Handling redirection failures in RRC connection redirection procedure
Methods and apparatuses involve a network node ( 22 ) of a wireless communication network ( 10 ) and a wireless device ( 12 ) attempting redirection with respect to the network ( 10 ). An overall bound limits how many times or for how long the wireless device ( 12 ) attempts redirection and provides a mechanism for the wireless device ( 12 ) to extend its redirection efforts to one or more redirection targets beyond those indicated by the network ( 10 ).
1 . A method performed by a User Equipment (UE), the method comprising: receiving a Radio Resource Control (RRC) release message indicating redirection of the UE; attempting the redirection towards one or more indicated redirection targets, as indicated in the release message, subject to an overall limit that bounds an overall number of redirection attempts made by the UE towards the one or more indicated redirection targets, or bounds an overall time allowed for the redirection attempts made by the UE towards the one or more indicated redirection targets; upon reaching the overall limit, attempting the redirection towards one or more further redirection targets, wherein at least one of the further redirection targets is not among the one or more indicated redirection targets, and performing Listen Before Talk (LBT) with respect to different parts of a cell, with attempts being governed by a limit on a total number of attempts or on a time allowed for attempting.
2 . The method of claim 1 , further comprising limiting a per-target time spent by the UE in attempting the redirection towards any one of the indicated redirection targets, according to a first timer or counter that limits a number of random access attempts or associated LBT Listen Before Talk (LBT) procedures that are permitted for the indicated redirection target before the UE is triggered to try a next one of the one or more indicated redirection targets.
3 . The method of claim 1 , wherein attempting the redirection towards the one or more indicated redirection targets subject to the overall limit comprises: limiting the overall time spent by the UE in attempting the redirection towards the one or more indicated redirection targets, according to a second timer or counter that defines a limit on the overall number of random access attempts or associated LBT procedures that are permitted overall for the one or more indicated redirection targets; and responsive to reaching the limit defined by the second timer or counter, selecting one or more further cells or cell parts as the one or more further redirection targets, and attempting redirection towards one or more of the one or more further redirection targets.
4 . The method of claim 1 , wherein attempting the redirection towards a currently-selected one of the one or more indicated redirection targets comprises performing one or more random access attempts towards the currently-selected redirection target, each random access attempt conditioned on performing a Listen-Before-Talk (LBT) procedure.
5 . The method of claim 4 , wherein the method comprises selecting a next, remaining one of the one or more indicated redirection targets upon reaching a limit on the number of redirection attempts or the time allowed for attempting redirection towards the currently-selected redirection target.
6 . The method of claim 5 , wherein the limit on the number of redirection attempts comprises a limit on the number of random access attempts or associated LBT procedures permitted for the currently-selected redirection target.
7 . The method of claim 1 , wherein the one or more indicated redirection targets are one or more cells or parts of cells, of a wireless communication network.
8 . The method of claim 1 , wherein attempting redirection towards the one or more further redirection targets comprising triggering a redirection failure recovery procedure in response to reaching the overall limit for attempting redirection towards the one or more indicated redirection targets, and wherein performing the redirection failure recovery procedure comprises selecting a cell of a wireless communication network for attempting access, without restricting cell selection to a list of cells or carrier frequencies indicated in or in association with the RRC release message.
9 . The method of claim 8 , further comprising at least one of: receiving signaling indicating one or more configuration parameter values for the UE to use for triggering the redirection failure recovery procedure; or using a predefined value or uses a rule to determine a value, for one or more configuration parameters used by the UE for triggering the redirection failure recovery procedure.
10 . A User Equipment (UE) comprising: communication interface circuitry configured for sending signals to and receiving signals from radio access nodes of a wireless communication network; and processing circuitry operatively associated with the communication interface circuitry and configured to: receive a Radio Resource Control (RRC) release message indicating redirection of the UE; attempt the redirection towards one or more indicated redirection targets, as indicated in the release message, subject to an overall limit that bounds an overall number of redirection attempts made by the UE towards the one or more redirection targets, or bounds an overall time allowed for the redirection attempts made by the UE towards the one or more indicated redirection targets; upon reaching the overall limit, attempt the redirection towards one or more further redirection targets, wherein at least one of the further redirection targets is not among the one or more indicated redirection targets; and perform Listen Before Talk (LBT) with respect to different parts of a cell, with attempts being governed by a limit on a total number of attempts or on a time allowed for attempting.
11 . The UE of claim 10 , wherein the processing circuitry is configured to limit a per-target time spent by the UE in attempting the redirection towards any one of the one or more indicated redirection targets, according to a first timer or counter that limits a number of random access attempts or associated LBT Listen Before Talk (LBT) procedures that are permitted for the indicated redirection target before the UE is triggered to try a next one of the one or more indicated redirection targets.
12 . The UE of claim 10 , wherein, for attempting the redirection towards the one or more indicated redirection targets subject to the overall limit, the processing circuitry is configured to: limit the overall time spent by the UE in attempting the redirection towards the one or more indicated redirection targets, according to a second timer or counter that defines a limit on an overall number of random access attempts or associated LBT procedures that are permitted overall for the one or more indicated redirection targets; and responsive to reaching the limit defined by the second timer or counter, select one or more further cells or cell parts as the one or more further redirection targets, and attempting the redirection towards one or more of the one or more further redirection targets.
13 . The UE of claim 10 , wherein, to attempt the redirection towards a currently-selected one of the one or more indicated redirection targets, the processing circuitry is configured to perform one or more random access attempts towards the currently-selected redirection target, each random access attempt conditioned on performing a Listen-Before-Talk (LBT) procedure.
14 . The UE of claim 13 , wherein the processing circuitry is configured to select a next, remaining one of the one or more indicated redirection targets upon reaching a limit on the number of redirection attempts or the time allowed for attempting redirection towards the currently-selected redirection target, wherein the limit on the number of redirection attempts comprises a limit on the number of random access attempts or associated LBT procedures permitted for the currently-selected redirection target.
15 . The UE of claim 10 , wherein the one or more indicated redirection targets are one or more cells or parts of cells, of the wireless communication network.
16 . The UE of claim 10 , wherein, for attempting redirection towards the one or more further redirection targets, the processing circuitry is configured to trigger a redirection failure recovery procedure in response to reaching the overall limit for attempting redirection towards the one or more indicated redirection targets, and wherein, to perform the redirection failure recovery procedure, the processing circuitry is configured to select a cell of the wireless communication network for attempting access, without restricting cell selection to a list of cells or carrier frequencies indicated in or in association with the RRC release message, and wherein the processing circuitry is configured to receive signaling indicating one or more configuration parameter values for the UE to use for triggering the redirection failure recovery procedure and/or use a predefined value or uses a rule to determine a value, for one or more configuration parameters used by the UE for triggering the redirection failure recovery procedure.
17 . A method performed by a network node of a wireless communication network, the method comprising: sending configuration information to a User Equipment (UE), indicating one or more configuration parameter values for the UE to use for triggering a redirection failure recovery procedure while performing a redirection procedure, wherein the redirection procedure is to be performed by the UE with respect to one or more indicated redirection targets, and wherein the configuration information indicates a first timer or counter that limits a number of random access attempts or associated Listen-Before-Talk (LBT) procedures that are permitted at the UE for any particular one of the one or more indicated redirection targets before the UE is triggered to try a next one of the one or more redirection targets, such that the first timer or counter limits a per-target time spent by the UE in attempting redirection towards any one of the one or more indicated redirection targets.
18 . The method of claim 17 , further comprising indicating the one or more configuration parameter values in a release message sent to the UE, in conjunction with releasing the UE from a connected mode, wherein the release message is a Radio Resource Control (RRC) message sent to the UE in conjunction with releasing the UE from an RRC_CONNECTED mode.
19 . The method of claim 17 , wherein the configuration information defines an overall limit on a number of redirection attempts by the UE or the time spent by the UE attempting redirection, for the redirection procedure, such that the UE triggers a redirection failure recovery procedure upon reaching the overall limit.
20 . The method of claim 17 , wherein the configuration information indicates a second timer or counter that limits an overall number of random access attempts or associated LBT procedures that are permitted at the UE for the one or more indicated redirection targets collectively, such that the second timer or counter limits an overall time spent by the UE in attempting redirection towards the one or more indicated redirection targets before the UE declares a redirection failure and triggers the redirection failure recovery procedure.
21 . A network node configured for operation in a wireless communication network, the network node comprising: communication interface circuitry; and processing circuitry configured to send, via the communication interface circuitry, configuration information to a User Equipment (UE), indicating one or more configuration parameter values for the UE to use for triggering a redirection failure recovery procedure while performing a redirection procedure, wherein the redirection procedure is to be performed by the UE with respect to one or more indicated redirection targets, and wherein the configuration information indicates a first timer or counter that limits a number of random access attempts or associated Listen-Before-Talk (LBT) procedures that are permitted at the UE for any particular one of the one or more indicated redirection targets before the UE is triggered to try a next one of the one or more redirection targets, such that the first timer or counter limits aper-target time spent by the UE in attempting redirection towards any one of the one or more indicated redirection targets.
22 . The network node of claim 21 , wherein the processing circuitry is configured to indicate the one or more configuration parameter values in a release message sent to the UE, in conjunction with releasing the UE from a connected mode.
23 . The network node of claim 22 , wherein the release message is a Radio Resource Control (RRC) message sent to the UE in conjunction with releasing the UE from an RRC_CONNECTED mode.
24 . The network node of claim 21 , wherein the configuration information defines an overall limit on a number of redirection attempts by the UE or the time spent by the UE attempting redirection, for the redirection procedure, such that the UE triggers a redirection failure recovery procedure upon reaching the overall limit.
25 . The network node of claim 21 , wherein the configuration information defines a limit on a number of redirection attempts made by the UE towards any particular one of one or more redirection targets indicated for the redirection procedure, or a time permitted to the UE for attempting redirection to any particular one of the one or more indicated redirection targets.
26 . The network node of claim 21 , wherein the configuration information indicates a second timer or counter that limits an overall number of random access attempts or associated LBT procedures that are permitted at the UE for the one or more indicated redirection targets collectively, such that the second timer or counter limits an overall time spent by the UE in attempting redirection towards the one or more indicated redirection targets before the UE declares a redirection failure and triggers the redirection failure recovery procedure.