Handover failure handling

[0001] The present invention is related to wireless communication systems.

BACKGROUND [0002] Internet Engineering Task Force, CH, No. 4, August 30, 2002 (XP015004020 ISSN: 5,0000-0004) "A Context Transfer Protocol for Seamless Mobility draft-koodli-seamoby-ct04.txt; draft-koodli-seamoby- ct-04.txt "(Rajeev Koodli et al.) discloses how to transfer state information (e.g. microfluidic contexts) between IP access routers during normal call forwarding procedures. It is further disclosed that when the mobile network node moves from one access router to another, information, e.g. about AAA state, QoS state and header compression state, may be forwarded from one access router to another.

In a developed universal terrestrial radio access network (E-UTRAN) of step 2, cases where a wireless transceiver unit (WTRU) after a radio link failure (RL) selects a cell that belongs to the same eNodeB node is marked as intended for further studies (FFS). It has been proposed that if the WTRU chooses another cell in the same eNodeB, this action can not be resumed without interaction between this WTRU and this eNodeB. Currently, radio access network 2 (RAN2) specifies that if the WTRU selects a cell from another eNodeB, it must go through the radio resource inertia (RRC) mode.

[0004] Currently, RAN2 decisions regarding RL link failures are determined on the basis of two phases. These two phases regulate the behavior associated with the failure of the RL link and are shown in Figure 1.

[0005] The first phase begins when a radio problem is detected, which leads to the detection of an RL link failure. As a result, there is no mobility of the WTRU unit based on the time system or other criteria (T₁) (for example, countdown).

[0006] The second phase begins when a radio link failure is detected, which leads to an RRC inactivity mode. The mobility of the WTRU is still available, which is based on the time system (T₂).

[0007] Table 1 below describes how mobility is currently supported in relation to an RL link failure.

<td colspan="2">Table 1: Mobility and failure of councils</td><td colspan="2">ium</td>

<td>cases</td><td>First phase</td><td>The second phase</td><td>The time T2 has expired</td>

<td>The EU returns to the same cell</td><td>There is a continuation as if there were no radio problems</td><td>Operation can not be resumed without interaction between UE and eNodeB, procedure to be used is FFS, usually not via RRC_IDLE</td><td>Go through RRC_IDLE</td>

<td>The UE selects a different cell in the same eNodeB</td><td>not applicable</td><td>FFS</td><td>Go through RRC_IDLE</td>

<td>The UE selects a cell of another eNodeB</td><td>not applicable</td><td>Go through RRC_IDLE</td><td>Go through RRC_IDLE</td>

[0008] A recent application splits the call forwarding into two (2) phases similar to an RL link failure and suggests a similar procedure for handling call forward failures. [0009] In the first phase, the WTRU attempts to access and synchronize to the target cell, e.g. during the operation of the T1 timing circuit. In the second phase, the WTRU interrupts the forwarding of the connection due to lack of success and tries to restore the lost connection to the network, e.g. during the T2 timeframe. After the second phase, the UE enters the RRC_IDLE mode.

[0010] Figure 2 shows two phases that control the behavior associated with a failover of a call forwarding in a network-controlled mobility, in accordance with the current request.

[0011] The first phase begins after the first synchronization attempt with the target cell; and leads to detection of connection failure. At this time, there is no mobility of the WTRU that is based on time or other criteria (for example, countdown) (T₁).

[0012] The second phase is triggered when a connection failure failure is detected leading to RRC_IDLE. The mobility of the WTRU unit is still available, based on the time system (T₂).

[0013] Table 2 describes how the mobility is handled with respect to call forward failures.

Table 2: Mobility and breakdown of call forwarding

<td>cases</td><td>First phase</td><td>The second phase</td><td>The time T2 has expired</td>

<td>The EU is entering to the cell target</td><td>There is a continuation as if there were no problems radio</td><td>The operation can not be resumed without interaction between the EU and eNodeB, the UE performs random access procedure according to 10.1.5</td><td>Go through RRC_IDLE</td>

<td>The EU returns to source cell</td><td>not applicable</td><td>The operation can not be resumed without interaction between the EU and eNodeB, the UE performs random access procedure according to 10.1.5</td><td>Go through RRC_IDLE</td>

<td>The EU chooses another cell than a cell target or source.</td><td>not applicable</td><td>Go through RRC IDLE</td><td>Go through RRC_IDLE</td>

[0014] Currently, it is also allowed to use random access based on non-contention when transferring a call. As such, the current absence of contention based on the random access procedure depicted in figure 3 includes the assignment of a random access preamble via dedicated downlink signaling (DL), where the eNodeB assigns a six-bit (6) preamble to the WTRU. random access in the absence of competition (i.e., random access preamble which is not within the set advertised by the BCH channel). This preamble is signaled by a call forwarding (HO) command, created by the target node eNodeB and sent from the source node eNodeB to forward the connection,

[0015] The WTRU then passes this assigned random access preamble without competing in the RACH procedure by an uplink. The random access response from the eNB node is sent to DL-SCH. This response is semi-synchronous (in a flexible window whose size is equal to one or more Transmission Timing Interval (TTI)) with message 1, and refers to either C-RNTI or RA-RNTI ( FFS) of the L1 / L2 control channel.

[0016] The random access response includes at least a time alignment of the information and a preliminary UL approval for handover and time alignment information for the arrival of the DL data. In addition, the RA preamble identifier refers to the determination of a radio network temporary interrogation (RA-RNTI) area in the L1 / L2 control channel.

[0017] This response is only intended for one WTRU in one downlink channel shared splice message (DL-SCH) if it relates to an RNTI (CRNTI) cell in the L1 / L2 control channel, or for one or more WTRUs. in one DL-SCH channel message, if it refers to RA-RNTI in the L1 / L2 control channel. [0018] There is a need to improve the method and apparatus for handling radio link failures and call forwarding.

BRIEF DESCRIPTION [0019] The disclosed method and apparatus are used to handle RL link failures and call forwarding based on context transfer and RACH procedures, which streamlines the failure handling procedures. After an RL link failure, the wireless transceiver (WTRU) joins the identity of the evolved Node-B (eNB) and / or cell as an information element (IE) in the RRC connection request and / or in the cell update message, or any other RRC message along with the WTRU identity.

BRIEF DESCRIPTION OF THE DRAWINGS [0020] A more detailed understanding can be obtained from the following description, given by way of example, in combination with the accompanying drawing, in which:

Figure 1 shows a classic radio link failure;

Figure 2 shows the classic failure of call transmission;

Figure 3 shows a classic random access procedure based on non-competition;

Figure 4 is a diagram of a wireless communication system; and

Figure 5 is a flowchart of the disclosed method for handling radio link failure.

DETAILED DESCRIPTION [0021] In this document, the term "wireless transceiver (WTRU)" includes, but is not limited to, user (UE) equipment, mobile station, stationary or mobile subscriber unit, pager, mobile phone, digital assistant personal computer (PDA), computer or any other type of user equipment capable of operating in a wireless environment. In this document, the term "base station" includes, but is not limited to, a Node-B, a location controller, an access point (AP), or any other type of interface device capable of operating in a wireless environment.

[0022] With reference to figure 4, the LTE wireless network (NW) 10 includes, for example, one or more WTRUs 20, each comprising a processor 21, one or more NodeBs 30, each including a processor 31 and one or more cells 40. Each cell 40 includes one or more NodeB nodes (NB or eNB) 30. Each of the processors 21 and 31 is adapted to implement the disclosed method for handling radio link failure (RL) and call forwarding failures.

[0023] Throughout the disclosed method, context information relates to any of a Radio Resource Control (RRC) context, a security context, a PDP (Packet Data Convergence Protocol) context, or any layer context that may be continued during mobility. However, for the sake of brevity, the context or context of the RRC may be used for each of the context types disclosed above.

[0024] When an RL link failure is detected by the WTRU 20, this WTRU 20 begins the mobility procedures (i.e., reselecting the cell). In the ordinary cell redial procedure, the WTRU 20 re-selects any cell available after the RL link failure and, by updating the cell or the radio resource control request (RRC), the WTRU 20 sends its WTRU identity to the eNodeB (eNB) node 30. The eNB node 30 detects, using the received WTRU identity, whether the WTRU 20 was controlled by this eNB 30 before the radio link failure occurred.

[0025] A method and apparatus is disclosed wherein, after a radio link failure (RL) or call forwarding failure (HO), the WTRU 20 joins as an information element (IE) in the RRC connection request in a cell update message or any other RRC message. , your WTRU identity (e.g. TMSI / IMSI / IMEI or the identity of any other UE) and the identity of the eNB and / or the identity of the cell.

Once the WTRU 20, after reselecting the cell, is registered to the eNB (i.e. to the target node eNB), the information contained in the IE element is forwarded to the target node eNB. If the target node eNB to which the WTRU is registering is different from the eNB node in which the WTRU 20 was registered prior to the failure of the RL link (i.e., the source node eNB), then the target node eNB contacts the source eNB with the use of identity an eNB and / or cell ID contained within the IE to inform the source node of the eNB about the identity of the WTRUs. The destination node of the eNB then requests the context parameter of the WTRUs 20 to the source node of the eNB. Alternatively, the eNB destination node may also inform the source node. eNB about cell identity.

[0027] If the source node eNB finds context information that matches the identity of the WTRU 20, the source node eNB sends this context information to the target node eNB. The eNB destination node may then send a response to WTRU cell update procedures 20, RRC connection request, or any other RRC procedure initiated by the WTRU indicating that the WTRU 20 may reuse the previous context.

[0028] If the context is not found by the source node of the eNB, the target node eNB performs procedures for establishing an update cell / call RRC, or any other RRC procedure. In this case, when the target node eNB receives a request to re-establish the RRC connection from the WTRU unit 20, it signals all parameters of the layer 1 and layers 2/3 as it would signal for the new RRC connection. The WTRU 20 may then delete any stored context information that has applied to the old cell. Alternatively, if the context is not found, the WTRU 20 can either go into the RRC inactivity mode without waiting for the T2 timer overflow and resume the procedures, or wait for the T2 timer overflow to go into the RRC idle mode.

[0029] A disclosed IE element, including eNB node information, in which the WTRU 20 was last registered may be connected by a WTRU unit 20. According to this alternative solution, the processor 21 attaches the identity of the eNB node and / or the cell identity to the IE element only upon detection. call forwarding failure.

[0030] If the target node eNB in ​​which the WTRU 20 registers is the same as the source eNB before the failure and if this eNB finds the context for the WTRU 20 (the eNB finds it by checking if it has a context, which is matched to the identity of the WTRU 20), then the eNB, after receiving the RRC CALL REQUEST from the WTRU 20 (or after receiving any other RRC procedures initiated by the WTRU), may request the WTRU 20 to use the same context information that it had before the failure. Otherwise, the eNB may signal to the WTRU 20 all parameters of layer 1 and layers 2/3 that this eNB would signal for a new RRC connection.

[0031] Described below is a flowchart of the disclosed method used to handle an RL failure over the WTRU processor 20. The RW (step 500) detects an RL failure to perform the initial procedure for accessing the selected target node eNB. access (step 501). The WTRU 20 then transmits the IE element to the target node eNB, attaching at least the eNB node ID to the eNB source node to which the WTRU 20 was previously registered (step 502). The WTRU 20 then receives the RRC context from the eNB target node (step 503) after this context has been obtained by the target node of the eNB, e.g. from the source node eNB.

[0032] According to the disclosed method, the duration of the period for which the target node of the eNB maintains the radio access control (RAC) context is preferably set depending on the implementation. This is also the case when determining whether the forwarding of context information between the eNB target node and the source node of the eNB occurs only after a radio link failure.

[0033] If the target node eNB in ​​which the WTRU 20 is registered is the same source node eNB in ​​which this WTRU was registered prior to handover of the call, then upon receipt of the RRC CALL REQUEST from the WTRU 20, or upon the reception of any other RRC procedures initiated by this WTRU may mean using the same context information for the WTRU 20 that it had before the failure occurred.

[0034] As will be appreciated by the person skilled in the art, registering a WTRU 20 in the same cell or the same eNB in ​​which it was registered prior to the failure of the RL link helps in saving network resources. As such, the disclosed method may alternatively also include the fact that during the cell selection procedure after an RL link failure, the WTRU 20 takes into account the identity of the source eNB node, thus preferring cells from the eNB source node, compared to cells from other eNBs. According to this alternative solution, it may be advantageous that the WTRU 20 prioritizes the detected eNBs in the following order: the last cell in which it was previously registered; a cell from the same eNodeB in which it was previously registered; and a cell from any other eNodeB node. [0035] During an emergency radio situation, other parameters for reselecting a cell may or may not be taken into account by the WTRU unit 20, because the main criteria after the failure are rapid registration and initiation of the call; to select a cell after a radio link failure, only the identity of the eNB (or cell identity) suffices with the signal strength of that cell. According to this method, the identities (eNB node and cells) may be broadcast in system information messages together with the cell ID. to select a cell after a radio link failure, only the identity of the eNB (or cell identity) suffices with the signal strength of that cell. According to this method, the identities (eNB node and cells) may be broadcast in system information messages together with the cell ID. to select a cell after a radio link failure, only the identity of the eNB (or cell identity) suffices with the signal strength of that cell. According to this method, the identities (eNB node and cells) may be broadcast in system information messages together with the cell ID.

[0036] For a call forwarding failure, a method is disclosed where, when the WTRU 20 moves to another cell and where that other cell belongs to the same eNB, based on the identity of the WTRU 20, the eNB to which this WTRU is 20, has moved, determines if it has the context of this WTRU 20. If the eNB has this context, the eNB indicates to the WTRU 20 to use the same context as before. The WTRU 20 may use the same context because the context is stored with respect to that eNB, and not with respect to that cell. According to this method, the same cell selection priorities described above for an RL link failure as disclosed above apply to failures of eNB node handover as another possible method.

[0037] When the WTRU 20 moves to a cell from a completely different eNB, in the case of a radio link failure, a procedure similar to that disclosed above can be used. It should be noted that during such a call forwarding procedure, the last identity of the eNB which the WTRU 20 may store may be the identity of the source eNB or the target node of the eNB, depending on at what stage of the procedure the failure of the handover occurred. According to the disclosed method, it is preferred that as long as the connection transfer is not successful, the WTRU 20 stores the source node eNB as the last eNB node in which it was registered. Whether the WTRU unit sends to the final eNB node to which it registers, the identity of the source eNB node or the eNB target node,

[0038] An important aspect of the ability to retrieve the context is for the WTRU to register in the cell and to send the message 1 (i.e. random access preamble) as quickly as possible in the RACH procedure. If a delay occurs in this process, the eNB can delete the context, so rendering the context retrieval process will be useless. Accordingly, a method for improving a random access channel (RACH) procedure for RL link failure and call forwarding failure is disclosed. According to this method, during the call forwarding procedure, a dedicated signature is assigned to the WTRU unit 20. This assigned dedicated signature is then used to access the source cell after an RL link failure or a connection forward failure.

[0039] If the call forwarding has been successful, the WTRU 20 may (implicitly or explicitly) release this signature back to the network in a message confirming the handover of the call. In the event of a failure during the call forwarding procedure, the WTRU 20 may use the second dedicated signature and attempt to access the network as soon as possible. Because the WTRU 20 unit uses a dedicated signature, it can return to normal operation after a failure.

[0040] In another embodiment, the broadcast channel (BCH) broadcasts a set of dedicated signatures, set only at the failure of the RL link, which is used by the WTRU 20 in the event of an RL link failure or a call forward failure. In another solution, in the case of an RL link failure, a set of universal dedicated signatures, valid in all cells, can be used. This set of universal dedicated signatures can be sent in a call forwarding message or broadcast in system information messages. The WTRU can then, after a failure, use this universal dedicated signature to access any cell.

[0041] A different RACH procedure is disclosed herein, wherein, instead of assigning to the WTRU a dedicated signature that is used in the event of a failure, at least one of the signatures (e.g., preamble) may be determined to access the cell after a failure. random access) from the current set broadcast on the BCH channel. According to this solution, the WTRU 20 obtains these reserved signatures from the BCH channel (or the call forwarding (HO) command may inform the WTRU 20 with reserved signatures for use in the event of a failure).

Once the WTRU 20 has learned these proprietary signatures, the WTRU 20 uses a reserved signature in the event of an RL link failure or call forwarding failure.

[0042] Another solution is also disclosed, where higher access classes are used to handle RL link failures. According to this solution, the WTRU 20 associates the provision of RL link failures with a higher access class service, and thus can complete redialing on the network with a shorter wait period and with a higher priority. In this scenario, when the WTRU 20 attempts to access the cell after the failure of the RL link, since this WTRU 20 may have a service with a higher access class, it may attempt to access the network 10 with a shorter wait period, or without it, between its various RACH access attempts. As such, the WTRU 20 may have a higher probability of accessing the network after an RL link failure compared to other WTRUs with a lower access class service,

[0043] In another RACH access method, the WTRU 20 increases its power linearly faster such that the network has a greater chance of detecting it and thereby increases the priority of the given WTRU 20. Table 3 describes the mobility of the WTRU 20 during an RL link failure according to that disclosed way.

abela 3: Mobility and failure of radio link

<td>cases</td><td>First phase</td><td>The second phase</td><td>The time T2 has expired</td><td>Cell selection priority</td>

<td>The EU returns to the same cell</td><td>Continue, as if they did not occur radio problems</td><td>Operation can not be resumed without interaction between the WTRU and the eNodeB node, the procedure to be used is FFS, usually not by RRC_IDLE</td><td>Go through RRC_IDL E</td><td>1</td>

<td>The EU chooses another cell in the same eNodeB</td><td>not applicable</td><td>The operation can not be resumed without interaction between the WTRU and the eNodeB node</td><td>Go through RRC_IDL E</td><td>2</td>

<td>The UE selects a cell from different eNodeB</td><td>not applicable</td><td>Operation can not be resumed without interaction between the WTRU and the eNodeB node, the procedure to be used is FFS, usually not by RRC IDLE</td><td>Go through RRC_IDL E</td><td>3</td>

[0044] For the second phase, in order to take action again when the WTRU 20 returns to the same cell, or when the WTRU 20 selects another cell at the same eNodeB node, or another eNB, a method is disclosed where the WTRU 20 accesses the cell via a random access procedure. The non-access stratum (NAS) identity used in the random access procedure is also used by the eNB to determine whether this eNB has the RRC context stored for the WTRU 20. If the eNB node finds the RRC context, which is matched to the identity of the WTRU 20, in response to the RRC CALL REQUEST the eNB sends a message (e.g. ANSWER, RRC JOINTS) or any other RRC procedures initiated by the WTRU to indicate this WTRU 20,

[0045] If the eNB does not have an RRC context that matches the identity of the WTRU 20, the new eNB is in direct contact with the previously registered eNB, using the eNB node sent by the WTRU 20. As disclosed above, alternatively the node The eNB can obtain from the unit (MME) mobility management the identity of the WTRU or the context of the WTRU. [0046] If the context was found on the old eNB and moved, it sends a message (e.g. ANSWER, in response to RRC CALL REQUEST).

RRC CONNECTIONS), or any other RRC procedures initiated by a WTRU unit, indicative of this WTRU unit 20, for re-use of that RRC context that is stored. If the context is not found either in the new or in the old eNB, the procedure for establishing the RRC connection takes place and the WTRU 20 discards the stored RRC contexts. In this case, when the network sends a response to the RRC procedure initiated by the WTRU unit 20, the network 10 determines whether the WTRU 20 can set the stack using the old context information it had before the failure, or, in response to the message, the network 10 sends to WTRU 20 units new parameters to set its stack. Once the WTRU 20 unit receives the response message from the network 10 and processes it,she finished the configuration on her side.

[0047] Table 4 below describes the mobility of the WTRU 20 during failures of handover of a call according to the disclosed method.

abela 1: Mobility and failure of connection forwarding

<td>cases</td><td>First phase</td><td>The second phase</td><td>The time T2 has expired</td><td>Priority cell selection</td>

<td>The UE enters the target cell</td><td>There is a continuation, as if there were no radio problems</td><td>Operation can not be left resumed without interaction between the EU and eNodeB</td><td>Go through RRC_IDLE</td><td>1</td>

<td>The EU is coming back to the source cell</td><td>not applicable</td><td>Operation can not be left resumed without interaction between the EU and eNodeB</td><td>Go through RRC_IDLE</td><td>2</td>

<td>The UE selects a different cell in the same eNodeB</td><td>not applicable</td><td>Operation can not be left resumed without interaction between the EU and eNodeB, the procedure to be used is FFS, usually not through RRC IDLE</td><td>Go through RRC_IDLE</td><td>3</td>

<td>The UE selects a cell from another eNodeB</td><td>not applicable</td><td>Operation can not be left resumed without interaction between the EU and eNodeB, the procedure to be used is FFS, usually not through RRC IDLE</td><td>Go through RRC_IDLE</td><td>4</td>

[0048] For the second phase, in order to take action again when the WTRU 20 returns to the same cell, or when the WTRU 20 selects another cell in the same eNB or other eNB, a method is disclosed where the WTRU is accessing to the cell via a random access procedure. The layer identity (NAS) used in the random access procedure is also used by the eNB to determine if this eNB has the RRC context stored for the WTRU 20. If the eNB finds the RRC context that matches the identity of the WTRU 20, the eNB sends in response to a RRC CALL REQUEST message (e.g. RRC CALL REPLY) or any other RRC procedures initiated by the WTRU,

[0049] If the eNB does not find the RRC context that matches the identity of the WTRU 20, the new eNB is in direct contact with the previously registered eNB, using the eNB node identity sent by the WTRU 20. As disclosed above, in another the solution to the eNB may obtain from the MME the identity of the WTRU or the context of the WTRU.

[0050] If the context is found on the old and transferred eNB, it sends, in response to the RRC CALL REQUEST, a message (e.g. RRC CALL REPLY), or any other RRC procedures initiated by the WTRU, indicating this WTRU 20 to re-use that RRC context that is stored. If the context is not found in either the new or the old eNB, the usual establishment of the RRC connection procedure takes place, and the WTRU 20 preferably discards the stored RRC contexts. It should be noted that the use of the cell selection priority column from tables 3 and 4 is an alternative method and that, regardless of this priority, if other priorities are used to select / reselect a cell, the disclosed procedure still applies.

Embodiments [0051]

A method of wireless communication, used in a wireless transceiver (WTRU) unit, comprising: detecting a failure, including at least one of a radio link failure (RL) and a call forwarding (HO);

transmitting the identity of the wireless transceiver (WTRU) and the information element (IE), including at least one of the identity of the source network B and the identity of the source cell to access the destination node of the network; and receiving context information from the network B target node, at least partially based on the IE element.

2. The method according to embodiment 1, further comprising performing a cell reselection to select an available destination node B.

3. A method according to any preceding embodiment, wherein the identity of the source node B is taken into account when selecting the available destination node B.

4. A method according to any preceding embodiment, wherein the redial includes first attempting to redial on the source node B; and trying to reselect the source cell associated with the identity of the source cell when the source node B is not available.

5. The method according to embodiment 4, wherein the destination node B and the target cell are other than the source node B and the source cell.

6. A method according to any preceding embodiment, further comprising storing context information prior to detecting a failure.

7. A method as in any of embodiments 1 - 6, wherein the context information includes an indication for using this stored context information.

8. A method as in any of embodiments 1 - 6, wherein the context information includes context information other than stored context information.

9. A method according to any preceding embodiment, further comprising accessing the network using at least one of the uses of a shorter waive or a larger linear increase in power.

10. A method according to any preceding embodiment, further comprising receiving at least one allocated dedicated signature while forwarding the call, said dedicated signature being used to access the source cell, after an RL link failure, or a call forward failure.

11. The method according to embodiment 10, wherein the at least one dedicated signature is received by a call forwarding command.

12. The method according to embodiment 10, further comprising receiving a handover command, including two dedicated dedicated signatures, wherein one of said dedicated signatures is used to access the destination node B and the other is used to access the source node B, in the event of an RL link failure or a connection failure.

13. The method according to embodiment 12, further comprising releasing the two dedicated signatures when the connection has been terminated.

14. A method according to any preceding embodiment, wherein the at least one dedicated signature from the signature set is claimed on the broadcast channel to access any cell from any node B, after an RL link failure, or a call forward failure.

15. The method according to embodiment 14, wherein the set of signatures reserved for dedicated access is received in the handover command.

16. A wireless transceiver unit comprising a processor adapted to implement the method as in any preceding embodiment.

17. Node B, comprising a processor, adapted to implement the method as in any preceding embodiment.

18. A processor adapted to implement the method as in any preceding embodiment.

19. A wireless transceiver (WTRU) unit comprising: a failure detection processor comprising at least one radio link failure (RL) or call forwarding failure (HO);

a transmitter for transmitting the identity of the WTRU and the information element (IE) to the destination node B, including at least one of the identity of the node B, and the identity of the cell; and a receiver for receiving context information from the target node eNode B, based at least in one part on the IE element.

20. A WTRU from position 19, where the identity of node B is the identity of source node B, in which the WTRU was registered before the failure was detected.

21. A WTRU from position 20, wherein the call identity is the cell identity in which the WTRU was registered before the failure was detected.

22. A WTRU from position 20, where the processor stores the identity of the source node B of the source node B.

23. A WTRU from position 22, where the processor performs cell redial to select an available destination node B.

24. The WTRU of item 23, wherein the processor uses the stored identity of the source node B, which is taken into account when selecting the destination node B.

25. The WTRU of position 24, wherein the processor attempts to reselect any other node B to the source node B, then, when the source node B is not available, attempts to re-select the source cell associated with the identity of the source cell.

26. The WTRU of item 25, wherein the destination node B and the target cell are other than the source node B and the source cell.

27. A WTRU from item 25 where the processor stores context information prior to the detection of a fault.

28. The WTRU of item 27, wherein the context information includes an indication for using this stored context information.

29. A WTRU entity from item 27, wherein the context information includes context information other than stored context information.

30. A method for handling a radio link failure (RL) and forwarding connection, comprising receiving at least one allocated dedicated signature when forwarding the call, and then the dedicated signature is used to access the source cell, after an RL link failure or handover.

31. The method according to item 30, wherein at least one dedicated signature is received by a handover command.

32. The method of item 31, further comprising receiving a handover command including two dedicated dedicated signatures, wherein one of these dedicated signatures is used to access the destination node B, and the other is used to access the source node B, in the case of when an RL link failure occurs or a call forwarding occurs.

33. The method of item 32, further comprising releasing the two dedicated signatures when the connection has been terminated.

34. The method according to item 30, wherein the at least one dedicated signature from the signature set is reserved on the broadcast channel to access any cell from any node B, after the failure of the RL link or call forwarding.

35. The method according to item 34, wherein the set of signatures reserved for dedicated access is received in the handover command.

[0052] Although the features and elements have been described above in specific combinations, each feature or element may be used alone, without other features and elements, or in different combinations, with or without other functions and elements. The methods or operating schemes provided herein may be implemented in a computer program, software or firmware included on a computer readable storage medium for execution by a general purpose computer or processor. Examples of computer readable data carriers include read-only memory (ROM), random access memory (RAM), register, cache memory, semiconductor memory devices, magnetic media, e.g. internal hard drives and removable drives,

[0053] Suitable processors include, by way of example, a general-purpose processor, a special purpose processor, a classical processor, a signal processor (DSP), a microprocessor assembly, one or more microprocessors connected to a DSP core, a controller, a microcontroller, specialized integrated circuits (ASICs) ), directly programmable gate array (FPGAs) systems, any other type of integrated circuit (IC) and / or state machine.

[0054] In order to implement a radio frequency transceiver for use in a wireless transceiver (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host base station may be used processor in conjunction with the software. The WTRU unit can be used in conjunction with modules implemented as hardware and / or software such as a camera, video camera module, videophone, speakerphone, vibrating device, speaker, microphone, television transmitter, headset, keyboard, module Bluetooth®, radio frequency unit (FM), liquid crystal display unit (LCD), screen monitor with organic light-emitting diodes (OLED),