WO2013175413A1

WO2013175413A1 - Method, apparatus and computer program for controlling a use equipment

Info

Publication number: WO2013175413A1
Application number: PCT/IB2013/054234
Authority: WO
Inventors: Keiichi Kubota; Brian Martin
Original assignee: Renesas Mobile Corporation
Priority date: 2012-05-24
Filing date: 2013-05-22
Publication date: 2013-11-28
Also published as: GB201209158D0; GB2491046B; GB2491046A

Abstract

A user equipment UE simultaneously having a first radio access bearer associated with a circuit-switched domain and a second radio access bearer associated with a packet-switched domain detects (108) an error on the second radio bearer. In response, the UE implements (110) a timer associated with the packet-switched domain according to an indication received (104) from a wireless network for how to implement that timer, without interrupting the first radio access bearer due to the error.

Description

METHOD, APPARATUS AND COMPUTER PROGRAM

FOR CONTROLLING A USE EQUIPMENT

Cross Reference to Related Application

This application claims the benefit under 35 U.S.C. § 119 and 37 CFR § 1.55 to UK patent application no. 1209158.3, filed on May 24, 2012, the entire content of which is incorporated herein by reference.

Technical Field

The present invention relates to a method, apparatus and computer program for operating a user equipment. The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, in specific embodiments, relate to re-establishing a dropped wireless connection such as a dropped voice call.

Background

Radio equipment manufacturers and wireless network operators strive to provide reliable and seamless service to the end user mobile terminals. It is inevitable that some shortfalls in wireless service are more noticeable to the end user than others. For example, a dropped voice call is more noticeable than a slow data rate on applications running in the background. Voice calls are often CS (circuit switched) whereas data-only connections are typically PS (packet switched) in modern cellular networks.

In the Universal Terrestrial Radio Access Network (UTRAN) system, after release 5 which introduced the high speed downlink packet access (HSDPA) version of it, the HSPDA technology would normally be used for services in the PS domain such as downloads using file transfer protocol (FTP) while the former Release 99 dedicated channel (DCH) would normally be used for services in the CS domain such as voice calls. Modern smartphones are capable of holding multiple connections at once and so can simultaneously have both circuit switched (CS) connections and packet switched (PS) connections. In this case, sometimes the CS connection will drop.

Different radio access technologies (RATs) handle dropped connections differently. In the UTRAN system, typically the mobile terminal (or more generally the user equipment UE) will recognise a dropped call as a radio link control (RLC) unrecoverable error, which occurs when the lower layer of the acknowledged-mode (AM) RLC has a communication problem with the peer end. When a UE detects the RLC unrecoverable error, the current 3 GPP standard mandates the UE to initiate a cell update procedure if a call re-establishment timer associated with the problematic radio bearer is set to a non-zero value. Further detail can be seen at 3GPP TS25.331 vlO.7.0 (2012-03) at sections 8.3.1.2, 8.3.1.13 and 8.3.1.14 which discuss handling for timers T314 and T315. When the UE detects the RLC unrecoverable error, any service is temporarily disrupted during the cell update procedure because all dedicated resources are temporarily released during the procedure or the service is dropped if the service domain does not support any call re-establishment procedure. So if a CS call with a mobile terminal is dropped while the mobile terminal also has one or more other PS connections, the procedure to recover the CS call also interrupts all the PS connections. Since both users and network operators consider dropping a CS voice call to be unacceptable, this may be beneficial if the PS interruptions served to reestablish the dropped CS voice call more quickly, but that is not typically the case. Relevant teachings in regard to the above problem may be seen at documents

R2-113178 by Renesas Mobile Europe entitled "Cell update-less RLC/PDCP unrecoverable error recovery" (3GPP TSG-RAN WG2 Meeting #74; Barcelona, Spain; 9-13 May 2011); R2-120533 by Nokia Siemens Networks entitled "PS RAB unrecoverable error in the multi-RAB configuration" (3 GPP TSG-RAN WG2 Meeting #77; Dresden, Germany; 2-10 February 2012); and R2-120722 by Qualcomm entitled "On avoiding PS RAB PLC unrecoverable error during mRAB" (also 3GPP TSG-RAN WG2 Meeting #77; Dresden, Germany; 2-10 February 2012).

Of these documents, the first is by the present applicant. The second has the network predict when a call might be dropped and pre-emptively release the PS bearer but does not appear to be a solution that can be standardised across multiple network operators to give the various users the same experience no matter where they roam. The third appears to foreclose the option of recovering the dropped PS service, leaving the PS user-plane (U-plane) without any recovery attempt, which appears likely to be quite frustrating to the end user who will see dropped PS connections even if there are no dropped CS voice calls.

Summary

According to a first aspect of the present invention, there is provided a method for controlling a user equipment, the method comprising: determining that the user equipment simultaneously has at least a first radio bearer associated with a circuit- switched domain and at least a second radio bearer associated with a packet-switched domain, and in response to detecting an error on the second radio bearer, implementing a timer associated with the packet-switched domain according to an indication received from a wireless network for how to implement the timer, without interrupting the first radio bearer due to the error.

According to a second aspect of the present invention, there is provided apparatus for controlling a user equipment, the apparatus comprising a processing system configured to cause the apparatus at least to: determine that the user equipment simultaneously has at least a first radio bearer associated with a circuit- switched domain and at least a second radio bearer associated with a packet-switched domain, and in response to detecting an error on the second radio bearer, implement a timer associated with the packet-switched domain according to an indication received from a wireless network for how to implement the timer, without interrupting the first radio bearer due to the error. In various implementations this apparatus may be the whole user equipment itself, or it may be one or more components thereof.

The processing system may comprise at least one memory storing computer program code and at least one processor.

According to a third aspect of the present invention, there is provided a computer program that is executable by at least one processor, in which the computer program, when executed, controls a user equipment to at least: determine that the user equipment simultaneously has at least a first radio bearer associated with a circuit-switched domain and at least a second radio bearer associated with a packet- switched domain, and in response to detecting an error on the second radio bearer, implement a timer associated with the packet-switched domain according to an indication received from a wireless network for how to implement the timer, without interrupting the first radio bearer due to the error.

There may be provided a computer readable memory tangibly storing a computer program as described above. In various implementations this computer readable memory and the processor(s) which execute it are disposed within, or are particularly adapted to be disposed within, a user equipment or to control a user equipment.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a logic flow diagram illustrating from the perspective of the UE the operation of an example a method, and a result of execution of computer program instructions embodied on a computer readable memory, for practising exemplary embodiments of these teachings; and Figure 2 shows a simplified block diagram of a user equipment in communication with two access nodes of a cellular network, which are exemplary electronic devices suitable for use in practising the exemplary embodiments of these teachings.

Detailed Description

As noted above, it has been reported in practice that CS voice calls are sometimes dropped when a user established a CS voice call and a PS data call simultaneously. The cause of the CS voice call being dropped in this case appears to be due to an RLC unrecoverable error on a PS radio bearer which has different coverage than the CS bearer for the voice call. Specifically, in 3GPP Rel-5, CS voice service is carried on dedicated channels DCHs while PS data service is carried on the high speed downlink shared channel HS-DSCH. Specifically, CS voice service is mapped on two or three radio bearers and each radio bearer is mapped to one DCH; this set of radio bearers is referred to as a radio access bearer (RAB). PS service is carried also on a RAB but this RAB has only one radio bearer. When more than one cell exists in the active set for the DCH, there is a soft handover gain, but only one cell is used for the HS-DSCH. Thus the coverage for the PS data service carried on the HS-DSCH is different from that for the CS voice service carried on the DCH, especially when the UE is located near the cell edge of the HS-DSCH service cell.

From this the present inventors have concluded that the RLC unrecoverable error which the UE senses per radio bearer as its trigger to initiate call re- establishment actually frequently occurs on the PS radio bearer rather than on any of the CS radio bearers carrying the voice call when the UE is near the cell edge. The UTRAN mandated behaviour for the UE to respond to a RLC unrecoverable error results in the release of all dedicated resources at least during the re-establishment procedure, so this error in the PS domain and on the PS radio bearer causes the viable CS radio bearers in the CS domain to be released, and this is what drops the CS voice call. To resolve this adverse result, one aspect of these teachings entails new signalling from the network to the UE that indicates whether:

a) the UE is to apply a call re-establishment timer associated with the PS domain (for example, existing timer T315 may be used for this new purpose) for radio bearers associated with the PS domain, or

b) the UE is to not immediately apply the call re-establishment timer (or postpone initiating a cell update procedure until the release of the CS voice service).

This call re-establishment timer is associated per RAB. Below are two different embodiments of behaviour for the UE in the event the indication is to not apply the timer (or not immediately apply it) and the conditions for not applying the timer are present in the UE. In one case, the UE implements the timer according to the information element or IE (that is, it does not apply the timer) by releasing the radio bearer where a RLC unrecoverable error is detected. In this manner, the UE behaves as if the call re-establishment timer is set to zero, and in fact internal of the UE the UE may drive whatever non-zero value that is present in the timer to zero. In the other case, the UE implements the timer according to the IE (that is, it does not immediately apply the timer) by postponing its initiation of a cell update procedure due to the RLC unrecoverable error detection on the radio bearer in the PS domain until the UE releases the CS call.

There are several different ways for the network to provide this new signalling, which by example might be a whole new information element IE. In one example, this new IE or indication may be broadcast in the whole cell via system information such as system information block #1 (SIB1). In another example, this new IE or indication may be sent in a downlink radio resource control (R C) message, such as for example any one or more of the R CConnectionSetup message, one or more RRC reconfiguration messages, the UTRA Mobilitylnformation message and/or the CellUpdateConfirm message. This new information element (IE), which is to be informed to the UE in system information or via one or more downlink RRC messages, tells the UE how to implement the call re-establishment timer that is associated with the PS domain. In the first embodiment, when a CS call is established and there is also a simultaneous PS service, the new IE indicates that the UE under those conditions shall not apply the call re-establishment timer associated with the PS domain for the radio bearer associated with PS domain. When the UE has both PS and CS services simultaneously, the UE implements the timer according to the IE indication by behaving as if the call re-establishment timer is set to zero (i.e. the UE releases the PS radio bearer on which the RLC unrecoverable error was detected). Even if the UE gets the new IE, it will implement the call re-establishment timer conventionally if it does not have both PS and CS bearers. Consider a specific example for this first embodiment. If the UE does not have a CS call established, whether or not the new IE with the indication is signalled in the SIB or in an RRC message, then the UE follows the conventional UE behaviour and applies the call re-establishment timer (for example, timer T315) associated with the PS domain for radio bearers associated with the PS domain. For the case in which this timer is set to some non-zero value, the UE will then initiate a cell update procedure in response to detecting any RLC unrecoverable error on the PS domain radio bearer.

But instead if the UE does have a CS call established at the same time as a PS service and the new IE with the indication how to implement the timer is present in the SIB or in some RRC message, then the UE implements the timer according to the received indication by not applying the call re-establishment timer, and the UE behaves as if the call re-establishment timer is set to zero by releasing the PS radio bearer in response to detecting an unrecoverable RLC error on it. In this manner, the UE's simultaneous CS bearer is not interrupted by the UE's detection of an RLC error on the PS bearer. In the second embodiment, when a CS call is established, the new IE indicates that, so long as it has a PS bearer and a CS bearer, the UE is not to immediately apply the call re-establishment timer associated with the PS domain for the radio bearer associated with the PS domain. If the simultaneous PS and CS bearer conditions are met, the UE implements the timer according to the IE indication by postponing its initiation of any cell update procedure due to the RLC unrecoverable error detected on the PS domain radio bearer, until the UE releases the CS call. Consider a specific example for this second embodiment. If the UE does not have a CS call established, then, whether or not the new IE with the indication is present in the SIB or in an R C message, the UE follows the conventional UE behaviour as outlined above in the example for the first embodiment: the UE applies the call re-establishment timer associated with the PS domain for radio bearers associated with the PS domain and initiates a cell update procedure in response to the RLC unrecoverable error it detected.

But instead if the UE does have a CS call established while also having a PS service that is active and the new IE with the indication how to implement the timer is present in the SIB or in some RRC message, then the UE implements the timer according to the received indication by not immediately applying the call re-establishment timer, and in this second embodiment the UE postpones its initiation of any cell update procedure due to the RLC unrecoverable error the UE detected on the PS domain radio bearer, until the UE releases the CS call.

With either of the above embodiments, the network operators can configure the T315 timer for PS call re-establishment (or whatever other timer might be used for the PS domain bearer) when only a PS radio bearer is established with a UE, but can by these teachings also avoid the CS call drop/CS service disruption even when the T315 timer is set to non-zero. This is because the UE will not initiate a cell update procedure due to the UE detecting a RLC unrecoverable error in the PS domain while a CS call is established, as seen from the above examples. If instead the UE does not have a CS call, it may disregard the IE and implement the timer conventionally in response to the RLC unrecoverable error. And if the network prefers the conventional UE behaviour in all cases regardless of whether or not the UE has simultaneous PS and CS bearers, the network can choose not to signal the new IE in the SIB or in RRC signalling.

Figure 1 shows a logic flow diagram which may be considered to illustrate the operation of an example of a method, and a result of execution of a computer program stored in a computer readable memory, and a specific manner in which components of an electronic device such as a UE or one or more components thereof are configured to cause that electronic device to operate. The various blocks shown in Figure 1 may also be considered as a plurality of coupled logic circuit elements constructed to carry out the associated function(s), or specific result of strings of computer program code stored in a memory. As will be noted, not all portions of Figure 1 are essential for practising these teachings.

Such blocks and the functions they represent are non-limiting examples, and may be practised in various components such as integrated circuit chips and modules, and the exemplary embodiments of this invention may be realised in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.

At block 102 of Figure 1 the network sends and the UE receives a call re-establishment timer. At block 104 the network sends and the UE receives an indication of how to implement the timer. As was detailed above, this indication may be in an information element newly designed to implement these teachings, and that new information element may be communicated to the UE via broadcast system information or via some R C signalling, such as for example any one or more of a R CConnectionSetup message, one or more RRC reconfiguration messages, a UTRANMobilitylnformation message, and a CellUpdateConfirm message. The indication tells the UE either to not apply the timer or to not immediately apply the timer, depending on the embodiment. The UE follows this indication if it meets the conditions set forth at block 106 and detects the error as at block 108. It is under those conditions and error which allows the UE to retain its CS domain radio bearers when there is only an error on the PS domain bearer. In the first embodiment above, the indication tells the UE to not implement the timer, which the UE does by releasing its PS domain bearer immediately as if the timer value were zero, and in fact the UE might implement this by actually zero-ing out any non-zero value that remains in its T315 timer. In the second embodiment above, the indication tells the UE to not immediately implement the timer, which the UE does by postponing its cell update procedure, which would otherwise arise due to error on the PS-domain bearer, until the CS domain bearers are released by the UE.

Block 106 states the conditions for the UE in which these teachings provide the greatest advantage over the conventional response to a RLC unrecoverable error. Specifically, the UE has simultaneously a first radio access bearer in the CS domain and a second radio access bearer in the PS domain. As noted above, conventionally there will be two or three CS radio bearers in the RAB for CS voice service. Since block 108 refers to an error which is detected per radio bearer rather than per RAB, for these purposes a first radio bearer can be regarded as representing the first RAB in the CS domain and a second radio bearer as representing the second RAB in the PS domain. If the UE has only PS domain radio bearers (one or more depending on whether the UE has one or more ongoing PS services) but no CS domain radio bearers, then the UE can disregard the IE with the indication for how to implement the timer and follow conventional procedures to implement it. If block 106 is considered the conditions for the UE to follow the IE rather than disregard it, then the event shown at block 108 of the UE detecting an unrecoverable error on the second radio bearer may be considered as the trigger for the UE to implement the timer, either according to the IE (e.g. not apply or postpone) if the conditions of block 106 are satisfied or conventionally if those conditions are not. Figure 1 closes with block 110 at which the UE implements the timer according to the received indication, without interrupting the first radio bearer in the CS domain due to the detected error (or any other radio bearers in the CS-domain RAB). In the first embodiment, the IE tells the UE to not apply the timer and so the UE releases the second radio bearer (which is its PS domain bearer) immediately as if the timer value were zero, and in the second embodiment the IE tells the UE to postpone implementing the timer and so the UE postpones its cell update procedure due to the error on the second radio bearer that was detected at block 108 until its first radio bearer (which in this example is any of the UE's two or three CS domain bearers in the same CS-RAB) is released by the UE itself. In practice, the UE would release all the radio bearers in that RAB at once when it terminates the CS service.

Reference is now made to Figure 2 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practising the exemplary embodiments of this invention. In Figure 2 there is a serving cell/serving network access node 22 such as a base transceiver station (termed a node B in the UTRAN system) which is adapted for communication over a wireless link 21 A with an apparatus 20 such as a mobile terminal or UE. The UE 20 may be in contact with multiple cells at once and so Figure 2 illustrates the serving cell 22 and also illustrates another network access node, such as for example another macro cell or as shown a micro/pico cell 23, which has a bidirectional wireless link 2 IB with the UE 20. Each of those illustrated wireless links may represent more than one logical and/or physical channels/bearers. So for example the UE may have its CS call on two or three CS- domain radio bearers of a RAB via some corresponding DCHs in link 21 A with the serving cell 22 and also with other corresponding DCHs in link 21B with the other cell 23, while simultaneously having a PS-domain radio bearer on a HS-DSCH only in link 21 A with the serving cell. In a more simple deployment, the UE is in a connected state with only the serving cell 22 and the illustrated micro/pico cell 23 may be seen as only a neighbour cell (macro, micro/pico, or otherwise) from which the UE 20 takes occasional measurements for handover purposes. The serving cell 22 and the other cell 23 may each be further communicatively coupled via respective data and control links 25, 27 to a higher network node 24 such as a radio network controller R C in the case of the UTRAN system or a mobility management entity/serving gateway MME/S-GW 24 in the case of the evolved UTRAN system.

The UE 20 includes processing means such as at least one data processor (DP) 20A, storing means such as at least one computer-readable memory (MEM) 20B storing at least one computer program (PROG) 20C, and communicating means such as a transmitter TX 20D and a receiver RX 20E for bidirectional wireless communications with the serving cell 22 (and with the other cell 23 if present) via one or more antennas 20F. Within the memory 20B of the UE 20 but shown separately as reference number 20G is also a computer program for decoding the indication received in the new IE from the network and implementing the timer according to how the indication directs conditional on the UE having simultaneous PS and CS radio bearers and detecting an error on the PS bearer, as is detailed above in various embodiments.

The serving cell 22 also includes processing means such as at least one data processor (DP) 22A, storing means such as at least one computer-readable memory (MEM) 22B storing at least one computer program (PROG) 22C, and communicating means such as a transmitter TX 22D and a receiver RX 22E for bidirectional wireless communications with its associated user devices 20 via one or more antennas 22F and a modem. The serving cell 22 also has stored in its memory at 22G software to compile the IE with the indication into its SI message or its RRC message(s) as the case may be in order to inform it to the UE 20, as is detailed by example above. The other cell/other network access node 23 is similarly functional with blocks

23A, 23B, 23C, 23D, 23E and 23F, which are similar in function to those blocks having the same suffix and described for the serving cell/serving network access node 22.

For completeness, the higher network node 24 is also shown to include a DP 24A, and a MEM 24B storing a PROG 24C, and additionally a modem 24H for communicating with at least the serving cell 22. While not particularly illustrated for the UE 20 or cells 22, 23, those devices are also assumed to include as part of their wireless communicating means a modem which may in one exemplary but non limiting embodiment be inbuilt on an RF front end chip so as to carry the respective TX 20D/22D/23D and RX 20E/22E/23E.

At least one of the PROGs 20C, 22C, 23C in the UE 20 and in the serving and other cells 22, 23 is assumed to include program instructions that, when executed by the associated DP 20A, 22A, 23 A, enable the device to operate in accordance with the exemplary embodiments of this invention as detailed more fully above. In this regard, the exemplary embodiments of this invention may be implemented at least in part by computer software stored on the MEM 20B, 22B, 23B which is executable by the DP 20A, 22A, 23A of the respective devices 20, 22, 23; or by hardware; or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Electronic devices implementing these aspects of the invention need not be the entire UE 20, or serving cell 22, or other cell 23, but exemplary embodiments may be implemented by one or more components of same such as the above described tangibly stored software, hardware, firmware and DP, or a system-on-a-chip SOC or an application specific integrated circuit ASIC or a digital signal processor DSP or a modem or a subscriber identity module commonly referred to as a SIM card.

Various embodiments of the UE 20 can include, but are not limited to: cellular telephones; data cards, USB dongles, laptop computers, personal portable digital devices having wireless communication capabilities including but not limited to laptop/palmtop/tablet computers, digital cameras and music devices, and Internet appliances. Various embodiments of the computer readable MEM 20B, 22B, 23B include any data storage technology type which is suitable to the local technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DP 20A, 22A, 23A include but are not limited to general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and multi-core processors.

Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description. While the exemplary embodiments have been described above in the context of the HSDPA version of the UTRAN system, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems, such as for example evolved UTRAN (E-UTRAN) or in the wideband code division multiple access (WCDMA) version of UTRAN, or in others that enable the UE to hold PS and CS connections/radio bearers that are concurrently active.

Some of the various features of the above non-limiting embodiments may be used to advantage without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A method for controlling a user equipment, the method comprising:

determining that the user equipment simultaneously has at least a first radio bearer associated with a circuit-switched domain and at least a second radio bearer associated with a packet-switched domain, and

in response to detecting an error on the second radio bearer, implementing a timer associated with the packet-switched domain according to an indication received from a wireless network for how to implement the timer, without interrupting the first radio bearer due to the error.

2. A method according to claim 1 , in which the timer is a call re-establishment timer and the indication comprises an information element which informs the user equipment either to not apply the timer or to not immediately apply the timer.

3. A method according to claim 2, in which the information element informs the user equipment to not apply the timer which the user equipment implements by setting the timer to zero and releasing the second radio bearer on which the error was detected, where the error is detected as a radio link control unrecoverable error.

4. A method according to claim 2 or claim 3, in which the information element informs the user equipment to not immediately apply the timer which the user equipment implements by postponing initiation of any cell update procedure due to the detected error until the user equipment releases the first radio bearer associated with a circuit switched domain, where the error is detected as a radio link control unrecoverable error.

5. A method according to any of claims 1 to 4, in which the indication is received in broadcast system information.

6. A method according to any of claims 1 to 4, in which the indication is received in radio resource control signalling comprising at least one of:

a R CConnectionSetup message,

one or more R C reconfiguration messages,

a UTRANMobilitylnformation message, and

a CellUpdateConfirm message.

7. Apparatus for controlling a user equipment, the apparatus comprising

a processing system configured to cause the apparatus at least to:

determine that the user equipment simultaneously has at least a first radio bearer associated with a circuit-switched domain and at least a second radio bearer associated with a packet-switched domain, and

in response to detecting an error on the second radio bearer, implement a timer associated with the packet-switched domain according to an indication received from a wireless network for how to implement the timer, without interrupting the first radio bearer due to the error.

8. Apparatus according to claim 7, in which the timer is a call re-establishment timer and the indication comprises an information element which informs the user equipment either to not apply the timer or to not immediately apply the timer.

9. Apparatus according to claim 8, in which the information element informs the user equipment to not apply the timer which the processing system implements by setting the timer to zero and releasing the second radio bearer on which the error was detected, where the error is detected as a radio link control unrecoverable error.

10. Apparatus according to claim 8 or claim 9, in which the information element informs the user equipment to not immediately apply the timer which the processing system implements by postponing initiation of any cell update procedure due to the detected error until the user equipment releases the first radio bearer associated with a circuit switched domain, where the error is detected as a radio link control unrecoverable error.

11. Apparatus according to any of claims 7 to 10, in which the indication is received in broadcast system information.

12. Apparatus according to any of claims 7 to 10, in which the indication is received in radio resource control signalling comprising at least one of:

a R CConnectionSetup message,

one or more R C reconfiguration messages,

a UTRANMobilitylnformation message, and

a CellUpdateConfirm message.

13. A computer program that is executable by at least one processor, in which the computer program when executed controls a user equipment to at least:

14. A computer program according to claim 13, in which the timer is a call re- establishment timer and the indication comprises an information element which informs the user equipment either to not apply the timer or to not immediately apply the timer.

15. A computer program according to claim 14, in which in the case that the information element informs the user equipment to not apply the timer, the computer program controls the user equipment to implement the timer by setting the timer to zero and releasing the second radio bearer on which the error was detected, where the error is detected as a radio link control unrecoverable error.

16. A computer program according to claim 14 or claim 15, in which in the case that the information element informs the user equipment to not immediately apply the timer, the computer program controls the user equipment to implement the timer by postponing initiation of any cell update procedure due to the detected error until the user equipment releases the first radio bearer associated with a circuit switched domain, where the error is detected as a radio link control unrecoverable error.

17. A computer program according to any of claims 13 to 16, in which the indication is received in broadcast system information.

18. A computer program according to any of claims 13 to 16, in which the indication is received in radio resource control signalling comprising at least one of: a R CConnectionSetup message,

one or more R C reconfiguration messages,

a UTRANMobilitylnformation message, and

a CellUpdateConfirm message.