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WO2020117114A1 - Procédé et dispositif sans fil pour accéder à une cellule cible - Google Patents

Procédé et dispositif sans fil pour accéder à une cellule cible Download PDF

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Publication number
WO2020117114A1
WO2020117114A1 PCT/SE2019/051213 SE2019051213W WO2020117114A1 WO 2020117114 A1 WO2020117114 A1 WO 2020117114A1 SE 2019051213 W SE2019051213 W SE 2019051213W WO 2020117114 A1 WO2020117114 A1 WO 2020117114A1
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WO
WIPO (PCT)
Prior art keywords
cell
wireless device
configuration
failure
handover
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE2019/051213
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English (en)
Inventor
Icaro L. J. Da Silva
Patrik Rugeland
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
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Filing date
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Priority to EP19892279.1A priority Critical patent/EP3892032A4/fr
Publication of WO2020117114A1 publication Critical patent/WO2020117114A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/305—Handover due to radio link failure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0061—Transmission or use of information for re-establishing the radio link of neighbour cell information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0072—Transmission or use of information for re-establishing the radio link of resource information of target access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/249—Reselection being triggered by specific parameters according to timing information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/20—Selecting an access point

Definitions

  • the present disclosure relates generally to a method and a wireless device for accessing a target cell when the wireless device has obtained and stored a configuration for at least one candidate target cell.
  • wireless device is used to represent any combination
  • M2M Machine-to-Machine
  • MTC Machine Type Communication
  • Another common generic term in this field is“User Equipment, UE” which is frequently used herein as a synonym for wireless device. This disclosure is thus not limited to any particular wireless device or UE, as long as it is capable of radio communication and of executing a handover from one access point to another.
  • the term“network node”, is used herein to represent any node or access point of a wireless network that is operative to communicate radio signals with wireless devices.
  • the wireless network may be operating according to Long Term Evolution LTE or according to 5G, also referred to as“New Radio” NR, both being defined by the third Generation Partnership Project, 3GPP.
  • the network nodes herein may refer to base stations, eNBs, gNBs, ng-eNBs, access points, etc., depending on the terminology used, although this disclosure is not limited to these examples.
  • the node ng-eNB is defined for 5G in the 3GPP document TS38.300 section 3.
  • RRC Radio Resource Control
  • 3GPP 3rd Generation Partnership Project
  • RRC Radio Resource Control
  • 3GPP 3rd Generation Partnership Project
  • UMTS Universal Mobile Telecommunications System
  • LTE Long Term Evolution
  • RRC Radio Resource Control
  • UMTS Universal Mobile Telecommunications System
  • LTE Long Term Evolution
  • RRC is used to control handover and cell selection procedures, including when a wireless device switches its network connection from a current cell, referred to as“source” cell, to a new cell, referred to as“target” cell.
  • radio conditions basically refers to quality and strength of received radio signals and also the amount of interference from other
  • a method is performed by a wireless device when operating in a wireless network, for accessing a target cell when the wireless device has obtained and stored a configuration for at least one candidate target cell.
  • the wireless device prioritizes the at least one candidate target cell for cell selection upon detecting a communication failure such as, e.g., handover failure, radio link failure, and failure to comply with a configuration for accessing the wireless network.
  • the wireless device then performs cell selection by selecting one of the prioritized at least one candidate target cell for which a configuration has been obtained and stored.
  • the wireless device further accesses the selected cell by applying the configuration stored for the selected cell.
  • the selected cell may be accessed via handover or re-establishment.
  • a wireless device when operating in a wireless network, is arranged to access a target cell when the wireless device has obtained and stored a configuration for at least one candidate target cell.
  • the wireless device is configured to prioritize the at least one candidate target cell for cell selection upon detecting a communication failure, which may be performed by means of a prioritizing module in the wireless device.
  • the wireless device is also configured to perform cell selection by selecting one of the prioritized at least one candidate target cell for which a configuration has been obtained and stored. This operation may be performed by means of a cell selection module in the wireless device.
  • the wireless device is further configured to access the selected cell by applying the configuration stored for the selected cell, which may be performed by means of an accessing module in the wireless device.
  • a computer program is also provided comprising instructions which, when executed on at least one processor in the above wireless device, cause the at least one processor to carry out the method described above.
  • a carrier is also provided which contains the above computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.
  • Fig. 1 illustrates a communication scenario involving a wireless device in a wireless network, where the examples and embodiments described herein may be used.
  • Fig. 2 is a flow chart illustrating a procedure in a wireless device, according to some example embodiments.
  • Fig. 3 is a block diagram illustrating how a wireless device may be structured, according to further example embodiments.
  • Figs 4A-C is a signaling diagram illustrating a conventional handover procedure for a wireless device from a source gNB to a target gNB.
  • Fig. 5 is a signaling diagram illustrating a conventional handover from a serving gNB to a target gNB when conditional handover is employed.
  • Fig. 6 is a schematic operation diagram illustrating a conventional way of handling Radio Link Failure, RLF, by means of first and second timers T1 , T2 upon detecting a radio problem.
  • Fig. 7 is a signaling diagram illustrating a conventional re-establishment procedure started by a wireless device denoted UE, in accordance with the 3GPP document TS 38.300.
  • Figs 8A-B is a signaling diagram illustrating how a handover procedure can be executed with substantially reduced signaling as compared to conventional procedures.
  • Figs 9-14 illustrate further scenarios, structures and procedures that may be employed when the solution is used, according to further possible embodiments.
  • a wireless device which is operable in a wireless network, e.g. including accessing a target cell when the wireless device has obtained and stored a configuration for at least one candidate target cell, or candidate cell for short.
  • target cell and candidate cell are used interchangeably. It is assumed that a cell is served by a corresponding network node. Hence, when it is mentioned herein that a cell performs some activity or operation, it means that it is a network node of the cell that actually performs the activity or operation.
  • FIG. 1 illustrates a communication scenario where the examples and embodiments described herein may be used.
  • a wireless device 100 is shown to operate in a wireless network 102, and is currently attached to a serving network node covering a serving cell 104, also referred to as a source cell which term will be used herein.
  • Some other nearby cells likewise covered and served by network nodes are also shown in the figure, denoted 106A-C, which can be seen as potential candidates, i.e. candidate target cells, for access by the device 100, e.g. via a handover procedure or a re-establishment procedure.
  • potential candidates i.e. candidate target cells
  • the term cell should be understood broadly as a radio coverage area covered and served by a network node which thus can provide communication services to wireless devices located in the cell.
  • the cells in this figure are schematically indicated by dashed lines which in reality may have any forms and shapes such as circles, sectors and beams.
  • the wireless device 100 performs measurements on signals transmitted from the cells 104, 106A-C and reports the measurements to the serving node of cell 104, which node then may decide that the wireless device should be attached to a target cell that can provide better reception of signals than the source cell 104.
  • so-called Radio Link Failure, RLF is used as an example of communication failure which implies that the radio link in the serving cell 104 is not good enough to be used for the communication between the device 100 and the network 102, commonly also referred to as “bad” radio conditions.
  • RLF Radio Link Failure
  • the examples and embodiments herein are not limited to the occurrence of RLF but could be employed also at other types of communication failure such as, e.g., handover failure and failure to comply with a configuration for accessing the wireless network.
  • the wireless device 100 In order to execute a commanded handover or re-establishment to a target cell, e.g. to one of cells 106A-C, the wireless device 100 needs to obtain various configuration information that should be used for accessing the target cell.
  • Such configuration information related to the target cell which may comprise an RRC configuration, is in the case of handover transmitted from the source cell 104, e.g. in a handover command to the device 100, which may be sent from the source cell 104 to the device after the reported measurements have been evaluated and a handover decision has been taken.
  • RRC configuration Radio Resource Control
  • configuration information related to the target cell is sent by the target cell in a re-establishment command to the device, after said device has selected that cell in a cell selection procedure.
  • the wireless device 100 is not able to access the target cell in time and the handover or re-establishment thus fails.
  • This can be solved by utilizing a configuration for at least one target cell X which has been obtained and stored in advance by the device 100, e.g. when transmitted from the source cell 104, well before any handover or re-establishment procedure has been decided and initiated.
  • the wireless device 100 further prioritizes the at least one target cell X for which the device 100 already has a configuration. Thereby, the wireless device 100 can primarily try to select one of the prioritized target cells X for which a configuration has already been obtained and stored, and access the selected target cell using the stored configuration without having to receive the
  • Fig. 2 illustrates a procedure in the wireless device 100 when operating in a wireless network 102, for accessing a target cell, e.g. one of cells 106A-C.
  • a first action 200 illustrates that the wireless device 100 obtains and stores a configuration for at least one candidate target cell, e.g. for the cells 106A-C, which may be done by signaling with a currently serving network node of cell 104 preferably at a time when the radio link is still“good”, that is before it might become worse resulting in RLF.
  • the wireless device 100 further detects a communication failure which basically implies that it is necessary, or at least better, to change connection to another cell, for whatever reason.
  • the communication failure in this context will often be referred to as a“failure” for short in the following text.
  • the wireless device 100 prioritizes the at least one candidate target cell, e.g. cells 106A-C, for cell selection upon detecting a communication failure as of action 202. This means that when cell selection becomes necessary the wireless device 100 will primarily try to select one of the prioritized candidate target cells for which a configuration has already been obtained and stored, if that cell can provide a sufficiently good radio connection for the device. It should be noted that action 204 may be performed prior to detecting a communication failure in action 202, so that actions 202 and 204 are taken in an opposite order. For example, the target cell(s) may be prioritized for cell selection according to action 204 basically when the respective configuration(s) is(are) obtained as of action 200.
  • the target cell(s) may be prioritized for cell selection according to action 204 basically when the respective configuration(s) is(are) obtained as of action 200.
  • the wireless device 100 performs cell selection by selecting one of the prioritized at least one candidate target cell for which a configuration has been obtained and stored in action 200. If none of the prioritized candidate target cell(s) is available and can provide a sufficiently good radio connection, the device 100 needs to select another non-prioritized cell and obtain its configuration in a conventional manner, which is however outside the embodiments herein.
  • the wireless device 100 accesses the selected cell by applying the configuration that has already been obtained and stored for the selected cell as of action 200.
  • the wireless device 100 may access the selected cell via handover or re
  • the stored configuration(s) may be so-called conditional handover configuration(s).
  • Conditional handover means basically that a handover is associated with a condition that must be fulfilled before a handover is triggered or initiated.
  • the condition may be based on radio conditions by requiring that signals from a certain neighbor or candidate cell becomes‘X’ dB better than the signals from the serving cell.
  • the wireless device initiates and executes the handover.
  • Conditional handover will be explained in more detail later below.
  • the cell selection in action 206 may be performed by evaluating at least one suitability criterion for the at least one candidate target cell.
  • another example embodiment may be that the at least one suitability criterion requires that a certain quality limit (or value) and a certain coverage limit (or value) are reached (or fulfilled) for the evaluated cell.
  • the cell selection in action 206 may be performed based on priorities provided by the network, e.g. in addition to evaluating at least one suitability criterion in the previous embodiment.
  • priorities of the network which may be different than the prioritization of cells made by the device 100 in action 204, may be dependent on aspects such as cell coverage, network capacity and load of each cell.
  • the above-mentioned communication failure detected in action 202 may comprise any of: handover failure, radio link failure (RLF), and failure to comply with a configuration for accessing the wireless network.
  • RLF radio link failure
  • said configuration for each of the at least one candidate target cell may comprise a Radio Resource Control, RRC, configuration.
  • RRC Radio Resource Control
  • the above communication failure may be declared when a predefined timer expires, which timer has been started when the communication failure was first detected.
  • the wireless device 100 in this embodiment starts the timer as soon as a communication failure, such as any of the above-mentioned communication failures, has been noticed or detected. If the communication failure still remains after the timer has expired, the wireless device 100 will proceed to perform cell selection in action 204, and so forth. If the communication failure has vanished when the timer expires, it is no longer necessary to change cell by performing a handover or re-establishment and the device 100 can remain connected to the source cell 104.
  • the block diagram in Fig. 3 illustrates a detailed but non-limiting example of how a wireless device 300 may be structured to bring about the above-described solution and embodiments thereof.
  • the wireless device 300 may be configured to operate according to any of the examples and embodiments of employing the solution as described herein, where appropriate, e.g. in the manner described for the wireless device 100.
  • the wireless device 300 is shown to comprise a processor“P”, a memory“M” and a communication circuit“C” with suitable equipment for transmitting and receiving information and messages in the manner described herein.
  • the communication circuit C in the wireless device 300 thus comprises equipment configured for communication using a suitable protocol for the communication depending on the implementation.
  • the solution is however not limited to any specific types of messages or protocols.
  • the wireless device 300 is, e.g. by means of units, modules or the like, configured or arranged to perform at least some of the actions of the flow chart in Fig. 2 and as follows.
  • the wireless device 300 may further correspond to the above- described wireless device 100 of Fig. 1.
  • the wireless device 300 is arranged to, when operating in a wireless network, access a target cell when the wireless device has obtained and stored a configuration for at least one candidate target cell, such as the cells 106A-C shown in Fig. 1.
  • the wireless device 300 is configured to prioritize the at least one candidate target cell for cell selection upon detecting a communication failure. This operation may be performed by a prioritizing module 300A in the wireless device 300, as also illustrated in action 204.
  • the wireless device 300 is also configured to perform cell selection by selecting one of the prioritized at least one candidate target cell for which a configuration has been obtained and stored. This operation may be performed by a cell selection module 300B in the wireless device 300, as also illustrated in action 206.
  • the wireless device 300 is further configured to access the selected cell by applying the configuration stored for the selected cell. This operation may be performed by an accessing module 300C in the wireless device 300, as also illustrated in action 208.
  • Fig. 3 illustrates various functional modules in the wireless device 300 and the skilled person is able to implement these functional modules in practice using suitable software and hardware equipment.
  • the solution is generally not limited to the shown structure of the wireless device 300, and the functional modules therein may be configured to operate according to any of the features, examples and embodiments described in this disclosure, where appropriate.
  • the functional modules 300A-C described above may be implemented in the wireless device 300 by means of program modules of a computer program comprising code means which, when run by the processor P causes the wireless device 300 to perform the above-described actions and procedures.
  • the processor P may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units.
  • the processor P may include a general purpose microprocessor, an instruction set processor and/or related chips sets and/or a special purpose microprocessor such as an Application
  • the processor P may also comprise a storage for caching purposes.
  • the computer program may be carried by a computer program product in the wireless device 300 in the form of a memory having a computer readable medium and being connected to the processor P.
  • the computer program product or memory M in the wireless device 300 thus comprises a computer readable medium on which the computer program is stored e.g. in the form of computer program modules or the like.
  • the memory M may be a flash memory, a Random-Access Memory (RAM), a Read-Only Memory (ROM) or an Electrically Erasable Programmable ROM (EEPROM), and the program modules could in alternative embodiments be distributed on different computer program products in the form of memories within the wireless device 300.
  • the solution described herein may be implemented in the wireless device 300 by a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions according to any of the above embodiments and examples, where appropriate.
  • the solution may also be implemented at the wireless device 300 in a carrier containing the above computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium. While the solution has been described with reference to specific exemplifying embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution.
  • the above mentioned problem of not obtaining the necessary configuration information in time will now be described in more detail.
  • the above wireless device 100 or 300 will frequently be referred to as a UE for short and the terms wireless device and UE are thus basically synonyms and used herein interchangeably.
  • handover is often referred to as FIO for short.
  • the term RAT used below denotes Radio Access Technology.
  • a connected wireless device such as an RRC_CONNECTED UE in LTE (also called Evolved Universal Terrestrial Radio Access, E-UTRA), can thus be configured by the network to perform measurements and use triggers for transmitting measurement reports to the network.
  • the network may send a handover command to the device/UE.
  • the handover command may be a message called
  • RRConnectionReconfiguration provided with a field called mobilityControllnfo
  • the handover command may be a message called RRCReconfiguration provided with a field called reconfigurationWithSync.
  • reconfigurations are actually prepared by the target cell upon an inter-node request from the source node e.g. over an X2 interface in case of E-UTRA/ Evolved Packet Core, EPC, or over an Xn interface in case of E-UTRA/5GC or NR, and takes into account the existing RRC configuration the device/UE has with the source cell (which are provided in the inter-node request).
  • the reconfiguration provided by the target node contains all information the UE needs to access the target cell, e.g.
  • SRB1 Signaling Radio Bearer
  • Figs 4A-C illustrate a conventional signaling procedure involving a UE, a source node, here denoted source gNB, and a target node, here denoted target gNB, during a handover procedure.
  • An Access and Mobility management Function, AMF, node is also shown in these figures and also in some of the following figures, which is a well-known node that handles control plane traffic in a core network.
  • the terms source node and target node are more or less interchangeable with the terms source cell and target cell, respectively.
  • Fig. 4A illustrates a handover preparation phase
  • Fig. 4B illustrates a handover execution phase following Fig. 4A
  • Fig. 4C illustrates a handover completion phase following Fig. 4B.
  • Mobility in RRC_CONNECTED is Network-based as the network has access to information regarding the current situation in the network, such as load conditions in cells, resources in different nodes, available frequencies, etc.
  • the network can also take into account the situation of many UEs in the network, for a resource allocation perspective.
  • the network prepares a target cell before the UE accesses that cell.
  • the source node provides the UE with the RRC configuration to be used in the target cell, including SRB1 configuration to send FIO complete.
  • the UE is provided by the target node with a target C-RNTI, i.e. the target node identifies the UE from a transmitted message MSG.3 on MAC level for the HO complete message. Hence, there is no context fetching performed, unless a failure occurs.
  • the network provides to the UE needed information on how to access the target cell, e.g. Random Access Channel (RACH) configuration, so the UE does not have to acquire system
  • RACH Random Access Channel
  • the UE may be provided with Contention-Free Random Access, CFRA, resources, i.e. in that case the target node identifies the UE from a preamble MSG.1 transmitted by the UE.
  • CFRA Contention-Free Random Access
  • the principle behind this is that the procedure can always be optimized with dedicated resources.
  • CFIO Conditional Flandover
  • Security is prepared before the UE accesses the target cell, e.g. keys for encryption need to be updated and“refreshed” before the UE sending the RRC Connection Reconfiguration Complete message, based on new keys and encrypted and integrity protected so that the UE can be verified in the target cell.
  • RRCConnectionReconfiguration message with the mobilityControllnfo field and RRCReconfiguration message with the reconfiguration With Sync field is normally sent when the radio conditions for the UE are already quite bad, as also explained above. As a result, the HO Command may not reach the UE in time, particularly if the message is segmented or there are retransmissions resulting in added delays.
  • condition handover or“early handover command”.
  • RRC signaling for the handover to the UE earlier.
  • the A3 event and other events that trigger measurement reports are defined by 3GPP, see for example 3GPP document TS 38.331 version 15.3.0, Release 15. As soon as the condition in the HO command is fulfilled, the UE executes the handover in accordance with the provided handover command.
  • Such a condition could e.g. be that the quality of the target cell or beam becomes ⁇ dB stronger than the serving cell.
  • the threshold X used in a preceding measurement reporting event should then be chosen lower than the threshold in the handover execution condition. This allows the serving cell to prepare the handover upon reception of an early measurement report and to provide the RRCConnectionReconfiguration message with the mobilityControllnfo field (or the RRCReconfiguration message with the ReconfigurationWithSync field) at a time when the radio link between the source cell and the UE is still stable. The execution of the handover can then be done at a later point in time, e.g. at a different signal threshold, which time is considered optimal for the handover execution.
  • Fig. 5 depicts an example of a signaling procedure where a UE reports signal measurements, e.g. so-called Radio Resource Management, RRM,
  • RRM Radio Resource Management
  • RRCConnectionReconfiguration (or RRCReconfiguration, in NR) for each of those candidates may differ e.g. in terms of the HO execution condition with respect to Reference signals to measure and a threshold to exceed, as well as in terms of a Random Access (RA) preamble to be sent from the UE when a certain condition is met.
  • RA Random Access
  • measurement reports are configured so that the network can detect when a cell in a particular frequency is better than the SpCell which is a primary cell of a master or secondary cell group. Then, upon the reception of a measurement report the network may trigger a handover. Radio conditions on the connection with the source node may drop, i.e. get worse, while the UE is sending measurement reports and/or the source node in the network is trying to transmit a handover command such as an
  • Radio Link Failure Upon detecting a radio problem, the UE starts a timer T1 which is denoted timer T310 in RRC. If there is no recovery while the timer is running, that timer expires, and the UE declares RLF and starts a second timer T2 which is denoted timer T311 in RRC, while it tries to perform cell selection and initiates re-establishment.
  • T1 timer
  • T311 timer
  • the UE shall: l>upon T310 expiry in PCell; or l>upon random access problem indication from MCG MAC while neither T300, T301, T304 nor T311 is running; or l>upon indication from MCG RLC that the maximum number of retransmissions has been reached:
  • the UE shall: l>upon T310 expiry in PSCell; or l>upon random access problem indication from SCG MAC; or l>upon indication from SCG RLC that the maximum number of retransmissions has been reached:
  • a handover command which comprises the RRCReconfiguration message with the reconfigurationWithSync field in NR or the
  • the UE starts a timer T304 with the value set to the field t304 in the message.
  • the UE Upon that, the UE applies the received message and tries to access the target cell. If the timer expires while the UE is trying to access the target cell, a handover failure is declared.
  • the NR RRC specifications in 3GPP document TS 38.331 capture that as follows, relevant parts underlined:
  • the UE shall perform the following actions to execute a reconfiguration with sync. l> stop timer T310 for the corresponding SpCell, if running; 1> start timer T304 for the corresponding SpCell with the timer value set to t304, as included in the reconfigurationWithSync;
  • the EE should perform the reconfiguration with sync as soon as possible following the reception of the RRC message triggering the reconfiguration with sync, which could be before confirming successful reception (HARQ and ARQ) of this message. l>reset the MAC entity of this cell group;
  • the UE shall:
  • the UE configuration includes state variables and parameters of each radio bearer. l>else if T304 of a secondary cell group expires:
  • MIB denotes Master Information Block
  • SSB Synchronization Signal Block
  • the re-establishment procedure may be initiated upon the declaration of a HO failure or RLF.
  • Other cases may also trigger the initiation of an RRC Re-establishment procedure, which may also be relevant in this context, such as an RRC connection reconfiguration failure of a CHO, or and integrity check failure, or mobility from NR, even though only intra-NR handovers and RLFs are highlighted.
  • RRC Re-establishment procedure which may also be relevant in this context, such as an RRC connection reconfiguration failure of a CHO, or and integrity check failure, or mobility from NR, even though only intra-NR handovers and RLFs are highlighted.
  • these operations are described as follows, relevant parts underlined:
  • the UE initiates the procedure when one of the following conditions is met: l>upon detecting radio link failure of the MCG. in accordance with 5.3.10: or l>upon re-configuration with sync failure of the MCG. in accordance with sub-clause 5.3.5.8.3: or l>upon mobility from NR failure, in accordance with sub-clause 5.4.3.5; or l>upon integrity check failure indication from lower layers concerning SRB1 or SRB2; or l>upon an RRC connection reconfiguration failure, in accordance with sub-clause 5.3.5.8.2.
  • the 3GPP document TS 38.300 summarizes the re-establishment procedure to a necessary level to understand the problem addressed herein and the solution described herein.
  • the UE upon declaring RLF or handover failure, the UE transmits an RRCReestablishmentRequest with a AS context identifier - source Physical Cell Identity (PCI) + source C-RNTI. If the target node is prepared e.g. if this was a failed handover, the target node may respond with an RRCReestablishmentRequest with a AS context identifier - source Physical Cell Identity (PCI) + source C-RNTI. If the target node is prepared e.g. if this was a failed handover, the target node may respond with an RRCReestablishmentRequest with a AS context identifier - source Physical Cell Identity (PCI) + source C-RNTI. If the target node is prepared e.g. if this was a failed handover, the target node may respond with an
  • RRCReestablishment message possibly multiplexed with an RRCReconfiguration message. Then, the UE transmits an RRCReconfigurationComplete and an RRCReestablishmentComplete.
  • the re-establishment procedure is reproduced in the 3GPP document TS 38.300 as follows:
  • a UE in RRC CONNECTED may initiate the re-establishment procedure to continue the RRC connection when a failure condition occurs (e.g. radio link failure, reconfiguration failure, integrity check failure).
  • a failure condition e.g. radio link failure, reconfiguration failure, integrity check failure.
  • Fig. 7 shows a signalling diagram in TS 38.300 which describes the re
  • the UE re-establishes the connection, providing the UE Identity (PCI+C- RNTI) to the gNB where the trigger for the re-establishment occurred.
  • PCI+C- RNTI UE Identity
  • the gNB If the UE Context is not locally available, the gNB, requests the last serving gNB to provide UE Context data. 3. The last serving gNB provides UE context data.
  • the gNB continues the re-establishment of the RRC connection.
  • the message is sent on SRB1.
  • the gNB may perform the reconfiguration to re-establish SRB2 and DRBs when the re-establishment procedure is ongoing. 6. If loss of DL user data buffered in the last serving gNB shall be prevented, the gNB provides forwarding addresses.
  • the gNB performs path switch.
  • the gNB triggers the release of the UE resources at the last serving gNB.
  • One of the actions the UE performs upon re-establishment is reverting to the configuration that has been used in the source cell, which is especially relevant in the case the UE has received an RRCReconfiguration message with the reconfigurationWithSync field and fails, e.g. due to T304 expiry.
  • a UE configured with multiple candidate target cells in a Conditional Handover message which experiences a handover failure (e.g. upon the expiry of timer T304 associated with a given target cell or upon the expiry of timer T310 while a CHO condition is running) could perform cell selection as specified in TS 38.304 in the case of NR.
  • the UE has stored the following configurations associated with cells A, B and C:
  • the UE may transmit a handover complete message after selecting either of A-C.
  • the selected cell is not a cell for which the UE has an RRC
  • the UE may perform an RRC Re-establishment procedure.
  • FIGs 8A-B an enhanced procedure for conditional handover failure recovery is shown where the procedural steps 1 -8 in Fig. 8A are followed by the procedural steps 9-15 in Fig. 8B.
  • step 10b of this procedure the UE selects a cell for which the UE has a stored an RRC configuration which is detected in step 10c, which is in accordance with action 206 in Fig. 2.
  • the UE shall:
  • the UE configuration includes state variables and parameters of each radio bearer.
  • the UE Upon selecting a suitable NR cell, the UE shall: l>stop timer T311;
  • SIB denotes System Information Block.
  • Event A2 (Serving becomes worse than threshold)
  • Event B1 (Inter RAT neighbour becomes better than threshold)
  • Event B2 (PCell becomes worse than a thresholdl and inter RAT neighbour becomes better than a threshold2) A conventional Cell Selection process will now be described.
  • the cell selection process for NR is defined in TS 38.304 (v15.1.0) as shown in the extract below, relevant parts underlined.
  • the UE shall scan all RF channels in the NR bands according to its capabilities to find a suitable cell.
  • This procedure requires stored information of frequencies and optionally also information on cell parameters from previously received measurement control information elements or from previously detected cells.
  • the cell selection criterion S is fulfilled when:
  • the signaled values Qrxievminoffset and Qquaiminoffset are only applied when a cell is evaluated for cell selection as a result of a periodic search for a higher priority Public Land Mobile Network (PLMN) while camped normally in a Visited PLMN (3GPP TS 23.122).
  • PLMN Public Land Mobile Network
  • the UE may check a cell selection (S) criterion of a cell using parameter values stored from a different cell of this higher priority PLMN.
  • S cell selection
  • the cell selection criteria and procedures in E-UTRAN are specified in TS 36.304.
  • a UE configured with RRC configurations for cells that are not the source/serving cell, e.g. RRCReconfiguration(s) obtained via a
  • conditional handover may experience a communication failure upon triggering a condition specific cell(s), i.e. when not being able to complete a cell switching procedure, such as in a conditional handover.
  • a communication failure may occur due to different reasons such as e.g. RLF triggering while the UE is monitoring a condition for conditional handover e.g. expiry of timer T311 , upon not being able to access a target cell that has triggered the condition for conditional handover e.g. upon the expiry of timer T304 or equivalent for conditional handover, upon not complying with an RRCReconfiguration prepared by a specific target cell, etc.
  • the current RRC specifications define that the UE shall perform cell selection as specified in TS 38.304 (or TS 36.304 in case of LTE) without providing any details of how to perform the cell selection.
  • the NR idle/inactive specifications TS 38.304 only define that the UE may perform cell selection by leveraging on stored information on frequencies/cells from previously received measurement control information or detected cells. In other words, to minimize the burden and to access the network as soon as possible, a typical UE implementation would rely on stored measurements, if up to date, and select a cell as long as it fulfills the suitability criteria before it initiates RRC re-establishment.
  • the procedure shown in Fig. 2 comprises a cell selection prioritization procedure in a UE which has been configured by a source node with a configuration for at least one target candidate cell-X of a target node (e.g. in a conditional handover configuration).
  • the procedure may comprise:
  • the solution takes advantage of the fact, that the UE has stored configurations of target cells which are already prepared to serve the UE when a failure is detected and when the UE needs to perform cell selection.
  • the UE may unnecessarily select a cell for which the UE lacks a configuration, e.g. the above-mentioned RRCReconfiguration message with the reconfigurationWithSync field. That could increase the amount of signaling and latency/delay to regain connectivity, e.g. if the UE would have to perform a RRC re-establishment and prior to that need to acquire necessary system information e.g. to obtain a RACH configuration.
  • the UE selects a prioritized cell for which it has already obtained and stored a configuration, which may include a RACH configuration. This means that the UE may access the cell via handover or re-establishment without the need to obtain all required system information via broadcasting, which would otherwise increase the access time even further.
  • the network may have provided a specific priority among the cells configured for conditional handover, taking into account aspects such as cell coverage, network capacity and load of each cell. Without this embodiment, the UE would disregard these priorities provided by the network and as a result could be subjected to a handover right after the re-establishment or conditional handover failure recovery in case the network priority of the accessed cell indicates that it is unsuitable, e.g. in terms of coverage, network capacity and/or load.
  • the UE upon cell selection, by prioritizing selection of any of the cells for which the UE has a stored configuration, e.g. RRCReconfiguration with reconfigurationWithSync, the UE also saves time by not having to perform additional measurements as the UE would already have measurements available for these cells, mainly since the UE is monitoring the CHO conditions for these cells. That may speed up the recovery mechanism even further and avoid a re establishment by triggering a handover complete.
  • a stored configuration e.g. RRCReconfiguration with reconfigurationWithSync
  • a conditional handover may also be called a conditional reconfiguration with sync.
  • the handovers are typically called an RRCReconfiguration with a reconfigurationWithSync (field containing configuration necessary to execute a handover).
  • the handovers are typically called an RRCConnectionReconfiguration with a mobilityControllnfo (field containing configuration necessary to execute a handover).
  • the procedures and features described herein are also applicable when any of the described steps and operations occurs in different RATs, for example: -
  • the UE is configured with a conditional HO in NR (for candidate NR and LTE cells), then the condition is triggered for an NR cell and UE executes the HO in NR;
  • the UE may select an LTE cell and apply the method: initiate handover execution in the selected LTE cell is the UE has a stored CHO configuration for the selected inter-RAT cell or initiate connection re-establishment in LTE or NR if the UE does not have stored CHO configuration for the selected inter-RAT cell.
  • the UE is configured with a conditional HO in LTE (for candidate NR and LTE cells), then the condition is triggered for an LTE cell and UE executes the HO in LTE;
  • the UE may select an NR cell and apply the method: initiate handover execution in the selected NR cell is the UE has a stored CHO configuration for the selected inter-RAT cell or initiate connection re-establishment in NR or LTE if the UE does not have stored CHO configuration for the selected inter-RAT cell.
  • the UE is configured with a conditional HO in NR (for candidate NR and LTE cells), then the condition is triggered for an LTE cell and UE executes the HO in LTE;
  • the UE may select an LTE cell and apply the method: initiate handover execution in the selected LTE cell is the UE has a stored CHO configuration for the selected inter-RAT cell or initiate connection re-establishment in LTE or NR if the UE does not have stored CHO configuration for the selected inter-RAT cell.
  • the UE is configured with a conditional HO in LTE (for candidate NR and LTE cells), then the condition is triggered for an NR cell and UE executes the HO in NR;
  • the UE may select an NR cell and apply the method: initiate handover execution in the selected NR cell is the UE has a stored CHO configuration for the selected inter-RAT cell or initiate connection re-establishment in NR or LTE if the UE does not have stored CHO configuration for the selected inter-RAT cell.
  • the UE is configured with a condition HO in RAT-1 for cells in RAT-1 or RAT-2, then the condition is triggered and UE executes the HO in RAT-2;
  • the UE may either select a cell in RAT-1 or RAT-2;
  • the UE may select a cell in RAT-1 or RAT-2 cell and apply the method: initiate handover execution in the selected cell of RAT-1 or RAT-2 if the UE has a stored CHO configuration for the selected inter-RAT cell or initiate connection re-establishment in RAT-1 or RAT-2 if the UE does not have stored CHO configuration for the selected inter-RAT cell.
  • the procedure is mostly described herein in the context of conditional handover, which should however not be seen as a limiting factor.
  • the procedure may also be applicable for handovers triggered by the reception of the
  • the UE may have stored configurations of multiple cells provided to the UE as a backup in case the intended handover has failed.
  • the procedure shown in Fig. 2 comprises a prioritization mechanism where the UE prioritizes the cells for which it has stored a configuration, e.g. an
  • RRCReconfiguration with a reconfigurationWithSync compared to other cells for which the UE does not have a configuration, e.g. an RRCReconfiguration with a reconfigurationWithSync, stored. That is done in order for the procedure to regain connectivity in another cell faster by omitting the operation of reading broadcasted system information and obtaining a configuration for the cell since the UE already has this configuration stored. It furthermore requires less signaling.
  • One way to implement the prioritization of cells with stored RRC configuration at the UE may be performed by the UE as follows:
  • RSRP Reference Signal Received Power
  • RSRQ Reference Signal Received Quality
  • SINR Signal to Interference and Noise Ratio
  • the listing of the cells to be prioritized i.e. the ones with a stored
  • RRCReconfiguration possibly with a reconfigurationWithSync may be retrieved from a set of messages the UE may have stored. For example, in one
  • the UE has a set of messages, each for a target candidate, as follows:
  • the cells to be prioritized are the ones indicated in each of the
  • the ServingCellConfigCommon Information element is used to configure cell specific parameters of a UE's serving cell.
  • the IE contains parameters which a UE would typically acquire from the SSB, the MIB or the SIBs when accessing the cell from IDLE state.
  • the network provides the above information in dedicated signaling when configuring a UE with a SCells or with an additional cell group (SCG).
  • the network also provides the information for SpCells (MCG and SCG) upon reconfiguration with sync.
  • Frequency information for the PCI is also provided in the same message.
  • Suitability criterion may be defined as in TS 38.304 and/or TS 36.304, where a cell is suitable when a certain acceptable quality (Squal) AND a certain coverage (Srxlev) limit are reached.
  • the cell selection criterion S is fulfilled when:
  • a cell for which the UE has a stored configuration e.g. RRCReconfiguration with reconfigurationWithSync
  • a ‘prioritized cell’ Any other cell which the UE does not have a stored configuration may be referred to as‘other cell’.
  • fulfilling the suitability criteria may be a way of qualifying a cell to be selected.
  • fulfilling the suitability criteria may be a way of qualifying a cell to be selected.
  • multiple cells that have been prioritized fulfill the suitability criterion i.e. multiple cells for which the UE has stored a configuration (e.g. an RRCReconfiguration that is valid for a target that is ready to be accessed)
  • additional criteria may be defined so that the UE selects one cell out of the multiple prioritized ones.
  • the UE When the UE has found a prioritized cell which fulfills the suitability criteria, the UE may:
  • o Selecting the best cell e.g. the one with highest RSRP and/or highest RSRQ and/or highest SINR) among the prioritized cells; o Selecting the best cell (highest RSRP and/or highest RSRQ and/or highest SINR) among the prioritized cells except if there is another cell (‘other cell’) for which the UE does not have a stored configuration (e.g. RRCReconfiguration with
  • the other cell is a threshold better than prioritized cell
  • ⁇ The other cell is better than a thresholdl AND prioritized cell is worse than a threshold2 ; o Selecting the cell among the prioritized cells which exceeds the configured threshold for applying the stored configurations (e.g. RRCReconfiguration with reconfigurationWithSync) by the largest amount (in RSRP and/or RSRQ and/or SINR).
  • the stored configurations e.g. RRCReconfiguration with reconfigurationWithSync
  • the UE may access the selected cell by leveraging on the stored configuration, e.g. RRC configuration. That may be done in some different ways such as the alternatives A and B below:
  • the selection of which procedure to apply, i.e. re-establishment according to alternative A above or opportunistic handover according to alternative B above, upon failure could be determined by a separate criterion, e.g. a separate set of thresholds (compared to the thresholds for which cell to select) or based on failure type.
  • the UE may perform re-establishment, whereas if the UE failed due to expiry of timer T304, the UE may apply the stored configurations.
  • the UE may select any other cell or a cell according to the criteria described above, i.e. based on measurement quantities such as RSRP and/or RSRQ and/or SINR, etc. Then, after cell selection the UE performs a re-establishment procedure.
  • the prioritization for cell selection may be performed per frequency i.e. the UE may select the frequency for which it has stored
  • a communication system includes a telecommunication network 3210 e.g. a WLAN, such as a 3GPP-type cellular network, which comprises an access network 3211 , such as a radio access network, and a core network 3214.
  • the access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, such as access nodes, AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c.
  • Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215.
  • a first user equipment (UE) such as a Non-AP STA 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c.
  • a second UE 3292 such as a Non-AP STA in coverage area 3213a is wirelessly connectable to the UE
  • UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is
  • the telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm.
  • the host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider.
  • the connections 3221 , 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220.
  • the intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown).
  • the communication system of Fig. 9 as a whole enables connectivity between one of the connected UEs 3291 , 3292 and the host computer 3230.
  • the connectivity may be described as an over-the-top (OTT) connection 3250.
  • the host computer 3230 and the connected UEs 3291 , 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211 , the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries.
  • the OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink
  • the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.
  • a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300.
  • the host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities.
  • the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions.
  • the host computer 3310 further comprises software 3311 , which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318.
  • the software 3311 includes a host application 3312.
  • the host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.
  • the communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330.
  • the hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Fig. 10) served by the base station 3320.
  • the communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310.
  • the connection 3360 may be direct or it may pass through a core network (not shown in Fig.
  • the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field
  • the base station 3320 further has software 3321 stored internally or accessible via an external connection.
  • the communication system 3300 further includes the UE 3330 already referred to.
  • Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located.
  • the hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, application-specific integrated circuits, field
  • the UE 3330 further comprises software 3331 , which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338.
  • the software 3331 includes a client application 3332.
  • the client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310.
  • an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310.
  • the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data.
  • the OTT connection 3350 may transfer both the request data and the user data.
  • the client application 3332 may interact with the user to generate the user data that it provides.
  • the host computer 3310, base station 3320 and UE 3330 illustrated in Fig. 10 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291 , 3292 of Fig. 9, respectively.
  • the inner workings of these entities may be as shown in Fig. 10 and independently, the surrounding network topology may be that of Fig. 9.
  • the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the user equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices.
  • Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).
  • the wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure.
  • One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the efficiency in communication and thereby provide benefits such as better utilization of resources in the network.
  • a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve.
  • the measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both.
  • sensors may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311 , 3331 may compute or estimate the monitored quantities.
  • the reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art.
  • measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like.
  • the measurements may be implemented in that the software 3311 , 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.
  • Fig. 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.
  • the communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figs 9 and 10. For simplicity of the present disclosure, only drawing references to Fig. 11 will be included in this section.
  • a first action 3410 of the method the host computer provides user data.
  • the host computer provides the user data by executing a host application.
  • the host computer initiates a transmission carrying the user data to the UE.
  • the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure.
  • the UE executes a client application associated with the host application executed by the host computer.
  • Fig. 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.
  • the communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figs 9 and 10. For simplicity of the present disclosure, only drawing references to Fig. 12 will be included in this section.
  • the host computer provides user data.
  • the host computer provides the user data by executing a host application.
  • the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure.
  • the UE receives the user data carried in the transmission.
  • Fig. 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.
  • the communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figs 9 and 10. For simplicity of the present disclosure, only drawing references to Fig. 13 will be included in this section.
  • the UE receives input data provided by the host computer.
  • the UE provides user data.
  • the UE provides the user data by executing a client application.
  • the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer.
  • the executed client application may further consider user input received from the user.
  • the UE initiates, in an optional third subaction 3630, transmission of the user data to the host computer.
  • the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.
  • Fig. 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.
  • the communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figs 9 and 10. For simplicity of the present disclosure, only drawing references to Fig. 14 will be included in this section.
  • the base station receives user data from the UE.
  • the base station initiates transmission of the received user data to the host computer.
  • the host computer receives the user data carried in the transmission initiated by the base station.

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Abstract

La présente invention concerne un procédé et un dispositif sans fil (100) permettant d'accéder à une cellule cible lorsque le dispositif a obtenu et stocké une configuration pour au moins une cellule cible candidate (106A-C). Les cellules cibles candidates sont classées par ordre de priorité pour une sélection de cellule lors de la détection d'une défaillance de communication. Le dispositif sans fil (100) effectue une sélection de cellule en sélectionnant l'une des cellules cibles priorisées pour lesquelles une configuration a été obtenue et stockée, et accède à la cellule sélectionnée en appliquant la configuration stockée pour la cellule sélectionnée.
PCT/SE2019/051213 2018-12-04 2019-11-29 Procédé et dispositif sans fil pour accéder à une cellule cible Ceased WO2020117114A1 (fr)

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