Limit redirections in an unlicensed mobile access network

The present invention provides a method and system to limit redirections by using a redirection counter contained within the mobile station (MS 132) registration request (663 or 667). Once the redirection counter has exceeded a certain value for a MS (132), the unlicensed network controller (UNC 142) will reject any registration request from that MS (132). More specifically, the present invention provides a method for limiting redirections of mobile stations (132) in an unlicensed radio access network (102) by initializing a redirection counter (1206), including the redirection counter in a registration request (1208), and incrementing the redirection counter each time a re-direct response is received in response to the registration request (1212).

FIELD OF THE INVENTION

The present invention relates in general to the field of mobile communications and, more particularly, to a method and system to limit redirections in an unlicensed mobile access network.

BACKGROUND ART

In any mobile communication system, such as a Global System for Mobile communications (GSM) network, active calls conducted between a mobile station (MS) and a base station need to be handed over to a different base station as the mobile station moves between different coverage areas, or cells. Depending on how each cell is defined, handover may require the active call to be re-routed simply through a different base station transceiver (BTS), through a different base station controller (BSC) or through a different mobile services switching center (MSC). Handover may also be necessary when capacity problems are met in any one cell.

Handover necessitates a certain amount of operation and maintenance activities on installation of a system, such as defining neighboring cells, as well as the BSC and MSC that controls the cell, defining which cell frequencies should be measured and what threshold value to use to initiate handover. In a conventional GSM network the BSC sends a MS a list of predetermined frequencies to be measured. Two lists may be sent out, a first list being used for idle mode, such as when the MS is roaming, and a second used for active mode when a call is ongoing. This second list defines which frequencies the MS should measure and report back on. These lists contain a set of values that refer to absolute radio frequency channel numbers (ARFCN) of neighboring cells. In addition to these frequency channel numbers the BSC also knows base station identity codes (BSIC) of all neighbouring cells. The MS measures the frequencies defined by these channel numbers and reports these measurements to the BSC. In practice, the MS will report on only the six best measurement values and only for those cell frequencies with which the MS can synchronize and consequently receive a BSIC. The measurement report sent back to the BSC by the MS includes a reference to the ARFCN, the BSIC and an indication of the received downlink signal strength. In fact the report does not specify the exact ARFCN but rather refers to the position this number occupied in the measurement list. On the basis of this report, the BSC decides whether handover is necessary and to which cell. The initiation of handover is performed according to the standard GSM mechanism for each vendor. Specifically, a message is sent by the base station controller to the MSC connected to the BSC indicating that handover is required. This message contains a cell identifier, encompassed in a cell global identity (CGI), which defines the mobile country code, mobile network code, location area code and cell identifier for the cell to which handover is requested. The CGI is fetched by the BSC from a list using the BSIC and ARFCN obtained for the cell. With this CGI the MSC is able to determine which other MSC handles the cell defined by the CGI value.

Recently proposals have been made to extend conventional cellular networks by including access networks that utilize a low power unlicensed-radio interface to communicate with MSs. The unlicensed mobile access (UMA) networks (UMANs) are designed to be used together with the core elements of a standard public mobile network and consist essentially of plug-in low-power unlicensed radio transceivers, or access points (AP), each designed to establish an unlicensed radio link with a MS and a controller or interface node connecting the unlicensed radio transceivers with the mobile core network. Suitable unlicensed-radio formats include digital enhanced cordless telecommunications (DECT), wireless local area network (WLAN) and Bluetooth. An adapted mobile handset capable of operating over both the standard air interface (e.g., the Um interface) and the unlicensed-radio interface means that the subscriber requires only one phone for all environments. The UMA network is constructed so that the core elements, such as the MSCs, of the public mobile network views the interface node as a conventional BSC. Such a UMA network and the MS for use with this UMA network are described in European patent application No. EP-A-1 207 708. The content of this application is incorporated herein by reference.

The low power and resultant low range of the unlicensed-radio interface means that several such UMA networks may be provided in relatively close proximity, for example one access network per floor of an office building or in a private home. The connection between the unlicensed-radio transceivers and the associated unlicensed network controller (UNC) is provided by a fixed broadband network. Preferably, communication over this network uses the internet protocol (IP), which greatly facilitates the installation of the UMA network, permitting a subscriber to plug-in an unlicensed-radio transceiver or in his own home and consequently install an unlicensed-radio access point (AP) himself. However, the flexibility of such UMA networks also presents difficulties. Since an access point can be freely installed and moved by a subscriber to a separate city, state or even country, yet still connect to its original UNC, the exact location of the AP cannot be tracked by the core network. This imposes huge demands on the operation and maintenance activities required for handover to and from the UMA network, as neighboring cells may change frequently. Also billing restraints in some areas may require the re-assignment of a relocated AP to a more appropriate UNC, particularly if revenue from calls originating from a specific AP must be accounted for in a specific region of a country. As a result, the configuration and relocation of MSs as they move in and out of APs and UMA networks poses a significant challenge to the expansion of services to UMA networks.

Furthermore, a redirect or reassignment function is required to connect the MS to the correct UNC via the APs. This facilitates the possibility of performing a handover to the licensed mobile spectra. Since the redirect function in the UNCs rely on data provisioned by human beings (or other machines) there is a possibility that the data is corrupt. As a result, the system is susceptible to infinite redirections.

SUMMARY OF THE INVENTION

The present invention provides a method and system to limit redirections by using a redirection counter contained within the MS registration request. Once the redirection counter has exceeded a certain value redirections for a MS, the UNC will reject any registration request from that MS. The UNC may also log the fact that the redirection counter has exceeded a certain value. This registration request cutoff system improves efficiency, reduces network loading, protects the system from infinite numbers of registration requests, and can aid in fault localization.

More specifically, the present invention provides a method for limiting redirections of mobile stations in an unlicensed radio access network by initializing a redirection counter, including the redirection counter in a registration request, and incrementing the redirection counter each time a re-direct response is received in response to the registration request. Typically, the redirection counter is initialized to zero on a first registration request. Additional steps may include creating the registration request, sending the registration request to an unlicensed mobile access network controller, or receiving a response to the registration request.

In addition, the present invention provides a method for limiting redirections of mobile stations in an unlicensed radio access network by receiving a registration request that contains a redirection counter, processing the registration request normally whenever the redirection counter does not exceeds a value, and sending a reject response whenever the redirection counter exceeds a value. The method may also include the steps of creating a log whenever the redirection counter exceeds the value, or creating the reject response. The methods described above can be implemented using a computer program embodied on a computer readable medium wherein each step is executed by one or more code segments.

The present invention also provides an electronic communication that includes a registration request and a redirection counter. The electronic communication is typically sent from a mobile station to an unlicensed mobile access network controller in an unlicensed radio access network.

Moreover, the present invention provides an apparatus within an unlicensed radio access network that limits redirections of one or more mobile stations by using a redirection counter to determine whether to reject a registration request. Likewise, the present invention provides an unlicensed-radio access system connected to a core network portion of a licensed mobile network, the unlicensed-radio access system including one or more access points adapted to communicate with mobile stations over an unlicensed-radio interface, one or more unlicensed mobile access point controllers connected to the core network portion of the licensed mobile network and a fixed broadband network connected to both the access points and the unlicensed mobile access point controllers, wherein the one or more unlicensed mobile access point controllers use a redirection counter in each registration request from the mobile stations to limit redirections of the mobile stations.

DESCRIPTION OF THE INVENTION

The present invention provides a method and system to limit redirections by using a redirection counter contained within the MS registration request. Once the redirection counter has exceeded a maximum value of redirections for a MS, the UNC will reject any registration request from that MS. The UNC may also log the fact that the redirection counter has exceeded a certain value. This registration request cutoff system improves efficiency, reduces network loading, protects the system from infinite numbers of registration requests, and can aid in fault localization.

Referring now toFIG. 1, a block diagram depicting parts of a GSM network100with a UMA network102in accordance with the present invention is shown. The GSM network100is essentially divided into a core network portion104and an access portion106. The elements of the core network104include the mobile switching centers (MSC)108and110, associated home location register (HLR)112and visitor location registers (VLR)114and116. The function and structure of these conventional GSM architecture elements are known to those in the art and will not be described in further detail here. The core network104also supports the General Packet Radio Service (GPRS), and to this end serving GPRS support nodes (SGSN)118and120are illustrated. Although not illustrated in the figure, it will be understood by those skilled in the art that the core network104may include access to other mobile and fixed-line networks, such as ISDN and PSTN networks, packet and circuit switched packet data networks such as intranets, extranets and the Internet through one or more gateway nodes.

The access portion106essentially consists of multiple base station subsystems (BSS)122, only one of which is illustrated. The BSS122includes one or more base station controllers (BSC)124and one or more base transceiver stations (BTS)126,128and130. The BSS122or BSC124communicates via defined fixed standard A and Gb interfaces with MSC110and SGSN120, respectively in the core network portion104. The BSC124communicates with the one or more BTS126,128and130via the defined Abisair interface. The BTS130communicates with mobile stations or terminals (MS or MT132over the GSM standard Um radio air interface. Note that the BSC124is often separate from the BTSs126,128and130and may even be located at the MSC110. The physical division depicted inFIG. 1serves to distinguish between the parts of the network making up the access network portion106and those that form the core network portion104.

In addition to the standard access network portion provided by the BSS122, the network depicted inFIG. 1further includes an unlicensed-radio access network (UMAN102). The components making up this UMAN102also enable the MS132to access the GSM core network104, and through this, other communication networks via an unlicensed-radio interface X. A used herein, unlicensed-radio means any radio protocol that does not require the operator running the mobile network to have obtained a license from the appropriate regulatory body. In general, such unlicensed-radio technologies must be low power and thus of limited range compared to licensed mobile radio services. This means that the battery lifetime of mobile terminals will be greater. Moreover, because the range is low the unlicensed-radio may be a broadband radio, thus providing improved voice quality. The radio interface may utilize any suitable unlicensed-radio protocol, for example a wireless LAN protocol, Bluetooth radio or Digital Enhanced Cordless Telecommunications (DECT). These radios have higher bandwidth and lower power consumption than conventional public mobile network radio.

The Bluetooth standard specifies a two-way digital radio link for short-range connections between different devices. Devices are equipped with a transceiver that transmits and receives in a frequency band around 2.45 GHz. This band is available globally with some variation of bandwidth depending on the country. Both data and voice channels are available. Each device has a unique 48-bit address from the IEEE 802 standard. Built-in encryption and verification is also available.

The element of the UMAN102adapted to communicate across the unlicensed radio interface is designated as an access point (AP)134,136,138and140(also referred to as a local or home base station (HBS)). The AP134handles the radio link protocols with MS132and contains radio transceivers that define a cell in a similar manner to the operation of a conventional GSM BTS130. The AP134is controlled by a unlicensed network controller (UNC)142,144or146(also referred to as a home base station controller (HBSC)), which communicates with MSC110over the GSM standard A interface and also with a serving GPRS support node SGSN120over a standard Gb interface, if available in the core network104. The joint function of the AP134and the UNC142emulates the operation of the BSS122towards the SGSN120and MSC110. In other words, when viewed from the elements of the core network104such as the MSC110and the serving GPRS support node (SGSN)120, the UMAN102constituted by the APs134,136,138and140and the UNC142looks like a conventional access network106.

The interface between the access points134, etc. and the UNC142is preferably provided by a fixed link. The home base station (not shown, but can be integrated in the AP) is intended to be a small device that a subscriber can purchase and install in a desired location such as the home or an office environment to obtain a fixed access to the UMA network. However, they could also be installed by operators in traffic hotspots. In order to reduce the installation costs on the part of the operator, the interface between the home base station (not shown) and the UNC142preferably exploits an already existing connection provided by a fixed network148. Preferably this network148is a broadband packet-switched network. Suitable networks might include those based on ADSL, Ethernet, LMDS, or the like. Home connections to such networks are increasingly available to subscribers.

Now referring toFIG. 2, a block diagram of the UMA high level functional architecture is shown. The UMAN102includes one or more APs134and one or more UNCs142(each having a Secure Gateway150(UNC SGW)), interconnected through a broadband IP network148. The UNC SGW150terminates secure remote access tunnels from the MS132and provides mutual authentication, encryption and data integrity for signaling, voice and data traffic. Note that each UNC142can have multiple UNC SGWs, or a UNC SGW pool can serve multiple UNCs. The UMAN102co-exists with the GSM/GPRS radio access network and interconnects to the GSM core network104via the same interfaces used by a standard GERAN BSS network element: GSM A-interface for circuit switched services; GPRS Gb-interface for packet services; and Wm-interface for authentication, authorization and accounting. The UNC142appears to the GSM/GPRS core network104as a GERAN BSS. The principle elements of transaction control (e.g., call processing) and user services are provided by the network elements in the core network104, namely the MSC110, SGSN/GGSN120, Authentication, Authorization and Accounting Proxy/Server152(AAA Proxy/Server) and the VLR/HLR116. The AAA Proxy/Server152interfaces with VLR/HLR116via D′/Gr′ interface. Whenever the MS132is roaming, the GSM/GPRS core network104will interface with the MS's Home Public Land Mobile Network154(HPLMN). Specifically, AAA Proxy/Server152will interface with AAA Server156via Wd interface. The AAA Server156will interface with HLR158via D′/Gr′ interface.

Broadband IP network148provides connectivity between the user premises and the UNC142. An AP134in the user premises provides the radio link to the MS132using unlicensed spectrum. The IP transport network extends all the way from the UNC142to the MS132, through an AP134. A single interface, Ut, is defined between the UNC142and the MS132. The Mt interface is an interface between the UNC142and the AP134. This interface may be used for special functions in some realizations. The Ut and Mt interfaces are collectively referred to as the Up interface.

The MS132provides dual mode (licensed and unlicensed) radios and the capability to switch between them. The MS132supports an IP interface to the AP134. In other words, the IP network from the UNC142extends all the way to the MS132. The MS132is defined for Bluetooth (using the Bluetooth PAN profile) as well as for 802.11. The AP134provides the radio link towards the MS132using unlicensed spectrum and connects through the broadband IP network148to the UNC142. The AP134provides Bluetooth (PAN profile) or 802.11 access point functions. The AP134may also use other radio access technologies, such as 802.16 or 802.20, etc. Any “standard” AP can be used to interconnect the MS132to the broadband IP network148.

A UNC142connects to a unique MSC110and SGSN120via the A-interface and Gb interface respectively. This does not preclude support of A-flex and Gb-flex features. The UNC142provides functions equivalent to that of a GSM/GPRS BSC. The UNC142connects via the IP transport network148to the AP134. The UNC142interfaces to the MS132using the Ut interface and maintains end-to-end communication with the MS132and relays GSM/GPRS signaling to the A/Gb interface towards the core network104. The UNC142performs the following functions: transcoding voice to/from the MS132to PCM voice when TFO/TrFO features are not being utilized from/to the MSC110; and the following Ut functionality: registration for UMA service access; set-up of UMA bearer paths for CS and PS services, including participation in establishment, management, and teardown of secure signaling and user plane bearers between the MS132and the UNC142; UMA equivalent functionality for paging and handovers; and transparent transfer of L3 messages between the MS132and core network104.

Referring now toFIG. 3, a block diagram depicting the logical roles of a UNC142in accordance with the present invention is shown. As previously described, the present invention provides a UNC142that can perform one, two or all three logical functions (e.g., provisioning300, default302and serving304). This logical division of roles in the UMA network improves network performance, improves reliability and provides improved load balancing. Accordingly, the present invention provides various procedures performed by the MS and the different UNCs with respect to one another. In addition, the present invention provides a method for the MS to contact the provisioning UNC to discover the default UNC that will be used to find the correct serving UNC.

Now referring toFIG. 4, a flow chart depicting a basic method400to assign a MS to a UNC in accordance with one embodiment of the present invention is shown. When a MS supporting UMA first attempts to connect to a UNC based on a UMA subscription, it needs to identify the default UNC. In order to do this it first connects to a provisioning UNC and then discovers a default UNC, which in turn can redirect the MS to a serving UNC. More specifically, the MS connects to a provisioning UNC in block402, and discovers with a default UNC in block404. This is only done once, as long as, the default UNC is available. After discovering the default UNC, the MS disconnects from the provisioning UNC, connects to the default UNC and registers with the default UNC in block404. A serving UNC is then determined to assign the MS to in block406and the MS is assigned to (registered with) the serving UNC in block408. The serving UNC can be the default UNC, the provisioning UNC or another UNC. If the serving UNC is the default UNC, the registration step in block408was already performed in block404. If, however, the serving UNC is not the default UNC, the MS is redirected to the serving UNC, disconnects from the default UNC, connects to the serving UNC and registers with the serving UNC in block408.

Referring now toFIG. 5, a flow chart depicting a more detailed method500to assign a MS to a UNC in accordance with the present invention is shown. The MS first joins an AP in block502. If the MS has stored UNC data, as determined in decision block504, the registration process for stored UNC entries is performed in block506. This process is further described in reference toFIG. 7. If the registration was accepted, as determined in decision block508, the service is established in block510. If, however, the MS does not have stored UNC data for the joined AP, as determined in decision block506, the discovery/registration process for the UNC is performed in block512. This process is further described in reference toFIG. 8. If registration was accepted, as determined in decision block514, service is established in block510. If however, the registration was not accepted, as determined in decision block514, so one or more rejection rules are executed in block516. This process is further described in reference toFIG. 11.

Now referring toFIGS. 6A and 6B, representative signaling sequences in accordance with the present invention are depicted. The description below assumes that the MS has already joined an AP that provides the unlicensed radio access. It is implementation specific what signal level should be deemed as sufficient for triggering the UMAN Discovery and Registration procedures. The Discovery procedure is performed by the MS when first attempting to obtain UMA service in order to determine the identity of the default UNC which may also serve as the serving UNC for that connection.

A MS supporting UMA may be provisioned (e.g. on the SIM) with the fully qualified domain name (FQDN) or IP address of the provisioning UNC and the associated Security Gateway (SGW). In case the SIM is not provisioned with the FQDN or IP address, the MS shall derive a FQDN for the provisioning UNC and the secure gateway, based on it's IMSI. The FQDN could, for example, comply with the following format: Provisioned UNC-SGW: sgw.uma.mncnnn.mccmmm.uma.3gppnetwork.org Provisioned UNC: punc.uma.mncnnn.mccmmm.uma.3gppnetwork.org where “nnn” and “mmm” are replaced with the IMSI MCC and MNC information in the SIM.

The MS shall set up a secure tunnel using the provisioned or derived address, and connect to the provisioning UNC. It shall then obtain the FQDN or IP address of the default UNC and the associated SGW, through the Discovery procedure. The default UNC serves as the primary registration destination address for the MS when it fails to register on an alternate serving UNC. These alternate serving UNC addresses are stored in the MS on the GSM CGI level when the MS is in GSM coverage or the AP level when there is no GSM coverage. Following the discovery procedure the MS shall establish a secure tunnel with the secure gateway of the default UNC and attempt to register with the default UNC. The default UNC network may also serve as the serving UNC for that connection. The procedure may result in the MS getting re-directed to a different serving UNC.

UNC redirection refers to the capability of a UNC to redirect an MS to a UNC distinct from the one it initially requests access to based on MS provided information and operator chosen policy. For example, the “appropriate” serving UNC is the UNC whose UMA service area “overlaps” the MS's umbrella GSM coverage. The correct serving UNC could be attached to the same MSC as the GSM BSC to which the umbrella GSM cell belongs. The correct serving UNC could be attached to a different MSC that can handover to the MSC which provides umbrella GSM coverage to the MS.

If no GSM coverage is available when an MS connects to the UNC for UMA service, then the UNC cannot reliably determine the location of the MS for the purposes of assigning the MS to the correct serving UNC (to enable handover and location-based services). The UNC shall permit the operator to determine the service policy in this case; e.g., the operator could provide service to the user with certain limitations (possibly with a user interface indication on the MS).

The MS is connected to the provisioning UNC by joining the MS to the UMAN via an access point (AP) and connecting the MS to the provisioning UNC via the AP. Each UNC is assigned one or more logical roles selected from a group of provisioning, default or serving. In addition, the present invention provides a method for assigning a MS to an UNC in an UMAN by joining the MS to the UMAN via an AP and attempting a discovery/registration process for one or more UNCs and assigning the MS to one of the UNC whenever the discovery/registration process is successful. The process also attempts a registration process for one or more previously connected UNC whose locations are stored on the MS and assigning the MS to the previously connected UNC whenever the registration process is successful. One or more rejection procedures can be executed whenever the discovery/registration process is unsuccessful. The above described methods can be implemented using a computer program embodied on a computer readable medium wherein each step is executed by one or more code segments.

Moreover, the present invention provides an apparatus within an UMA network that facilitates the assignment of one or more MSs within the UMA network. The apparatus includes an UNC that is assigned one or more logical roles selected from a group of provisioning, default or serving. The logical roles of provisioning, default and serving are distributed over one or more UNC.

The UNC is a provisioning UNC with respect to a first set of MS; a default UNC with respect to a second set of MSs, and a serving UNC with respect to a third set of MSs. Furthermore, the present invention provides an unlicensed-radio access system connected to a core network portion of a licensed mobile network. The unlicensed-radio access system includes one or more APs adapted to communicate with MSs over an unlicensed-radio interface, one or more UNC connected to the core network portion of the licensed mobile network and a fixed broadband network connected to both the APs and the UNCs, wherein the UNCs provide the logical roles of provisioning, default and serving in order to facilitate the assignment of the MSs within the UMA network.651: If the MS600has a provisioned or derived FQDN of the provisioning SGW606, it performs a DNS query651(via the AP that provides the unlicensed radio access) to resolve the FQDN to an IP address. If the MS600has a provisioned IP address for the provisioning SGW606, the DNS step651and652will be omitted.652: The DNS Server602returns a response.653: The MS600establishes a secure tunnel to the provisioning SGW606.654: If the MS600has a provisioned or derived FQDN of the provisioning UNC608, it performs a DNS query654(via the secure tunnel) to resolve the FQDN to an IP address. If the MS600has a provisioned IP address for the provisioning UNC608, the DNS step will be omitted.655: The DNS Server610returns a response655.656: The MS600establishes a TCP session to a well-defined port of the provisioning UNC608.657: The MS600queries the provisioning UNC608for the default UNC615, using URR DISCOVERY REQUEST657. The message contains:GSM Cell Info;Either current camping GSM CGI, or last CGI where the MS successfully registered, along with an indicator stating which one it is;AP Identity;The broadcast air-interface MAC address for the AP being used by the MS;MS Identity;IMSI.658: The provisioning UNC608returns the URR DISCOVERY ACCEPT message658, using the location information provided by the MS600(e.g. the CGI), to provide the FQDN or IP address of the default UNC615and its associated default SGW614. This message can also contain a TCP port number to used against the default UNC615. In addition, this is done so that the MS600is directed to a “local” default UNC to optimize network operations.659: Alternately, the provisioning UNC608may return a URR DISCOVERY REJECT indicating the reject cause659. Various causes may trigger a reject, including:Network Congestion: In this case the request can not be served right now. The MS600should wait for a random time before initiating a second attempt. For each successive failed attempt the MS600should double the waiting time. After 5 failed attempts, the MS600should restart the discovery procedure.Location not allowed: The MS600is attempting to connect to an operator that does not have a roaming agreement with the home operator of the MS600. The MS600shall not attempt any more discovery procedures from this forbidden location, i.e., country, PLMN or location indicated in the URR DISCOVERY REJECT message659. The MS600can retry the discovery procedure with the stored provisioning UNC608(e.g., in the SIM) when it is no longer in a forbidden location.UMA service not allowed: Operator policy determines that no UMA service is available. The MS600shall not re-attempt discovery on this UMA network. This condition shall be maintained until MS powers off.IMSI not allowed: Operator policy determines that the IMSI is not allowed. The MS600shall not re-attempt discovery on this UMA network. This condition shall be maintained until MS powers off.Unspecified: No cause is returned. The MS600shall not re-attempt discovery on this UMA network. This condition shall be maintained until MS powers off.AP not allowed: Operator policy determines that no UMA service is available on this AP. The MS600can retry the discovery procedure from another AP.If the MS600fails to receive any response from the provisioning UNC608, the MS600shall behave as if it received a URR DISCOVERY REJECT659with cause Network Congestion.660: The first TCP connection656is then released660.661: If the provisioning UNC608and default UNC616are behind the same SGW, which in this case would be provisioning SGW606, the same secure tunnel653can be used. Otherwise, the first secure tunnel653is released660and a new secure tunnel is established662.662: If the MS600was only provided the FQDN of the default SGW614, the MS600shall first resolve the IP address through a DNS query (via WLAN interface). The MS600shall then set up a secure tunnel662to the default SGW614. If the MS600was provided only the FDQN of the default UNC616, the MS600shall then resolve the IP address through a DNS query (via the secure tunnel662).663: The MS600then sets up a TCP session663to a well-defined port or to the port returned in URR DISCOVERY ACCEPT658on the default UNC616.664: The MS600shall attempt to register on the default UNC616by transmitting the URR REGISTER REQUEST664. The message contains:GSM Cell Info;Either current camping GSM CGI, or last CGI where the MS600successfully registered, along with an indicator stating which one it is;AP Identity;The broadcast air-interface MAC address for the AP being used by the MS600;MS Identity;IMSI.665: If the default UNC616wishes to re-direct the MS600to another serving UNC624, it shall respond with a URR REGISTER REDIRECT665providing the FQDN or IP address of the target serving UNC624and associated SGW622. Alternatively, the default UNC616may reject the registration and in this case the default UNC616shall respond with a URR REGISTER REJECT (not shown) indicating the reject cause. This could be triggered due to various causes such as:Redirection due load balancing: The specific UNC is overloaded and the MS600is redirected to another UNC.Network Congestion: The MS600can not be served right now. The MS600shall wait for a random time before a second attempt. For each successive failed attempt the MS shall double the waiting time. After 5 failed attempts, the MS600shall re-initiate the registration procedure.Restart discovery at provisioning UNC608: The MS600shall re-initiate the discovery procedure by contacting the stored provisioning UNC604(e.g. in the SIM).Location not allowed: The MS600shall not attempt to register with this UNC. The MS600can retry the discovery procedure with the stored provisioning UNC608(e.g. in the SIM).UMA service not allowed: Operator policy determines that no UMA service is available. The MS600shall not re-attempt to register on this UMA network. This condition shall be maintained until MS600powers off.AP not allowed: Operator policy determines that no UMA service is available on this AP. The MS600can retry the registration procedure from another AP.Alternately, the default UNC616may return a URR REGISTER ACCEPT664to accept the registration, per step668.666: The second TCP connection663is then released666.667: If the default UNC616and serving UNC624are behind the same SGW, which in this case would be provisioning SGW614, the same secure tunnel662can be used. Otherwise, the first secure tunnel662is released667and a new secure tunnel is established668.668: If the MS600was redirected and only provided the FQDN of the serving SGW622, the MS600shall first resolve the IP address through a DNS query (via WLAN interface). The MS600shall then set up a secure tunnel to the serving SGW622. If the MS600was provided only the FDQN of the serving UNC624, the MS600shall then resolve the IP address through a DNS query (via the secure tunnel). The MS600then sets up a TCP session to a well-defined port on the serving UNC624.669: The MS600shall attempt to register on the serving UNC624by transmitting the URR REGISTER REQUEST669. The message contains:GSM Cell Info: Either current camping GSM CGI, or last CGI where the MS600successfully registered, along with an indicator stating which one it is.AP Identity: The broadcast air-interface MAC address for the AP being used by the MS600.MS Identity: IMSI.670: If the serving UNC624accepts the registration attempt it shall respond with a URR REGISTER ACCEPT670. The message contains:Cell description comprising the BCCH ARFCN, PLMN color code, and base-station color code;Location-area identification comprising the mobile country code, mobile network code, and location area code corresponding to the UNC cell;Cell identity identifies the cell within the location area.671: Alternately, the serving UNC624may reject the request or redirect the MS600to another serving UNC624.Referring now toFIG. 7, a flow chart depicting a registration process506for UNC entries stored in a MS in accordance with one embodiment of the present invention is shown. The MS shall store (e.g. on the SIM) the address of the provisioning UNC and of the default UNC (along with the associated SGWs). The MS shall also store on the GSM CGI level when the MS is in GSM coverage or the AP level when there is no GSM coverage (e.g. on the SIM) the following information on each previously UNC for which the MS was able to complete a successful registration procedure. These alternate serving UNC addresses are stored in the MS.Cell Global Identity (CGI) of the GSM cell the MS was on prior to registration;Serving SGW identity address received following successful registration;Serving UNC IP Address received following successful registration.

The number of such entries to be stored in the MS can be one or several. For a particular AP, only the last successfully registered UNC association shall be stored. A MS may preferentially join a WLAN AP whose association with a serving UNC has been stored in memory.

On joining a WLAN if the MS is in GSM coverage, as determined in decision block700, and has stored serving UNC information for the current GSM CGI, as determined in decision block702, the MS shall attempt to register with the serving UNC by establishing a secure tunnel to the serving SGW in block706. If, however, the MS is not in GSM coverage, as determined in decision block700, and has stored serving UNC information for the current AP ID, as determined in decision block704, the MS shall attempt to register with the serving UNC by establishing a secure tunnel to the serving SGW in block706.

After the secure tunnel is established in block706, the MS sets up a TCP session to port on the serving UNC in block708and requests registration on the serving UNC in block710. If the UNC accepts the MS, registration is completed and service is established in block712. If the UNC redirects the MS to another UNC, a secure tunnel is established in block706and process repeats as herein described. The UNC may still reject the MS for any reason even though it may have served the MS before. In such a case, the MS shall delete from its stored list the address of the serving UNC on receiving a registration reject in block714.

If the MS does not receive a response to the Registration Request sent to the serving UNC, the entry is deleted in block714. Thereafter, or if the MS has not stored serving UNC information for the current GSM CGI, as determined in decision block702, or has not stored serving UNC information for the current AP ID, as determined in decision block704, the MS will check for stored entries for the default UNC, as determined in decision block716. If the MS does not have stored entries for the default UNC, it shall attempt the discovery/registration procedure with the provisioning UNC in order to obtain a new default UNC in block718. This process is described in more detail in reference toFIG. 8.

If, however, the MS does have stored entries for the default UNC, as determined in decision block716, the MS shall attempt to register with the default UNC in order to obtain a new serving UNC for the joined AP by establishing a secure tunnel to the default SGW in block720, setting up a TCP session to port on the default UNC in block722and request registration on the default UNC in block724. If the request is accepted, the registration is completed and service is established in block712. If the UNC redirects the MS to another UNC, a secure tunnel is established in block706and process repeats as herein described. If the request is rejected or the MS does not receive a response to the registration request sent to the default UNC, for a length of time, the default UNC is deleted from the stored list in block726. The MS shall then attempt the discovery/registration procedure with the provisioning UNC in order to obtain a new default UNC in block718. This process is described in more detail in reference toFIG. 8.

Now referring toFIGS. 8,9and10, flow charts depicting a UNC discovery/registration process512(FIG. 5) and 718(FIG. 7) for a MS in accordance with one embodiment of the present invention are shown. When the MS joins a WLAN, for which it does not have a stored serving UNC in its memory, it shall attempt to register with the default UNC. The Discovery and Registration procedures consist of the following steps:Joining a WLAN;Discovery of Default UNC, through the Provisioning UNC;Registration with the Default UNC;Potential redirection to a Serving UNC or rejection;Registration with a Serving UNC.Through the Registration procedure the MS may get re-directed to another serving UNC. This could be based on the following, among other reasons:Current location indicated through the overlapping GERAN Cell Global Identity or other location attributes;Indication of joined AP;Load balancing in the NW;Operator Policy;Roaming agreements in case of a roaming MS.A successful registration procedure results in the UNC establishing a context for the MS. The MS obtains the necessary system information for the UMAN it has registered on and can trigger a normal Location/Routing Area Update procedure with the CN.

More specifically, if the MS has a provisioned or derived FQDN of the provisioning SGW at800, the MS will perform a DNS Query to resolve the FQDN to an IP address for the provisioning SGW in block802. Thereafter, or if the MS has a provisioned IP address for the provisioning SGW at804, a secure tunnel is established to the provisioning SGW in block806. Thereafter, if the MS has a provisioned or derived FQDN of the provisioning UNC at808, the MS will perform a DNS Query to resolve the FQDN to an IP address for the provisioning UNC in block810. Thereafter, or if the MS has a provisioned IP address for the provisioning UNC at812, a TCP connection is established to the provisioning UNC in block814and the provisioning UNC is queried for the default UNC in block816. If there is no response, the no response procedures are executed in block810. If the query is rejected, the rejection procedures are executed in block820. The no response procedures810and rejection procedures820are described in more detail in reference toFIG. 11.

If the query is accepted and an IP address for the default UNC is received based on MS location information at822, a secure tunnel to the default SGW is established in block826. On the other hand, if the query is accepted and an FQDN of the default UNC and associated default SGW is received based on MS location information at824, a DNS query is performed to resolve the FQDN to an IP address for the default SGW in block828and a secure tunnel to the default SGW is established in block830. If the MS has a FQDN of the default UNC at832, a DNS query is performed to resolve the FQDN to an IP address for the default UNC in block834. Thereafter, or if the MS has an IP address for the default UNC at836, or the secure tunnel has been established in block826, a TCP session to port on the default UNC is set up in block838. The MS then requests registration on the default UNC in block840.

If the request is accepted, the registration is completed and service is established in block842. If there is no response, the no response procedures are executed in block844. If the request is rejected, the rejection procedures are executed in block846. The no response procedures844and rejection procedures846are described in more detail in reference toFIG. 1. If a re-direct is received along with an IP address for the serving UNC and associated serving SGW at848, a secure tunnel to the serving SGW is established in block852. On the other hand, if the re-direct is received along with a FDQN of the serving UNC and associated serving SGW at850, a DNS query is performed to resolve the FQDN to an IP address for the serving SGW in block854and a secure tunnel to the serving SGW is established in block856. If the MS has a FQDN of the serving UNC at858, a DNS query is performed to resolve the FQDN to an IP address for the serving UNC in block860. Thereafter, or if the MS has an IP address for the serving UNC at862, or the secure tunnel was established in block852, a TCP session to port on the serving UNC is set up in block864. The MS then requests registration on the serving UNC in block866.

If the request is accepted, the registration is completed and service is established in block868. If there is no response, the no response procedures are executed in block870. If the request is rejected, the rejection procedures are executed in block872. The no response procedures870and rejection procedures872are described in more detail in reference toFIG. 11. If a re-direct is received the process repeats at points874to848and876to850.

Referring now toFIG. 11, a flow chart depicting rejection procedures516(FIG. 5),820(FIG. 8),846(FIG. 9) and 872(FIG. 10) and no response procedures818(FIG. 8),844(FIG. 9) and 870(FIG. 10) in accordance with one embodiment of the present invention is shown. If the rejection is network congestion or there is no response, and no previous attempt has failed, as determined in decision block900, the MS will wait before initiating the next discovery or registration attempt in block902. If, however, a previous attempt has failed, as determined in decision block900, and there have been less than five failed attempts, as determined in decision block904, the waiting time will be doubled in block906and the MS will wait before initiating the next discovery or registration attempt in block902. If, however, there have been five failed attempts, as determined in decision block904, the discovery or registration process is restarted in block908.

If the rejection was Location Not Allowed, the MS will not attempt discovery or registration from this forbidden location, i.e., country, PLMN or location indicated in the URR DISCOVERY REJECT message, in block910and the MS can retry discovery or registration procedure with a stored provisioning UNC in block912when it is no longer in a forbidden location. If the rejection was AP Not Allowed, no service is available on the joined AP in block914and the MS can retry discovery or registration procedure on another AP in block916. If the rejection was Redirection Due to Load Balancing, the MS is re-directed to another UNC in block918. If the rejection was Restart Discovery at Provisioning UNC, the MS restarts the discovery procedure by contacting the stored provisioning UNC in block920. If the rejection was UMA Service Not Allowed or IMSI Not Allowed or the rejection is Unspecified, no service is available and no re-attempts to register are allowed in block922.

Now referring toFIG. 12, a flow chart1200depicting a redirection counter system on a MS1202in accordance with the present invention is shown. If this is the first registration attempt by the MS1202, as determined in decision block1204, the redirection counter is set to zero in block1206. Thereafter, and if this is not the first registration attempt by the MS1202, as determined in decision block1204, the registration request containing the redirection counter is sent to the appropriate UNC. If the MS1202receives a re-direct response, as determined in decision block1210, the redirection counter is incremented in block1212. Thereafter, or if a re-direct response is not received, the process returns to decision block1204to send out the next registration request.

In another embodiment, the present invention provides a method for limiting redirections of mobile stations in an unlicensed radio access network by initializing a redirection counter, including the redirection counter in a registration request, and incrementing the redirection counter each time a re-direct response is received in response to the registration request. Typically, the redirection counter is initialized to zero on a first registration request. Additional steps may include creating the registration request, sending the registration request to an unlicensed mobile access network controller, or receiving a response to the registration request.

Referring now toFIG. 13, a flow chart depicting reducing the number of redirections from a UNC1302in accordance with the present invention is shown. The UNC1302receives a registration request containing a redirection counter in block1304. If the redirection counter does not exceed a certain value, as determined in decision block1306, normal processing continues in block1308. If, however, the redirection counter exceeded the value, as determined in decision block1306, the registration request is rejected in block1310and the event is logged1312.

Similarly, the present invention provides a method for limiting redirections of mobile stations in an unlicensed radio access network by receiving a registration request that contains a redirection counter, processing the registration request normally whenever the redirection counter does not exceeds a value, and sending a reject response whenever the redirection counter exceeds a value. The method may also include the steps of creating a log whenever the redirection counter exceeds the value, or creating the reject response. The methods described above can be implemented using a computer program embodied on a computer readable medium wherein each step is executed by one or more code segments.

The present invention also provides an electronic communication that includes a registration request and a redirection counter. The electronic communication is typically sent from a mobile station to an unlicensed mobile access network controller in an unlicensed radio access network.

Moreover, the present invention provides an apparatus within an unlicensed radio access network that limits redirections of one or more mobile stations by using a redirection counter to determine whether to reject a registration request. Likewise, the present invention provides an unlicensed-radio access system connected to a core network portion of a licensed mobile network, the unlicensed-radio access system including one or more access points adapted to communicate with mobile stations over an unlicensed-radio interface, one or more unlicensed mobile access point controllers connected to the core network portion of the licensed mobile network and a fixed broadband network connected to both the access points and the unlicensed mobile access point controllers, wherein the one or more unlicensed mobile access point controllers use a redirection counter in each registration request from the mobile stations to limit redirections of the mobile stations.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification, but only by the claims.