS) for the postpaid. The home subscriber server (HSS) is a database that stores data specific to each subscriber. The main stored data include subscriber identities, authentication parameters and service profile. The policy charging and rules function (PCRF) provides the PGW entity with the rules to apply for the traffic (rate, quality of service, charging mode) when establishing the bearer. This information is stored in the subscription profile repository (SPR) when the subscription is created. I.1.2. Security architecture The mutual authentication between the mobile and the MME entity is based on the EPS-AKA (Authentication and Key Agreement) mechanism: - the HSS entity provides the MME entity with the authentication vector (RAND, AUTN, RES, KASME) from the secret key Ki created during the subscription of the mobile; - the MME entity provides the mobile with the random number (RAND) and the seal (AUTN) of the network; - the mobile calculates the seals (AUTN, RES) and the key KASME from its key Ki stored in the uni

versal subscriber identity module (USIM) of its universal integrated circuit card (UICC) and compares the seal (AUTN) received with that calculated; xxvi Wi-Fi Integration to the 4G Mobile Network - the mobile transmits its seal (RES) to the MME entity, which compares it to that received from the HSS entity; - the KASME key is used to protect the signaling exchanged between the mobile and the MME entity as well as the control and traffic data on the radio interface. I.1.3. Bearer establishment The EPS network transports the mobile data stream (IP packets) transparently to the PGW entity that is routing the packets. The IP packet is transported in bearers built between the entities of the EPS network (Figure I.2). EPS Bearer Radio Access Bearer Radio Bearer S1 Bearer S5 Bearer GTP-U GTP-U GTP-C Figure I.2. Bearer establishment The data radio bearer (DRB) is built between the mobile and the eNB entity. The RRC (Radio Resource Control) signaling, exchanged between the mobile and the eNB entity, is responsible for the construction of this bearer. The S1 bearer is built between the eNB and SGW entities. The S1-AP signaling, exchanged between the eNB and MME entities, and the GTPv2 (GPRS Tunneling Protocol-Control) signaling, exchanged between the MME and SGW entities, are responsible for the construction of this bearer. The S5 bearer is built between the SGW and PGW entities. The GTPv2- C signaling, exchanged between the SGW and PGW entities, is responsible for the construction of this bearer. Introduction xxvii The connection of the radio bearer and the S1 bearer, carried out by the eNB entity, constitutes the EPS radio access bearer (E-RAB). The connection of the E-RAB and S5 bearers, made by the SGW entity, constitutes the EPS bearer. The S1 and S5 bearers are GTP-U (GPRS Tunneling Protocol User) tunnels, which allow the IP packet of the mobile to be transported in the IP packet of the bearer transmitted between the entities of the EPS network. The PGW entity is the only entity in the EPS network that routes the mo

bile IP packet. The IP transport network that allows communication between the entities of the EPS network routes the IP packet that is the S1 or S5 bearer. The eNB and SGW entities do not perform routing. They only provide the connection between the bearers. I.2. Wi-Fi network I.2.1. Network architecture The Wi-Fi (Wireless Fidelity) network consists of an access point (AP) that bridges the Wi-Fi radio interface with the Ethernet interface to the local area network (LAN) (Figure I.3). Router Figure I.3. Wi-Fi network architecture xxviii Wi-Fi Integration to the 4G Mobile Network The BSS (Basic Service Set) cell is the radio zone covered by the access point. The BSS identifier (BSSID) of the BSS cell is the MAC address of the access point. Several BSS cells can be deployed to cover an area. The set of cells constitute an ESS (Extended Service Set) network. The ESS network is identified by the service set identifier (SSID). Wi-Fi technology has defined the data link layer and physical layer of the radio interface (Figure I.4): - the data link layer consists of two sub-layers, namely the LLC (Logical Link Control) sub-layer and the MAC (Medium Access Control) sub-layer; - the physical layer has defined two sub-layers, namely the PLCP (Physical Layer Convergence Protocol) sub-layer and the PMD (Physical Medium Dependent) sub-layer. Bridging consists of modifying the data link layer and the physical layer used on both sides of the access point. Station Access Point Router Wi-Fi Ethernet Wi-Fi Ethernet Figure I.4. Protocol architecture The LLC sub-layer is not specific to Wi-Fi technology. It is also used for other data link layer protocols, such as the Ethernet MAC sub-layer. It indicates the nature of the encapsulated data, for example an IP packet. Introduction The MAC sub-layer defines the procedure of access to the physical medium shared between the different mobiles of the cell. The CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) procedure solves the collision problems that occur when two mobiles sim

ultaneously access the physical medium. Particular MAC frames can be used for management functions (radio channel scanning, authentication, association) or transmission control (acknowledgment of received frames). The PLCP sub-layer allows adaptation of the MAC sub-layer to the PMD sub-layer, providing signal-processing parameters for the receiver and indicating the bit rate of the frame. The PMD sub-layer defines the characteristics of the radio transmission. I.2.2. Security architecture The 802.1x mechanism defines the mobile access control to the Wi-Fi network that is performed between the mobile and the RADIUS (Remote Authentication Dial-In User Service) server. The 802.1x mechanism relies on EAP-Method (Extensible Authentication Protocol) authentication messages, for which several protocols are defined: - EAP-CHAP (Challenge Handshake Authentication Protocol) protocol allows the authentication of the mobile by the RADIUS server, based on a password; - EAP-TLS (Transport Layer Security) protocol allows mutual authentication of the RADIUS server and the mobile, based on certificates; - EAP-TTLS (Tunneled Transport Layer Security) protocol allows mutual authentication of the RADIUS server based on certificate and of the mobile based on password. Data protection on the radio interface introduces an extension of the MAC header: - TKIP (Temporal Key Integrity Protocol) extension for the WPA (Wi-Fi Protected Access) mechanism based on RC4 (Rivest Cipher) algorithms for encryption and MICHAEL for integrity checking; Wi-Fi Integration to the 4G Mobile Network - CCMP (Counter-mode/CBC-MAC-Protocol) extension for the WPA2 mechanism based on the AES (Advanced Encryption Standard) algorithm for encryption and integrity checking. I.2.3. Physical layers The 802.11a interface defines the OFDM (Orthogonal Frequency Division Multiplexing) physical layer operating in the U-NII (Unlicensed- National Information Infrastructure) frequency band at 5 GHz. The 802.11g interface defines the ERP (Extended Rate Physical) physical layer

operating in the ISM (Industrial, Scientific and Medical) frequency band at 2.4 GHz. The 802.11a/g interfaces have a bit rate of 6, 9, 12, 18, 24, 36, 48 or 54 Mbps depending on the modulation and coding scheme (MCS): - the sub-carriers of the OFDM system are modulated in BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16-QAM (Quadrature Amplitude Modulation) or 64-QAM; - the binary convolutional coding (BCC) is used with a coding rate of 1/2, 2/3 or 3/4. The 802.11n interface defines the HT (High Throughput) physical layer operating in the U-NII and ISM frequency bands at 5 and 2.4 GHz. The 802.11n interface uses the OFDM system for which the modulation of the sub-carriers is the one defined for the 802.11a/g interfaces and introduces a new value (equal to 5/6) for the coding rate and a new error correction code LDPC (Low-Density Parity Check). The 802.11n interface has a maximum rate of 600 Mbps obtained from two new features: - the aggregation of two radio channels to obtain a bandwidth of 40 - the spatial multiplexing SU-MIMO (Single User - Multiple Input Multiple Output) of two to four streams for a user. Introduction The 802.11ac interface defines the VHT (Very High Throughput) physical layer operating only in the U-NII frequency band at 5 GHz. The 802.11ac interface introduces new features to achieve a maximum rate of 6.9 Gbps: - the aggregation of eight radio channels to obtain a bandwidth of 160 - the spatial multiplexing SU-MIMO of two to eight streams for a user; - the space multiplexing MU-MIMO (Multi-User - MIMO) supporting four users, with a maximum of four streams for each user, the total number of streams being limited to eight; - the 256-QAM modulation. I.3. Wi-Fi integration into the 4G mobile network The integration of the Wi-Fi network into the 4G mobile network has an impact on the architecture of the EPC core network, which has several variants depending on the following characteristics: - the Wi-Fi access is trusted or untrusted by the operator; - the mobility is ma

naged by the network or the mobile. I.3.1. Mutual authentication Mutual authentication is performed between the mobile and the AAA (Authentication, Authorization and Accounting) server. It uses the AKA mechanism adapted to the EAP-Method protocol: - the HSS entity provides the AAA server with the authentication vector (RAND, AUTN, RES); - the AAA server provides the mobile with the random number (RAND) and the seal (AUTN) of the network; - the mobile calculates the seals (AUTN, RES) from its key Ki stored in the USIM module of its UICC card and compares the received seal (AUTN) with that calculated; xxxii Wi-Fi Integration to the 4G Mobile Network - the mobile transmits its seal (RES) to the AAA server, which compares it with that received from the HSS entity. The EAP-AKA' protocol is an evolution of the EAP-AKA method, which concerns the key derivation mechanism. I.3.2. Architecture based on the S2a interface The architecture based on the S2a interface corresponds to trusted Wi-Fi access and network-based mobility. The mobile stream travels through the Wi-Fi radio interface and tunnel S2a, built between the access point and the PGW entity, to access the PDN (Figure I.5). The S2a interface supports several mechanisms for establishing the tunnel: - the PMIPv6 (Proxy Mobile IP version 6) mechanism relies on the signaling provided by the mobility extension of the IPv6 header exchanged between the Wi-Fi access and the PGW entity and on the GRE (Generic Routing Encapsulation) tunnel for the mobile stream; - the MIPv4 FA (Mobile IP version 4 Foreign Agent) mechanism is based on the MIPv4 signaling and the IP tunnel in IP for the mobile stream; - the GTPv2 (GPRS Tunneling Protocol version 2) mechanism relies on the GTPv2-C signaling exchanged between the trusted Wi-Fi access and the PGW entity and on the GTP-U tunnel for the mobile stream. S2a Tunnel Wi-Fi GRE / IP over IP / GTP-U Access Mobility / MIPv4/GTP-C Figure I.5. Session establishment - Architecture based on S2a interface Introduction xxxiii I.3.3. Architecture

based on the S2b interface The architecture based on the S2b interface corresponds to untrusted Wi- Fi access and network-based mobility. The mobile stream travels through the SWu tunnel, built between the mobile and the evolved packet data gateway (ePDG), and the S2b tunnel, built between the ePDG and PGW entities, to access the PDN (Figure I.6). Wi-Fi Access SWu Tunnel S2b Tunnel GTP-U Mobility / GTP-C Figure I.6. Session establishment - Architecture based on S2b interface The S2b interface supports the PMIPv6 or GTPv2 mechanism for tunnel establishment. The SWu interface supports the IPSec (IP Security) mechanism, including IKEv2 (Internet Key Exchange version 2) signaling and the ESP (Encapsulating Security Payload) tunnel for the mobile stream. I.3.4. Architecture based on the S2c interface The architecture based on the S2c interface corresponds to trusted or untrusted Wi-Fi access and mobile-based mobility. The mobile stream passes through the S2c tunnel built between the mobile and the PGW entity to access the PDN (Figure I.7). In the case of untrusted Wi-Fi access, the S2c tunnel passes through the SWu tunnel built between the mobile and the ePDG entity (Figure I.7). The S2c interface supports the DSMIPv6 (Dual-Stack Mobile IP version 6) mechanism for the establishment of the S2c tunnel built between the mobile and the PGW entity. xxxiv Wi-Fi Integration to the 4G Mobile Network Trusted Wi-Fi Access Wi-Fi Access S2c Tunnel IP over IP DSMIPv6 Untrusted Wi-Fi Access Wi-Fi Access SWu Tunnel S2c Tunnel IP over IP DSMIPv6 Figure I.7. Session establishment - Architecture based on S2c interface In the case of trusted Wi-Fi access, this interface supports DSMIPv6 signaling and the IP tunnel in IP for the mobile stream. In the case of trusted Wi-Fi access, the ESP tunnel, established between the mobile and the ePDG entity, protects the S2c interface. I.3.5. Network discovery and selection Mobile networks are becoming more and more heterogeneous. It is possible for a mobile to be covered simultaneously by differen

t networks: traditional cellular networks, small cells integrating LTE and Wi-Fi accesses and stand-alone Wi-Fi access points. Given this variety, choosing the best network for a mobile is essential. The access network discovery and selection function (ANDSF) allows network detection and selection between LTE and Wi-Fi accesses. The rules defined by the 4G mobile network operator are provided by the ANDSF server, which is an optional element of the EPC core network. Hotspot 2.0 (HS2.0) is a working group of WFA. The target of the HS2.0 job is to facilitate the use of the Wi-Fi access point in a 4G mobile network. The HS2.0 certification program is called Passpoint. Introduction The key features of version 1 are based on the 802.11u standard and include additions to the access point beacon and the ANQP (Access Network Query Protocol) server that provides rules defined by the Wi-Fi service operator. Version 2 allows the mobile to identify the home operator and the partners that should be used when the home operator is not directly accessible. I.4. Wi-Fi and LTE access aggregation The integration of the Wi-Fi network to the 4G mobile network brings changes to the EPC core network, the anchor point being realized by the PGW entity. The aggregation of LTE and Wi-Fi channels is another approach that does not impact the structure of the EPC core network (Figure I.8). LTE access operates in a licensed frequency band. The LTE Advanced and LTE Advanced Pro evolutions, respectively, defined an aggregation of 5 and 32 LTE channels. The eNB entity is the anchor point for channel aggregation. LAA (Licensed Assisted Access) aggregation is an extension of LTE aggregation. The LTE transmission is performed on LTE and Wi-Fi frequency bands, between the mobile and the eNB entity, without an intermediate access point. The eNB entity is the anchor point for channel aggregation. LWA (LTE-Wi-Fi Aggregation) uses LTE and Wi-Fi frequency bands. Transmission over the Wi-Fi radio channel is between the mobile and the access point in accord

ance with 802.11 standard. The eNB entity is the anchor point for channel aggregation. MPTCP (Multi-Path Transmission Control Protocol) aggregation has the advantage of transmitting data using multiple paths without causing changes in existing infrastructures (4G mobile network, Wi-Fi network). The aggregation is performed by an MPTCP server. xxxvi Wi-Fi Integration to the 4G Mobile Network LTE Aggregation LAA Aggregation 1,8 GHz 1,8 GHz 2,6 GHz 5 GHz LWA Aggregation MPTCP Aggregation 1,8 GHz 1,8 GHz Wi-Fi Wi-Fi 5 GHz 5 GHz Access MPTCP Access Point Server Point Figure I.8. Wi-Fi and LTE access aggregation Architecture Based on Wi-Fi Access 1.1. Functional architecture EPS (Evolved Packet System) is the name of the 4G mobile network. It consists of an evolved packet core (EPC) and an evolved universal terrestrial radio access network (E-UTRAN). The E-UTRAN network presents the LTE (Long-Term Evolution) radio interface to the mobile. Wi-Fi (Wireless Fidelity) interface is subsequently integrated into the EPS network and is a component of a set of technologies grouped under the term Non-3GPP Access. Its introduction has an impact on the core network (EPC) architecture, which has several variants depending on the following characteristics: - Wi-Fi access is trusted or untrusted by the operator; - mobility is managed by the network or the mobile. 1.1.1. Architecture based on the S2a interface The functional architecture based on the S2a interface corresponds to trusted Wi-Fi access and network-based mobility (Figure 1.1). Wi-Fi Integration to the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2018. Published by ISTE Ltd and John Wiley & Sons, Inc. Wi-Fi Integration to the 4G Mobile Network Server Trusted Wi-Fi Access Figure 1.1. Functional architecture based on the S2a interface The mobile stream travels through the Wi-Fi radio interface and the S2a tunnel to access the packet data network (PDN). The PGW (PDN Gateway) entity is an IP (Internet Protocol) router that acts as a gateway for the mobile stream.

The home subscriber server (HSS) and the AAA (Authentication, Authorization and Accounting) server provide the following functions: - mutual authentication of the mobile and the AAA server via the interfaces SWx and STa. This authentication has the effect of opening Wi-Fi access to the mobile; - transfer of the mobile profile comprising a list of access point names (APN) and the quality of service (QoS) level of the S2a tunnel and Wi-Fi interface, to the PGW entity, via the interface S6b, and to trusted Wi-Fi access, via the STa interface. The policy charging and rules function (PCRF) also provides the traffic profile, including the QoS level of the S2a tunnel to the PGW entity, via the Gx interface, and to trusted Wi-Fi access via the Gxa interface. The mobile profile is stored in the HSS entity for mounting the default bearers, and in this case, the presence of the PCRF is optional. The presence of the PCRF entity is mandatory for the mounting of dedicated bearers on the initiative of an application function (AF), whose first example of implementation is the VoLTE (Voice over LTE) that provides telephone service. Architecture Based on Wi-Fi Access The characteristics of the dedicated bearer of the IP packet containing the voice are only stored in the SPR (Subscriber Profile Repository) database associated with the PCRF entity. Trusted WLAN access network (TWAN) includes the following features: - WLAN AN: this feature includes Wi-Fi access points; - TWAG (Trusted WLAN Access Gateway): this function terminates tunnel S2a; - TWAP (Trusted WLAN AAA Proxy): this function terminates the STa interface. The transparent connection mode provides a single connection to the PGW entity without mobility support between the LTE and Wi-Fi radio accesses. The IPv4 and/or IPv6 address of the mobile is provided by the TWAG function: - in the case of a statefull configuration, the TWAG function acts as a DHCP (Dynamic Host Configuration Protocol) server; - in the case of a stateless configuration, the TWAG function broadcasts the

prefix of the IPv6 address. The single-connection mode supports mobility between LTE and Wi-Fi accesses. This mode also supports non-seamless WLAN offload (NSWO), for which traffic is routed directly to the Internet network through TWAG function. The multiple-connection mode supports NSWO and multiple-access PDN connectivity (MAPCON), for which the various connections to the PDN network pass through the LTE (e.g. telephone service) or Wi-Fi (e.g. Internet service) interfaces according to the policy of the operator. Mobility between LTE and Wi-Fi radio accesses is possible. The connection on the Wi-Fi interface is established by the WLCP (WLAN Control Plane) protocol. The connection is identified by the MAC address of the mobile associated with a MAC address of the TWAG function. For the single- or multiple-connection mode, the IPv4 and/or IPv6 address of the mobile is provided by the PGW. Wi-Fi Integration to the 4G Mobile Network The PGW entity shall allocate the downlink packets to different S2a bearers based on the TFT (Traffic Flow Template) packet filters set up during the establishment of the S2a bearer (Figure 1.2). Flows (IP packets) Wi-Fi Layer filter bearer filter Figure 1.2. Connection to the PDN network for architecture based on the S2a interface TWAN function of the trusted Wi-Fi access shall assign the uplink packets to different S2a bearers based on the TFT packet filters set up during the establishment of the S2a bearer (Figure 1.2). 1.1.2. Architecture based on the S2b interface The functional architecture based on the S2b interface corresponds to untrusted Wi-Fi access and network-based mobility (Figure 1.3). Server Untrusted Wi-Fi e-PDG Access Figure 1.3. Functional architecture based on the S2b interface Architecture Based on Wi-Fi Access The mobile stream passes through the SWu and S2b tunnels to access the PDN network via the PGW entity. The SWu tunnel is built between the mobile and the evolved packet data gateway (ePDG). The S2b tunnel is built between the ePDG and PGW entities. The HSS en

tity and the AAA server provide the following functions: - mutual authentication of the mobile and the AAA server, via the SWx and SWa interfaces. This authentication has the effect of opening Wi-Fi access to the mobile; - mutual authentication related to the establishment of the SWu tunnel, via the SWx and SWm interfaces; - transfer of the mobile profile comprising a list of access point names (APN) and the quality of service (QoS) level of the S2b tunnel, to the PGW entity via the interface S6b, to the ePDG entity via the SWm interface and to the untrusted Wi-Fi access via the SWa interface. The PCRF entity provides the QoS level of the S2b tunnel to the PGW via the Gx interface and the ePDG via the Gxb interface. The PCRF entity provides the QoS level of the SWu tunnel to the ePDG entity via the Gxb interface. In this case, the ePDG entity provides the QoS level to be applied on the Wi-Fi radio interface via the SWn interface. The mobile must establish a SWu instance for each PDN connection. When the mobile connects to the PDN network, a default bearer must be established on the S2b interface. This connection is maintained for the duration of the connection. Dedicated bearers can be built for the same PDN connection, based on the rules provided by the PCRF. An SWu instance transports the packets of all the S2b bearers for the same connection to the PDN network between the mobile and the ePDG entity. The ePDG entity shall release the SWu instance when the S2b default bearer of the associated connection to the PDN network is released. Wi-Fi Integration to the 4G Mobile Network Two IPv4 and/or IPv6 addresses are assigned to the mobile: - an address for the SWu tunnel built between the mobile and the ePDG entity, provided by the untrusted Wi-Fi access; - an address for the flow transiting in this tunnel, provided by the PGW entity. The connection to the PDN network is described in Figure 1.4. Flows (IP packets) Correspondance SWu instance S2b identifier Tunnel filter Bearer Correspondance SWu instance filter Figur

establishment of the S2a tunnel. The construction of S2a tunnel requires the selection of the PGW entity by Wi-Fi access, from information provided by the AAA server during authentication. This information can be the IP address of the PGW entity, the full qualified domain name (FQDN) or the APN. Trusted Wi-Fi access retrieves the IP address of the PGW entity by performing DNS (Domain Name System) resolution on the FQDN or APN. 1.2.1.1. PMIPv6 mechanism The PMIPv6 (Proxy Mobile IP version 6) mechanism relies on the signaling provided by the mobility extension of the IPv6 header exchanged between Wi-Fi access and the PGW entity (Figure 1.7) and on the GRE (Generic Routing Encapsulation) tunnel of the mobile stream (Figure 1.8). Control plane Mobility Extension of IPv6 header Trusted Wi-Fi Access Figure 1.7. Protocol architecture based on S2a interface Control plane for PMIPv6 mechanism Architecture Based on Wi-Fi Access User plane IP packet 802.11 802.11 GRE Tunnel Trusted Wi-Fi Access Figure 1.8. Protocol architecture based on S2a interface User plane for PMIPv6 mechanism The MIPv6 mechanism requires functionality in the IPv6 stack of a mobile node. The exchange of signaling messages between the mobile node and the home network agent makes it possible to create and maintain a correspondence between its address in the home network and the foreign network. Network-based mobility supports the mobility of IPv6 nodes without mobile involvement by extending MIPv6 signaling between the TWAG function and the PGW entity. This approach to support mobility does not require the mobile node to be involved in the exchange of signaling messages. The PMIPv6 protocol is an extension of the MIPv6 protocol. A mobile node can operate in an IPv4, IPv6 or IPv4/IPv6 environment. The PMIPv6 protocol independently supports the mobility of the IPv4 address and the transport of IP packets in an IPv4 network. 1.2.1.2. MIPv4 mechanism The MIPv4 FA (Mobile IP version 4 Foreign Agent) mechanism is based on MIPv4 signaling (Figure 1.9) and the I

P in the IP tunnel of the mobile stream (Figure 1.10). Wi-Fi Integration to the 4G Mobile Network Control plane MIPv4 MIPv4 MIPv4 MIPv4 802.11 802.11 Trusted Wi-Fi Access Figure 1.9. Protocol architecture based on S2a interface Control plane for MIPv4 FA mechanism User plane IP packet 802.11 802.11 Trusted Wi-Fi Access Figure 1.10. Protocol architecture based on S2a interface User plane for MIPv4 FA mechanism MIPv4 signaling is exchanged, on the one hand, between the mobile and trusted Wi-Fi access and, on the other hand, between the trusted Wi-Fi access and the PGW entity. The MIPv4 protocol allows Wi-Fi access, playing the role of a foreign agent, to assign the mobile an IPv4 address in a foreign network. The MIPv4 protocol makes it possible to register with the PGW entity, which plays the role of a home agent, the correspondence between the mobile IPv4 address in the home network, provided by the PGW entity, and the IPv4 address in the foreign network. Architecture Based on Wi-Fi Access 1.2.1.3. GTPv2 mechanism The GTPv2 (GPRS Tunneling Protocol version 2) mechanism is based on the GTPv2-C (Control) signaling exchanged between the trusted Wi-Fi access and the PGW entity (Figure 1.11) and on the GTP-U (User) tunnel of the mobile flow (Figure 1.12). Control plane Trusted Wi-Fi Access Figure 1.11. Protocol architecture based on S2a interface Control plane for GTPv2 mechanism User Plane IP packet GTP-U GTP-U 802.11 802.11 GTP-U GTP tunnel Trusted Wi-Fi Access Figure 1.12. Protocol architecture based on S2a interface User plane for GTPv2 mechanism The GTPv2-C protocol allows the activation or deactivation of a session as well as the creation, modification or release of GTP-U bearers. The PMIPv6 and GTPv2 mechanisms can transport IPv4 or IPv6 streams in IPv4 or IPv6 tunnels. The MIPv4 mechanism allows the transport of only IPv4 streams in IPv4 tunnels. Wi-Fi Integration to the 4G Mobile Network 1.2.2. Architecture based on the S2b interface The S2b interface is the point of reference between the PGW and ePDG entitie

s. This interface supports the PMIPv6 (Figures 1.13 and 1.14) or GTPv2 mechanism for the establishment of the S2b tunnel. Control plane 802.11 802.11 Untrusted Wi-Fi Access Figure 1.13. Protocol architecture based on S2b interface Control plane for PMIPv6 mechanism User plane IP packet GRE tunnel 802.11 802.11 IPSec IPSec tunnel Untrusted Wi-Fi Access Figure 1.14. Protocol architecture based on S2b interface User plane for PMIPv6 mechanism The SWu interface is the point of reference between the ePDG entity and the mobile. This interface supports the IPSec (IP Security) mechanism, including IKEv2 (Internet Key Exchange version 2) signaling (Figure 1.13) and the ESP (Encapsulating Security Payload) tunnel of the mobile stream (Figure 1.14). Architecture Based on Wi-Fi Access The construction of the SWu tunnel requires the retrieval of the IP address of the ePDG entity by the mobile. This IP address can be configured in the mobile by various means. The mobile can also perform a DNS resolution on the FQDN of the ePDG entity. The mobile automatically builds the FQDN from the identity of the operator contained in its international mobile subscriber identity (IMSI) or from the tracking area identifier (TAI), where the mobile is located. The construction of the S2b tunnel requires the selection of the PGW entity by the ePDG entity, from information provided by the AAA server during the authentication for the establishment of the SWu tunnel. 1.2.3. Architecture based on the S2c interface The S2c interface is the point of reference between the PGW entity and the mobile. This interface supports the DSMIPv6 (Dual-Stack Mobile IP version 6) mechanism for the establishment of the S2c tunnel built between the mobile and the PGW entity. In the case of trusted Wi-Fi access, this interface supports DSMIPv6 signaling (Figure 1.15) and IP in IP tunnel (Figure 1.16) of the mobile stream. Control plane MIPv6 MIPv6 802.11 802.11 Trusted Wi-Fi Access Figure 1.15. Protocol architecture based on S2c interface Control plane for trusted Wi-

Fi access Wi-Fi Integration to the 4G Mobile Network User plane IP packet 802.11 802.11 Trusted Wi-Fi Access Figure 1.16. Protocol architecture based on S2c interface User plane for trusted Wi-Fi access In the case of untrusted Wi-Fi access, the IPSec tunnel established between the mobile and the ePDG entity protects the S2c interface. The MIPv6 protocol allows IPv6 mobile nodes to move while maintaining accessibility and ongoing sessions. The DSMIPv6 protocol prevents the IPv4/IPv6 dual-stack mobile from running both MIPv4 and MIPv6 mobility protocols simultaneously. The DSMIPv6 protocol also takes into account the case where the mobile moves in a private IPv4 network. The mobile node must be able to communicate with the PGW entity, which acts as a home agent, through a NAT (Network Address Translation) device. In the case of untrusted Wi-Fi access, the S2c tunnel is established from the IP address of the PGW provided by the AAA server during the authentication for the establishment of the SWu tunnel. The mobile can also retrieve the IP address of the PGW entity by querying a DHCP (Dynamic Host Configuration Protocol) server or by performing DNS resolution on the FQDN of the PGW. 1.3. DIAMETER protocol The DIAMETER protocol is used to perform authentication, authorization and accounting functions. Architecture Based on Wi-Fi Access The authentication function makes it possible to control the access of the mobile to the 4G mobile network from a stored secret, on the one hand, in the universal subscriber identity module (USIM) of the universal integrated circuit card (UICC) of the mobile and, on the other hand, in the HSS entity. The authorization function retrieves the service and traffic profile of the mobile stored in the HSS and SPR databases. The accounting function allows generation of events from the PGW entity to the charging entities for the prepaid or postpaid service. 1.3.1. AAA server interfaces The DIAMETER protocol is supported on the interfaces between, on the one hand, the AAA server and, on the ot

her hand (Figure 1.17): - trusted Wi-Fi access via the STa interface; - untrusted Wi-Fi access via the SWa interface; - PGW entity via the S6b interface; - ePDG entity via the SWm interface; - HSS entity via the SWx interface. Server Trusted Untrusted Wi-Fi Wi-Fi Access Access Figure 1.17. AAA server interfaces using the DIAMETER protocol Wi-Fi Integration to the 4G Mobile Network The SWx interface is used by the AAA server to retrieve the authentication data; the subscriber profile and the parameters for the PMIPv6, MIPv41 FA, GTPv2 and DSMIPv6 mechanisms. The SWx interface is used to register the address of the PGW and the AAA server in the HSS when establishing tunnel S2a, S2b or S2c. The SWx interface is used by the HSS entity for updating the mobile profile and for detaching it. Table 1.1 summarizes the DIAMETER messages exchanged on the SWx interface. Messages Comments AAA server request to retrieve Multimedia-Authentication-Request (MAR) authentication data HSS entity response containing Multimedia-Authentication-Answer (MAA) authentication data AAA server request to register the PGW Server-Assignment-Request (SAR) entity and retrieve the mobile profile HSS entity response containing mobile Server-Assignment-Answer (SAA) profile Registration-Termination-Request (RTR) HSS server request for mobile detachment Registration-Termination-Answe (RTA) AAA server response to RTR request Push-Profile-Request (PPR) HSS entity request for mobile profile update Push-Profile-Answer (PPA) AAA server response to PPR request Table 1.1. DIAMETER messages on the SWx interface The STa and SWa interfaces share the same authentication procedure. During the authentication phase, the AAA server decides whether Wi-Fi access is trusted or untrusted and communicates the decision to the Wi-Fi access point. The STa and SWa interfaces are used to carry information relating to the PMIPv6, MIPv4 FA (only in the case of the STa interface), GTPv2 and DSMIPv6 mechanisms. Architecture Based on Wi-Fi Access The STa and SWa interfaces are used

for detaching the mobile, the procedure being at the initiative of the Wi-Fi access or the AAA server. The STa and SWa interfaces are used to renew mobile authentication. The procedure is initiated by the AAA server in the event that the subscriber's profile stored in the HSS entity is changed, or at the initiative of the Wi-Fi access that wants to verify that the subscriber's profile is not modified. Table 1.2 summarizes the DIAMETER messages exchanged on the STa and SWa interfaces. Messages Comments Wi-Fi access request to register and retrieve Authenticate and Authorize Request (AAR) the mobile profile AAA server response containing mobile Authenticate and Authorize Answer (AAA) profile AAA server request for mobile Re-Auth-Request (RAR) authentication renewal Re-Auth-Answer (RAA) Response from Wi-Fi access to RAR request Wi-Fi access request for ending the mobile Session Termination Request (STR) session Session Termination Answer (STA) AAA server response to STR request AAA server request for termination of Abort-Session-Request (ASR) mobile session Abort-Session-Answer (ASA) Response from Wi-Fi access to ASR request Wi-Fi access request used for the EAP-AKA Diameter-EAP-Request (DER) authentication procedure AAA server response used for the EAP-AKA Diameter-EAP-Answer (DEA) authentication procedure Table 1.2. DIAMETER messages on the STa and SWa interfaces The S6b interface is used by the PGW entity to communicate to the AAA server its address when the tunnel S2a, S2b or S2c is established. 18 Wi-Fi Integration to the 4G Mobile Network The S6b interface is used by the PGW entity to retrieve the subscriber's profile and the PMIPv6 and GTPv2 mechanism information. The S6b interface is used by the PGW entity to retrieve mobile authentication data for the DSMIPv6 mechanism. The authentication data is used to control the establishment of the IPSec mechanism to protect the DSMIPv6 signaling exchanged between the mobile and the PGW entity. The S6b interface is used for terminating the mobile session, the procedur

e being initiated by the PGW entity or the AAA server. Table 1.3 summarizes the DIAMETER messages exchanged on the S6b interface. Messages Comments PGW entity request to register and retrieve Authenticate and Authorize Request (AAR) the mobile profile AAA server response containing mobile Authenticate and Authorize Answer (AAA) profile AAA server request for mobile Re-Auth-Request (RAR) authentication renewal Re-Auth-Answer (RAA) PGW response to RAR request PGW request for termination of mobile Session Termination Request (STR) session Session Termination Answer (STA) AAA server response to STR request AAA server request for termination of Abort-Session-Request (ASR) mobile session Abort-Session-Answer (ASA) PGW response to ASR request Request of the PGW entity used for the EAP- Diameter-EAP-Request (DER) AKA authentication procedure for the DSMIPv6 mechanism AAA server response used for the EAP-AKA Diameter-EAP-Answer (DEA) authentication procedure Table 1.3. DIAMETER messages on the S6b interface Architecture Based on Wi-Fi Access The SWm interface is used for the mutual authentication procedure of the mobile and the AAA server, which is implemented during the establishment of the SWu tunnel. The SWm interface is used by the ePDG entity to retrieve the subscriber's profile and the PMIPv6 and GTPv2 mechanism information. The SWm interface can also be used to transmit to the ePDG entity, the IP address or the FQDN of the PGW entity. The SWm interface is used for terminating the mobile session, the procedure being initiated by the ePDG entity or the AAA server. Table 1.4 summarizes the DIAMETER messages exchanged on the SWm interface. Messages Comments Authenticate and Authorize Request Request from the ePDG entity to register itself (AAR) and retrieve the mobile profile Authenticate and Authorize Answer AAA server response containing mobile profile (AAA) AAA server request for mobile authentication Re-Auth-Request (RAR) renewal Re-Auth-Answer (RAA) Response of the ePDG entity to the RAR request Request from ePDG

entity for termination of Session Termination Request (STR) mobile session Session Termination Answer (STA) AAA server response to STR request AAA server request for termination of mobile Abort-Session-Request (ASR) session Abort-Session-Answer (ASA) Response of the ePDG entity to the ASR request Request of the ePDG entity used for the Diameter-EAP-Request (DER) EAP-AKA authentication procedure for the DSMIPv6 mechanism AAA server response used for the EAP-AKA Diameter-EAP-Answer (DEA) authentication procedure Table 1.4. DIAMETER messages on the SWm interface Wi-Fi Integration to the 4G Mobile Network 1.3.2. PCRF interfaces The DIAMETER protocol is also supported on the interfaces between, on the one hand, the PCRF entity and, on the other hand (Figure 1.18): - PGW entity via the Gx interface; - trusted Wi-Fi access via the Gxa interface; - ePDG entity via the Gxb interface. Trusted Wi-Fi Access Figure 1.18. PCRF interfaces using the DIAMETER protocol The Gx, Gxa and Gxb interfaces make it possible to request the PCRF entity to: - retrieve the rules to apply to the default bearer created by the EPS network; - inform the PCRF entity of the termination of the session on the EPS network. The Gx, Gxa and Gxb interfaces allow the PCRF entity to provide the rules to be applied for the dedicated bearer. Table 1.5 summarizes the DIAMETER messages exchanged on the Gx, Gxa and Gxb interfaces. Architecture Based on Wi-Fi Access Messages Comments Request from PGW, ePDG or trusted Wi-Fi Credit-Control-Request (CCR) entities to retrieve the mobile profile Credit-Control-Answer (CCA) PCRF response containing the mobile profile Request from the PCRF entity containing the Re-Auth-Request (RAR) mobile profile Response of PGW, ePDG or trusted Wi-Fi Re-Auth-Answer (RAA) access to the RAR request Table 1.5. DIAMETER messages on the Gx, Gxa and Gxb interfaces MAC Layer 2.1. Frame structure 2.1.1. Frame header The MAC (Medium Access Control) header, described in Figure 2.1, encapsulates an LLC (Logical Link Control) frame whose size is

less than or equal to 2,304 bytes. Prot. Protocol Sub type Retry Order Frame Duration Address 1 Address 2 Address 3 Address 4 Trame LLC Control Fragment Sequence Number Number Figure 2.1. MAC header structure Frame Control: this field consists of a sequence of several subfields: - Protocol Version: this subfield is coded on two bits and takes the value 00; - Type and Subtype: the subfields are coded, respectively, on two and four bits. They identify the function of the frame. There are three types of Wi-Fi Integration to the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2018. Published by ISTE Ltd and John Wiley & Sons, Inc. Wi-Fi Integration to the 4G Mobile Network frames, namely the traffic frame, the control frame and the management frame. For each type of frame, subtypes are defined; - To DS and From DS: these two subfields are coded on one bit. They indicate the direction of transmission of the frame (Table 2.1); - More Fragments: this subfield is coded on a bit. It takes the value of ONE for traffic or management frames, if other fragments follow; - Retry: this subfield is coded on a bit. It takes the value of ONE to signal the retransmission of a frame; - Power Management: this subfield is coded on a bit. It takes the value of ONE when the station signals the switch to standby state; - More Data: this subfield is coded on a bit. It takes the value of ONE when the access point signals to the terminal that frames are stored in the buffer; - Protected Frame: this subfield is coded on a bit. It takes the value of ONE when the frame payload is secured by the WPA1 (Wi-Fi Protected Access) or WPA2 mechanism; - Order: this subfield is coded on a bit. It takes the value of ONE to indicate that the frame is transmitted as part of an ordered service. To DS From DS Meaning All control and management frames Traffic frames in ad hoc mode Traffic frames to the local area network (LAN) Traffic frames from the LAN Traffic frames exchanged between access points Table 2.1. To DS and From DS subfield values Dura

tion/AID: this field is coded on 16 bits: - Duration indicates the time during which the radio resource is immobilized; MAC Layer - AID (Association Identifier) indicates the name of an association identifier in the case of the transmission of a PS (Power Save)-POLL control frame. Address: there are four address fields, each of which is six bytes long. The construction rule is identical to that of an Ethernet MAC address. These fields indicate the basic service set identifier (BSSID), source address (SA), destination address (DA), transmitter address (TA) and receiver address (RA). To DS From DS Address 1 Address 2 Address 3 Address 4 BSSID BSSID BSSID Table 2.2. Meaning of Address fields Sequence Control: this field contains two subfields: - Sequence Number: this subfield is coded on 12 bits. It indicates the number of the frame modulo-4096; - Fragment Number: this subfield is coded on four bits. It indicates the number of the fragment in the frame. The value is equal to ZERO for the first fragment. All fragments of the same frame have the same value of the frame number. FCS (Frame Check Sequence): this field is coded on 32 bits. It contains the cyclic redundancy code for error detection. 2.1.2. Structure of control frames The Type subfield is set to 01 for control frames. The RTS (Request To Send) frame is transmitted by the station to request the access point to access to the radio resource. The RA field contains the MAC address of the access point and the TA field of the station (Figure 2.2). The Subtype subfield is set to 1011. Wi-Fi Integration to the 4G Mobile Network The CTS (Clear To Send) frame is transmitted by the access point to allow the station to access the radio resource. The RA field contains the MAC address of the station (Figure 2.2). The Subtype subfield is set to 1100. RTS frame Frame Duration Control CTS frame Frame Duration Control Frame ACK frame Duration Control PS-Poll frame Frame BSSID Control Figure 2.2. Structure of control frames The ACK (Acknowledgment) frame is transmitted to ackn

owledge the received frame. This can be a traffic frame, a management frame or the PS- Poll control frame. The RA field copies the MAC address contained in the Address 2 field of the received frame (Figure 2.2). The Subtype subfield is set to 1101. The PS-POLL frame is sent by the station to warn the access point that it has left sleep mode. The BSSID field contains the MAC address of the access point and the TA field of the station. The AID field is an identifier assigned to the station during the association phase (Figure 2.2). The Subtype subfield is set to 1010. 2.1.3. Structure of management frames The Type subfield is set to 00 for management frames. The BEACON management frame is a beacon channel that broadcasts information on the network. It contains mandatory fields and optional fields (Figure 2.3). The Subtype subfield is set to 1000. MAC Layer Short Short Channel Privacy Pollable Preamble Agility mandatory optional Beacon Supported Timestamp Interval Frame Destination Source Duration BSSID Message Control Address Address Beacon Figure 2.3. Structure of the BEACON management frame Timestamp: this field is coded on 64 bits. It contains the timestamp of the frame. Beacon Interval: this field is coded on 16 bits. It indicates the frequency of emission of the beacon channel. Capability Information: this field is coded on 16 bits. It contains the characteristics of the access point: - the type of network architecture (ESS, IBSS); - the implementation of the security (Privacy); - the use of a short preamble for the 802.11g radio interface; - the use of a short slot time for the 802.11g radio interface; - the use of the DSSS-OFDM physical layer for the 802.11g radio interface. SSID (Service Set Identifier): this field has a variable length less than or equal to 34 bytes. It provides the identifier of the ESS (Extended Service Set) network. Supported Rates: this field is composed of several information elements. Each element has a variable length less than or equal to 10 bytes and specifies the rates supported

by the access point. The PROBE REQUEST management frame is used by the station to request the characteristics of the radio interface of the access point. The PROBE REQUEST frame is a broadcast frame. The Subtype subfield is set to 0100. 28 Wi-Fi Integration to the 4G Mobile Network When the station has sent the PROBE REQUEST frame, it will arm a timer. If there is no response before expiration, then the station repeats the process on another radio channel. The access point provides its characteristics in the PROBE RESPONSE management frame when the value of the SSID contained in the PROBE REQUEST frame corresponds to that of the access point. The PROBE RESPONSE management frame is transmitted in unicast. The Subtype subfield is set to 0101. The AUTHENTICATION management frame is used for the authentication of the station (Figure 2.4). Authentification Authentification Status Challenge Algorithm Transaction Number Sequence Number Frame Destination Source Duration BSSID Message Control Address Address Authentication Figure 2.4. Structure of the AUTHENTICATION management frame Authentication Algorithm Number: this field is coded on 16 bits. It identifies the authentication mode. The following two modes are defined: - OSA (Open System Authentication): this mode corresponds to open access to the network. This mode is used for the WPA1 and WPA2 mechanisms; - SKA (Shared Key Authentication): this mode requires the station to send a seal to access the network. This mode is used for the WEP (Wired Equivalent Privacy) mechanism. Authentication Transaction Sequence Number: this field is coded on 16 bits. It contains the number of the authentication sequence. Status Code: this field is coded on 16 bits. It indicates whether the operation was successful or not. Challenge Code: this field, used for the WEP mechanism, has a variable size less than or equal to 255 bytes. It contains a string of bits, emitted in clear by the access point and then encrypted by the station. MAC Layer The association phase is implemented from four m

anagement frames, namely ASSOCIATION REQUEST, ASSOCIATION RESPONSE, REASSOCIATION REQUEST and REASSOCIATION RESPONSE. These frames introduce new fields (Figure 2.5). Association Request Listen Supported Interval Rates Listen Current AP Reassociation Request Supported Interval Address Rates Association Response Status Association Supported Reassociation Response Rates Frame Destination Source Duration BSSID Message Control Address Address Figure 2.5. Structure of management frames relating to the association phase Listen Interval: this field is coded on 16 bits. It contains the value of the number of BEACON frames during which the station will remain in standby. The access point uses this information to estimate the size of the buffer needed to store the data. Current AP Address: this field is coded on six bytes and contains the MAC address of the access point. This field is used when the station changes the access point. It indicates the address of the old access point to the new one SO that the latter can retrieve the stored data. AID: this field is coded on 16 bits and contains the identifier of the station allocated by the access point. The DISASSOCIATION and DEAUTHENTICATION management frames are used to terminate association and authentication, respectively. They contain a 16-bit field, indicating the reason for the shutdown (Figure 2.6). Wi-Fi Integration to the 4G Mobile Network Frame Destination Source Duration BSSID Message Control Address Address Reason Code Figure 2.6. Structure of the management frames DISASSOCIATION and DEAUTHENTICATION 2.2. Procedures 2.2.1. Timers The transmission of several frames is separated by an inter-frame interval. Several types of intervals are defined, each determining a priority level: - SIFS (Short Inter-Frame Space): this interval corresponds to the highest priority level. It is used following the RTS and CTS control frames and the traffic frame; - DIFS (DCF Inter-Frame Space): this interval has a longer duration (DIFS = SIFS + 2 ST (Slot Time)). It is used following an

ACK control frame when the traffic frame has been correctly received; - EIFS (Extended Inter-Frame Space): this interval is used when the transmitter has not received an acknowledgment. Its duration is equal to SIFS + (8 X ACK) + (PLCP header) + DIFS. 2.2.2. Mobile registration Mobile registration at the access point is done in three phases, namely scanning, authentication and association. The purpose of scanning is to recover the characteristics of the radio interface, which can be either passive or active. When the scanning is passive, the station scrutinizes the BEACON channel on each radio channel. When the scanning is active, the station transmits a PROBE REQUEST management frame, containing the network identifier (SSID), broadcast to all the access points, using a broadcast BSSID. MAC Layer The access point recognizable in the SSID corresponds to the PROBE RESPONSE management frame containing the characteristics of the radio interface of the access point (Figure 2.7). Probe Station Request Probe Response Probe Response Figure 2.7. Active scanning In OSA mode, authentication is done in two steps: - the station sends the AUTHENTICATION management frame by mentioning the authentication mode; - the access point responds with the AUTHENTICATION management frame containing the status (success or failure). In SKA mode, authentication is done in four steps: - the station sends the AUTHENTICATION management frame by mentioning the authentication mode; - the access point sends the AUTHENTICATION management frame containing a bit string in the Challenge Text field; - the station sends the AUTHENTICATION management frame containing the encrypted bit string in the Challenge Text field; - the access point verifies the response of the station and sends the AUTHENTICATION management frame containing the status (success or failure). The aim of the association phase is to check that the transmission characteristics of each part (the station, the access point) are compatible. It is carried out in two phases: - the station se

nds the ASSOCIATION REQUEST management frame; Wi-Fi Integration to the 4G Mobile Network - the access point sends the ASSOCIATION RESPONSE management frame containing the AID assigned to the station and the status (success or failure). The cell change is initiated by the station, by issuing REASSOCIATION REQUEST management frame to a new access point. This frame contains the MAC address of the old access point. The new access point responds with the REASSOCIATION RESPONSE management frame that contains the new identifier (AID) assigned to the station. In the meantime, the station must perform an authentication phase. 2.2.3. Data transfer The distributed coordination function (DCF) mode implements the CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) mechanism. A station first listens to the radio channel before transmitting. To avoid collisions, the backoff mechanism is used before transmission of frame if the radio channel is busy. The use of RTS and CTS control frames makes it possible to limit the impact of a collision to the single short RTS frame (Figure 2.8). SIFS, traffic source destination Back-off traffic other station Figure 2.8. Use of control frames for data transfer The use of RTS and CTS control frames, for the transmission of unicast frames from the station and the access point, and multicast or broadcast frames from the station, depends on a configuration parameter, corresponding to the size of the frame. MAC Layer The multicast or broadcast frames transmitted by the access point are transmitted without RTS and CTS control frames. The transmitted unicast traffic frames must be acknowledged by an ACK control frame (Figure 2.8), as well as multicast or broadcast traffic frames sent by the station. The multicast or broadcast traffic frames sent by the access point are not acknowledged. When a frame is sent, the transmitter arms a timer. If the acknowledgment is not received when the latter expires, the transmitter will try retransmitting again using the EIFS interval. If the radio channel i

s available for a longer time than the DIFS, the station can transmit without the backoff timer. If the radio channel is busy and another station wishes to transmit, it must use the backoff timer, which is the product of a random number and the time of the time slot (ST) (Figure 2.9). ST (SlotTime) traffic Station A traffic Station B traffic Station C traffic Station D traffic Station E Figure 2.9. Backoff mechanism Wi-Fi Integration to the 4G Mobile Network This timer avoids the collision, which occurs only when two stations have drawn the same random number. At startup, the random number is chosen in the contention window between 0 and 15. At each collision, the contention window is doubled until it reaches the maximum value 1023. The radio channel is declared inaccessible after N access attempts, N being a parameter of the transmitter. For a station, the consumption of this timer stops when the radio resource has been allocated. It resumes when the resource becomes free after the DIFS timer. 2.2.4. Clear channel assessment Clear channel assessment (CCA) is determined at the physical level or at the logical level. At the physical level, the station is based on the detection of energy or the carrier in the radio channel. At the logical level, the station uses the Duration field of the MAC header. Logical level detection solves the problem of hidden stations. If two stations A and B are separated by an obstacle, these two stations being connected to the same access point, each station cannot detect a transmission from the other station. The frames coming from the access point and containing the Duration field provide each station with an indication of the occupancy time of the radio channel. The Duration field of the RTS frame contains the occupancy time of the radio channel. It is equal to the sum of the duration of three SIFS intervals, CTS and ACK control frames and a traffic frame (Figure 2.10). The Duration field of the CTS frame contains an update of the occupancy time of the radio channel. It is equal to t

hat indicated by the RTS frame minus the sum of the durations of one SIFS interval and CTS control frame (Figure 2.10). MAC Layer Station 1 Frame Access Point 3 SIFS + CTS + Data Frame + Ack Duration 2 SIFS + Data Frame + Ack Figure 2.10. Duration field for RTS and CTS control frames The Duration field of the ACK frame is set to ZERO in the case where the bit More Fragment is ZERO. In the case where this bit is at ONE, it contains the occupancy time of the radio channel for the transmission of the next fragment. It is equal to the sum of the durations of two SIFS intervals, a fragment and an ACK control frame (Figure 2.11). Station 1 Fragment X Fragment X+1 Access Point Fragment X 3 SIFS + 2 Ack + Fragment X+1 Duration ACK X 2 SIFS + Ack + Fragment X+1 Figure 2.11. Duration field for ACK control frame A station wakes up to recover data stored at the access point. It does not know the size of the pending data. The Duration field of the PS-POLL frame contains only the duration of one SIFS interval and an ACK control frame (Figure 2.12). Station PS-Poll Access Point PS-Poll SIFS + Ack Duration Figure 2.12. Duration field for the PS-POLL control frame 36 Wi-Fi Integration to the 4G Mobile Network 2.2.5. Frame fragmentation A MAC frame can be fragmented to reduce the impact of interference. In the case of a faulty reception, only the corrupted fragment is retransmitted, rather than the complete frame. Frame fragmentation is performed if the length of the frame is greater than a value defined by the network administrator. Fragments have the sequence number at the same value. The fragment number is incremented by one unit for each transmitted fragment. The More Fragment field (value of ONE) of the MAC header tells the receiver if other fragments will be transmitted. Fragments and control frames are separated by one SIFS interval to immobilize the radio channel during transmission of all fragments (Figure 2.13). Frag0 Fragl Backoff source destination Figure 2.13. Frame fragmentation 2.2.6. Standby management In order to

save the battery consumption and increase its autonomy, the station can implement the standby mechanism. The station notifies the access point by transmitting a traffic frame (possibly a null frame) with the Power Management bit set to ONE. The station regularly listens for a beacon frame according to the information provided in the Listen Interval field of the ASSOCIATION management frame. The access point informs the station, via its BEACON channel, whether unicast, multicast or broadcast frames are pending (Figure 2.14). It is possible that, in the transmit interval of the beacon channel, the radio MAC Layer channel is busy. In this case, the station must extend the period of activity for the treatment of the beacon channel. TIM (Traffic Indication Map): this optional field of the BEACON management frame indicates to a station in standby that data is pending. These data are either unicast data (TIM information) or multicast data (DTIM information). This field has a variable length less than or equal to 256 bytes and is composed of the following subfields: - DTIM Count: this subfield indicates the number of BEACON frames before the next DTIM. When the value is zero, the TIM field contains DTIM information; - DTIM Period: this subfield indicates the number of BEACON frames separating two DTIM frames; - Bitmap Control and Partial Virtual Bitmap: these two subfields allow the identification of stations with pending data by the AID parameter. The station sends a PS-POLL frame to warn the access point. The latter can respond immediately after one SIFS or postpone the transfer. In all cases, the station must remain awake until data transfer. If more than one frame is waiting, then the access point informs the station via the More Data field in the MAC header (Figure 2.14). DTIM interval Beacon interval PS-POLL Unicast media Broadcast awake awake awake awake Station Figure 2.14. Standby management Wi-Fi Integration to the 4G Mobile Network 2.3. Security 2.3.1. Security mechanism The security of the radio interface sta

rted with the WEP mechanism. Because of its weaknesses, it was supplanted by the WPA1 mechanism and then by the WPA2 mechanism. The mechanisms WPA1 and WPA2 constitute the RSN (Robust Security Network) architecture. The three mechanisms WEP, WPA1 and WPA2 specifically implement third-party access control and data protection services (confidentiality and integrity control). For the WEP mechanism, third-party access control is based on the RC4 (Rivest Cipher) algorithm. Access control takes place during the authentication phase, which is a procedure associated with the MAC data link protocol. The WPA1 and WPA2 mechanisms use the 802. 1x mechanism described in Chapter 6 for access control. The authentication WPA phase is preceded by the procedure putting the security policy in agreement between the access point and the station, during the association phase. For the WEP and WPA1 mechanisms, encryption is executed by the RC4 algorithm. For the WEP mechanism, the master key (MK) is used for the encryption of each Wi-Fi frame. For the WPA1 mechanism, encryption is obtained using a temporary key derived from the MK. In association with encryption, a protocol is added to the MAC data link layer: - WEP protocol in the case of the WEP mechanism; - temporal key integrity protocol (TKIP) in the case of the WPA1 mechanism. MAC Layer For the WPA2 mechanism, encryption is based on the advanced encryption standard (AES) algorithm and the header of the MAC data link protocol is completed by the CCMP (Counter-mode/Cipher block chaining MAC (Message Authentication Code) Protocol) header. In the case of the WEP mechanism, the integrity control is provided by a cyclic redundancy check (CRC) encrypted with the RC4 algorithm. In the case of the WPA1 mechanism, integrity control uses the MICHAEL algorithm. In the case of the WPA2 mechanism, integrity control is obtained using the AES encryption algorithm. 2.3.2. Security policies The security policies supported by the access point are transmitted in BEACON and PROBE RESPONSE frames durin

2.3.3. MAC header extension 2.3.3.1. WEP protocol The WEP protocol adds eight bytes to the MAC header (Figure 2.15): - WEP header is composed of initialization vector (IV) and KeyID fields: - IV field, coded on three bytes, is the initialization vector used to generate the pseudo-random sequence of the RC4 algorithm; Wi-Fi Integration to the 4G Mobile Network - KeyID field, coded on two bits, enables the selection of a key from among four possible ones; - integrity check value (ICV) field, coded on four bytes, is the result of the calculation of a CRC-32 applied to MAC service data unit (MSDU). The LLC frame constitutes the MSDU data. 4 bytes 4 bytes 4 bytes header header Ciphered part 3 bytes b0 to b5 Reserved b6, b7 KeyID Figure 2.15. Format of WEP encapsulation The 128-bit (or 64-bit) secret is composed of a 104-bit (or 40-bit) WEP key concatenated with the 24-bit IV. The secret determines the start sequence of the pseudo-random sequence of the RC4 algorithm (Figure 2.16). Pseudo-random Secret sequence Concatenation Algorithm exclusive ciphered Concatenation CRC-32 Figure 2.16. WEP processing of the transmission chain Encryption consists of executing an exclusive OR of data, including the MSDU and ICV fields, on the one hand, and the pseudo-random sequence of the RC4 algorithm, on the other. MAC Layer Upon reception of the MAC frame, the following operations are executed (Figure 2.17): - the secret is reconstituted from the WEP key and the IV field; - the pseudo-random sequence is initialized using the secret; - the unscrambled data (MSDU and ICV) are generated by the exclusive OR of the encrypted data and the pseudo-random sequence; - the local calculation of the CRC-32 on the MSDU data is compared to the ICV field received. If the two values are equal, then the MSDU data integrity check is positive; otherwise, the MSDU data are deleted. Pseudo-random Secret sequence Concatenation Algorithm exclusive Ciphered CRC-32 Figure 2.17. WEP processing of the reception chain 2.3.3.2. TKIP The TKIP reuses the format of

the WEP protocol. It adds four bytes to the WEP header to introduce an extension of the initialization vector. It adds eight bytes to the MSDU data to join the MIC (Message Integrity Code) field containing the seal calculated using the MICHAEL algorithm. The TKIP header is composed of the following fields (Figure 2.18): - the TSCO and TSC1 (TKIP Sequence Counter) fields constitute the initialization vector and are used during the second phase of the key mixing (key derivation) function; Wi-Fi Integration to the 4G Mobile Network - the TSC2 to TSC5 fields constitute an extension of the initialization vector and are used during the first phase of the key mixing (key derivation) function; - the WEPseed field is calculated from the TSC1 field; - the ExtIV field, coded on one byte, indicates the presence (bit set at ONE) of the TSC2 to TSC5 fields of the IV extension; - as for the WEP protocol, the KeyID field, coded on two bits, enables the selection of one key from among four possible ones. 4 bytes 4 bytes 8 bytes 4 bytes 4 bytes header header Ciphered part 1 byte 1 byte WEPseed 1 byte 1 byte 1 byte 1 byte b0 to b4 Reserved 1 byte Ext IV b6, b7 KeyID Figure 2.18. Format of TKIP encapsulation The processing of the transmission chain is shown in Figure 2.19. The MIC seal is calculated using the MAC addresses of the source and the destination, the priority byte and the MSDU data. The priority byte contains the priority level of the frame. The generation of the MIC or TMK is described in section 6.2.1. The set composed of MSDU and MIC data can be fragmented. In this case, the initialization vector is increased by one unit for each fragment. Conversely, the IV extension keeps the same value for all fragments of a single MSDU. MAC Layer For each MSDU, two key mixing (key derivation) phases are used to calculate the secret used for WEP processing: - the first phase operates using the transmit address (TA), the TK and the TSC2 to TSC5 vectors; - the second phase operates using the TTAK (TKIP-mixed Transmit Address and Key)

key, the TK, and the TSCO and TSC1 vectors. The TTAK constitutes an intermediary key produced during phase one. Phase 1 Key Mixing Initialisation vector Phase 2 RC4 key Key Mixing process (transmission) Ciphered DA/SA Priority Fragmentation MICHAEL Figure 2.19. TKIP processing of the transmission chain The processing of the reception chain is shown in Figure 2.20. Phase 1 Key Mixing Phase 2 Key Mixing RC4 key Ciphered MICHAEL Fragment process assembly (reception) Clear Clear Figure 2.20. TKIP processing of the reception chain Wi-Fi Integration to the 4G Mobile Network The receiver extracts the TSC fields from the TKIP header and verifies the sequencing in order to protect itself from replays. The combination of the TSC fields with the TK and the MAC transmit address (TA) enables the initialization vector and the RC4 key to be reconstituted for the WEP decryption. If the WEP processing indicates a positive check from the ICV field, the fragments are reassembled. The result of the MIC seal calculation using the MIC key and unscrambled MSDU data is compared to the value of the MIC field received. If the two values match, the integrity control is positive and the MSDU data are accepted. 2.3.3.3. CCMP The CCMP adds 16 bytes to the MAC header (Figure 2.21): - eight bytes for the CCMP header; - eight bytes for the MIC seal. The CCMP header resembles the TKIP header. It is constructed from the packet number (PN), the ExtIV field, coded on one bit and indicating the presence (bit set at ONE) of the PN2 to PN5 fields, and the KeyID field, coded on two bits, used to select a key from among four possible keys. 4 bytes 4 bytes 8 bytes 4 bytes header header Ciphered part 1 byte 1 byte 1 byte 1 byte 1 byte Reserved 1 byte b0 to b4 Reserved 1 byte Ext IV b6, b7 KeyID Figure 2.21. Format of CCMP encapsulation MAC Layer The processing of the transmission chain is shown in Figure 2.22. header construction Address 2 Nonce Priority construction Ciphered Algorithm increment TK key Clear Figure 2.22. CCMP processing of the transmissio

n chain The AES algorithm provides the MIC seal and encryption of the MSDU and MIC data. It is supplied by the following values: - AAD (Additional Authentication Data) parameter, built from the MAC header, with the exception of fields that can be modified during a retransmission (e.g. the Duration field); - Nonce parameter, built from the priority byte, the second address contained in the MAC header (A2) and the frame number (PN). The value of the PN field is increased by one unit for each frame generated; - TK. The processing of the CCMP received chain is shown in Figure 2.23. header construction Address 2 Nonce Priority construction Algorithm Clear TK key Ciphered Replay Figure 2.23. CCMP processing of the reception chain Wi-Fi Integration to the 4G Mobile Network The AES algorithm is used to reproduce unscrambled MSDU data. It is supplied by the following values: - AAD parameter; - Nonce parameter; - MIC field to execute an integrity control; - TK. A check on the PN field enables protection from replays. 2.4. Quality of service 2.4.1. EDCA mechanism The EDCA (Enhanced Distributed Channel Access) mechanism is an extension of the DCF mechanism. It is based on the differentiation of user priority (UP) levels. The priority level is the same as that set for the Ethernet frame. The ability to implement the EDCA mechanism is indicated by the access point in the Capability Information field of the BEACON or PROBE RESPONSE management frames. The EDCA mechanism defines four access categories (AC), each category corresponding to a queue (Table 2.3): - a priority level belongs to an access category; - an access category contains two priority levels. TID field User Priority UP Access Category AC Designation AC-BK Background AC-BK Background AC-BE Best Effort AC-BE Best Effort AC-VI Video AC-VI Video AC-VO Voice AC-VO Voice Table 2.3. Correspondence between the priority levels and the access categories MAC Layer The EDCA mechanism defines the parameters used for access to the radio channel: - the arbitration inter-frame spa

ce (AIFS) during which the mobile detects that the radio channel is free, before triggering the backoff mechanism or the transmission: AIFS[AC] = AIFSN[AC] X SlotTime + SIFSTime; - the minimum length of the contention window CWmin (Contention Window) and the maximum CWmax used for the backoff mechanism; - TXOP (Transmission Opportunity) time during which the mobile transmits when it has access to the radio channel. The EDCA parameters are stored in the mobile and can be updated by the access point in the EDCA Parameter Set information element transmitted in the BEACON, ASSOCIATION RESPONSE, REASSOCIATION RESPONSE and PROBE RESPONSE management frames. The modification of the EDCA parameters is indicated in the QoS Capability information element present in the BEACON management frame that does not contain the EDCA Parameter Set information element and in the (RE)ASSOCIATION REQUEST management frames (RE). The default values of the EDCA parameters are shown in Table 2.4. Access category CWmin CWmax AIFSN TXOP (ms) AC-BK 1,023 AC-BE 1,023 AC-VI 3,008 AC-VO 1,504 Table 2.4. Default values of EDCA parameters 48 Wi-Fi Integration to the 4G Mobile Network 2.4.2. Impact on the MAC header The MAC header of the traffic frame inserts the two-byte QoS Control field following the Address 4 field (Figure 2.24). Bit 0-3 Bit 4 Bit 5-6 Bit 7 Bit 8-15 Ack Policy Reserved Reserved Frame Duration Address 1 Address 2 Frame Address 3 Address 4 Control Control byte 2 0 2304 Figure 2.24. Evolution of MAC header structure The presence of the QoS Control field is indicated by the Subtype field (value equal to 1,000). The TID (Traffic Identifier) subfield, coded on three bits, provides the priority level (UP) of the access to the radio channel. The Ack Policy subfield, coded on two bits, identifies the MAC frame acknowledgment rule: - 00: the frame must be acknowledged. The receiver of the MAC frame must return an ACK frame after the SIFS interval; - 01: the frame must not be acknowledged. Acknowledgment is performed in the upper layers. Th

is combination is also used for multicast or broadcast frames; - 11: the block acknowledgment mechanism must be used. 802.11a/g Interfaces 3.1. 802.11a interface 3.1.1. PLCP sub-layer On transmission, the physical layer convergence procedure (PLCP) converts the PLCP service data units (PSDU) from the MAC (Medium Access Control) layer to form the PLCP protocol data units (PPDU), adding a preamble and a header. On reception, the preamble and header facilitates demodulation of the signal and the delivery of the PSDU data units. The PLCP frame ends with tail and padding bits. The PLCP header contains the LENGTH and RATE fields, a reserved bit, an even parity bit and the SERVICE field (Figure 3.1). The LENGTH and RATE fields, the reserved bit and the even parity bit, the SIGNAL set, constitute an OFDM (Orthogonal Frequency-Division Multiplexing) symbol and are transmitted with the most robust modulation and coding scheme: - BPSK (Binary Phase-Shift Keying) modulation; - coding rate of 1/2. The SERVICE field, the PSDU data units, the tail and padding bits, the DATA set, are transmitted at the rate indicated in the RATE field and constitute several OFDM symbols (Table 3.1). Wi-Fi Integration to the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2018. Published by ISTE Ltd and John Wiley & Sons, Inc. Wi-Fi Integration to the 4G Mobile Network The first seven bits of the SERVICE field are used to synchronize the descrambler on reception. The other nine bits are reserved for later use. The LENGTH field encodes the number of bytes of the PSDU data unit. The tail bits of the SIGNAL symbol allow the decoding of the RATE and LENGTH fields. The RATE and LENGTH fields allow the mobile to predict the duration of the PLCP frame, even if the bit rate is not supported by the mobile. PLCP header Reserved LENGTH Parity SERVICE 4 bits 1 bit 12 bits 1 bit 6 bits 16 bits 6 bits Preamble SIGNAL Figure 3.1 Format of PLCP frame RATE field Rate (Mbps) Table 3.1. Rates of DATA field 802.11a/g Interfaces 3.1.2. PMD sub-layer 3.1.2.1

. Transmission chain The transmission chain consists of the following operations (Figure 3.2): a) Produce the PLCP preamble field, composed of: - ten repetitions of a short training sequence, used for ACG (Automatic Control Gain) convergence, diversity selection, timing acquisition and coarse frequency acquisition in the receiver; - two repetitions of a long training sequence, used for channel estimation and fine frequency acquisition in the receiver, preceded by a guard interval (GI). b) Produce the PLCP header field from the RATE, LENGTH and SERVICE fields by filling the appropriate bit fields. c) Calculate from the RATE field the number of data bits per OFDM symbol (NDBPS), the coding rate (R), the number of bits in each OFDM sub- carrier (NBPSC) and the number of coded bits per OFDM symbol (NCBPS). d) Append the PSDU data unit to the SERVICE field. Extend the resulting bit string with bits to ZERO (at least six bits) SO that the resulting length is a multiple of NDBPS. The resulting bit string constitutes the DATA part of the frame. e) Initiate the scrambler with a pseudo-random non-zero seed, generate a scrambling sequence and XOR it with the extended string of data bits. f) Replace the six scrambled bits at ZERO following the data with six non-scrambled bits at ZERO. Those bits return the convolutional encoder to the zero state and are denoted as tail bits. g) Encode the extended, scrambled data string with a convolutional encoder (R = 1/2). Omit some of the encoder output string, chosen according to puncturing pattern, to reach the desired coding rate. h) Divide the encoded bit string into groups of NCBPS bits. Within each group, perform an interleaving of the bits according to a rule corresponding to the desired RATE. i) Divide the resulting coded and interleaved data string into groups of NBPSC bits. For each of the bit groups, convert the bit group into a complex number according to the modulation encoding tables. Wi-Fi Integration to the 4G Mobile Network j) Divide the complex number string into groups

of 48 complex numbers. Each such group is associated with one OFDM symbol. In each group, the complex numbers are numbered 0 to 47 and mapped hereafter onto OFDM sub-carriers numbered -26 to -22, -20 to -8, -6 to -1, 1 to 6, 8 to 20 and 22 to 26. The sub-carriers -21, -7, 7 and 21 are skipped and, subsequently, used for inserting pilot sub-carriers. The 0 sub-carrier, associated with center frequency, is omitted and filled with the value 0. The total number of the sub-carriers is 52 (48 + 4). k) For each group of sub-carriers -26 to 26, convert the sub-carriers to the time domain using inverse Fourier transform. Prepend to the Fourier- transformed waveform a circular extension of itself, thus forming a GI, and truncate the resulting periodic waveform to a single OFDM symbol length by applying time domain windowing. 1) Append the OFDM symbols one after another, starting after the SIGNAL symbol describing the RATE and LENGTH fields. m) Up-convert the resulting complex baseband waveform to a radio signal according to the center frequency of the desired channel and transmit. Transmission Convolution Interleaving encoder Mapping insertion modulation Reception Deinterleaving Convolution demodulation removal Demapping encoder Figure 3.2. Transmission and reception chain 3.1.2.2. Scrambler The DATA field, composed of SERVICE, PSDU data unit, tail and pad parts, shall be scrambled with a length-127 scrambler (Figure 3.3). The same scrambler is used to scramble transmit data and to descramble receive data. When transmitting, the initial state of the scrambler shall be set to a pseudo-random non-zero state. 802.11a/g Interfaces The seven least significant bits (LSB) of the SERVICE field shall be set to all zeros prior to scrambling to enable estimation of the initial state of the scrambler in the receiver. X Superscript(1) Scrambled Figure 3.3. Scrambler diagram 3.1.2.3. Convolutional encoder The convolutional encoder shall use the generator polynomials g0 = 1338 and g1 = 1718 and produce two sequences from the scrambled D

ATA field (Figure 3.4). The rates are derived from the two sequences by employing puncturing. Puncturing is a procedure for omitting some of the encoded bits in the transmitter and inserting bits at ZERO into the convolutional decoder on the receive side in place of the omitted bits. encoded scrambled DATA A scrambled encoded scrambled DATA B Figure 3.4. Convolutional encoder diagram 3.1.2.4. Interleaving All encoded data bits shall be interleaved by a block interleaver with a block size corresponding to the number of bits in a single OFDM symbol (NCBPS). Wi-Fi Integration to the 4G Mobile Network The interleaver is defined by a two-step permutation. The first permutation ensures that adjacent coded bits are mapped onto non-adjacent sub-carriers. The second ensures that adjacent coded bits are mapped alternately onto less and more significant bits of the constellation, and therefore long runs of low-reliability (LSB) bits are avoided. 3.1.2.5. Modulation and coding scheme The modulation and coding scheme determines the rate of the DATA field (Table 3.2). The sub-carriers are modulated using phase modulation (BPSK or QPSK) or mixed phase and amplitude modulation (16-QAM or 64-QAM). Forward error correction (FEC) is a convolution code used with a coding rate of 1/2, 2/3 or 3/4. Number of Number of Number of Coding DATA bits Modulation bits per sub- encoded per OFDM (Mbps) carrier DATA bits symbol 16-QAM 16-QAM 64-QAM 64-QAM Table 3.2. Parameters of the modulation and coding scheme 802.11a/g Interfaces 3.1.2.6. Structure of the preamble and OFDM symbols The preamble consists of a short learning sequence of TSHORT duration and a long learning sequence of TLONG duration. The short learning sequence contains 10 short symbols t1 to t10. The long learning sequence consists of a guard time TGI2 and two long symbols T1 and T2 (Figure 3.5 and Table 3.3). The SIGNAL symbol, of TSIGNAL duration, and the different symbols DATA, of TSYM duration, start with a guard time TGI (Figure 3.5 and Table 3.3). Short SIGNAL training sequ

ence training sequence symbol symbol symbol SIGNAL DATA 1 DATA 2 Preamble Figure 3.5. Structure of the preamble and OFDM symbols Parameters Duration TFFT FFT or IFFT period 3.2 us (1/AF) TGI Duration of guard interval GI 0.8 us (TFFT/4) TGI2 Duration of guard interval GI2 1.6 us (TFFT/2) TSHORT Duration of short training symbol 8 us (10x TFFT/4) TLONG Duration of long training symbol 8 us (TG12+2xTFFT) TPREAMBLE Preamble duration 16 us (TSHORT + TLONG) TSIGNAL Duration of SIGNAL symbol 4 us (TGH+FFT) TSYM Duration of DATA symbol 4 us (TGI+TFFT) Table 3.3. Values of the duration of the different parameters A short training symbol consists of 12 sub-carriers, which are modulated by the elements of the sequence S: S-26,26 = ((13/6) X 0, 1+j, 0, 0, 0, -1-j, 0, 0, 0, 1+j, 0, 0, 0, -1-j, 0, 0,0, -1-j, 0, 0, 0, 1+j, 0, 0, 0, 0,0, 0, 0, -1-j, 0, 0, 0, -1-j, 0, 0, 0, 1+j, 0, 0, 0, 1+j, 0, 0, 0, 1+j, 0, 0, 0, 1+j, 0,0} 56 Wi-Fi Integration to the 4G Mobile Network A long training symbol consists of 53 sub-carriers, including the value 0 at central frequency, which are modulated by the elements of the sequence L: L-26,26 = {1, 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1, 1, 1, , -1, 1, 1, 1, 1, 0, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, -1, -1, -1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 1} 3.1.2.7. OFDM multiplexing The complex numbers are numbered from 0 to 47 and are subsequently mapped onto OFDM sub-carriers numbered -26 to -22, -20 to -8, -6 to -1, 1 to 6, 8 to 20 and 22 to 26. Sub-carriers -21, -7, 7 and 21 are ignored and subsequently used for the insertion of pilot sub-carriers. The sub-carrier 0, associated with the central frequency, is omitted and filled with the value 0. Parameters Values NSD (number of sub-carriers assigned to the DATA field) NSP (number of sub-carriers assigned to pilots) NST (total number of sub-carriers) 0.3125 MHz AF (spacing between sub-carriers) (20 MHz/64) Table 3.4. Parameters of OFDM multiplexing 3.1.2.8. Frequency plan The 802. 11a interface operates in the 5 GHz U-NII (Unl

icensed-National Information Infrastructure) band, divided into three sub-bands: - sub-band A covering the frequency band 5.150-5.350 GHz; - sub-band B covering the frequency band 5.470-5.725 GHz; - sub-band C covering the frequency band 5.725-5.825 GHz. 802.11a/g Interfaces The bandwidth of the radio channel is equal to 20 MHz. Table 3.5 provides, for each sub-band, the channel number and the value of the center frequency. Sub-band A Sub-band B Sub-band C Central Central Central Channel Channel Channel frequency frequency frequency number number number (GHz) (GHz) (GHz) 5.180 5.500 5.745 5.200 5.520 5.765 5.220 5.540 5.785 5.240 5.560 5.805 5.260 5.580 5.280 5.600 5.300 5.620 5.320 5.640 5.660 5.680 5.700 Table 3.5. U-NII band at 5 GHz Countries apply their own regulations to authorized channels, authorized users and maximum power levels in these frequency ranges. Table 3.6 summarizes the rules applied in Europe for sub-bands A (5.150-5.350 GHz) and B (5.470-5.725 GHz). Dynamic frequency selection (DFS) allows access points to automatically select frequency channels with low levels of interference. Transmit power control (TPC) automatically reduces output power when other networks are in range. Reduced power means reduced interference problems and increased battery capacity. Wi-Fi Integration to the 4G Mobile Network Radio channels Maximum power TPC function DFS function 36 to 48 200 mW 200 mW 48 to 64 100 mW 100 to 140 500 mW Table 3.6. European regulations 3.2. 802.11g interface The 802.11g interface, called ERP (Extended Rate Physical), must be compatible with the 802.11 interface, called DSSS (Direct Sequence Spread Spectrum), which provides the bit rates at 1 and 2 Mbps. The 802.11g interface must also be compatible with the 802.11b interface, called HR (High Rate)/DSSS, which provides the bit rates at 1, 2, 5.5 and 11 Mbps. The 802.11g interface implements the functions of the 802.11a interface, except that it uses the ISM (Industrial, Scientific and Medical) frequency band at 2.4 GHz. The ERP access point

is able to work in any combination of ERP and non-ERP modes. For example, the access point could operate only in an ERP-OFDM mode, in a mixed mode ERP-OFDM and ERP-HR/DSSS or in a mixed mode ERP-HR/DSSS/and not ERP. The DSSS/OFDM mode uses an 802.11b-compatible header and a payload using OFDM multiplexing. 3.2.1. PLCP sub-layer An ERP station must support three different formats for the PLCP header. The first format corresponds to the ERP-HR/DSSS mode. It includes the long preamble defined for the 802.11b interface, with a redefinition of the reserved bits. 802.11a/g Interfaces The second format corresponds to the ERP-HR/DSSS mode. It includes the optional short preamble for the 802.11b interface. The third format corresponds to the ERP-OFDM mode. It includes the preamble and header defined for the 802.11 interface. The DSSS-OFDM mode uses a format that includes the short or long preamble and the header of the 802.11b interface associated with the preamble and the header of the 802.11a interface. This mode is optional. 3.2.1.1. ERP-HR/DSSS mode The structure of the PLCP frame is described in Figure 3.6. Preamble header SIGNAL SERVICE LENGTH 16 bits 8 bits 8 bits 16 bits 16 bits Preamble PLCP header Long : 144 bits / 1 Mbps / BPSK Long preamble: 48 bits / 1 Mbit/s / BPSK Short 72 bits / 1 Mbps / BPSK Short preamble: 48 bits / 2 Mbps / QPSK Figure 3.6. PLCP frame for ERP-HR/DSSS mode The difference with the PLCP header of the 802.11b interface is in the SERVICE field bits set to support the optional packet binary convolutional code (PBCC): - bits b0, b1 and b4 are reserved and must be set to ZERO; - bit b2 is used to indicate that the transmission frequency and the symbol clock are derived from the same oscillator. For ERP mode, the locked clock bit must be set to ONE; - bit b3 is used to indicate whether the data uses the PBCC option; - bits b5, b6 and b7 are used to resolve DATA field length ambiguities for the optional PBCC mode; - bit b7 is also used to resolve DATA field length ambiguities for CCK (Complement

ary Code Keying) mode; - bits b3, b5 and b6 are set to ZERO for the CCK mode. 60 Wi-Fi Integration to the 4G Mobile Network 3.2.1.2. ERP-OFDM mode The structure of the PLCP frame is described in Figure 3.7. PLCP header Reserved LENGTH Parity SERVICE Signal 4 bits 1 bit 12 bits 1 bit 6 bits 16 bits 6 bits Extension Preamble SIGNAL Signal Extension Figure 3.7. PLCP frame for ERP-OFDM mode The PLCP frame is followed by a period (Signal Extension) without transmission with a duration of 6 us. The SIFS time for the 802.11a interface is equal to 16 us to allow additional time for the convolutional decoding process to complete. To be compatible with the 802.11b interface, the SIFS time for 802.11g interface is equal to 10 us. This extra length extension of 6 us thus makes it possible to ensure that the convolutional decoding process ends. 3.2.1.3. DSSS-OFDM mode The structure of the PLCP frame is described in Figure 3.8. Short / Long header training SIGNAL Signal preamble Extension sequence 802.11a 802.11b OFDM signal Figure 3.8. PLCP frame for DSSS-OFDM mode The SIGNAL field of the PLCP header must be set to a value of 3 Mbps. The PLCP header is similar to that described for the ERP-HR/DSSS mode. 802.11a/g Interfaces The payload of the PLCP frame consists of a long learning sequence, the OFDM SIGNAL field, which provides information on the rate and length of the DATA field, and a signal extension section to provide additional processing time for convolutional decoding. 3.2.2. PMD sub-layer The 802.11g interface operates in the ISM band at 2.4 GHz, covering the 2.4-2.4835 GHz frequency band. The bandwidth of the radio channel is equal to 22 MHz for the 802.11b interface and 20 MHz for the 802.11g interface. Figure 3.9 shows the channel number and the value of the center frequency. To avoid overlapping channels, it is recommended to use channels 1, 6 and 11. Channel 14 has been designated for specific use in Japan. The radio spectrum from 2.400 to 2.450 GHz (channels 1 to 8) is shared with radio amateurs. Channels 1, 5,

9 and 13 are used by domestic image transmitters and analog and digital Webcams. The 2.450 GHz frequency is that of microwave ovens that can disrupt, more or less, Wi-Fi channels 7 to 10. The maximum authorized power, inside and outside buildings, is 100 mW. Channel number 2.412 2.417 2.422 2.427 2.432 2.437 2.442 2.447 2.452 2.457 2.462 2.467 2.472 2.484 Central frequency (GHz) 22 MHz Figure 3.9. ISM band at 2.4 GHz Source: http://en.wikipedia.org/wiki/IEEE_802.11g-2003 802.11n Interface 4.1. MAC layer evolution Table 4.1 summarizes the features provided by the MAC (Medium Access Control) layer. Features Mandatory/optional Description Reception A-MPDU Mandatory Transmission MAC frame aggregation Optional A-MPDU Reception A-MSDU Mandatory Transmission Aggregation of MAC frame payload Optional A-MSDU Block Ack Mandatory Acknowledgment for a block of MAC frames Detection of radio channel occupancy time Protection Mandatory by non-802. 11n compatible stations Mandatory Reduced inter-frame interval Spatial Multiplexing Power save by reducing Mandatory Power Save the number of spatial flows Power Save Power save by modifying the radio access Optional Multi-Poll procedure for smaller frames Non-TKIP Mandatory TKIP is no longer allowed Phased Coexistence Alternating radio channels Optional Operation at 20 and 40 MHz Table 4.1. Features of MAC layer Wi-Fi Integration to the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2018. Published by ISTE Ltd and John Wiley & Sons, Inc. Wi-Fi Integration to the 4G Mobile Network 4.1.1. Management frames 4.1.1.1. HT Capabilities information element The management frames indicate that the access point has an 802.11n interface by including the HT (High Throughput) Capabilities information element. The information provided by the HT Capabilities Info field is described in Table 4.2. Information Designation LDPC Coding Capability LDPC error correction code Bandwidth of the radio channel Supported Channel Width Set (20 MHz / 40 MHz) SM Power Save Power save for spatial multiple

xing HT_Greenfield HT GF format for PLCP header Short GI for 20 MHz Short guard interval for the 20 MHz radio channel Short GI for 40 MHz Short guard interval for the 40 MHz radio channel Tx STBC Transmission for the space-time diversity STBC Rx STBC Reception for the space-time diversity STBC HT-Delayed Block Ack Delayed acknowledgment mechanism Maximum size of frame aggregation Maximum A-MSDU Length A-MPDU (3,839 or 7,935 bytes) DSSS/CCK Mode in 40 MHz Using the DSSS/CCK mode for 40 MHz radio channel Forty MHz Intolerant Prohibition to use 40 MHz radio channel L-SIG TXOP Protection Support L-SIG TXOP protection mechanism Table 4.2. Information of HT Capabilities Info field A-MPDU Parameters: this field indicates the maximum size of the frame aggregation A-MPDU that the access point can receive and the minimum time between two MPDU data units of the aggregation. Supported MCS Set: this field indicates the modulation and coding schemes supported by the access point, for transmission and reception. 802. 11n Interface HT Extended Capabilities: this field indicates whether PCO (Phased Coexistence Operation) mode or RD (Reverse Direction) protocol is supported. Transmit Beamforming Capabilities: this field describes the supported features for beamforming. ASEL Capability: this field describes the supported features for antenna selection. The HT Capabilities information element is included in BEACON frames SO that mobiles can determine that the 802.11r interface is available. A mobile inserts the HT Capabilities information element into the PROBE REQUEST frame to search for 802.11n access points. The HT Capabilities information element is also included in the management frames ASSOCIATION REQUEST, ASSOCIATION RESPONSE, REASSOCIATION REQUEST, REASSOCIATION RESPONSE and PROBE RESPONSE. 4.1.1.2. HT Operation information element The HT Operation information element provides the mobile with the characteristics of the 802.1 11n interface and contains the following fields: Primary Channel: this field indicates the number of

the primary radio channel. This channel is used for management frames. Secondary Channel Offset: this field indicates whether the secondary radio channel has a frequency higher or lower than that of the primary channel. STA Channel Width: this field indicates the bandwidth that the access point uses in reception. RIFS mode: this field indicates whether the use of the reduced inter- frame space (RIFS) is allowed. 66 Wi-Fi Integration to the 4G Mobile Network HT Protection: this field indicates the protection mechanism to avoid interference with mobiles that are not compatible with the 802. 11n interface. Non-greenfield STA present: this field indicates if the HT_GF mode is supported by the access point. OBSS Non-HT STAs present: this field indicates that an overlapping basic service set (OBSS) contains mobiles that are not compatible with the 802.11n interface requiring protection. Dual Beacon, Dual CTS, STBC Beacon: these three modes are used when the beacon channel uses the diversity in STBC transmission. L-SIG Protection Full Support: this field indicates whether the L-SIG protection mechanism is supported. PCO Active, PCO Phase: these two fields indicate the use of the PCO mode, which makes it possible to switch a radio channel between 20 and 40 MHz. These fields are used to indicate that the PCO mode is in operation and whether the radio channel is currently 20 or 40 MHz. Basic MCS set: this field indicates the modulation and coding schemes supported by the access point. The HT Operation information element is included in the management frames BEACON, ASSOCIATION RESPONSE, REASSOCIATION RESPONSE and PROBE RESPONSE. 4.1.2. Structure of the MAC header The 802.11n interface modifies the structure of the protocol header by adding the HT Control field (Figure 4.1) after the QoS Control field. The presence of the HT Control field is indicated by the Order bit of the Frame Control field set to ONE, for QoS Data traffic frames and management frames. 802.11n Interface Bit 0-15 Bit 16-17 Bit 18-19 Bit 20-21 Bit 22-23 B

Interpretation of MFB/ASELC information Identifier of the sequence relating to a MFSI (MCS Feedback Sequence Identifier) request for a recommendation on the value of the modulation and coding scheme (MCS) MFB/ASELC (MCS Feedback and Antenna MCS recommended value or features of Selection Command) antenna selection Table 4.3. Information of Link Adaptation Control field Calibration Position: this field indicates the position in the exchange sequence relative to the calibration sounding. Calibration Sequence: this field contains the identifier of the exchange sequence. CSI/Steering: this field indicates the type of response for beamforming. 68 Wi-Fi Integration to the 4G Mobile Network NDP Announcement: this field indicates whether an empty frame is transmitted after the data unit. AC Constraint: this field indicates whether the data in the RD protocol belongs to a single access category (AC). RDG More PPDU: this field is interpreted differently, for the RD protocol, if it is transmitted by the initiator (allocation of a resource or not) or the responder (the frame is the last transmitted or not). 4.1.3. Frame aggregation 4.1.3.1. A-MPDU frame The A-MPDU (Aggregate MAC Protocol Data Unit) frame is an A-MPDU sub-frame sequence (Figure 4.2). Each A-MPDU sub-frame contains a delimiter, an MPDU frame and pad bytes. IP packet IP packet MAC header MAC header Delimiter Delimiter A-MPDU sub-frame A-MPDU sub-frame A-MPDU frame Figure 4.2. Structure of A-MPDU frame With the exception of the last A-MPDU sub-frame, the padding bytes are added SO that the size of each A-MPDU sub-frame is a multiple of four bytes. The delimiter contains the size of the MPDU frame, an error check (CRC) on the frame size and a signature that can be used to detect a delimiter. The unique pattern is set to 4E in hexadecimal notation. As each A-MPDU sub-frame gets its own MAC header, the encryption is applied to each sub-frame independently. Since each A-MPDU sub-frame 802. 11n Interface has its own error detection sequence, an error will only affect

the A-MPDU sub-frame, and the other A-MPDU sub-frames can be recovered. All A-MPDU sub-frames must have the same destination on the radio link. On the other hand, the destination or the source address of the MPDU frame may be different. 4.1.3.2. A-MSDU frame The A-MSDU (Aggregate MAC Service Data Unit) frame is a sequence of A-MSDU sub-frames (Figure 4.3). Each A-MSDU sub-frame contains an A-MSDU header, an MSDU data unit and pad bytes. Header Header A-MSDU sub-frame A-MSDU sub-frame MAC header A-MSDU frame MPDU frame Figure 4.3. Structure of A-MSDU frame The A-MSDU header consists of three fields: the MAC addresses of the destination and source of the MAC frame and the length of the MSDU data unit. With the exception of the last A-MSDU sub-frame, padding bytes are added SO that the size of each A-MSDU sub-frame is a multiple of four bytes. Since the A-MSDU sub-frames of the same A-MSDU frame are contained in the same MPDU data unit, the same encryption applies to all the sub-frames. Both forms of aggregation may be combined: an A-MPDU frame may contain an A-MSDU frame. Wi-Fi Integration to the 4G Mobile Network 4.1.4. Control frames 4.1.4.1. Block acknowledgment The block acknowledgment mechanism improves the efficiency of the channel by grouping multiple acknowledgments in a single control frame. There are two types of mechanisms: immediate acknowledgment and delayed acknowledgment. The immediate acknowledgment mechanism is suitable for high- bandwidth and low-latency applications, whereas the delayed acknowledgment mechanism is suitable for applications that tolerate moderate latency. The original design of the acknowledgment mechanism requires that each transmitted frame be acknowledged separately by the Ack control frame (Figure 4.4). Standard acknowledgment Source Destination Immediate block acknowledgment Block Source Destination Block Delayed block acknowledgment Block Source Destination Block Figure 4.4. Block acknowledgment If the immediate acknowledgment mechanism is used, then the recipient must respo

nd to a BlockAckReq frame with a BlockAck frame (Figure 4.4). When the recipient sends the BlockAck frame, the initiator retransmits all frames that are not acknowledged in the BlockAck frame, either in another block or individually. 802. 11n Interface If the delayed acknowledgment mechanism is used, then the recipient must respond to a BlockAckReq control frame with an Ack control frame. The recipient must then send his response in a BlockAck control frame, which the initiator acknowledges by an Ack control frame (Figure 4.4). The block acknowledgment mechanism has been introduced with the QoS mechanism. The block acknowledgment mechanism was initially optional, but the efficiency gains coupled with the aggregate frame transmission resulted in BlockAck control frame support being required for the 802.11n interface. The initial definition of the block acknowledgment mechanism took into account the processing of frame-related sequence numbers and fragment numbers. For the 802.11n interface, the block acknowledgment mechanism can be compressed, thus only processing the sequence number. 4.1.4.2. Control frame structure The BlockAckReq control frame is transmitted by the source of several MAC frames for block acknowledgment (Figure 4.5). Fragment number Initial segment (value to ZERO) number Initial segment TID value number Frame Duration BlockAckReq Control Control Information Multi Compressed Reserved TID_INFO Policy Bitmap Frame Duration BlockAck Control Control Information TID value Initial segment Bitmap number Initial segment number Bitmap Figure 4.5. Control frame structure Wi-Fi Integration to the 4G Mobile Network The BAR or BA Control field contains the following information: - Ack Policy: this bit indicates whether the block acknowledgment is immediate (bit to ZERO) or not (bit to ONE); - Multi-TID: this bit indicates whether the block acknowledgment applies to several priority levels (bit to ONE) or not (bit to ZERO); - Compressed Bitmap: this bit indicates whether the block acknowledgment is compressed (

bit to ONE) or not (bit to ZERO); - TID_INFO: this four-bit coded subfield provides the value of the TID (Traffic Identifier) field, for which a block acknowledgment is required. The BAR or BA Information field contains the value of the sequence number of the first transmitted MAC frame. If the block acknowledgment applies to several priority levels, the sequence number is indicated for each priority level. The BlockAck control frame is transmitted by the recipient of the MAC frames for block acknowledgment. Each bit in the bitmap of the Information field acknowledges (bit to ONE) or not (bit to ZERO) the frame that has this offset from the initial sequence number. 4.2. PLCP sub-layer The PLCP (Physical Layer Convergence Procedure) sub-layer supports the following three modes: - NON_HT mode: the PLCP header is identical to that defined for the 802.11a/g interfaces (Figure 4.6). NON_HT mode support is required; - HT_MF (Mixed Format) mode: the PLCP header contains a preamble compatible with that defined for the 802.11a/g interfaces SO that it can be processed by mobiles that do not handle the 802.11n interface (Figure 4.6). HT_MF mode support is required; 802.11n Interface - HT_GF (Greenfield) mode: the PLCP header does not contain fields compatible with the 802.11a/g interfaces (Figure 4.6). Support for HT_GF format is optional. A mobile that does not support the HT_GF mode must be able to detect that a transmission of an HT_GF frame is in progress. SERVICE NON_HT L-STF L-LTF L-SIG HT_MF L-STF L-LTF L-SIG HT-SIG HT-STF HT-LTF HT-LTF HT-LTF HT-LTF HT LTF DATA HT LTF Extension HT_GF HT-GF-STF HT-LTF1 HT-SIG HT-LTF HT-LTF HT-LTF HT-LTF HT LTF DATA HT LTF Extension Figure 4.6. PLCP frame structure L-STF (Non-HT Short Training Field): this field is identical to the short training sequence of the 802.11a/g interfaces. L-LTF (Non-HT Long Training Field): this field is identical to the long training sequence of the 802.11a/gi interfaces. L-SIG (Non-HT Signal): this field is identical to the SIGNAL field of the 802.11a/g

interfaces. This field allows mobiles that do not handle the 802.11n interface to determine the radio channel occupancy time, the bit rate being 6 Mbps. HT-SIG (HT Signal): Table 4.4 describes the information in this field. Wi-Fi Integration to the 4G Mobile Network Information Bit number Designation Index of the modulation and coding scheme (76 values) Channel Bit to ZERO for a bandwidth at 20 MHz Bandwidth Bit at ONE for a bandwidth at 40 MHz HT Length Size in bytes of the PSDU payload Bit to ONE for smoothing the assessment of channel Smoothing aggregation. Bit to ZERO for independent assessment of each channel Bit to ZERO if the PPDU data unit is a sounding Not Sounding Bit to ONE if not Bit to ONE if the data unit contains A-MPDU sub-frames Aggregation ZERO bit if not 2 bits to ZERO if transmission diversity is not used STBC (Space- Time Block If not, value indicating the difference between the number Coding) of spatial/temporal diversity streams and the number of spatial flows FEC (Forward Bit to ZERO for LDPC (Low-Density Parity Check) Error coding Correction) Bit to UN for BCC (Binary Convolutional Code) coding Short GI Bit to ONE if a short guard interval is used (Guard Interval) ZERO bit if not Indicates the number of extension spatial streams. Number of Set to 0 for no extension spatial stream. extension spatial Set to 1 for 1 extension spatial stream. streams Set to 2 for 2 extension spatial streams. Set to 3 for 3 extension spatial streams. Cyclic redundancy code Tail of the convolutional encoder Table 4.4. HT-SIG field structure 802.1 11n Interface HT-STF (HT Short Training Field): this field has the same purpose as the L-STF field. There are two types of HT-LTF (HT Long Training Field): - DATA HT-LTF field helps to set the MIMO (Multiple Input Multiple Output) mechanism; - HT-LTF Extension field is used for beamforming. The number of HTF LTF fields depends on the number of spatial flows. This field is optional. 4.3. PMD sub-layer Table 4.5 summarizes the features provided by the PMD (Physical Mediu

m Dependent) sub-layer. Features Mandatory/optional BPSK, QPSK, 16QAM, 64QAM Modulation Mandatory BCC error correction code Mandatory LDPC error correction code Optional Short guard interval (400 ns) Optional MIMO (up to four streams) Optional Beamforming Optional Optional Table 4.5. Characteristics of PMD sub-layer 4.3.1. Transmission chain Transmission in the HT_MF and HT_GF modes is generated from the following function blocks: a) Scrambler scrambles the data to reduce the probability of long sequences of bits to ZERO or to ONE. b) Encoder parser, if BCC encoding is to be used, demultiplexes the scrambled bits among NES (number of BCC encoders for the Data field) BCC encoders, in a round robin manner. Wi-Fi Integration to the 4G Mobile Network c) FEC encoders encode the data to enable error correction. An FEC encoder may include a binary convolutional encoder followed by a puncturing device, or it may include an LDPC encoder. d) Stream parser divides the outputs of the encoders into blocks that are sent to different interleaver and mapping devices. The sequence of the bits sent to an interleaver is called a spatial stream. e) Interleaver interleaves the bits of each spatial stream (changes order of bits) to prevent long sequences of adjacent noisy bits from entering the BCC decoder. Interleaving is applied only when BCC encoding is used. f) Constellation mapper maps the sequence of bits in each spatial stream to constellation points (complex numbers). g) STBC encoder spreads constellation points from Nss spatial streams into NSTS space-time streams using a space-time block code. STBC is used only when NSS<NSTS. h) Spatial mapper maps space-time streams to transmit chains. This may include one of the following: - direct mapping: constellation points from each space-time stream are mapped directly onto the transmit chains (one-to-one mapping); - spatial expansion: vectors of constellation points from all the space- time streams are expanded via matrix multiplication to produce the input to all the transmit chain

s; - beamforming: similar to spatial expansion, each vector of constellation points from all the space-time streams is multiplied by a matrix of steering vectors to produce the input to the transmit chains. i) Inverse discrete Fourier transform (IDFT) converts a block of constellation points to a time domain block. j) CSD (Cyclic Shift Diversity) insertion is where the insertion of the cyclic shifts prevents unintentional beamforming. CSD insertion may occur before or after the IDFT. k) GI insertion prepends to the symbol a circular extension of itself. 1) Windowing optionally smooths the edges of each symbol to increase spectral decay. 802.11n Interface Figure 4.7 shows the blocks used to generate the HT-SIG field of the PPDU data unit in HT_MF mode. GI Insertion Windowing GI Insertion Windowing GI Insertion Windowing Single spatial stream GI Insertion Windowing Transmission streams Figure 4.7. Transmission chain - Diagram 1 These blocks are also used to generate the NON_HT part of the PPDU data unit in HT_MF mode. The BCC encoder and the interleaver are not used when generating the L-STF and L-LTF fields. Figure 4.8 shows the blocks used to generate the DATA field for HT_MF and HT_GF modes. A subset of these blocks consisting of the constellation mapper and the CSD blocks, as well as the blocks on the right, including the spatial mapping block, is also used to generate the HT-STF, HT-GF-STF and HT-LTF fields. The HT-GF-SIG field is generated using the blocks shown in Figure 4.7, augmented by additional CSD blocks and spatial mapping. 78 Wi-Fi Integration to the 4G Mobile Network Constellation GI Insertion Interleaver Mapper Windowing Constellation GI Insertion Interleaver Mapper Windowing Constellation GI Insertion Interleaver Mapper Windowing Constellation Interleaver GI Insertion Mapper Windowing Spatial streams Space-time streams Transmission streams Figure 4.8. Transmission chain - Diagram 2 4.3.2. Frequency plan The 802.11n interface operates in the N-NII (Unlicensed-National Information Infrastructure) ba

nd, at 5 GHz, as the 802.11a interface, and in the ISM (Industrial, Scientific and Medical) band, at 2.4 GHz, as the 802.11g interface. The 802.11n interface uses the 20 MHz radio channel, as for the 802.11a/g interfaces, and offers the possibility of aggregating two adjacent radio channels in the U-NII band at 5 GHz (Figure 4.9). Sub-band A Sub-band B Sub-band C Channel number 20 MHz 40 MHz USA and Japan only Figure 4.9. Frequency plan 4.3.3. Frequency multiplexing For the 20 MHz radio channel band, for HT modes, the complex numbers are numbered 0 to 51 and are subsequently mapped onto OFDM (Orthogonal Frequency-Division Multiplexing) sub-carriers, numbered -28 to -22, -20 to -8, -6 to -1, 1 to 6, 8 to 20 and 22 to 28 (Table 4.6). 802.11n Interface Sub-carriers -21, -7, 7 and 21 are ignored and subsequently used for the insertion of pilot sub-carriers. Parameters NON_HT HT 20 MHz HT 40 MHz NSD Number of sub-carriers assigned to the DATA field NSP Number of sub-carriers assigned to pilots NST Total number of sub-carriers AF Spacing between sub-carriers 0.3125 MHz (20 MHz/64) Table 4.6. OFDM multiplexing parameters For the 40 MHz radio channel band, the complex numbers are numbered 0 to 107 and are subsequently mapped onto OFDM sub-carriers numbered -57 to -54, -52 to -26, -24 to -12, -10 to -1, 1 to 10, 12 to 24, 26 to 52 and 54 to 57 (Table 4.6). Sub-carriers -53, -25, -11, 11, 25 and 53 are ignored and subsequently used for the insertion of pilot sub-carriers. Sub-carrier 0, associated with the central frequency, is omitted and filled with the value of ZERO. 4.3.4. Space multiplexing 4.3.4.1. MIMO mechanism The MIMO mechanism consists of simultaneously transmitting m signals and receiving them on n antennas, with m <n, using the same radio channel. Each receiving antenna receives the m transmitted signals, each signal being modified by the transfer function between the transmitting and receiving antennas. There is thus a transmission matrix H of size m X n (Figure. 4.10). The MIMO mechanism, by spatially multip

lexing m signals, makes it possible to increase the rate of the radio channel with the same factor. The MIMO mechanism uses the transmission matrix H to perform spatial demultiplexing. Wi-Fi Integration to the 4G Mobile Network For the SU (Single User) MIMO mechanism, the m transmitted signals are destined for the same user. Figure 4.10. MIMO mechanism 4.3.4.2. STBC mechanism When the number of transmitters (m) is greater than the number of receivers (n), the additional transmitters are used to effect transmit diversity, thereby improving the quality of the received signal by protecting the transmission from fading. The STBC mechanism performs space and time diversity. The signal S corresponding to a spatial flux is divided into two parts, S1 and S2. The complex numbers of the S (= S1 + S2) constellation of Nss spatial streams (Nss = 1) are distributed over NSTS space-time flows (NSTS = 2) (Figure 4.11). Frequency Space * conjugate complex S = S1+S2 Process diversity diversity Frequency Figure 4.11. STBC mechanism 802.11n Interface 4.3.4.3. Beamforming Beamforming allows a transmitter, called a beamformer, to focus the energy of several sources of the same signal in the direction of the receiver, called a beamformee. Phase reception increases the signal-to-noise ratio of the received signal (Figure 4.12). The two received S signals are out of phase Signal S Process Result The two received S signals are in phase Figure 4.12. Beamforming mechanism For the explicit beamforming, a device measures the radio channel and uses this measurement to directly calculate the direction matrix. The active channel measurement is performed by transmitting a sounding to the beamformee, which responds with a frame that indicates how the sounding was received. For implicit beamforming, frames such as ACK control frames or data transmitted on pilot channels can be used to estimate the direction matrix. 4.3.5. Modulation and coding scheme The value of the modulation and coding scheme (MCS) determines the rate value from the following p