Method of Operating a Dual SIM Wireless Communications Device
Contents
1. necessary to be familiar with some of the interactions between the SIM and the GSM cellular telephone network These will now be described Nov 4 2010 Major GSM Network Components 0029 The major elements of the GSM telephone network are 0030 the Mobile Station MS this consists of the mobile telephone handset commonly referred to as the Mobile Equipment ME together with the Subscriber Identification Module SIM 0031 the Base Station subsystem BSS This consists of a number of Base Transceiver Stations BTS which manage the transmission and reception over the radio or air interface together with a Base Station Controller BSC which controls the BTSs by allocating releasing and handing over radio channels 0032 the Network Switching Subsystem NSS which links the BSCs to a Mobile services Switching Centre MSC and thence to wider telephone and data networks such as the Public Switched Telephone Network PSTN the Packet Switched Public Data Network PSPDN and the Integrated Services Digital Network ISDN 0033 Associated with the NSS are a number of entities used for identification and administration purposes 0034 the Home Location Register HLR which holds persistent subscriber data together with the cur rent VLR see below 0035 the Authentication Centre AuC which is responsible for subscriber authentication this is usu ally associated with the HLR 0036 the Visitor Location Registe2. or because their employer pays for them to have a work SIM 0008 Different GSM networks are largely compatible and a SIM issued by and registered on one network usually referred to as the home network may be used on a completely different GSM network run by a differ ent operator this is known as roaming While national roaming between different GSM networks in the same country is not unknown most network operators do not allow it as it unecessarily diverts a portion of their call revenues to their domestic competitors Roaming is most common when subscribers travel to different coun tries this is known as International or Global roaming and is widely perceived as one of the key benefits of Nov 4 2010 GSM technologies However it is well known that the call charges levied by a network operator on both incom ing and outgoing calls when a subscriber is away from their home network and roaming internationally are often an order of magnitude greater than would normally be applied In order to avoid these excessive roaming charges people may purchase local SIM cards for use in the country where they will be travelling This is espe cially popular where a country border can be crossed by land e g between Hong Kong and Mainland China 0009 Although increasing numbers of people possess multiple SIMs it remains the case that GSM mobile phones are designed and sold for use with only one SIM card This forces users with dual SIMs
3. perform the IMEI check at any access attempt except IMSI detach and during an estab lished call at any time when a dedicated radio resource is available in accordance with the security policy of the PLMN operator The network shall terminate any access attempt or ongoing call when receiving any of the answers black listed 1 e on the black list or unknown equipment i e not on the white list from the EIR 0096 It should be noted that while the allocation of an IMEI to an ME is compulsory its interrogation by the net work is optional and IMEIS are not registered and tracked in the same way that IMSIs are While a network could in theory check IMEIS for simultaneous usage this is not envisaged in the GSM standards However allocations of a separate IMEI to each SIM or SIM socket on an ME would serve to prevent any problems which may be caused by the same IMEI being involved in two separate IMSI registrations 0097 This invention allows multiple GSM SIMs to func tion ina single handset without needing to disable all but one of the SIMs and thereby missing out on incoming calls and message notifications This is of great utility to mobile tele phone users seeking to minimise roaming charges and also to those users who need to maintain access to two subscriber accounts at all times 0098 Although the present invention has been described with reference to particular embodiments it will be appreci ated that modif
4. share the same physical channel it does not permit multiple dedicated traffic channels ona single device Only one SIM can be in active traffic mode at any one time Note however that call collisions between US 2010 0279698 A1 incoming calls on different SIMs are in principle no different to call collisions on a single SIM and can be handled in the same way 0088 Inan enhancement to this invention an ME support ing multiple SIMs would also support a separate International Mobile Equipment Identifier IMET for each SIM or SIM socket 0089 The IME is a unique number allocated to an ME at manufacture time which also contains indications of manu facturer and modes According to GSM 02 16 0090 network operator can make administrative use of the IMEI in the following manner 0091 Three registers are defined known as white lists grey lists and black lists The use of such lists is at the operators discretion 0092 The white list is composed of all number series of equipment identities that are permitted for use 0093 The black list contains all equipment identities that belong to equipment that need to be barred 0094 Besides the black and white list administrations have the possibility to use a grey list Equipments on the grey list are not barred unless on the black list or not on the white list but are tracked by the network for evalu ation or other purposes 0095 It shall be possible to
5. to adopt one of two solutions 0010 Swap SIM cards when they need to use an alter nate GSM account On most GSM phones this requires the phone to be switched off and the battery removed in order to gain access to the SIM holder this is a relatively complex operation which is difficult to accomplish on the move as it can require juggling a phone a battery a battery cover and two SIMs Furthermore once a SIM is removed from a handset calls to that number have to be diverted which involves extra expense for the subscriber either to pick up voicemail or to pay for a call diver sion 0011 Carry two mobile phones one for each SIM This ensures that no calls to either SIM will be lost However most people regard having to carry multiple phones and chargers as an inconvenience The additional expense of a second handset is also a deterrent 0012 The problems caused by the inability of GSM hand sets to support more than a single SIM at any one time is well known and there have been a number of attempts to overcome the problem 0013 Examples of prior art which adapts handsets to make use of two SIM cards include the disclosures of EP 0586081 from Nokia Mobile Phones and AU 1953299 from Newcom Technologies PTY Ltd both of which describe a digital mobile telephone capable of holding multiple SIMS only one of which can be active at any one time Such devices have been commercially manufactured the Benefon Twin handset is an examp
6. 2010 ing channels in GSM are logical channels that are normally assigned by the BTS according to the last three digits of the IMSI This is to group multiple subscribers onto a single paging channel for load balancing and battery power man agement This means that a device implementing this inven tion may if its SIMs are allocated different paging channels needto wake up more often because the device must listen to each of the paging channels that are assigned to each of the authenticated SIM cards 0069 Inthis way the ME can receive a Mobile terminated call from any of its SIM cards that have been authenticated with the PLMN 0070 also make mobile originated calls from any of its authenticated SIM cards by requesting a dedicated channel via the RACH 0071 The implementation of this invention also requires 0072 1 that the MS supports access to multiple simul taneous SIM cards This may be provided either 0073 by the MS having multiple physical SIM card interfaces or 0074 by multiplexing several SIM cards onto a single physical SIM card interface 0075 2 that there is sufficient memory in the ME to allow for the necessary multiple instantiations of logical control channels 0076 3 that the software in the ME handling the GSM protocol be modified 0077 to register multiple SIMs in turn 0078 to subsequently monitor the paging channels allocated to each SIM for network notifications 0079 to correctly a
7. DIATE ASSIGNMENT message on the CCCH MS notifies the BSS of its presence in the cell by means of a LOCATION UPDATING REQUEST message containing IMSI BSS passes the IMSI to the NSS which looks up the matching telephone number or MSISDN and Ki for that IMSI in the HLR and AuC AuC in the NSS generates RAND and transmits it to MS in AUTHENTICATION REQUEST message and also computes SRES from the Ki and RAND RAND received by MS and transferred by the ME to the SIM as part of a RUN GSM ALGORITH message SIM computes its own version of SRES from Ki and RAND and returns that to the ME MS sends its version of the SRES back to to the NSS in the AUTHENTICATION RESPONSE message Does NSS SRES match SRES received Yes NSS accepts location update via a LOCATION UPDATE ACCEPT message transmitted to the MS which also contains a Temporary International Mobile Subscriber Identifier TMSI The TMSI is also stored in the appropriate record in the VLR Dedicated control channel released MS enters idle mode periodically listens for notifications on appropriate paging sub channel US 2010 0279698 A1 Send AUTHENTICATION REJECT message and release control channel Patent Application Publication Nov 4 2010 Sheet 3 of 3 US 2010 0279698 A1 Figure 3 Yes Is another PLMN MS switches on locates synchronises and starts
8. SIM cards can be supported with the following permu tations of SIM cards and PLMNs 0062 Multiple SIM cards issued by the same network provider when used on their home PLMN e g two or more UK Vodafone SIM cards can both be used on the UK Vodafone network 0063 Multiple SIM cards issued by any network pro viders when all of them are being used away from their home PLMN provided they are all enabled for roaming on the PLMN being visited e g two or more roaming French Orange SIM cards can both be used when roam ing on the UK Vodafone network 0064 One or more SIM cards issued by the same net work provider when used on their home PLMN together with one or more SIM cards issued from any other net work providers which are enabled for roaming on the PLMN being visited e g one UK Vodafone SIM card together with one roaming French Orange SIM card can both be used on the UK Vodafone network 0065 For the purposes of clarification it must be noted that the invention does not support permutations of SIM cards and PLMNs where the SIM cards are issued by different network providers and where there is no locally available PLMN on which they can both roam because in such cases it would not be possible to register all SIMs on the same BSS It follows therefore that a UK Vodafone SIM card and a UK Orange SIM card even if both enabled for international roaming cannot be used together in the UK since no UK networks permit national ro
9. SMS while in during the active mode The BSS and the MS switch the communi cations context between the various control channels on demand to support relevant channels and sub channels as required 0059 Some MEs already reserve resources for up to 6 logical control channels on power up in order to anticipate the worse case call scenario In order to fully support multiple SIMs more resources may need to be reserved as the number of possible instantiations of logical control channels would be larger Smartphones with access to unallocated resources in the form of heap memory may be able to allocate additional instantiations on the fly as needed 0060 As described above multiple instantiations of the control channels can be used to allow a single handset with a single GSM radio to support the registration of multiple SIMs provided that all those SIMs are registered with the same US 2010 0279698 A1 BSS Clearly there is no problem with this if both SIMs have been issued by the same network provider However even where the SIMs have been issued by different network pro viders registration with the same BSS is still possible by making use of the fact that roaming SIM cards can normally access any BSS belonging to any network within receiving range so for example if able to roam in the UK a SIM can access at least the PLMNs operated by Vodafone O2 Orange and T Mobile 0061 By means of this invention therefore multiple active
10. US 20100279698A1 a2 Patent Application Publication Pub No US 2010 0279698 A1 as United States Wong 43 Pub Date Nov 4 2010 54 METHOD OF OPERATING A DUAL SIM 86 PCT No PCT GB07 02368 WIRELESS COMMUNICATIONS DEVICE 8 371 1 2 4 Date Jul 23 2010 75 Inventor Lawrence Wong Surrey GB 30 Foreign Application Priority Data Correspondence Address Jun 26 2006 0612634 6 Saul Ewing LLP Philadelphia Attn Patent Docket Clerk Penn National Insurance Plaza 2 North Second St 7th Floor Harrisburg PA 17101 US 73 Assignee Symbian Software Limited London GB 21 Appl No 12 303 772 22 PCT Filed Jun 26 2007 Mobile Stations SIM and Handset MS SIM ME Base Station Subsystem 8M Base Transceiver Station Bis SIM Base Station Controller BSC Transceiver Station SIM Transceiver Station BTS SIM Publication Classification 51 Int CI H04W 8 00 2009 01 H04W 72 00 2009 01 GIUS C 455 450 455 558 57 ABSTRACT A wireless telecommunications device is configured so that it is capable of handling multiple instantiations of GSM control channels and thereby capable of holding multiple SIMs can register each SIM with the network consecutively and main tain idle network connections for each SIM using separate control channels This allows call
11. aming across UK PLMNs However the same combination of cards can be taken across the Channel for example and used with this invention on a PLMN oper ated by a non UK network provider such as Orange France SFR or Bouygues 0066 In a preferred implementation of this invention an ME that is first switched on scans the available GSM net works to identify which one to select as the PLMN Should one of the SIMs in the system be able to identify its home network that PLMN should be given priority This selection of the home network has the benefit of avoiding roaming charges for at least one SIM and should also offer a reasonable possibility that the second or further roaming SIMs can also successfully register on the same PLMN If there is no home network available but there is a PLMN that both SIMs can use then the strongest of that type is chosen instead 0067 Once a PLMN has been selected the registration of multiple SIMs requires a relatively straightforward software modification in the ME which simply consists of iterating steps 2 to 10 of the GSM subscriber registration and authen tication procedure outlined above for each SIM in the hand set This modified procedure together with the selection of the PLMN is shown diagrammatically in FIG 3 0068 Once the multiple registrations have been success fully completed the ME must now wake up periodically to monitor its paging channel s As described earlier the pag Nov 4
12. decoding messages on the common channels of the BSS of strongest available PLMN MS locates synchronises and starts decoding messages from next strongest 1 15 it home network of an available SIM No Mark as best available PLMN if this has not yet 4 Yes been done available Can all SIMs use PLMN Use best available PLMN BSS allocated a dedicated control chanel channel via an IMMEDIATE ASSIGNMENT message on the PT CCCH MS request a dedicated control channel from the BSS via a CHANNEL REQUEST message on the CCCH MS notifies the BSS of its presence in the cell by means of a LOCATION UPDATING REQUEST message containing IMSI BSS passes the IMSI to the NSS which looks up the matching telephone number or MSISDN and Ki for that in the HLR and AuC OR eee AuC in the NSS generates RAND and transmits it to MS in AUTHENTICATION REQUEST message and also computes SRES from the Ki and RAND v RAND received by MS and transferred by the ME to the SIM as part of a RUN GSM ALGORITH message MS sends its version of the SRES back to to the NSS in the AUTHENTICATION RESPONSE message J SIM computes its own version of SRES from Ki and RAND and returns that to the ME Send AUTHENTICATION No gt REJECT message and release control channel Does NSS SRES match SRES received Yes Y NSS accepts location u
13. e alternate SIM and cannot make use of it when calls are made to its telephone number it appears to the network as if the phone is turned off A user would therefore miss both incoming calls and any text messages or other forms of data communication directed at the inactive SIM card These would therefore be either diverted or stored picking up these messages generally costs the user time and or money and can result in delays in receiving messages 0017 The only method disclosed to date for supporting simultaneous multiple SIMs in a GSM telephone is equiva lent to building two separate phones in the same case with the same power supply akin to Siamese twins Such a telephone has been disclosed in patent WO99 41921 from Telital SPA It duplicates all the hardware and software required to enable a wireless GSM connection for each SIM i e a second pro cessor power amplifier and controller transceiver frequency synthesizer base band unit DSP SIM holder and electron ics This allows users to switch between the two SIMs for making calls and have both SIMs active simultaneously for receiving calls and messages 0018 However the constraints of mobile telephone manu facturing costs and battery life mean this is not a commer cially feasible solution no handsets implemented the Telital patent are known to have ever been available 0019 The present invention enables a single GSM mobile telephone to support two SIMs simultaneously
14. hing telephone number or MSISDN and Ki for that IMSI in the HLR and AuC 0051 5 The AuC in the NSS generates a random num ber RAND that is transmitted back to the MS as part of a AUTHENTICATION REQUEST message The AuC also computes a unique key known as a Signed Result SRES from the Ki allocated to the SIM and the RAND 0052 6 This random number is received in the MS and transferred by the ME to the SIM as part ofa RUN GSM Nov 4 2010 ALGORITHM message the SIM computes its own ver sion ofthe SRES Result SRES from the Ki allocated to the SIM and the RAND and returns that to the ME 0053 7 The MS sends its version of the SRES back to the NSS in the AUTHENTICATION RESPONSE mes sage 0054 8 The NSS authenticates the MS only if the SRES in the message matches the SRES which it has computed locally Note that in the case of a roaming SIM the NSS will need to contact the issuing PLMN to obtain the SRES 0055 9 Once authenticated the NSS accepts the loca tion update via a LOCATION UPDATE ACCEPT mes sage transmitted to the MS which also contains a Tem porary International Mobile Subscriber Identifier TMSI The TMSI is also stored in the appropriate record in the VLR 0056 10 The dedicated control channel can now be released and the MS enters idle mode during which it periodically listens for notification of calls and SMSs on the appropriate paging sub channel which is allocated according to an algori
15. ications may be effected whilst remaining within the scope of the present invention as defined by the appended claims 1 A method of operating a wireless telecommunications device containing multiple subscriber identities which have been allocated by one or a plurality of wireless networks by Nov 4 2010 which the said multiple subscriber identities are enabled and activated for simultaneous use on a single wireless network 2 A method according to claim 1 in which the device is a GSM mobile telephone handset and the subscriber identity is contained in an IMSI 3 A method according to claim 1 in which the multiple subscriber identities are made available on the device either via separate SIMs or multiplexed on a single SIM module 4 A method according to claim 1 in which the device is enabled to identify a wireless network on which all available subscriber identities may be registered giving preference to a wireless network which is the home network for at least one of the said subscriber identities 5 A method according to claim 1 in which the device is enabled to support multiple active instances of logical control channels each of which is assigned to a specific subscriber identity and b registers each subscriber identity with the network in turn and c moves each subscriber identity to idle mode when it monitors the logical control channels assigned to each and d responds to a notification on the logical contro
16. l channel addressed to a specific subscriber identity by requesting dedicated traffic channel for that subscriber identity and moving to active traffic mode only for that subscriber identity while other subscriber identities registered on the handset remain in idle mode 6 A method according to claim 1 in which each subscriber identity is assigned a different unique ME number 7 A method according to claim 1 in which the subscriber identity used by the device when initiating connections to the network is a a default subscriber identity selected by the user of the device or b a subscriber identity selected by the user of each device each time a connections is initiated or c a subscriber identity selected according to a set of rules set up by the user taking into account any or all of the location of the device the destination of the connection the time the connection is being made and the history of connections made by the device 8 A method according to claim 1 in which the device maintains separate memory storage for data and messages associated with each subscriber identity 9 A method according to claim 1 in which any or all of the subscriber identities may be selectively disabled by the user 10 A method according to claim 1 in which in the event that not all subscriber identities can be registered on a single network the user is allowed to choose which subscriber iden tities shall be disabled 11 A wireless telecom
17. le ofa prior device in this area This GSM telephone had two SIM sockets but could only support one SIM at a time The phone had to be switched off and then switched on again in order to change SIM The user manual forthis device can beobtained from http benefon com prod ucts twin 0014 Other examples of similar art include dual or even triple SIM adapters such as those marketed under the Ghost brand by various resellers and those sold by companies such as Magicsim http www magicsim com All these adapters are similar to the Benefon Twin in that they require the telephone to be switched off and on again when SIMs are changed For some of these devices the SIMs alternate on each power cycle Others have a mechanical switch that can be used to select the desired subscriber identity The Magic sim devices use SIM Tookit commands to enable the user to select the desired SIM from an on screen menu 0015 See http www m 99 co uk Mobile Phone Twin SIM adapters GVC Ghost Dual and Triple SIM gvc ghost dual and triple sim html for a summary of these devices While these devices do solve the mechanical prob lem outlined above in that the user no longer has to juggle both SIMs the telephone the battery and the battery cover at US 2010 0279698 A1 the same time they have a key deficiency in that they do not permit a subscriberto have both SIMs active at the same time 0016 While one SIM is selected it disables th
18. munications device arranged to operate in accordance with a method as claimed in claim 1 12 An operating system for causing a wireless telecom munications device to operate in accordance with a method as claimed in claim 1
19. n use into a number of logical channels which are defined by recurring patterns of timeslots and frequencies One physical channel can support many logical channels US 2010 0279698 A1 0042 Some of these logical channels are termed common control channels CCCHs and are typically shared by every MS in a particular cell for communicating when any particu lar MS is in idle mode not engaged in a call 0043 Among these channels are the Frequency Correc tion Channel FCCH and the Synchronisation Channel SCH which are used by the BSS to transmit informa tion that is used by an MS to identify and subsequently establish communications with that BSS The Broadcast Control Channel BCCH is used by the BSS to transmit infrastructure information concerning network and cell ID and frequencies to be used by the other channels These are common control channels that are transmitted by the BSS to every MS in a cell which only need to listen to these control channels when they require the information transmitted for example on power up or before a location area handover 0044 Other common control channels are used for communications between the BSS and a specific MS The MS can send messages to the BSS on the shared Random Access Channel RACH which uses a slotted Aloha Collision Sense Multiple Access CSMA proto col similar to that used by other network topologies sharing a common transmission medium The BSS sends control informa
20. pdate via a LOCATION UPDATE ACCEPT message transmitted to the MS which also contains a Temporary International Mobile Subscriber Identifier TMSI The TMSI is also stored in the appropriate record in the VLR Dedicated control channel released MS enters idle mode periodically listens for notifications on appropriate paging sub channel Another SIM No US 2010 0279698 A1 METHOD OF OPERATING A DUAL SIM WIRELESS COMMUNICATIONS DEVICE 0001 The invention discloses an improved method of operating a wireless telecommunications device and in par ticular to a method of operating a dual SIM wireless com munications device 0002 The term wireless telecommunications device includes any digital or other device capable of wireless com munications which includes without limitation Mobile Tele phones and Smartphones together with any computing devices with such capabilities These may include Desktop and Laptop computers Personal Digital Assistants PDAs Digital Cameras and Digital Music together with converged devices incorporating the functionality of one or more of the classes of such devices together with many other industrial and domestic electronic appliances 0003 For simplicity the description of this invention pri marily references mobile telephone handsets however such references should be expansively construed to refer to any wireless telecommunications devices with comparable func
21. r VLR which holds information concerning the Mobile Stations which are in a specific area 0037 the Equipment Identity Register EIR which holds information relating to manufacturer models identities of Mobile Stations 0038 This simplified architecture is shown in FIG 1 Note that the Network Switching Subsystems owned by the various GSM networks are able to communicate with each other this ability is what enables subscriber roaming 0039 A single GSM network is often referred to as a Private Land Mobile Network PLMN GSM SIM Cards 0040 A GSM SIM contains two unique numbers which are allocated by the network operator The first of these is known as the International Mobile Subscriber Identifier IMSI and is used to identify the SIM to any GSM network to which the mobile equipment containing the SIM wishes to connect The SIM includes codes for the country and PLMN as well as the individual subscriber The second unique num ber stored in the SIM is known as the Ki This is kept private even from the subscriber it cannot be read from the SIM and is never transmitted over the air Both the IMS and the Ki are each unique to the SIM in which they are stored The PLMN which issued the SIM keeps copies of each IMSI and Ki which it has issued normally in the HLR GSM Signalling 0041 GSM signalling provides a method of communicat ing between a BSS and a number of MSs by dividing up the physical communication channels i
22. s and messages to be received on any registered SIM PLMN Network Switching External Subsystem Networks NSS Visitor Location Register VLR Home Location Register HLR PSTN Mobile services Switching ISDN Centre MSC PSPON elc Authentication Equipment Centre Identity Register EIR Other PLMINs Nov 4 2010 Sheet 1 of 3 US 2010 0279698 A1 Patent Application Publication SNW1d 23O ala ony 1 Ayquep 2 juawdinb3 uongonueuiny NGdSd osw anuag Nas BUIYDIMS seovues apqow NiSd 47A JeisiBeu 47H 207 JOJISIA Uongo0 SSN SXIOMJ3N wa sAsqng pewag OMEN s18 uones JBAIBOSUBL uoneis J8AISSSUEJ osa uogejs aseg uoneis Jaalaosuel aseg ssa uejsAsqns 001835 eseg eunDiJ 0 O90 Wis m WIS o NI WIS 96 Q wis U WIS SW pue WIS 500135 allqoN Patent Application Publication Figure 2 Nov 4 2010 Sheet 2 of 3 MS switches on locates synchronises and starts decoding messages on the common channels of the BSS MS request a dedicated control channel from the BSS via a CHANNEL REQUEST message on the CCCH BSS allocated a dedicated control chanel channel via an IMME
23. ssociate control channels with the SIM to which they were assigned by the BSS 0080 4 that the user interface and associated elements in the ME be adapted to handle multiple SIMs For example 0081 users need to be able to select which SIM is to be used for making calls while a default may work in some circumstances it is not difficult to envisage situations where charging policies and contract details make it preferable for certain calls to certain numbers or calls made a particular times to be charged to one specific subscriber account associated with the selected SIM 0082 users may need to know the SIM to which any incoming calls and data messages are directed 0083 logs and other administrative details would need to take account of the existence of more than one SIM 0084 users may need or wish to selectively disable SIMs in their handset in which case it would revert to conventional single SIM operation 0085 Note that some of these tasks can be simplified by making use of the memory storage available in each SIM for example SMS messages could be stored in the memory of the SIM to which they were addressed 0086 The software in the ME would also have to correctly handle call collisions where incoming calls to one SIM occur during an incoming call to another SIM 0087 It is not possible to take both calls simultaneously while this invention permits an ME to instantiate multiple logical control channels which all
24. thm incorporating the last three digits of the IMSI Messages from the BSS would be addressed to the MS over the common paging channels by means of its TMSI 0057 key perception behind this invention is that the GSM protocols and authentication procedures make use of distinct logical control channels but do not necessarily require the use of separate physical control channels There fore a device equipped with only a single GSM radio need not be restricted from registering and supporting multiple SIMs provided that those multiple SIMs can use the same common control channel This is in fact the case where multiple SIMs can all be registered with the same BTS so all the SIMs are in the same cell on the same network The main limitation in respect of using multiple logical control channels is in fact a limitation of the ME the handset needs to allow sufficient memory in its protocol stack for tracking multiple instantia tions of the logical control channels There is no need for multiple instances of any radio hardware since the logical control channels for all the SIMs are carried on the same physical channel 0058 In fact many GSM handsets currently available do allocate resources for multiple cases of the various common and dedicated control channels These are used for such com mon GSM features such as call handoffs from cell to cell supporting call holding accepting second incoming calls making conference calls and receiving
25. tion to the MS on the Paging and Access Grant Channel PAGCH this is a slotted proto col divided into a number of sub channels with the MS waking up to listen only to its allocated sub channel and conserving power by switching its radio off at other times 0045 Other logical channels are used for the transfer of data to and from one particular MS when it is in dedicated mode These include a number of dedicated control channels such as the bidirectional Stand Alone Dedicated Control Channel SDDCH used for authentication together with the main traffic channels used for transfer of data such as voice GSM Subscriber Registration and Authentication 0046 A full account of this procedure can be found in ETSI 04 08 However a simplified account of one typical case of a single SIM telephone registering with a new cell in a GSM network will now be described with reference to FIG 2 0047 1 When the MS is switches on it locates syn chronises with and starts decoding messages on the common control channels of the BSS 0048 2 The MS request a dedicated control channel from the BSS via a CHANNEL REQUEST message on the CCCH the BSS allocates a dedicated control chan nel via an IMMEDIATE ASSIGNMENT message on the CCCH 0049 3 The MS notifies the BSS of its presence in the cell by means of aLOCATION UPDATING REQUEST message this message contains the IMSI 0050 4 The BSS passes the IMSI to the NSS which looks up the matc
26. tionality 0004 Since the first commercial services began in 1991 GSM Groupe Sp cial Mobile or Global System for Mobile communications has become the most widely used technol ogy for mobile wireless telecommunications with about 75 of the worldwide market and over 1 5 billion subscribers on over 100 different GSM compatible networks The system has evolved through GPRS General Packet Radio Services and EDGE Enhanced Data rates for GSM Evolution to 3GSM Third Generation GSM networks 0005 All GSM devices incorporate a SIM Subscriber Identity Module card which holds all the information needed for the GSM Network Provider to establish the identity of the person using the phone allocate the appropriate telephone number and bill the costs of any calls to the appropriate account holder When the SIM card is moved from one GSM handset to another GSM handset the identity of the sub scriber moves with it Similarly the removal ofthe SIM card from a GSM handset and its replacement with another SIM card results in the GSM handset identifying itself to the net work as a different subscriber and being allocated a different telephone number 0006 Itis becoming increasingly common for individuals to have more than one GSM subscription There may be a number of reasons for this 0007 People may use one GSM number for work or business calls and another for personal calls either for reasons of convenience or for easier accounting
27. using only a single GSM radio 0020 According to a first aspect of the present invention there is provided a method of operating a wireless telecom munications device containing multiple subscriber identities which have been allocated by one or a plurality of wireless networks by which the said multiple subscriber identities are enabled and activated for simultaneous use on a single wire less network 0021 According to a second aspect of the present inven tion there is provided a computing device arranged to operate in accordance with a method of the first aspect 0022 According to a third aspect of the present invention there is provided an operating system for causing a computing device to operate in accordance with the first aspect 0023 Embodiments of the present invention will now be described by way of further example only with reference to the accompanying drawings in which 0024 FIG 1 shows an architecture for a GSM telephone network 0025 FIG 2 shows a procedure for GSM subscriber authentication and registration which occurs when a SIM based handset requests a communication channel to be estab lished with a subscriber network and 0026 FIG 3 shows an embodiment of the present inven tion 0027 The present invention enables a single GSM mobile telephone to support two SIMs simultaneously using only a single GSM radio 0028 Inorder to understand the preferred implementation of this invention it is
Download Pdf Manuals
Related Search