US 20090286542A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2009/0286542 A1 ROBERTS et al. (43) Pub. Date: Nov. 19, 2009

(54) METHOD AND APPARATUS FOR Publication Classification TRANSTONING FROMA FIRST RAT TO A (51) Int. Cl. SECOND RAT H04.736/00 (2009.01) (75) Inventors: Gideon ROBERTS, Surrey (GB); H04M I/00 (2006.01) Sukhdev SAINI, Surrey (GB) (52) U.S. Cl...... 455/436: 455/552.1 Correspondence Address: CONLEY ROSE, PC. 5601 GRANITE PARKWAY, SUITE 750 (57) ABSTRACT PLANO, TX 75024 (US) A method, in a wireless communications device having a first (73) Assignee: RESEARCH IN MOTION protocol stack for use with a first radio access technology and LIMITED, Waterloo (CA) a second protocol stack for use with a second radio access technology, the method for transitioning from a first radio (21) Appl. No.: 12/463,124 access technology to a second radio access technology, the method comprising: maintaining a list of available commu (22) Filed: May 8, 2009 nication cells associated with the second radio access tech nology, and transferring information associated with more Related U.S. Application Data than one available communication cell associated with the (60) Provisional application No. 61/052,085, filed on May second radio access technology from the first protocol stack 9, 2008. to the second protocol stack.

2O1 Start

2O2 Maintain List of available UMTS cells

2O3 Identify transition from GPRS to UMTS required

2O4. Transfer List of available UMTS cells from GPRS protocol stack to UMTS protocol stack

Attempt to connect to a 2O5 first listed available UMTS Cell

Attempt to connect 2O7 Attempt to further listed Successful? available UMTS cell

END 208 Patent Application Publication Nov. 19, 2009 Sheet 1 of 4 US 2009/0286542 A1

112 110

Fig. 1 Patent Application Publication Nov. 19, 2009 Sheet 2 of 4 US 2009/0286542 A1

Maintain List of available UMTS cells

2O3 ldentify transition from GPRS to UMTS required

204 Transfer List of available UMTS cells from GPRS protocol stack to UMTS protocol stack

Attempt to connect to a 205 first listed available UMTS Cell

Attempt to connect 2O7 Attempt to further listed

Successful? available UMTS Cell

Fig. 2 Patent Application Publication Nov. 19, 2009 Sheet 3 of 4 US 2009/0286542 A1

Star"

302 Maintain List of available GPRS Celts

303 identify transition from UMTS to GPRS required

304 Transfer List of available GPRS Cells from UMTS protocol stack to GPRS protocol stack

Attempt to connect to a 305 first listed available GPRS cell

306 Attempt to connect 307 Attempt to further listed

Successful? available GPRS Cell

308 END Fig. 3 Patent Application Publication Nov. 19, 2009 Sheet 4 of 4 US 2009/0286542 A1

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METHOD AND APPARATUS FOR 0008 FIG. 1 is a schematic diagram showing an overview TRANSTONING FROMA FIRST RAT TO A of a network and a UE device; SECOND RAT 0009 FIG. 2 is a flow diagram showing, at a high level, a process performed by the UE during an inter-RAT cell rese CROSS-REFERENCE TO RELATED lection as described herein; APPLICATIONS 0010 FIG. 3 is a flow diagram showing, at a high level, a 0001. The present application claims priority to U.S. Pro process performed by the UE during an alternative inter-RAT visional Patent Application No. 61/052,085, filed May 9, cell reselection; and 2008, by Gideon Roberts, et al, entitled “Method and Appa 0011 FIG. 4 is a block diagram illustrating a mobile ratus for Transitioning From a First RAT to a Second RAT device, which can act as a UE in accordance with the (31496-US-PRV 4214-08000), which is incorporated by approach described herein. reference herein as if reproduced in its entirety. DETAILED DESCRIPTION OF THE DRAWINGS TECHNICAL FIELD 0002 This application relates to telecommunication sys 0012 Consider a wireless mobile device, generally tems in general, having for example application in UMTS referred to as user equipment (UE), which complies with the (Universal Mobile Telecommunications System) and in par 3GPP specifications for the UMTS protocol. The 3GPP ticular relates to a method and apparatus for transitioning 25.304 specification, V 7.1.0, incorporated herein by refer from a first Radio Access Technology (RAT) to a second ence and referred to herein as the 25.304 specification, Radio Access Technology (RAT). addresses the subject of User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected BACKGROUND mode. (0013 Section 5.2 of the 25.304 specification defines cell 0003. In a typical cellular radio system, mobile user equip selection and reselection in idle mode. This applies to UES ment (UE) communicates via a radio access radio network that support at least a UMTS () network. Different types of (RAN) to one or more core networks. User equipment (UE) measurements are used in different RATs and modes for cell comprises various types of equipment such as mobile tele selection and reselection. The performance requirements for phones (also known as cellular or cell phones), laptops with the measurements are specified in 3GPP TS 25.133 “Require wireless communication capability, personal digital assis ments for Support of Radio Resource Management (FDD) tants (PDAs) etc. These may be portable, hand held, pocket and 3GPP TS 25.123 “Requirements for Support of Radio sized, installed in a vehicle etc and communicate Voice and/or Resource Management (TDD), both incorporated herein by data signals with the radio access network. reference. The non- can control the RAT(s) in 0004. In the following, reference will be made to UMTS which the cell selection should be performed, for instance by and to particular standards. However it should be understood indicating RAT(s) associated with the selected Public Land that this disclosure is not intended to be limited to any par Mobile Network (PLMN), and by maintaining a list of for ticular mobile telecommunications system or standard. bidden registration area(s) and a list of equivalent PLMNs. 0005. The radio access network covers a geographical area The UE selects a suitable cell and the radio access mode based divided into a plurality of cell areas. Each cell area is served on idle mode measurements and cell selection criteria. by at least one base station, which in UMTS may be referred 0014. In order to speed up the cell selection process, stored to as a Node B. Each cell is identified by a unique identifier information for several RATs may be available in the UE. which is broadcast in the cell. The base stations communicate When camped on a cell, the UE shall regularly search for a at radio frequencies over an with the UEs within better cell according to the cell reselection criteria. If a better range of the base station. Several base stations may be con cell is found, that cell is selected. The change of cell may nected to a (RNC) which controls imply a change of RAT. The non-access stratum is informed various activities of the base stations. The radio network if the cell selection and reselection results in changes in the controllers are typically connected to a core network. received system information. For normal service, the UE has 0006 UMTS is a third generation public land mobile tele to camp on a suitable cell, tune to that cell's control channel(s) communication system. Various standardization bodies are so that the UE can receive system information from the known to publish and set standards for UMTS, each in their PLMN. respective areas of competence. For instance, the 3GPP (0015 Section 5.2.5.1 of the 25.304 specification defines (Third Generation Partnership Project) has been known to the UE activity in a camped normally state for the case of publish and set standards for GSM (Global System for connection to a UMTS cell. When camped normally, the UE Mobile Communications) based UMTS, and the 3GPP2 performs necessary measurements for the cell reselection (Third Generation Partnership Project 2) has been known to evaluation procedure. The UE also executes the cell reselec publish and set standards for CDMA (Code Division Multiple tion evaluation process when appropriately triggered. The Access) based UMTS. Within the scope of a particular stan cell reselection evaluation process may be triggered by a UE dardization body, specific partners publish and set standards internal trigger or when information on the broadcast control in their respective areas. channel (BCCH) used for the cell reselection evaluation pro cedure has been modified. BRIEF DESCRIPTION OF THE DRAWINGS 0016. Problems with inter-RAT cell reselection in a UE 0007 Embodiments will now be described, by way of have been identified, particularly in the case of an inter-RAT example only, with reference to the attached drawings, in cell reselection from a 2GRAT (such as GSM or GPRS) to a which: 3GRAT (such as UMTS). There are thus proposed strategies US 2009/0286542 A1 Nov. 19, 2009

for a method and apparatus for transitioning from a first RAT GPRS protocol stack to the UMTS protocol stack. At 205 the to a second RAT. A number of such strategies are detailed UE attempts to connect to a first listed available UMTS cell. below. At 206 a determination is made as to whether the attempt was 0017. Other aspects and features of the proposed strategy successful. If the attempt was not successful, then the UE will become apparent to those ordinarily skilled in the art attempts to connect to a further available UMTS cell as listed upon review of the following description of specific embodi in the list transferred from the GPRS protocol stack to the ments of a method and apparatus for transitioning from a first UMTS protocol stack. If the attempt was successful, then the RAT to a second RAT. method ends at 208. 0.018. In the case where a UE is connected to a network, it maintains a list of UMTS cells that it could use. When the 0025. As used herein, “list’ is understood to mean any UE determines it should transition to a UMTS cell, it selects method and organization of data that allows the stack Soft the one with the biggest ReceivedSignal Code Power (RSCP) ware for a RAT to keep track of a plurality of sets of data, each value. The 2G protocol stack of the UE transfers this infor set of data being the data associated with an available cell and mation for this cell to the 3G protocol stack which tries to retrievable in any manner associable with the cell. No par connect to it. ticular relationship or ordering between the sets of data is 0019. However, it is possible that the 3G cell for which the implied, other than having the property of being retrievable information is transferred is not suitable for communication. by the stack software. One exemplar embodiment would be a The parameters required to determine if the 3G cell is suitable formal list structure, each list element having pointers or data for the UE are broadcast on the Broadcast Control Channel structures configured to contain, or otherwise enable retrieval (BCCH). If the 3G protocol stack finds that the 3G cell for of the data in a particular data set. The method used to which the information is transferred is not suitable for com organize the list elements could be implemented using any of munication, then the 3G protocol stack must signal back to the ways known to person of skill in the applicable software the 2G protocol stack for details of alternative 3G cells. This engineering arts. Further other data structures can be used as signaling between the protocol stacks delays the initiation of well, as would be known to a person of skill in the software the transfer and can result in a communication disruption engineering arts. between the UE and the network. 0026 FIG. 3 is a flow diagram showing, at a high level, a 0020. According to the method disclosed herein, the infor process performed by the UE during an alternative inter-RAT mation for more than one UMTS cell is transferred from the cell reselection as described herein. At 301 the method is 2G protocol stack to the 3G protocol stack, such that if the first initiated. While operating on a UMTS (3G) network the UE 3G cell is not suitable, then the UE can try the next one that maintains a list of available GPRS (2G) cells, as shown at 302. was transferred, without having to refer back to the 2G pro This list is maintained by the UMTS protocol stack. At 303 tocol stack. the UE identifies that a transition is required from UMTS to 0021. The method disclosed herein thus reduces the GPRS. At 304 the UE transfers the list of available GPRS amount of signaling required between the 2G and 3G protocol cells from the UMTS protocol stack to the GPRS protocol stacks during inter-RAT cell reselection. stack. At 305 the UE attempts to connect to a first listed 0022. The method disclosed herein may be implemented available GPRS cell. At 306 a determination is made as to in a user equipment device of a wireless communications whether the attempt was successful. If the attempt was not network. Referring to the drawings, FIG. 1 is a schematic successful, then the UE attempts to connect to a further avail diagram showing an overview of a network and a user equip able GPRS cell as listed in the list transferred from the UMTS ment device. Clearly in practice there may be many user protocol stack to the GPRS protocol stack. If the attempt was equipment devices operating with the network but for the sake successful, then the methodends at 308. Where comments are of simplicity FIG. 1 only shows a single user equipment made below with reference to FIG. 2, these could also be device 100. For the purposes of illustration, FIG. 1 also shows applied to FIG. 3. a radio access network 119 (UTRAN) used in a UMTS sys (0027. While operating on a GPRS (2G) network the UE is tem having a few components. It will be clear to a person required to make measurements on cells of other radio access skilled in the art that in practice a network will include far technologies. These requirements are given in 3GPP specifi more components than those shown. cation TS 05.08 v 8.15.0, incorporated herein by reference 0023 The network 119 as shown in FIG.1 comprises three and referred to herein as the 05.08 specification. Section 6.6.4 Radio Network Subsystems (RNS) 102. Each RNS has a of the 05.08 specification states that for a multi-RATUE, cells Radio Network Controller (RNC) 104. Each RNS 102 has or frequencies with other radio access technologies may be one or more Node B 102 which are similar in function to a included in 3G Cell Reselection list (see 3GPP TS 04.18, Base Transmitter Station of a GSM radio access network. incorporated herein by reference). The network controls the User Equipment UE 100 may be mobile within the radio measurements for reselection of these cells by the parameter access network. Radio connections (indicated by the straight Qsearch I broadcast on BCCH. Qsearch I defines a thresh dottedlines in FIG.1) are established between the UE and one old and also indicates whether these measurements shall be or more of the Node BS in the UTRAN. performed when RLA C (a running average of received sig 0024 FIG. 2 is a flow diagram showing, at a high level, a nal level) of the serving cell is below or above the threshold. process performed by the UE during inter-RAT cell reselec These measurements may be performed less frequently than tion as described herein. At 201 the method is initiated. While measurements of GSM cells, in order to conserve UE power. operating on a GPRS (2G) network the UE maintains a list of The UE is able to identify and select a new best UTRAN cell available UMTS (3G) cells, as shown at 202. This list is on a frequency, which is part of the 3G Cell Reselection list, maintained by the GPRS protocol stack. At 203 the UE within 30 seconds after it has been activated under the con tifies that a transition is required from GPRS to UMTS. At dition that there is only one UTRAN frequency in the list and 204 the UE transfers the list of available UMTS cells from the under good radio conditions. US 2009/0286542 A1 Nov. 19, 2009

0028 Section 6.6.5 of the 05.08 specification describes particular design of the communication subsystem 911 will the algorithm implemented for determining cell reselection be dependent upon the communication network in which the from GPRS (or GSM) to UTRAN. If the 3G Cell Reselection device is intended to operate. For example, mobile station 900 list includes UTRAN frequencies, the UE updates the value may include a communication Subsystem 911 designed to RLA C for the serving cell and each of the at least 6 strongest operate within the MobitexTM mobile communication system, non-serving GSM cells at least every 5 seconds. The UE then the DataTACTM mobile communication system, GPRS net reselects a suitable UTRAN cell if its measured RSCP value work, UMTS network, or EDGE network. exceeds the value of RLA C for the serving cell and all of the 0033 Network access requirements will also vary depend suitable non-serving GSM cells by the value XXX Ooffset ing upon the type of network 902. For example, in the Mobi for a period of 5 seconds and, for FDD, the UTRAN cells tex and DataTAC networks, mobile station 900 is registered measured ratio of energy per modulating bit to the noise on the network using a unique identification number associ spectral density (“Ec/No) value is equal or greater than the ated with each mobile station. In UMTS and GPRS networks, value FDD Qmin. In case of a cell reselection occurring however, network access is associated with a Subscriber or within the previous 15 seconds, XXX Ooffset is increased by user of mobile Station 900. A GPRS mobile Station therefore 5 dB. Ec/No and RSCP are the measured quantities: FDD requires a subscriber identity module (SIM) card in order to Qmin and XXX Ooffset are broadcast on BCCH of the serv operate on a GPRS network. Without a valid SIM card, a ing cell. XXX indicates other radio access technology/mode. GPRS mobile station will not be fully functional. Local or Note that the parameters required to determine if the UTRAN non-network communication functions, as well as legally cell is Suitable are broadcast on BCCH of the UTRAN cell. A required functions (if any) Such as "911" emergency calling, UE may start reselection towards the UTRAN cell before may be available, but mobile station 900 will be unable to decoding the BCCH of the UTRAN cell, leading to a short carry out any other functions involving communications over interruption of service if the UTRAN cell is not suitable. If the network.902. The SIM interface 944 is normally similar to more than one UTRAN cell fulfils the above criteria, the UE a card-slot into which a SIM card can be inserted and ejected would usually select the cell with the greatest RSCP value. like a diskette or PCMCIA card. The SIM card can have 0029. At 204 and 304 the UE transfers a list of available approximately 64K of memory and hold many key configu UMTS cells from the one protocol stack to another protocol ration 951, and other information 953 such as identification, stack. Taking 204 as an example, the transferred list com and subscriber related information. prises information relating to a plurality of UMTS cells, but 0034. When required network registration or activation not necessarily all UMTS cells in the list of available UMTS procedures have been completed, mobile station 900 may cells maintained by the GPRS protocol stack. The transferred send and receive communication signals over the network list may comprise a subset of the list maintained by the GPRS 902. Signals received by antenna 916 through communica protocol stack. This Subset may be selected as a predeter tion network 902 are input to receiver 912, which may per mined number of UMTS cells with the biggest current RSCP form such common receiver functions as signal amplification, value, for example. Alternatively, the subset may be deter frequency down conversion, filtering, channel selection and mined as all UMTS cells with RSCP values above a certain the like, and in the example system shown in FIG.3, analog to threshold. digital (AND) conversion. A/D conversion of a received sig 0030. If none of the UMTS cells in the transferred list are nal allows more complex communication functions such as suitable for communication by the UE, then the 3G protocol demodulation and decoding to be performed in the DSP 920. stack refers back to the 2G protocol stack. Even in such a In a similar manner, signals to be transmitted are processed, situation, the amount of signaling between the 3G and the 2G including modulation and encoding for example, by DSP 920 protocol stack is reduced because the 3G protocol stack has and input to transmitter 914 for digital to analog conversion, not had to refer back to the 2G protocol stack after each frequency up conversion, filtering, amplification and trans UMTS cell was found to be unsuitable. mission over the communication network 902 via antenna 0031 Turning now to FIG. 4, this is a block diagram 918. DSP 920 not only processes communication signals, but illustrating a mobile device, which can act as a UE and co also provides for receiver and transmitter control. For operate with the apparatus and methods of FIGS. 1 to 3, and example, the gains applied to communication signals in which is an exemplary wireless communication device. receiver 912 and transmitter 914 may be adaptively controlled Mobile station 900 is preferably a two-way wireless commu through automatic gain control algorithms implemented in nication device having at least voice and data communication DSP 920. capabilities. Mobile station 900 preferably has the capability 0035) Mobile station 900 preferably includes a micropro to communicate with other computer systems on the Internet. cessor 938 which controls the overall operation of the device. Depending on the exact functionality provided, the wireless Communication functions, including at least data and Voice device may be referred to as a data messaging device, a communications, are performed through communication two-way pager, a wireless e-mail device, a cellular telephone subsystem 911. Microprocessor 938 also interacts with fur with data messaging capabilities, a wireless Internet appli ther device subsystems such as the display 922, flash memory ance, or a data communication device, as examples. 924, random access memory (RAM) 926, auxiliary input/ 0032. Where mobile station 900 is enabled for two-way output (I/O) subsystems 928, serial port 930, keyboard 932, communication, it will incorporate a communication Sub speaker 934, microphone936, a short-range communications system 911, including both a receiver 912 and a transmitter subsystem 940 and any other device subsystems generally 914, as well as associated components such as one or more, designated as 942. preferably embedded or internal, antenna elements 916 and 0036 Some of the subsystems shown in FIG. 4 perform 918, local oscillators (LOs) 913, and a processing module communication-related functions, whereas other Subsystems such as a digital signal processor (DSP) 920. As will be may provide “resident’ or on-device functions. Notably, apparent to those skilled in the field of communications, the some subsystems, such as keyboard 932 and display 922, for US 2009/0286542 A1 Nov. 19, 2009

example, may be used for both communication-related func transmission would be generated by a microphone936. Alter tions, such as entering a text message for transmission over a native voice or audio I/O Subsystems, such as a voice message communication network, and device-resident functions such recording Subsystem, may also be implemented on mobile as a calculator or task list. station 900. Although voice or audio signal output is prefer 0037 Operating system software used by the micropro ably accomplished primarily through the speaker 934, dis cessor 938 is preferably stored in a persistent store such as play 922 may also be used to provide an indication of the flash memory 924, which may instead be a read-only memory identity of a calling party, the duration of a voice call, or other (ROM) or similar storage element (not shown). Those skilled voice call related information for example. in the art will appreciate that the operating system, specific 0041) Serial port 930 in FIG.4, would normally be imple device applications, or parts thereof, may be temporarily mented in a personal digital assistant (PDA)-type mobile loaded into a volatile memory such as RAM 926. Received station for which synchronization with a user's desktop com communication signals may also be stored in RAM926. puter (not shown) may be desirable, but is an optional device 0038. As shown, flash memory 924 can be segregated into component. Such a port 930 would enable a user to set pref different areas for both computer programs 958 and program erences through an external device or software application data storage 950,952,954 and 956. These different storage and would extend the capabilities of mobile station 900 by types indicate that each program can allocate a portion of providing for information or software downloads to mobile flash memory 924 for their own data storage requirements. station 900 other than through a wireless communication Microprocessor 938, in addition to its operating system func network. The alternate download path may for example be tions, preferably enables execution of software applications used to load an encryption key onto the device through a on the mobile station. A predetermined set of applications that direct and thus reliable and trusted connection to thereby control basic operations, including at least data and Voice enable secure device communication. communication applications for example, will normally be 0042. Other communications subsystems 940, such as a installed on mobile station 900 during manufacturing. A pre short-range communications Subsystem, is a further optional ferred software application may be a personal information component which may provide for communication between manager (PIM) application having the ability to organize and mobile station 900 and different systems or devices, which manage data items relating to the user of the mobile station need not necessarily be similar devices. For example, the Such as, but not limited to, e-mail, calendar events, Voice subsystem 940 may include an infrared device and associated mails, appointments, and task items. Naturally, one or more circuits and components or a BluetoothTM communication memory stores would be available on the mobile station to module to provide for communication with similarly enabled facilitate storage of PIM data items. Such PIM application systems and devices. would preferably have the ability to send and receive data items, via the wireless network 902. In a preferred embodi EXTENSIONS AND ALTERNATIVES ment, the PIM data items are seamlessly integrated, synchro nized and updated, via the wireless network 902, with the 0043. In the foregoing specification, the disclosure has mobile station user's corresponding data items stored or asso been described with reference to specific embodiments ciated with a host computer system. Further applications may thereof. It will, however, be evident that various modifica also be loaded onto the mobile station 900 through the net tions and changes may be made thereto without departing work 902, an auxiliary I/O subsystem 928, serial port 930, from the scope of the technique. The specification and draw short-range communications subsystem 940 or any other Suit ings are, accordingly, to be regarded in an illustrative rather able subsystem 942, and installed by a user in the RAM926 than a restrictive sense. or preferably a non-volatile store (not shown) for execution 0044. It is to be noted that the methods as described have by the microprocessor 938. Such flexibility in application actions being carried out in a particular order. However, it installation increases the functionality of the device and may would be clear to a person skilled in the art that the order of provide enhanced on-device functions, communication-re any actions performed, where the context permits, can be lated functions, or both. For example, secure communication varied and thus the ordering as described herein is not applications may enable electronic commerce functions and intended to be limiting. other such financial transactions to be performed using the 0045. It is also to be noted that where a method has been mobile Station 900. described it is also intended that protection is also sought for 0039. In a data communication mode, a received signal a device arranged to carry out the method and where features Such as a text message or web page download will be pro have been claimed independently of each other these may be cessed by the communication subsystem 911 and input to the used together with other claimed features. microprocessor 938, which preferably further processes the 0046. Furthermore it will be noted that the apparatus received signal for output to the display 922, or alternatively described herein may comprise a single component such as a to an auxiliary I/O device 928. A user of mobile station 900 UE or UTRAN or other user equipment or access network may also compose data items such as email messages for components, a combination of multiple such components for example, using the keyboard932, which is preferably a com example in communication with one another or a Sub-net plete alphanumeric keyboard or telephone-type keypad, in work or full network of such components. conjunction with the display 922 and possibly an auxiliary 0047. A portion of the disclosure of this patent document I/O device 928. Such composed items may then be transmit contains material which is subject to copyright protection. ted over a communication network through the communica The copyright owner has no objection to the facsimile repro tion subsystem 911. duction by anyone of the patent document or patent disclo 0040. For voice communications, overall operation of sure, as it appears in the Patent and Trademark Office patent mobile station 900 is similar, except that received signals file or records, but otherwise reserves all copyright rights would preferably be output to a speaker 934 and signals for whatsoever. US 2009/0286542 A1 Nov. 19, 2009

What is claimed is: 9. A method according to claim 1, wherein the second radio 1. A method, in a wireless communications device having access technology is a 2G access technology. a first protocol stack for use with a first radio access technol 10. A method according to claim 9, wherein the second ogy and a second protocol stack for use with a second radio radio access technology is GSM or GPRS. access technology, the method for transitioning from a first 11. A method according to claim 1, wherein the first radio radio access technology to a second radio access technology, access technology is 3G. the method comprising: 12. A method according to claim 11, wherein the first radio access technology is UMTS. maintaining a list of available communication cells asso 13. A wireless communications apparatus having a first ciated with the second radio access technology, and protocol stack for use with a first radio access technology and transferring information associated with more than one a second protocol stack for use with a second radio access available communication cell associated with the sec technology, the wireless communications apparatus arranged ond radio access technology from the first protocol stack tO: to the second protocol stack. maintain a list of available communication cells associated 2. A method according to claim 1, further comprising: with the second radio access technology; attempting to connect to a first available communication cell transfer information associated with more than one avail associated with the second radio access technology, wherein able communication cell associated with the second information associated with the first available communica radio access technology from the first protocol stack to tion cell was transferred from the first protocol stack to the the second protocol stack; and second protocol stack. transition from a communication cell associated with the 3. A method according to claim 2, wherein if the attempt to first radio access technology to a communication cells connect to the first available communication cell is unsuc associated with the second radio access technology. cessful, the method further comprising attempting to connect 14. A computer program comprising program code for use to a further available communication cell associated with the in a wireless communications apparatus, the wireless com second radio access technology, wherein information associ munications apparatus having a first protocol stack for use ated with the further available communication cell was trans with a first radio access technology and a second protocol ferred from the first protocol stack to the second protocol stack for use with a second radio access technology, the stack. computer program causing the wireless communications apparatus to: 4. A method according to claim 1, further comprising maintain a list of available communication cells associated establishing a communication connection to a communica with the second radio access technology; tion cell associated with the second radio access technology. transfer information associated with more than one avail 5. A method according to claim 1, wherein the first radio able communication cell associated with the second access technology is a 2G access technology. radio access technology from the first protocol stack to 6. A method according to claim 5, wherein the first radio the second protocol stack; and access technology is GSM or GPRS. transition from a communication cell associated with the 7. A method according to claim 1, wherein the second radio first radio access technology to a communication cells access technology is 3G. associated with the second radio access technology. 8. A method according to claim 7, wherein the second radio access technology is UMTS. c c c c c