Abstract:
Techniques are provided for handling of a first type call as it affects an authentication procedure in a communication network. For example, it is assumed that, in a communication network, a first computing device comprises user equipment and a second computing device comprises an authentication function for authenticating the user equipment. Thus, a method comprises receiving at the second computing device from the first computing device an authentication rejection message, receiving at the second computing device from the first computing device a first type call indicator message, and making a decision regarding proceeding with or dropping an authentication procedure for the first computing device at the second computing device based on the receipt of the authentication rejection message and the first type call indicator message.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Continuation of U.S. patent application Ser. No. 12/437,276, filed May 7, 2009, which claims the benefit of U.S. Provisional Application No. 61/169,929, filed on Apr. 16, 2009. The disclosures of these applications are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to communication networks, and more particularly to communication networks wherein provision is made for handling of an emergency call as it affects an authentication procedure. 
     BACKGROUND 
     This section introduces aspects that may help facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art. 
     According to the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T), by way of example, a Next Generation Network (NGN) is a packet-based network able to provide services including telecommunication services and able to make use of multiple broadband, quality-of-service (QoS)-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies. It may offer unrestricted access by users to different service providers. It may support generalized mobility which may allow consistent and ubiquitous provision of services to users. 
     Consistent with NGN development efforts, Long Term Evolution (LTE) is a Third Generation Partnership Project (3GPP) with an aim of trying to improve the Universal Mobile Telecommunications System (UMTS) mobile phone standard and to provide an enhanced user experience and simplified technology for next generation mobile broadband. LTE radio access technology has been referred to as Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and the network has been referred to as an Evolved Packet System (EPS). Architecture of the EPS network is described in the 3GPP Technical Specifications 23.401 and 23.402, the disclosures of which are incorporated herein by reference in their entirety. 
     SUMMARY 
     Embodiments of the invention provide techniques for handling of an emergency call as it affects an authentication procedure in a communication network. 
     In a first aspect, wherein it is assumed that, in a communication network, a first computing device comprises user equipment and a second computing device comprises an authentication function, a method comprises receiving at the second computing device from the first computing device an authentication rejection message, receiving at the second computing device from the first computing device a first type call indicator message, and making a decision regarding proceeding with or dropping an authentication procedure for the first computing device at the second computing device based on the receipt of the authentication rejection message and the first type call indicator message. 
     In one or more illustrative embodiments, the authentication procedure may comprise: sending in accordance with a first authentication attempt an authentication request from the second computing device to the first computing device; receiving at the second computing device from the first computing device an authentication failure message, the authentication failure message being sent by the first computing device in response to the authentication request sent by the second computing device; and initiating at the second computing device a second authentication attempt in response to the authentication failure message; such that the second authentication attempt is ceased at the second computing device in response to the first type call indicator message. The second authentication attempt may comprise a re-synchronization procedure. 
     The communication network may comprise an Evolved Packet System (EPS) architecture, wherein the first computing device comprises Mobile Equipment (ME) and a UMTS Subscriber Identity Module (USIM), and the second user device comprises a Mobility Management Entity (MME). The authentication procedure may comprise an Authentication and Key Agreement (AKA) protocol. 
     Advantageously, illustrative embodiments of the invention provide improved performance of packet-based emergency call setup in an LTE environment. 
     These and other features and advantages of the present invention will become more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a mobile roaming architecture according to an embodiment of the invention. 
         FIG. 2  is a diagram of an authentication procedure according to an embodiment of the invention. 
         FIG. 3  is a diagram of a re-synchronization procedure according to an embodiment of the invention. 
         FIG. 4  is a diagram of an emergency call handling procedure according to an embodiment of the invention. 
         FIG. 5  is a diagram of a hardware architecture of a communication network suitable for implementing authentication and emergency call services according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of an LTE (or EPS) roaming architecture  100  is depicted in  FIG. 1 . As shown, the architecture  100  includes a Home Public Land Mobile Network (HPLMN)  110  and a Visited Public Land Mobile Network (VPLMN)  120 . 
     In HPLMN  110 , there is illustratively shown a Home Subscriber Server (HSS)  112 , a packet data network (PDN) gateway server  114 , a policy and charging rules function (PCRF) server  116 , and network operator&#39;s Internet Protocol (IP) services  118 . These IP services may include but are not limited to IP Multimedia Subsystem (IMS), a Packet Switching System (PSS), etc. As used herein, a “network operator” (or “telecom operator”) may be defined as a company that owns and operates a telecommunications network and thus provides services (IMS, PSS, etc.) to subscribers, e.g., an NGN operator is a network operator that owns and operates an NGN network. Thus, two defining features of a network operator may be: (1) owning the network; and (2) providing services to subscribers, for a charge. A third feature may be that the network operators are typically regulated, which may make them legally responsible for ensuring privacy of communications, etc. Examples of network operators may include, by way of example only, AT&amp;T or Verizon. 
     In VPLMN  120 , there is illustratively shown Serving GPRS Support Node (SGSN)  122  (where GPRS refers to a General Packet Radio Service) for legacy networks such as but not limited to GSM Edge Radio Access Network (GERAN, where GSM refers to a Global System for Mobile communications) and UTRAN (UMTS Terrestrial Radio Access Network). Also illustratively shown is Mobility Management Entity (MME)  124 , serving gateway  126 , E-UTRAN (Evolved UTRAN network)  128 , and User Equipment  130 . 
     The serving gateway  126  is a local mobility anchor for E-UTRAN mobility, switching packets between interfaces for mobiles in connected mode. For mobiles in idle mode, the serving gateway  126  is responsible for terminating the down-link data path and when down-link data is received, buffering the data and triggering a paging procedure by signaling the MME  124 . 
     The MME  124  is the control-plane function for E-UTRAN access. It is responsible for authentication and critical management for mobile devices as well as for tracking and paging procedures for mobiles in idle mode. 
     The UE  130  (or Mobile Station (MS)) is composed of Mobile Equipment (ME) and UMTS Subscriber Identity Module (USIM). Examples of mobile station or user equipment may include but are not limited to a mobile telephone, a portable computer, a wireless email device, a personal digital assistant (PDA) or some other user mobile communication device. 
     The E-UTRAN  128  is composed of access nodes including at least one eNodeB (eNB) node, which serves as a base station for the UEs to access the VPLMN network. 
     In one embodiment, UE  130  (ME+USIM), eNodeB (E-UTRAN  128 ), MME  124 , and HSS  112  are the network elements affected by illustrative principles of the invention, as will be explained below in detail. 
     Thus, it is to be understood that UE (User Equipment) is ME (Mobile Equipment)+USIM. USIM is a software and file system located on the physical device UICC (which is a Universal Integrated Circuit Card, commonly known as the “SIM card” in a mobile phone). UICC is a tamper-resistant Smart Card. USIM terminates AKA (Authentication and Key Agreement), an authentication and key agreement protocol (cited below) standardized by 3GPP. UMTS and EPS use similar versions of AKA. 
     This is how a successful AKA procedure typically operates:
         1. Upon initial attach, UE sends its attach request with International Mobile Subscriber Identity (IMSI) in it to eNodeB (cell site, part of E-UTRAN).   2. eNodeB forwards it to MME, the MME looks at the routing labels in the IMSI and knows where the UE&#39;s home system with its HSS is located.   3. MME forwards a request message with IMSI in it to that HSS.   4. HSS does certain calculations: selects random # RAND, uses RAND and shared with USIM root key K to calculate authentication token AUTN, XRES (Expected Response), and another root key K ASME .   5. HSS than replies to MME with AKA AV (Authentication Vector). EPS AV has the following parameters: RAND, AUTN, XRES, and K ASME .   6. When MME receives EPS AV, it holds on to XRES and K ASME , and forwards RAND and AUTN through eNodeB and ME to the USIM.   7. The first thing that USIM does is authenticate AUTN, and ONLY after its successful authentication, USIM calculates RES and its own K ASME .   8. Then USIM sends root key K ASME  to ME for derivation of the other EPS keys, and sends RES through ME and eNodeB to the MME.       

     MME compares RES (received from the USIM) with XRES (received from the HSS). If they are equal to each other, then USIM (and USIM+ME=UE) is accepted to the serving network. 
     Accordingly, in one embodiment, the UE is assumed to support an application protocol that is aware of the Authentication and Key Agreement (AKA) algorithm. Furthermore, in this illustrative embodiment, the UE is assumed to support a UMTS Subscriber Identity Module (USIM) application that implements the AKA algorithm. Details on USIM applications may be found in 3GPP Technical Specifications TS 31.102 and TS 31.103, the disclosures of which are incorporated by reference herein in their entirety. Details on AKA may be found in is 3GPP Technical Specification TS 33.102, the disclosure of which is incorporated by reference herein in its entirety. 
     While this particular embodiment utilizes aspects of a 3GPP authentication protocol, it is to be understood that such a protocol is one example of a security protocol that may be used. Thus, other suitable security protocols that provide similar facilities and features as the 3GPP authentication protocol may be considered as being within the scope of embodiments of the invention. 
     The E-UTRAN Initial Attach procedure is used for Emergency Attach by UEs that need to perform emergency services but cannot gain normal services from the network. These UEs are in limited service state (Limited Service Mode or LSM) as defined in 3GPP Technical Specification TS 23.122 (“Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode”), the disclosure of which is incorporated by reference herein in its entirety. 
     UEs that can attach normally to a cell, i.e., UEs that are not in limited service state, shall initiate normal initial attach when not already attached. 
       FIG. 2  depicts an illustrative authentication and key establishment procedure  200 , e.g., Authentication and Key Agreement (AKA) procedure or protocol. The purpose of the AKA procedure is to authenticate the user and establish a new root key K ASME  between the MME and the USIM. During the authentication, the USIM verifies the freshness of the authentication vector that is used. 
     It is to be understood that the messages sent between the entities shown in  FIG. 2  (and in  FIGS. 3 and 4  to be described below) are signals that are transmitted and received in accordance with the one or more communication protocols that are implemented by the entities. It is also to be understood that the sequence of the message transfers can be rearranged or modified (with some additional messages being added and/or some being deleted) while still providing one or more of the advantages attributable to the principles of the invention. 
     The MME invokes the procedure by selecting the authentication vector (AV). The MME  124  sends to the USIM (UE  130 ) the random challenge RAND and an authentication token for network authentication AUTN from the authentication vector. This is shown in step  1  of  FIG. 2   
     In step  2  of  FIG. 2 , the USIM sends a response to the random challenge back to the MME in the form of an authentication response RES. Assuming an appropriate response, authentication proceeds as normal (i.e., as described above). 
     However, assuming a synchronization failure, the UE  130  sends a synchronization failure message (user authentication reject CAUSE message in step  3  of  FIG. 2 ) to the MME  124  rather than the appropriate response. 
     Upon receiving a synchronization failure message from the UE, the MME sends an authentication data request with a “synchronization failure indication” to the HSS  112 , together with the parameters:
     RAND sent to the MS in the preceding user authentication request, and   AUTS received by the MME in the response to that request, as described in TS 33.102.   

     This is depicted in  FIG. 3 , which depicts a procedure  300  for achieving re-synchronization by combining a user authentication request answered by a synchronization failure message with an authentication data request with synchronization failure indication answered by an authentication data response. 
     As shown, after step  1  (MME sends challenge) and step  2  (UE sends a AUTS response), the MME sends RAND and AUTS to HSS in step  3 . 
     Note that the MME  124  will not react to unsolicited “synchronization failure indication” messages from the UE  130 . 
     Note also that the MME  124  does not send new user authentication requests to the user before having received the response to its authentication data request from the HSS  112  (or before it is timed out). 
     When the HSS  112  receives (in step  3  of  FIG. 3 ) an authentication data request with a “synchronization failure indication,” it acts as follows:
     1. The HSS retrieves SQN MS  from Conc(SQN MS ) by computing Conc(SQN MS )⊕f5* K (RAND). Note that SQN refers to Sequence Number and ‘Cont’ refers to concatenation function.   2. The HSS checks if SQN HE  is in the correct range, i.e., if the next sequence number generated SQN HE  using would be accepted by the USIM.   3. If SQN HE  is in the correct range then the HSS continues with step (6) below, otherwise it continues with step (4) below.   4. The HSS verifies AUTS.   5. If the verification is successful, the HSS resets the value of the counter SQN HE  to SQN MS .   6. The HSS sends an authentication data response with a new batch of authentication vectors to the MME (Qi in step  4  of  FIG. 3 ). If the counter SQN HE  was not reset, then these authentication vectors can be taken from storage, otherwise they are newly generated after resetting SQN HE . In order to reduce the real-time computation burden on the HSS, the HSS may also send only a single authentication vector in the latter case.   

     Whenever the MME  124  receives a new authentication vector from the HSS  112  in an authentication data response to an authentication data request with synchronization failure indication, it deletes the old one for that UE  130  in the MME. 
     The UE  130  may now be authenticated based on a new authentication vector from the HSS  112 . 
     A problem may arise, however, during the course of the above authentication session. Assume that the UE  130  is in need of making an Emergency Call (EC) while in the middle of AKA (re-)authentication and, for one or more reasons, AUTN validation on the USIM fails (user authentication reject CAUSE in  FIG. 2 ). 
     Under normal conditions (see, e.g., the above cited TS 33.102), the UE  130  will either request new AKA authentication upon MAC (Media Access Control) authentication failure, or will enter AUTS procedure (re-synchronization with its HSS) upon SQN mismatch. In such cases, the MME  124  will not receive RES and UE  130  will not produce K ASME . 
     In other words, the UE  130  will wait for either new AKA (MAC failure), or resynchronization with HSS and new AKA after that. New AKA round-trip can be up to about 10-15 seconds, and resynchronization with HSS might take about the same time. In the worst case, the UE  130  will have to wait about 30 seconds to be able to proceed with the intended call. The MME  124  can neither control re-synchronization time, nor estimate it for communicating to the UE  130  intending to make emergency call. It is realized that this feature interaction may be unacceptable and/or unnecessary for such emergency calling. 
     In accordance with one embodiment, a solution is provided as follows.  FIG. 4  illustrates a procedure  400  for implementing such a solution. 
     It is realized that since the ME of the UE  130  (note that, as explained above, the ME is part of the UE  130  but functionally separate from the USIM) knows of the intent to make an emergency call, the ME can communicate its intent via an Emergency Call (EC) Indicator to the MME  124 . 
     Assume, as shown in  FIG. 4 , that the MME sends user authentication request in step  1  to the ME (of the UE), which then forwards request in step  2  to the USIM (also of the UE). Further assume that upon receiving Authentication Failure from the USIM (step  3 ), the ME forwards it to the MME (step  4 ) and will stop expecting a new AKA, or re-synchronization+new AKA. Instead, it will assume unauthenticated attach mode and proceed with such mode. 
     On the network side, the MME  124  will know of the UE&#39;s intent to make an EC via EC Indicator sent in step  5 . Upon receiving Authentication Failure from the UE, the MME will stop following the normal authentication/re-synchronization procedure (outlined above in  FIGS. 2 and 3 ). Instead, the MME will assume unauthenticated attach mode and proceed with such mode. The MME will allow only the EC to go through. 
     Note that since the EC indicator message in the example above is sent after the authentication failure message is received by the MME, the authentication procedure may advantageously be ceased or dropped. Alternatively, the EC indicator message may be received earlier in the same authentication session but before authentication actually begins, in which case, the authentication procedure may advantageously not be initiated or dropped altogether. Thus, it is to be appreciated that the EC indicator message, whenever it is received in the session, may advantageously serve to permit the MME to make a decision regarding the authentication procedure (e.g., whether to drop or proceed). 
     In any case, after the EC call ends, both parties (UE and MME) reset themselves to a normal authentication procedure. It is the presence of EC Indicator that essentially controls ME and MME behavior during authentication failure while attempting to make the EC. 
     For an Emergency Attach, the ME of the UE sets the Attach Type to “Emergency” and proceeds with an unauthenticated Emergency Call. 
     If the MME  124  is configured to support Emergency Attach and the UE indicated Attach Type “Emergency,” the MME skips the authentication and security setup or the MME accepts that the authentication may fail and continues the attach procedure. 
     If the MME  124  is not configured to support Emergency Attach, the MME rejects any Attach Request that indicates Attach Type “Emergency.” 
     Lastly,  FIG. 5  illustrates a generalized hardware architecture of a communication network  500  suitable for implementing authentication and emergency call handling services according to the above-described principles of the invention. 
     As shown, user equipment  510  (corresponding to UE  130 ) and MME server  520  (corresponding to MME  124 ) are operatively coupled via communication network medium  550 . The network medium may be any network medium across which the user equipment and the web servers desire to communicate. By way of example, the network medium can carry IP packets end to end and may involve any of the communication networks mentioned above. However, the invention is not limited to a particular type of network medium. Typically, user equipment  510  could be a client machine or device, and MME  520  could be a server machine or device. Not expressly show here, but understood to be operatively coupled to the MME and/or the UE, are the other network elements shown in  FIG. 1  (which can have the same processor/memory configuration described below). 
     As would be readily apparent to one of ordinary skill in the art, the servers and clients may be implemented as programmed computers operating under control of computer program code. The computer program code would be stored in a computer (or processor) readable storage medium (e.g., a memory) and the code would be executed by a processor of the computer. Given this disclosure of the invention, one skilled in the art could readily produce appropriate computer program code in order to implement the protocols described herein. 
     Nonetheless,  FIG. 5  generally illustrates an exemplary architecture for each device communicating over the network medium. As shown, user equipment  510  comprises I/O devices  512 , processor  514 , and memory  516 . MME server  520  comprises I/O devices  522 , processor  524 , and memory  526 . 
     It should be understood that the term “processor” as used herein is intended to include one or more processing devices, including a central processing unit (CPU) or other processing circuitry, including but not limited to one or more signal processors, one or more integrated circuits, and the like. Also, the term “memory” as used herein is intended to include memory associated with a processor or CPU, such as RAM, ROM, a fixed memory device (e.g., hard drive), or a removable memory device (e.g., diskette or CDROM). In addition, the term “I/O devices” as used herein is intended to include one or more input devices (e.g., keyboard, mouse) for inputting data to the processing unit, as well as one or more output devices (e.g., CRT display) for providing results associated with the processing unit. 
     Accordingly, software instructions or code for performing the methodologies of the invention, described herein, may be stored in one or more of the associated memory devices, e.g., ROM, fixed or removable memory, and, when ready to be utilized, loaded into RAM and executed by the CPU. That is, each computing device ( 510  and  520 ) shown in  FIG. 5  may be individually programmed to perform their respective steps of the protocols depicted in  FIGS. 2 through 4 . 
     Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be made by one skilled in the art without departing from the scope or spirit of the invention.