Patent Publication Number: US-2002013163-A1

Title: Cellular communications device

Description:
[0001] The present invention relates to the routing of calls originating in a cellular communications network. The present invention is applicable to, but not limited to, calls originating from within cellular communications systems or networks compliant with standards such as the Global System for Mobile Communications (GSM), and also the Universal Mobile Telecommunication System (UMTS) currently under standardisation.  
       [0002] In a cellular communications system, the area over which service is provided is divided into a number of smaller areas called cells. Typically each cell is served from a base transceiver station (BTS) which has a corresponding antenna or antennas for transmission to and reception from a user station, normally a mobile station such as a mobile telephone. An established cellular radio communication standard is GSM (Global System f or Mobile Communications). A further harmonised standard currently being defined is the Universal Mobile Telecommunications system (UMTS).  
       [0003] A user of a mobile telephone can select a number to be called by any one of a number of inputting steps. One is to dial or key-in a number digit-by-digit. Another is to input an instruction for a previously-stored number or a previously-dialled number, to be called. Any of these input instructions can be performed via a keyboard, or in the case of certain mobile telephones via a voice-activation process. In the present specification the terminology ‘select a number’ is to be understood as encompassing any one or any combination of these possibilities.  
       [0004] In conventional arrangements when the user selects a number and the mobile telephone calls that number by transmitting a call request for that number to a switching component (in the case of a GSM network this is typically a Mobile Services Switching Centre (MSC)) of the cellular network, the switching component then connects the call to the Public Switched Telephone Network (PSTN) which itself further connects the call to either a direct subscriber of the PSTN itself (i.e. a PSTN receiver) or on to further telecommunications networks as required in order to reach the final selected destination.  
       [0005] According to one aspect the present invention provides a mobile terminal, for example a mobile telephone, for use with a cellular communications network, comprising means for allowing a user to input a number to be called, means for adding a stored access code to the number to be called, and means for transmitting the access code and the number to be called to the cellular communications network.  
       [0006] According to another aspect the present invention provides a mobile telephone, comprising a processor for controlling operation of the mobile telephone, and a SIM, the SIM comprising means for interfacing with the processor of the mobile telephone to receive digits of a number to be called from the processor, and means for prefixing a-routing code to the number to be called, and means for returning the routing code attached to the number to be called to the processor, the mobile telephone further comprising means for initiating a call in the cellular communications network using the routing code attached to the number to be called.  
       [0007] According to a further aspect the present invention provides a subscriber identification module (SIM) card for a mobile telephone, the SIM card comprising a stored routing prefix, means for receiving some or all of the digits of a user-selected number from the mobile telephone, means for adding the routing prefix to the received number to provide a modified number, and means for forwarding the modified number to the mobile telephone so that the mobile telephone can initiate a call using the modified number. 
     
    
    
     [0008] Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:  
     [0009]FIG. 1 is a schematic illustration of a communications arrangement having a number of possible connection routes for calls originating in a first cellular communications network;  
     [0010]FIG. 2 is a schematic illustration of a mobile telephone which is operable to initiate a call requiring routing over the communications arrangement of FIG. 1;  
     [0011]FIG. 3 is a schematic illustration of a subscriber identification module (SIM) forming part of the mobile telephone shown in FIG. 2;  
     [0012]FIG. 4 is a schematic illustration showing details of the first cellular network;  
     [0013]FIG. 5 is a schematic illustration of a routing switch which forms part of the communications arrangement shown in FIG. 1;  
     [0014]FIG. 6 is a flow diagram illustrating a process for routing a call via the routing switch;  
     [0015]FIG. 7 is a flow diagram illustrating a further process for routing a call via the routing switch in which the original call is connected to a further call set up by the routing switch;  
     [0016]FIG. 8 is a flow diagram illustrating a process for routing a call via the routing switch in which a new call from the routing switch to the calling mobile telephone is connected to a call set up from the routing switch to the called party; and  
     [0017]FIG. 9 is a flow diagram illustrating a process for routing a call in which the routing is determined by the mobile telephone of FIG. 2 and SIM of FIG. 3. 
    
    
     [0018]FIG. 1 schematically illustrates a communications system with a number of possible connection routes. A first cellular network  6  (e.g. Vodafone) provides service to a large number of user stations. For the sake of clarity one example of such user stations is shown, namely a mobile telephone  2 . The mobile telephone  2  receives service from the first cellular network  6  via a radio link  4 . The first cellular network  6  is coupled via a communications link  8  to the public switched telephone network (PSTN)  10  (e.g. the British Telecom network). The PSTN  10  is further coupled to a routing switch  27  via a communications link  22 , and a further landline network  28  (e.g. the Cable and Wireless network) via a communications link  30 . The PSTN  10  is also coupled to further cellular networks (e.g. Orange, Cellnet etc), of which for clarity only a second cellular network  16  (coupled via a communications link  14 ) is shown. The PSTN  10  is further coupled to a large number of direct subscribers each having a PSTN receiver (such as a telephone or a facsimile apparatus), of which for clarity only telephone  12  is shown in FIG. 1. The second cellular network  16  provides service to a large number of user stations of which for clarity only a mobile telephone  20  coupled via a radio link  18  is shown.  
     [0019] The present embodiment will be described in relation to a call originating from the mobile telephone  2 . In the present embodiment, when the user of the mobile telephone  2  selects the number of a required destination, it prefixes the selected number with an ‘access prefix’, which in this embodiment is a four digit code, which causes the call to be directed initially to the routing switch  27  via the first cellular network  6  and the PSTN  10 . The routing switch  27  removes the access prefix, determines the most appropriate route through the various telecommunications networks for the call, and then routes the call over that appropriate route. In the present embodiment, the most appropriate route is the one that will cost the least to the user of the mobile telephone  2 . For example, the least cost route to the telephone  12  may be via the further landline network  28  and then back to the PSTN  10  for final routing to the telephone  12 . Other examples of determined routes, including routes going via second cellular network  16  will be described later in further embodiments.  
     [0020] Further details of the mobile telephone will now be described with reference to FIG. 2. As shown, the mobile telephone  2  comprises a main processor  44  which is coupled to a subscriber identification module (SIM)  46 ; a memory  48 ; a microphone  50  and loudspeaker  51  enabling the user to input voice and hear audio output; a user interface such as a keyboard  52  by which the user can input numbers to be called and other information and also can access and control various features of the mobile telephone  2 ; a display  54  on which the number to be called and other information can be displayed; and a radio transmitter and receiver  56 , coupled to an antenna  58 , for transmitting and receiving communications from the first cellular network  6 . In the present embodiment the mobile telephone  2  is compliant with the GSM standard.  
     [0021] The SIM  46  is used to provide user-specific data and also algorithms and data specific to the cellular network providing the service to the mobile telephone. In the present embodiment, the SIM  46  is compatible with the processor  44  according to protocols specified in section 11.11 of the GSM specification. Further details of the SIM  46  will now be described with reference to FIG. 3. As shown, the SIM  46  comprises a SIM processor  62  coupled to an interface  64  for interfacing the SIM processor  62  to the main processor  44  of the mobile telephone; a random-access-memory (RAM)  66  and a read-only-memory (ROM)  68 .  
     [0022] In the present embodiment the SIM processor  62  is programmed to carry out the standard SIM procedures specified in section 11.11 of the GSM specification in a conventional fashion. The interface  64  is similarly compliant with section 11.11 of the GSM specification and thereby provides compatibility between the SIM  46  and the main processor  44  of the mobile telephone  2 . The ROM  68  is a permanent memory containing start-up information employed by the SIM processor  62  on initial start-up. The RAM  66  is a non-volatile electrically-erasable memory which is employed by the SIM processor  62  as its working memory. Because the RAM  66  is non-volatile, i.e. its data is retained when the power is turned off, it is conveniently used to store effectively ‘permanent’ SIM information such as its unique international mobile subscriber identity number, the mobile telephone ISDN number (i.e. the international telephone number of the user of the mobile telephone) and internal authentication codes, and also to store ‘semi-permanent’ information such as telephone numbers stored by the user.  
     [0023] In the present embodiment, the SIM processor  62  and the RAM  66  of the SIM  46  and the main processor  44  of the mobile telephone  2  together implement a route-specifying function, as follows. Both the SIM  46  and the main processor  44  are programmed to perform a feature which is termed ‘call control by SIM’ which forms part of the ‘SIM application took kit’ and which is specified in section 11.14 of the GSM specification. According to this ‘call control by SIM’ function, digit strings selected by the user are first passed to the SIM  46  before being transmitted to the first cellular network  6 . Then, under ‘call control by SIM’, the SIM has the ability to allow, bar or modify the call. The SIM also has the ability to replace a call request (i.e. dialled digit string) with another call request. In this embodiment, this functionality of the SIM and the main processor is used to control the appropriate routing of the call. In particular, the SIM  46  is programmed so that, after the input digit string has been passed to it under the ‘call control by SIM’ function, it inserts the earlier described four-digit access prefix to form a ‘prefixed number’ comprising the access prefix and the initial digit string, and then returns this prefixed number to the main processor  44  which then transmits it to the first cellular network  6 .  
     [0024]FIG. 4 schematically illustrates further details of the first cellular network  6 . As mentioned above, the service area of the first cellular network  6  is divided into a number of smaller areas called cells, each of which is served via a base transceiver station (BTS). In FIG. 4 only the base transceiver station which is providing service to the mobile telephone  2  via the radio link  4  is shown, and in fact this base transceiver station is co-sited with a base station controller (BSC) thereby providing a joint base station controller/base transceiver controller (BSC/BTS)  40 . The base station controller/base transceiver station  40  is coupled via a communications link  38  to a mobile services switching center (MSC)  36 , which itself is coupled to the PSTN  10  via the communications link  8 . The mobile services switching center  36  also provides service for a number of other joint base station controller/base transceiver stations via corresponding further communications links, of which only communications links  37  and  39  are illustrated in FIG. 4.  
     [0025] In operation, when the above described call from the mobile telephone  2  is received by the base station controller/base transceiver station  40  it forwards it over link  38  to the mobile service switching center  36 . The mobile service switching center  36  performs the switching function for the first cellular network  6 , and in the present embodiment recognises the access prefix and causes the call to be forwarded to the PSTN over the communications link  8 . Likewiser the PSTN  10  also recognises the access prefix and routes the call to the routing switch  27  via the communications link  22  shown in FIG. 1.  
     [0026] Further details of the routing switch  27  will now be described with reference to FIG. 5. As shown, the routing switch  27  comprises a processor  78  which is coupled to an input unit  76 , an output unit  80 , a memory  82  and a user interface  88 . In the present embodiment, the routing switch  27  is implemented in the form of a suitably programmed computer apparatus. In operation, when the routing switch  27  receives the prefixed telephone number for a call via the input unit  76 , the processor  78  removes the access prefix digits and then compares at least the initial digits of the originally dialled telephone number with routing information held in the memory  82 .  
     [0027] In the present embodiment the routing switch processor  78  is programmed to determine the lowest cost route for each call. The memory  82  therefore contains data specifying the lowest cost route for each call as determined by that call&#39;s international and national dialling codes, further cross-referenced to the time of day and the network and location of the call originator. In this embodiment, this routing data is regularly updated by the operator of the routing switch  27  by inputting the updated information via the user interface  88 . In this embodiment, after the routing switch processor  78  has determined the lowest cost route over the available networks, it then directly forwards the call over that route via the output unit  80 .  
     [0028] Details of the operation of the present embodiment will now be described with reference to FIG. 6 which is a flow diagram illustrating the process steps employed. At step S 2  the user of the mobile telephone  2  selects a number to be called, for example, by dialling (i.e. keying in) a new number using keyboard  52 . At step S 4  the main processor  44  receives the selected number, as follows. As the user keys in each digit, the main processor  44  controls the display to present the digits so far keyed in. When the user has keyed all of the digits, he presses a send button contained in keyboard  52 . When this happens, the main processor is able to determine that the keyed-in digits it has so far received form the final version of the selected number. At step S 6 , the main processor forwards the selected number to the SIM  46  according to the ‘call control by SIM function’ as described earlier with reference to FIGS. 2 and 3. At step S 8 , the SIM  46  adds the four-digit access prefix to the selected number to provide a prefixed number. At step S 10  the SIM  46  returns the prefixed number to the main processor  44 .  
     [0029] At step S 12  the main processor  44  controls the mobile telephone  2  in calling the prefixed number. The number is transmitted from the radio transmitter and receiver  56  via the antenna  58  over the radio link  4  where it is received by the joint base station controller/base transceiver station  40  of the first cellular network  6  in conventional manner.  
     [0030] At step S 14  the first cellular network  6  routes the call to the routing switch  27 . More particularly, the call is first forwarded from the joint base station controller/base transceiver station  40  via the communications link  38  to the mobile services switching center  36 . The mobile services switching center (MSC)  36  analyses the called number and recognises the access prefix. In the present case MSC  36  compares the access prefix with look-up information it holds and this indicates to it that the call is to be routed to the routing switch  27 . The mobile services switching center (MSC)  36  further determines that it is to route the call to routing network  24  via the PSTN  10 . When the PSTN  10  receives the call it similarly recognises the prefix and, following analysis of its own look-up tables, forwards the call to the routing switch  27  over the communications link  22 , thus completing the directing of the call from the first cellular communications network  6  to the routing switch  27 .  
     [0031] At step S 18  the routing switch  27  removes the access prefix from the called number. At step S 20  the routing switch  27  determines the appropriate (i.e. lowest cost) route for the call, in the manner described earlier with reference to FIG. 5.  
     [0032] At step S 22 , the routing switch  27  directly routes the call over the determined route to the selected number. In the present example the originally dialled number corresponds to the telephone  12  coupled to the PSTN  10 . Furthermore, in the present example, the routing switch  27  determines that the lowest cost route for the call is via the further landline network  28  then back to the PSTN  10  at the local exchange for the telephone  12 . In the present embodiment, the routing switch  27  directly routes the call over the determined route by simply forwarding the connection and call request over the desired route. This is known as ‘single stage call set up’.  
     [0033] A second embodiment of a method of operating the communications arrangement will now be described with reference to FIG. 7. In the second embodiment the method steps S 2  to S 20  are performed in the same way as with the first embodiment described above and will not, therefore, be described again. However, rather than employing ‘single stage call set up’, this embodiment employs a procedure called “two stage call set up”, which will be described with reference to steps S 24 , S 26  and S 28  of FIG. 7. In particular, at S 24 , the routing switch  27  does not directly forward the present call but instead sets up a further call to the selected number over the appropriate route. At step S 26 , the routing switch  27  determines that the called party at the selected number has answered. When the called party has indeed answered, then at step  528 , the routing switch  27  connects together the original call and the further call thus completing the route.  
     [0034] In a third embodiment of the method, rather than either ‘single stage call set up’ or ‘two stage call set up’ being employed, a procedure known as ‘call back’ could be employed for implementing the determined route. The process steps employed in such an embodiment are shown in FIG. 8. Steps S 2  to S 20  and S 24  and S 26  are implemented in the same fashion as they were in the second embodiment and will not be described again. However, in this embodiment, after step S 26 , the procedure moves to step S 30  where the routing switch clears down the original call as made by the mobile telephone  2 . As is conventional in cellular networks, the first cellular network  6  will thus close down the call at the originating terminal i.e. the mobile telephone  2 , in response to the routing switch clearing the call. Thus the mobile telephone  2  is made available to receive a call. At step S 32 , the routing switch  27  then makes a new call to the mobile telephone  2 . At step S 34 , the mobile telephone  2  answers the call. This can be performed manually by the user of mobile telephone  2 , however in this embodiment the main processor  44  is programmed to answer the call automatically. In this embodiment, the main processor  44  is controlled to do this by the SIM  46 , which is pre-programmed to instruct the main processor  44  to auto-answer the next call received after a prefixed outgoing call has been closed down. Thereafter, at step S 36 , on determining that the mobile telephone  2  has answered the new call, the routing switch  27  connects this new call to the further call it has established at step S 24 , thus completing the whole of the route.  
     [0035] In the above embodiments, the SIM  46  cooperated with the main processor  44  of the mobile telephone  2  to prefix a four-digit access prefix to numbers selected by the user. Thereafter, the function of determining the lowest cost route was carried out by the routing switch  27 . In the fourth embodiment of the present invention, some or all of the function of determining the lowest cost route is performed by corresponding functionality programmed into the SIM  46 . In this embodiment, the SIM  46  has more than one choice of access prefixes, and chooses from them which access prefix to add to the user-selected number according to the choice of route it determines.  
     [0036] The fourth embodiment will now be described in further detail with reference to FIG. 9 which is a flow diagram illustrating the process steps employed. Steps S 2 , S 4  and S 6  are carried out in the same way as with the earlier described embodiment and will not be described again. However, thereafter, at step S 7  the SIM  46  determines an access prefix from a plurality of candidate access prefixes by carrying out the procedures of comparing the national and international dialling code of the destination telephone number, and time of day and location of the caller, with information stored in it in corresponding fashion to the procedures described earlier which were performed by the routing switch  27 . In this embodiment, the routing data and the different access prefixes are loaded into the SIM before it is first used in the mobile telephone.  
     [0037] Thereafter, at step S 9 , the SIM  46  adds the determined access prefix to the selected number to provide the prefixed number. Step S 9  therefore corresponds to step S 8  of the previous embodiments. At step S 10  the SIM  46  forwards the prefixed number to the main processor  44  and thereafter at step S 12  the mobile telephone  2  calls the prefixed number, as was the case with the earlier described embodiments. Thereafter, at step S 13  the first cellular network  6  routes the call according to the access prefix. This is performed in the same fashion as step S 14  was performed in the earlier embodiments, however, in this embodiment, the call will not be directed to the routing switch  27  but will instead be directly routed to the destination via the route specified according to the prefixed number.  
     [0038] In the above embodiments, the routing switch selected the lowest cost route for the call. In other embodiments, other criteria can be employed. For example, the route providing the highest quality of service, or the route providing the most available bandwidth may be the criteria employed in other embodiments. In yet further embodiments, the routing switch may be programmed to route calls over a specific further landline network or other specific further network on the basis of a commercial agreement between the operators of the routing switch and such specific further networks.  
     [0039] In the above embodiments, the routing data stored in the memory of the routing switch was updated manually by operator input through the user interface. In other embodiments, this information may be updated automatically or semiautomatically via the input unit or any other suitable input.  
     [0040] In the above embodiments, the number to be called was selected by the user entering a new number via the keyboard of the mobile telephone. In other embodiments, the number to be called may be selected by a voice command or may be selected by retrieving the number from the user&#39;s phone book which is stored in either the main processor memory or the SIM memory.  
     [0041] In the above embodiments, the mobile telephone  2  display only displayed the selected number without including the prefix. This was consistent with the requirement for the user to press a send button on the keyboard of the mobile telephone. In other embodiments, in which other user procedures can be employed, such as automatic sending of the number without direct user interaction, the number could be displayed with or without the prefix.  
     [0042] In the above embodiments, although the first cellular network recognised the access prefix, it nevertheless forwarded the call to the PSTN  10  which finally diverted the call to the routing switch  27 . This is the commercially preferred approach, however, and in other embodiments the first cellular network  6  itself may directly divert the call to the routing switch  27  over a suitable direct communications link.  
     [0043] In the above embodiments the routing switch  27  determined that the lowest cost route for a call intended for the telephone  12  was via the further landline network  28  and the PSTN  10 . In other examples, the routing switch  27  may determine that the lowest route call is simply back through the PSTN  10 . In other examples, the call may be intended for the further mobile telephone  20  coupled over radio link  18  to the second cellular network  16 , all as shown in FIG. 1. In this case the routing switch  27  may determine that the lowest cost route is via the further landline network  28  and the second cellular network  16 , or alternatively back via the PSTN  10  and on to the second cellular network  16 . It is to be appreciated that in the case of each possibility involving routing back through the PSTN  10 , the routing switch  27  and/or the further landline network  28  will direct the call to the PSTN  10  such that it enters the PSTN  10  at a local exchange providing the lowest overall cost or other required criteria.  
     [0044] In the fourth embodiment described above, the SIM  46  determined an appropriate access prefix from a number of possibilities. In a further embodiment, the SIM  46  may have either one or more such choices plus a further choice of adding no access prefix in circumstances where no specific re-routing of the call will achieve cost reduction or improvements in any other criteria being applied.  
     [0045] In each of the above embodiments, a four digit access prefix was added to the start of the originally selected number. In other embodiments the number of digits may be other than four. Furthermore, the access code may be inserted within the digit string or at the end of the digit string of the originally selected number, provided its location is known in advance by the other elements of the routing system.  
     [0046] In each of the above embodiments, the main processor of the telephone passed all of the selected digits to the SIM  46  which then formed the prefixed number. In other embodiments, the main processor may be arranged to pass just some of the originally selected number to the SIM, and after the SIM returns those digits with the prefix, the main processor then adds the remaining digits before the call is made.  
     [0047] In the above described fourth embodiment, routing was fully determined by the SIM which then added a suitable prefix or access code in order for the call to be routed over the determined route. In other embodiments, the SIM may as one choice determine a routing prefix that routes the call to the routing switch for further decision making.  
     [0048] In all of the above embodiments, the necessary algorithms and data for the routing procedures are all programmed into the SIM  46  before it is first used in the mobile telephone  2 , and thereafter the data is not updated. However in other embodiments, this data may be replaced or revised after initial use by further algorithms and data which may be downloaded into the SIM  46 . This downloading of the new data and algorithms may be performed whilst the SIM is in situ using data received over the cellular communications network or using a SIM programming module.  
     [0049] In the above embodiments, the different networks shown in FIG. 1 are each implemented with separate hardware. It is to be appreciated however that in other embodiments, some or all of the components of two or more of the different networks shown, including either or both of the cellular networks, the routing network and one or more networks forming the further landline network, can be comprised partly or totally of hardware that is shared between one or more of the networks. In such a situation, the division between different networks can be determined or derived from any relevant organisational or commercial basis.  
     [0050] Furthermore, it is to be appreciated that the present invention can be applied to other arrangements of communications systems and networks. For example, more than one PSTN can be included; and the routing switch  27  can be directly coupled to either of the cellular networks shown or indeed further cellular networks not shown. Also, details of either of the cellular networks shown or indeed any other cellular networks can vary compared to the above embodiments, in particular by including alternative components serving the same or different roles compared to the joint base station controller/base transceiver station (BSC/BTS)  40  and/or the mobile services switching center (MSC)  36 . Similarly, the present invention can be applied to communications arrangements linking more than one country. For example, the further landline network may be replaced by an international telephone network, and the first cellular network may be a network a user is using whilst roaming, rather than being the user&#39;s home network.  
     [0051] With respect to the overall arrangement of networks and communications arrangements shown in FIG. 1, it is also to be appreciated that other possible hierarchical and access format are possible. For example, in arrangements complying with UMTS, other public data networks may be employed other than the PSTN  10 , and mobile packet switches may be employed rather than mobile services switching centers (MSCs).  
     [0052] In the above embodiments the original call is made from a mobile station Comprising a mobile telephone. The present invention is however applicable to calls made from any other type of user station or terminal in a cellular communications system, including a mobile telephone comprising any sort of communication link with an appropriate external device such as a computer or electronic organizer. The invention is applicable to calls made for the purposes of transmitting speech and/or other information or data, including multimedia services such as facsimile, audio, video and so on. The call can also be a call intended for transmission over a route including a packetized data network such as the Internet.  
     [0053] In each of the above embodiments, a GSM compliant SIM as shown in FIG. 3 was employed. It is to be appreciated that SIMS with other combinations of functionality can be employed in other embodiments of the invention, provided such SIMs provide any appropriate means for prefixing numbers selected by the host apparatus they are to be used in or with. Furthermore, as those skilled in the art of cellular communications arrangements will realise, the term ‘SIM’ as used in the description and claims is not limited to the GSM-specified item, but includes any appropriate module or circuit (or plural modules and/or circuits) that are incorporated into user stations to add client or network-specific data to the operation of a non-client-specific or non-network-specific user station apparatus.  
     [0054] Yet further, in other embodiments of the invention, all of the procedures described above as being shared between the SIM  46  and the main processor  44  of the mobile telephone  2  can in fact be performed solely by just the main processor  44  of the mobile telephone or alternatively by more than one processor of the mobile telephone, i.e. without any contribution by the SIM or indeed even in a mobile telephone that has no SIM at all.