Abstract:
A method of managing mobility of a mobile terminal in a communication network comprising a plurality of access points and an access points discovery server adapted for providing the mobile terminal with a list of network access points to which the mobile terminal can connect is disclosed. In some embodiments, the method comprises the following processes implemented by the access points discovery server: recovery, from a credits management server, of a credits usage profile associated with the mobile terminal and generation of the list of access points as a function of said credits usage profile.

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase of Application No. PCT/FR2013/051461 entitled “MANAGEMENT OF MOBILITY IN A COMMUNICATION NETWORK AS A FUNCTION OF A CREDITS USAGE PROFILE” filed Jun. 21, 2013, which designated the United States, and which claims the benefit of French Application No. 1257055 filed Jul. 20, 2012. 
     GENERAL TECHNICAL FIELD 
     The invention relates to the field of cellular communications, and more particularly the management of mobility or movement between 3GPP and non-3GPP access networks such as specified by the standard 3GPP, in particular in the technical specifications TS 24.302 and TS 24.312. 
     STATE OF THE ART 
     When a user of a mobile communications terminal is subscribed to a telecommunications operator, this telecommunications operator allows the user to connect to a communications network by means of his mobile terminal, enabling taking out a subscription to then access several types of services originating from one IP (Internet Protocol) network, such as the Internet network. 
     When this network is a 3GPP cellular network (for example, Edge, 3G, 3G+, 4G, LTE) it comprises a network core, as well as a 3GPP access network comprising a set of 3GPP access points (NodeB for 3G) by which the terminal connects. 
     In addition to the 3GPP access network, the operator can provide its subscribers with non-3GPP access points (designated by the term “hot spot”) to increase coverage and capacity of the 3GPP access network. 
     The communications terminal can provide mobility from a 3GPP access network to a non-3GPP network, and vice versa. 
     In the 3GPP standard, especially in specifications TS 24.302 and TS 24.312, an access point discovery server (Access Network Discovery and Selection Function, (ANDSF)) is provided. In particular, on request from a moving mobile terminal, this ANDSF server supplies a list of access points near the position of the mobile terminal. The access points relate to non-3GPP access networks (for example Wi-Fi, Wimax) and/or 3GPP access networks (for example Edge, 3G, 3G+, 4G, LTE). 
     In addition, this ANDSF server comprises a database comprising information on the topology of access networks and information on rules for selecting an access network, especially rules of a telecommunications operator, enabling ordering the list of types of access and access points which the terminal can preferably use. 
     To receive the list, the terminal sends a request to the ANDSF server so that in case of a change in position of the mobile terminal or in case of degradation of the quality of the radio link, the terminal can retrieve the list of available access points near the mobile terminal. 
     The mobile terminal stores in memory a list of access points to which it can connect, prepared by the ANDSF server, then moves to an access network of the list, if necessary by making use of this list of access points. 
     This list of access points is in the form of an ordered list of access points near the mobile terminal, optionally classified by types of access network (3G, 4G, Wifi, Wimax). 
     Management of mobility currently deployed by the ANDSF server is based only on connectivity criteria, optionally involving rules so that access to a service passes via a certain type of access to let the terminal obtain the service with better service quality (Quality Of Service, (QoS)). 
     But in managing mobility there is a need to consider a profile of the user of the mobile terminal relative to his needs in terms of services subscribed to from a telecommunications operator, and especially credits which the user has to utilise different access networks. 
     PRESENTATION OF THE INVENTION 
     The invention responds to this need and according to a first aspect proposes a method for management of mobility of a mobile terminal in a communications network comprising a plurality of access points and an access point discovery server adapted to supply the mobile terminal with a list of access points of the network to which the mobile terminal can connect, the method comprising the following steps conducted by the access point discovery server: 
     retrieval, from a credits management server, of a credits usage profile linked to the mobile terminal; 
     generation of the list of access points as a function of said credits usage profile. 
     The method of the invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combinations:
         retrieval of the credits usage profile comprises sending a request from the credits management server and the receipt of at least one message comprising the credits usage profile, sent by the credits management server following receipt of said request;   the request is a request subscribing to updating of credits and the message comprising the credits usage profile is sent by the credits management server following modification of the credits usage profile linked to the mobile terminal;   modification of the credits usage profile comprises depletion of at least one credit allocated to the user of the mobile terminal in the credits usage profile or the recharging of at least one depleted credit allocated to the user of the mobile terminal in the credits usage profile;   the method further comprises sending the list of access points to the mobile terminal, said mobile terminal selecting a fresh access point where it can attach in the event of roaming mobility by way of said list;   the mobile terminal is attached initially to a 3GPP access network and where the list comprises access points belonging to a non-3GPP network.       

     According to a second aspect, the invention relates to an access point discovery server capable of transmitting to a mobile terminal a list of access points to which the mobile terminal can connect, among a plurality of access points of a communications network, the access point discovery server being configured to: retrieve, from a credits management server, a credits usage profile linked to the mobile terminal; and generate the list of access points as a function of said credits usage profile. 
     According to a third aspect, the invention relates to a credits management server comprising a database in which is stored the credits usage profile of the user of a mobile terminal, the credits management server being configured to transmit to an access point discovery server said credits usage profile following receipt of a request sent by said access point discovery server. Advantageously, the request sent by the access point discovery server is a request subscribing to updating of credits, the server being configured to transmit the credits usage profile to the access point discovery server following updating of the credits usage profile. 
     According to a fourth aspect, the invention relates to a mobile terminal comprising a selection module of an access point of a communications network, this selection module being configured to select the access point in a list of access points received from an access point discovery server of the communications network, this list of access points being generated as a function of a credits usage profile retrieved by the access point discovery server from a credits management server. 
     According to a fifth aspect, the invention relates to a management system for movement of a mobile terminal comprising a credits management server according to the third aspect of the invention and an access point discovery server according to the second aspect of the invention. 
     According to a sixth aspect, the invention relates to a computer program product comprising code instructions for execution of a method according to the first aspect of the invention, when the latter is executed by a processor. 
     Based on the credits usage profile relative to subscribed services the mobility of a mobile communications terminal is optimised to maximise user experience quality. 
    
    
     
       PRESENTATION OF FIGURES 
       Other characteristics, aims and advantages of the invention will emerge from the following description which is purely illustrative and non-limiting, and which must be considered in conjunction with the appended drawings, in which: 
         FIG. 1  schematically illustrates a communications network of an operator; 
         FIG. 2  schematically illustrates deployment of access points of a communications network of an operator; and 
         FIG. 3  illustrates a management method for movement of a mobile terminal, in a communications network, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In relation to  FIG. 1 , a communications network according to the invention is illustrated. 
     The network comprises several APi access points enabling access to access networks  10  and at least one mobile terminal UE. An access network lets the mobile terminal UE connect to an IP (Internet Protocol) network of Internet type to access services. 
     An access point APi (i=1, 2, 3) defines a coverage area Zi (i=1, 2, 3) in which the mobile terminal UE is located relative to an access point. These access points are either 3GPP access points, or non-3GPP access points. In the case of a 4G access network, the access points are equipment called “eNodeB”. In the case of a 3G access network, the access points are “NodeB”. In the case of a 2G or GPRS access network, the access points are BTS (Base Transceiver Station). In the case of a WiFi access network, the access points are “hotspots”. Finally, in the case of WIMAX an access network, the access points are base stations. 
     The network comprises an access point discovery server, designated by ANDSF, which manages a list of access points, a credits management server (Online Charging System) and a mutual authentication server (Bootstrap Serving Function, (BSF)). 
     The ANDSF access point discovery server can be implemented in the form of a server dedicated to this sole functionality of discovery of access points or in the form of a software module installed in a server having other functions in the network, especially a PCRF server in charge of applying certain network policies and invoicing rules. 
     The ANDSF, OCS and BSF terminologies are reprised from 3GPP standards and are used hereinbelow, without the invention being limited to the sole entities mentioned in these standards, the invention applying to any network having physical entities having the same functionalities as these entities. 
     A user of a mobile terminal UE previously takes out a subscription to one or more services from a telecommunications operator. 
     In this way, each user has a use profile, with credits associated with the services to which he has subscribed (“Online charging”), stored in a real-time credit account database saved in the credits management OCS server. This credits usage profile is used to identify whether the user has an available account, whether he can use the network from which he has taken out a subscription and which type of service on the network he can use as a function of his credits already used and remaining credits. 
     The credits usage profile is updated in the credits management OCS server each time the service is used, for example periodically, on completion of a service session, or when the credits are depleted. 
     Reference is now made to  FIG. 2  which illustrates a mobile terminal UE located in the coverage area Z 1 , Z 2 , Z 3  of three access points AP 1 , AP 2 , AP 3  of a communications network. 
     It is considered that the mobile terminal UE is connected to the access point API and that it is accessing a certain type of service. 
     It is specified here that “connected to an access point” means that the mobile terminal UE has an open session with the access point to receive a service. 
     It is also specified that “covered by an access point” means that the mobile terminal UE is located in a coverage area of an access point APi. 
     If the mobile terminal UE is mobile in the network, it can move from the access point AP 1  to another access point AP 2 , AP 3  which can be selected by means of the management method for movement described hereinbelow. 
     In relation to  FIG. 3 , this described a management method for mobility of a mobile terminal UE according to an embodiment of the present invention. 
     Prior to moving between access points, the mobile terminal UE detects (a step not detailed) the necessity of initiating the mobility procedure based on a triggering event, for example an event such as degradation of the transmission channel of the service. 
     When it is decided to initiate mobility, the terminal can first initiate with the ANDSF server to set up a communications session with the latter. 
     For this to happen, in a step S 1 , the terminal UE is authenticated with the ANDSF server, for example by using the procedure described in technical specification TS 33.402 (“UE-ANDSF communication security” procedure) which allows the ANDSF server to retrieve security information between the terminal UE and the ANDSF server from the BSF priming function server, as well as the rules for defining access which could be used by the terminal UE as a function of its subscription profile and its preferences. 
     Following S 1  authentication, the terminal UE sends (step S 2 ) to the ANDSF server a request for retrieval of a list of access points, via which it can connect to access a service. This request contains typically an identifier of the mobile terminal UE. 
     The ANDSF server then retrieves (step S 3 ) from the credits management OCS server the credits usage profile of the user of the mobile terminal UE, this profile being linked to the mobile terminal UE. 
     This retrieval is done by sending (step S 31 ), as a function of information retrieved during authentication, a request to the OCS server to verify the credits usage profile of the user of the mobile terminal UE, this request comprising an identifier of the mobile terminal UE or of its user. This request may especially be a “Diameter/Radius” query of the type “Debit Unit Request” such as indicated in technical specification TS 32.299. 
     Following receipt of this request, the OCS server retrieves the use profile linked to the mobile terminal UE, or to its user, by the identifier transmitted in the request and in response sends (step S 32 ) the ANDSF server a message containing the credits usage profile of the user and especially information relative to consumption of the service. This message can be in the form of a response with the protocol “Diameter” or “Radius” of the type “Debit Unit Response” such as described in technical specification TS 32.299. 
     In a first embodiment, the credits usage profile can be retrieved on request from the ANDSF server, and this can be repeated over time. 
     In another advantageous embodiment the request sent to the OCS server is a request for subscription to updating credits, indicating that the OCS server should send the credits usage profile at each updating of this credits usage profile (for example by sending a request of type “CC-Request-type (=EVEN-Req)” to which the OCS server responds by a message of “CC-Requested-action subscriber ID=CHECK-BAL”) type. 
     In this latter case, with each significant modification of e this credits usage profile (for example when a credit of the user is depleted relative to a certain type of access network or by comparison when a credit is recharged for a certain type of access network), the credits management OCS server sends the ANDSF access point discovery server a message for updating of credits containing the credits usage profile so that this ANDSF server is informed permanently of the state of credits of the user. 
     This message can take the form “CAA (Result−Balance=ENOUGH-CREDIT, NO CREDIT)”. 
     In particular, it is possible to send such a message for updating of credits only when one of the credits of the user is depleted or, on the contrary, when a depleted credit is recharged so as to inform the ANDSF server only of those modifications of credits which impact the possibility (or not) of using an access network. 
     In another embodiment, this message for updating of credits can be sent only when one of the credits of the user drops below a threshold for which it is preferable to change access network. 
     As a function of this information, as well as optionally of the access networks which the ANDSF server has identified as a function of the location of the user, the ANDSF server sets up (step S 4 ) a list of access points as a function of the credits usage profile it has received from the OCS server. 
     This list is advantageously an ordered list, set up from a set of possible access points of the communications network by arranging these access points (optionally combined by type of access point) as a function of this credits usage profile. In this case, the access points first appearing in this ordered list are prioritised relative to the following ones, the mobile terminal first trying to attach to the first access point of the list, then to the second access point in case of failure to attach to the first access point, and so on. Alternatively, the list generated by the ANDSF server can contain only some of the access points selected as a function of this credits usage profile. 
     So, by way of example, when the consumption credit 3G data of the user is expired, the ANDSF server can decide to generate an ordered list of access points in which the access points WiFi are prioritised relative to the “NodeB” access points so that the user may continue to utilise his service by way of a non-3GPP access network on which he still has credits. As a result, when the user recharges his consumption credit of 3G data the ANDSF server can modify the ordered list to change the priority granted to the 3G access points, available again. 
     Alternatively, every time when the consumption credit of 3G data of the user has expired, the ANDSF server can decide to generate a list of access points containing no more 3G “NodeB” stations, but only non-3GPP “WiFi” access points to oblige the user to use a non-3GPP access network on which he still has credits to continue accessing this service. As a result, when the user recharges his consumption credit of 3G data, the ANDSF server can modify the list to reintroduce the 3G access points, available again. 
     Once set up by the ANDSF server, this list is then sent (step S 5 ) to the mobile terminal UE which can make a decision on mobility from information received from the ANDSF and initiate (step S 6 ), if necessary, moving by selecting a fresh access point within this list. This mobility is then managed by the terminal following the 3GPP or non-3GPP recommendations. 
     For example, if following transmission of the request from the terminal UE to the ANDSF server, the terminal is accessing a service on a 3GPP network and if according to its credits usage profile coming from the OCS server, its use credit of this service on the 3GPP access network is low, whereas this is not the case on a non-3GPP access network, the ANDSF server can prioritise the non-3GPP access network rather than the 3GPP network, by sending back a list of access points in which the non-3GPP access points are prioritised relative to the 3GPP access points, or even a list containing non-3GPP only access points as indicated earlier. 
     As a consequence, the ANDSF server sends the terminal UE the list of access points prioritised as a function of the credits usage profile, which allows the terminal UE to initiate movement between the two access networks by taking into account credits of the user. In this way, as a function of the credits usage profile the terminal UE toggles from the 3GPP access network to the non-3GPP access network (or inversely according to the case), which lets it economise its credit consumption on the 3GPP access network, or else continue its service which it would have not been able to continue on the 3GPP network for lack of credit. 
     The invention is not limited to the method described above but relates also to a system for management of movement of a mobile terminal comprising a credits management OCS server comprising a database in which is stored the credits usage profile of the user of a mobile terminal UE and ANDSF access point discovery server capable of transmitting to a mobile terminal UE a list of access points to which the mobile terminal can connect, from a set of access points of a communications network. 
     The credits management server is configured to transmit (step S 32 ) to an ANDSF access point discovery server said credits usage profile following receipt (step S 31 ) of a request sent by said ANDSF access point discovery server. 
     The ANDSF access point discovery server is configured to retrieve (step S 3 ), from a credits management OCS server, a credits usage profile linked to the mobile terminal UE and to generate (step S 4 ) the list of access points selected as a function of said credits usage profile. 
     For its part, the mobile terminal UE comprises an access point selection module configured to select one (or more) access point in the list of access points received from the ANDSF access point discovery server when this list of access points has been generated as a function of a credits usage profile retrieved by this ANDSF server from the credits management OCS server. This selection module can take the form of a computer program executed by the processor of the mobile terminal UE. 
     Also, the invention relates to a computer program product comprising code instructions for execution of the method described above, when the latter is executed by a processor.