Abstract:
The invention provides a method of controlling LA-based update procedure in a mobile radio communications network, and including the step of determining the reason for the LA-based update request, and varying connection procedures upon receipt of such request and responsive to the determination, and so can also provide a mobile radio communications network device arranged for operation in the network including plural terminal devices, the network device being arranged to forward to a target network device an indication of reasoning for a LA-based update procedure (during CSFB to the legacy system for example). Further the invention can also be embodied in a mobile radio communications network target device arranged for operation in the network including plural terminal devices and further arranged to monitor for an indication from a network device for reasoning for a LA-based update procedure, and further arranged to vary a connection procedure responsive to the said monitoring.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/JP2011/051840 filed Jan. 24, 2011, claiming priority based on United Kingdom Patent Application No. 1002446.1 filed Feb. 15, 2010, the contents of all of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a network update procedure and to related network devices, and, in particular, to Location Area updates within a mobile radio communications network. 
     BACKGROUND ART 
     Due to the very nature of a mobile radio communications network, such as a cellular network, there often arises a requirement for a mobile terminal device such as so-called User Equipment to change its manner of operation whether due to a handover between cells and/or a handover between networks and related communication systems. 
     In view of the wide variety of communication systems, and in particular legacy communication systems that are in existence, to optimise connectivity and to minimize limiting effects on handset terminal performance, functionality allowing movement between different systems can provide particular advantageous. 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in view of the requirements of such different systems, it is often disadvantageously found that noticeable delays arise when both seeking to switch between such systems and subsequently establishing connectivity within the new system. 
     The present invention seeks to provide for a method of controlling update procedures within a network system and having advantages over known such procedures. 
     As a further illustration, according to current 3GPP Re1-8 and Re1-9 specifications, when the User Equipment (UE) moves to legacy 2G/3G systems from, for example, an Evolved Packet System (EPS) which will generally be for Circuit Switched Fall Back (CSFB) purposes, the UE can initially be arranged to determine the Location Area (LA) within the new cell. 
     If the LA is identified as having changed, the UE initially performs a LA update procedure. If the target 2G/3G system is in a Network Mode of Operation (NMO) II then an LA update procedure is performed, whereas if the target 2G/3G system is in NMO I as defined in 3GPP technical specification 23 272, a combined RA (Routing Area)/LA update procedure is performed. Subsequent to the update procedure, a UE then continues with the circuit switched call establishment. 
     It is recognised that a potential limitation with CSFB is the additional delay required to establish call set-up. In particular, it is noted that it takes a relatively long time for the UE in CSFB to switch to the legacy target 2G/3G system, whether via handover or NACC (Network Assisted Cell Change), or whether via connection re-direction, and further delay is also experienced when it is required to make or to answer a circuit switched call. 
     As examples, typical added delays in the call-setup procedure within CSFB can be in the order of between two and five seconds. 
     It is also noted that, upon the UE attempting a LA or combined RA/LA update in CSFB, the delay could be further exasperated if the mobile switching centre (MSC) or the serving GPRS (General Packet Radio Service) support mode (SGSN) is controlled to run some or all of the security procedures such as, for example, the authentication procedure, identification procedure and/or TMSI (Temporary Mobile Subscriber Identity) re-allocation procedure. 
     Since some of these procedures also involve reading of the SIM (Subscriber Identity Module)/USIM (Universal SIM) card, they can be considered as potential sources of considerable extra delay to calls set up within CSFB. 
     The present invention in particular seeks to provide for system update procedures, and related network devices, which can offer advantages over such known limitations. 
     Solution to Problem 
     According to the first aspect of the present invention there is provided a method of controlling Location Area-based update procedure in a mobile radio communications network, and including the step of determining the reason for the Location Area-based update request, and varying connection procedures upon receipt of such request and responsive to the said determination. 
     Unnecessary connection procedures can then readily be avoided so as to reduce delays associated with the update. 
     As will be appreciated, the determination can control the connection procedure of a network element. 
     The method can include the step of providing at a network element an indication of the said reason for the Location Area-based update request. 
     As the step of determining the said reason within a target network element, can also be provided and the said target network element can comprise a Mobile Switching Centre or a Serving GPRS Support Node. 
     The connection procedure can comprise a security procedure and in the form of at least one of authentication procedure, an identification procedure or a TMSI re-allocation procedure. 
     Of course the said step of determining the reason for the update request can be based on service-type signalling and/or a determination of whether Circuit Switched Fall-Back is required. 
     Advantageously a time period responsive to result of the said determination step, can be provided and the method can further include the step of monitoring for a Location Area-based update request during the said time period. 
     According to another aspect of the present invention there is provided a mobile radio communications network device arranged for operation in the network including a plurality of terminal devices, the network device being arranged to forward to a target network device an indication of reasoning for a Location Area-based update procedure. 
     According to a further aspect of the present invention there is provided a mobile radio communications network target device arranged for operation in the network including a plurality of terminal devices and further arranged to monitor for an indication from a network device as defined above for reasoning for a Location Area-based update procedure, and further arranged to vary a connection procedure responsive to the said monitoring. 
     The target device can be arranged to vary connection procedure responsive to identification of a relocation request originating from a terminal device, or can further be arranged to vary connection procedure responsive to identification of a service request originating from a terminal device. 
     In particular, the target device can be arranged to vary connection procedure responsive to identification of a Circuit Switched Fall-Back originating from a terminal device. 
     The target device can also include means for establishing a time period and arranged to monitor for receipt of a Location Area-based update during said time period and so as to initiate variation in the connection procedure. 
     Advantageous Effects of Invention 
     According to one particular aspect of the present invention therefore it can be appreciated that the control arrangement advantageously seeks to make the MSC/SGSN aware of the requirement behind the request for the LA update procedure, whether or not the update procedure is for CSFB purposes such that connectivity procedure such as the related security procedures can be employed in a modified and, ideally, less intensive manner. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a flow diagram illustrating one particular aspect of the present invention. 
         FIG. 2  is a signalling diagram between network elements according to an exemplary embodiment of the present invention. 
         FIG. 3  is a further signalling diagram between network elements according to another aspect of the present invention. 
         FIG. 4  is a schematic block diagram of a network element according to one exemplary embodiment of the present invention. 
         FIG. 5  is a schematic block diagram of a network element according to another exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Exemplary embodiments of the invention will be described hereinafter by way of example only, with reference to the accompanying drawings. 
     Within the current text of the illustrated exemplary embodiments, the connectivity procedure that is to be varied in accordance with the reasoning behind the update request comprises one or more of the security procedures associated with the update. 
     As will be appreciated, if the update is required for CSFB purposes, then in order to reduce the burden that delays within CSFB can place with the overall update procedure revised versions of the associated security procedures can be provided. 
     As one example, revised version of the authentication procedure can be employed. It is of course noted that some network operators routinely employ such authentication for example, when RAT (Radio Access Technology) or PLMN (Public Land Mobile Network) changes are required. Generally under normal circumstances, the LA update procedures do not necessarily exhibit automatic delays. However, it is noted that if the LA update procedure occurs in relation to CSFB, the delay to the call setup is relatively large and disadvantageously noticeable. A revised security procedure according to the present invention can require that authentication is exercised only when merely needed for example, when it is identified that there is a problem with the UE context exchange between the MME (Mobility Management Entity) and the SGSN/MSC. As illustrated in  FIG. 1 , the authentication procedure can advantageously be skipped if required thereby advantageously reducing the delay experienced in the CSFB procedure. 
     In addition, or as an alternative, identity check procedures could be employed only when required and not necessarily routinely and in the same manner as the aforementioned authentication procedure. 
     Yet further, TMSI re-allocation procedures can likewise be employed only when required and not on a routine basis. Also, if required, a shorter version of the TMSI re-allocation within the LA accept message might be adopted rather than a stand alone TMSI re-allocation procedure. 
     Considerations in relation to the change the authentication procedure are illustrated in relation to  FIG. 1 . As will be seen, at the start  10  of the procedure, an indication of the requirement for authentication is provided at step  12  and prior to receipt of a location update request by a specifically identified User Equipment (UE 1 )  14  is received at the SGSN/MSC  16 . 
     The SGSN/MSC  16  determines whether or not to switch to a new radio access technology is required at  18  and, if not, it is determined at step  20  whether or not the UE 1  context have been fetched from the MME. If no such fetching of the context is determined at step  20 , the procedure continues to its conclusion at step  22  as indicated. However, if at step  20 , is determined at the UE 1  context has been fetched from the MME, it is confirmed at step  24  it is confirmed that the status for the authentication only remains “false”. 
     Returning to step  18 , it is there determined that there has been a switch to a new radio access technology, the procedure continues to  26  where the status for the requirement for authentication is revised to “true” and a determination is subsequently made at step  28  as to whether a CSFB timer for the specific user equipment UE 1  is still running. If at step  28 , it is determined that the timer is still running, then the investigation at step  20  concerning fetching of the UE 1  context from the MME is determined as before. 
     If, however, it is determined at step  28  that the CSFB timer is not running, then the procedure continues to its conclusion at step  22  as indicated. 
     An important aspect of the present invention therefore is the provision of the aforementioned CSFB timer and this is described further in relation to  FIGS. 2 and 3  of the present application. 
     Turning now to  FIG. 2 , there is illustrated a signalling diagram between a user equipment  30 , MME  32  and SGSN  34 , a network system and wherein the user equipment  30  is evolved in a handover from an evolved packet system to a legacy 2G/3G system for example, CSFB purposes. As illustrated, the MME  32  issues a forward relocation request signal  38  which includes both indication of the cause for such a request (in this case that CSFB is required) and also confirms the identify of the specific user equipment  30 . 
     Upon receipt of the request  38  the SGSN  34  functioning as a target network device checks and identifies both the cause so the aforementioned cause and the UE identify, and upon identifying the cause as CSFB-related, the SGSN  34  initiates a timer, referred to herein as the “CSFB timer” for that specific UE  30  and at step  40 , with that timer running, should an actual LA update such as signal  42  be received from the user equipment  30 , the SGSN  34  can be arranged to provide at step  44  less intense, or “light security versions” within the LA update procedure thereby limiting the delays that might arise from the SF procedure. 
     The appropriate “light security” procedures  46  are then employed as required. 
     That is, during a HO (Handover) for CSFB purposes to target 2G/3G system in NMO  1  configuration (see FIG.  2 )—the target SGSN checks the “RAN cause” Ie and the UE identity in the Forward Relocation Request signal from source MME to target SGSN. If the value of the RAN cause indicates CSFB then the SGSN shall start a timer (let&#39;s call it “CSFB timer”, of few seconds) for the UE that is in CSFB. If during the span of this CSFB timer the SGSN receives a request for LA update (by combined RA/LA update procedure) from the identified UE in CSFB, the SGSN will exercise light security during this LA update. 
     Turning now to  FIG. 3 , there is provided a signalling diagram according to another aspect of the present invention. 
     Again, a UE  30  and an associated MME  32  are indicated but, in this exemplary embodiment, the target network device comprises MSC  48 . 
     As before, a handover is initiated from the user equipment  34  at step  50  from an Evolved Packet System to a legacy 2G/3G system for CSFB purposes but this time a Service Request signal with specific service type indicator that indicates CSFB and UE identifier (for example IMSI)  52  is provided by the MME  32  to the MSC  48 . 
     The MSC checks the service type and UE identifier and, if it is noted that the service type comprises “CS MO (Mobile Originated) call indicators” or any other indicator that indicates a request for CSFB the MSC starts the CSFB timer for that specific user equipment  30  as indicated at  54 . 
     Then, if, within the period of the aforementioned timer, an LA update signal  56  (and via an LA update procedure) is received from the UE  30  at the MSC  48 , the reduced less intense, version of the security procedures are initiated such that “light security” functionality is provided as indicated at step  58 . 
     During HO for CSFB purpose to target 2G/3G system in NMO II configuration and MSC not changed (see  FIG. 3 ). If the CSFB is for MT (Mobile Terminated) call, the MSC already is aware of UE identity that is in CSFB. If the CSFB is for MO call, the MME indicates that to the MSC over the SGs interface (interface between the MME and the MSC/VLR (Visitor Location Register)) via “CS MO call indicator” (CSFB indicator). In both (MT and MO) cases the MSC starts a CSFB timer for that UE in CSFB. If during the span of the CSFB timer the MSC receives a request for LA update (by LA update procedure) from the identified UE in CSFB, the MSC will exercise light security during this LA update. 
     Turning now to  FIG. 4 , there is provided schematic illustration of a network device such as a mobile management entity  32  as illustrated in  FIGS. 2 and 3 . 
     The MME  32  includes transceiver arrangement and related interfaces  62 , an appropriate control processor  64  and associated memory arrangement  66 . As will be appreciated the control processor  64  is arranged to provide control signalling to the target network elements such as the SGSN  34  of  FIG. 2  or the MSC  48  of  FIG. 3  serving to provide service information to indicate the reasoning behind the change request. 
     Turning now to  FIG. 5 , there is provided a schematic illustration of a target network elements such as the SGSN  34  of  FIG. 2  and the MSC  48  of  FIG. 3 . 
     As illustrated, the target network element includes transceiver functionality and related interfacing  68  and which connects to a control processor  70  which includes specific timer functionality  72  so as to provide for the required time period within which an actual update request is monitored at the target network element as discussed hereinbefore. 
     Of course, the network target element  34 ,  48  also includes a memory arrangement  74  as indicated and it should of course be appreciated that the functionality of the device as illustrated in  FIGS. 4 and 5  can be provided by way of software control instructions if required. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. 
     For example, the present invention can be materialized by a computer program for causing a CPU (Central Processing Unit) or the like to execute the processes shown in  FIG. 2  or  3 . 
     The program can be stored and provided to a computer using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (compact disc read only memory), CD-R (compact disc recordable), CD-R/W (compact disc rewritable), and semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). The program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g. electric wires, and optical fibers) or a wireless communication line. 
     This application is based upon and claims the benefit of priority from United Kingdom patent application No. 1002446.1, filed on Feb. 15, 2010, the disclosure of which is incorporated herein in its entirety by reference. 
     REFERENCE SIGNS LIST 
       30  UE 
       32  MME 
       34  SGSN 
       48  MSC 
       62  TRANSCEIVER ARRANGEMENT AND RELATED INTERFACES 
       64  CONTROL PROCESSOR 
       66  MEMORY ARRANGEMENT 
       68  TRANSCEIVER FUNCTIONALITY AND RELATED INTERFACING 
       70  CONTROL PROCESSOR 
       72  TIMER FUNCTIONALITY 
       74  MEMORY ARRANGEMENT