WO2018201487A1

WO2018201487A1 - Method and apparatus for carrying out a group handover

Info

Publication number: WO2018201487A1
Application number: PCT/CN2017/083340
Authority: WO
Inventors: Ying Huang; Lin Chen; Yuqin Chen
Original assignee: Zte Corporation
Priority date: 2017-05-05
Filing date: 2017-05-05
Publication date: 2018-11-08
Also published as: CN110720238A

Abstract

A method and apparatus for performing a group handover in a wireless network involves receiving a handover command from a source wireless cell, transmitting the handover command to a first remote user equipment and to a second remote user equipment, accessing a target wireless cell, receiving a radio resource control message from the first remote user equipment indicating that the first remote user equipment has completed a reconfiguration for the handover, receiving a radio resource control message from the second remote user equipment indicating that the second remote user equipment has completed a reconfiguration for the handover, combining the radio resource control message from the first remote user equipment with the radio resource control message of the second remote equipment into a combined radio resource control message, and transmitting the combined radio resource control message to the target wireless cell.

Description

METHOD AND APPARATUS FOR CARRYING OUT A GROUP HANDOVER

TECHNICAL FIELD

The present disclosure is related generally to handovers in wireless networks and, more particularly, to a method and an apparatus for carrying out a group handover.

BACKGROUND

There has been an increased interest in device-to-device ( “D2D” ) communication in cellular networks. This is particularly true with low-cost devices that use machine-type communications ( “MTC” ) . One example of such low cost devices is wearables, which are always in close proximity to a smartphone that can serve as a relay. Various short-range communication technologies could be used for communication between the wearables (i.e., remote user equipment ( “UEs” ) and the smartphone (serving as a relay UE) . Service continuity is an important aspect in commercial use cases. With currently deployed systems, when there is a handover, the remote UEs and relay UE would each carry out their own individual handover procedure from the source evolved Node B ( “eNB” ) to the target eNB. This incurs a signaling overhead cost as well as a power consumption cost to the remote UE.

DRAWINGS

While the appended claims set forth the features of the present techniques with particularity, these techniques, together with their objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:

FIG. 1 depicts the interaction between UEs and between each individual UE and a telecommunication system in a device-to-device ( “D2D” ) context, in an embodiment.

FIG. 2 illustrates a basic hardware architecture for a computing device, according to an embodiment.

FIGS. 3A and 3B illustrate a scenario in which one or more remote UEs are paired with a relay UE, according to an embodiment.

FIG. 4 is a signal flow diagram depicting an enhanced group handover procedure, according to an embodiment.

FIG. 5 is a signal flow diagram depicting an S1 handover procedure.

FIG. 6 illustrates a layered architecture used in a hop by hop radio resource control ( “RRC” ) technique, according to an embodiment.

FIG. 7 illustrates a layered architecture used in an end to end RRC technique, according to an embodiment.

FIG. 8 illustrates a layered architecture used in another end to end RRC technique, according to an embodiment.

FIG. 9 illustrates a layered architecture used in still another end to end RRC technique, according to an embodiment.

DESCRIPTION

The present disclosure is generally directed to a method and apparatus for carrying out a group handover. According to various embodiments, a relay user equipment receives a combined handover command from a source wireless cell (e.g., a source eNB) , transmits a handover command to a first remote user equipment (e.g., a wearable device) and (if present) to a second remote user equipment (e.g., another wearable device) , accesses a target wireless cell, receives a radio resource control reconfiguration complete message from the first remote user equipment indicating that the first remote user equipment has completed a reconfiguration for the handover, receives a radio resource control reconfiguration complete message from the second remote user equipment indicating that the second remote user equipment has completed a reconfiguration for the handover, and transmits a combined radio resource control reconfiguration complete message to the target wireless cell indicating that the first remote user equipment, the relay user equipment, and (if present) the second user equipment has completed a reconfiguration for the handover. It is to be noted that there may be more than two remote UEs.

Turning to FIG. 1, the interaction between UEs and between each individual UE and a telecommunication system in a D2D context will now be described. The system 100 includes a radio access network ( “RAN” ) 102 (an example of which is am Evolved Universal Terrestrial Radio Access Network ( “EUTRAN” ) ) , a core network (an example of which is an Evolved Packet Core ( “EPC” ) 104, a proximity services ( “ProSe” ) function (e.g., executing on one or more servers) 106, and a ProSe application server 108. The various components communicate with one another via interfaces or “reference points. ” For example, a first UE 110 and a second UE 112 communicate with one another through a PC5 reference point, both UEs communicate with the RAN 102 through a Uu reference point, the UEs communicate with the ProSe function 106 through a PC3 reference point, the RAN 102 communicates with the core network 104 through an S1 reference point, the core network 104 communicates with the ProSe function 106 through a PC4a reference point, and the ProSe function communicates with the ProSe application server 108 through a PC2 reference point.

The RAN 102 includes multiple communication nodes, including cellular base stations (such as an evolved Node B or “eNB” ) . The core network 104 includes components that support the RAN 102, such as a mobile management entity ( “MME” ) 114 (e.g., executing on a computing device such as a server) . The MME 114 carries out such functions as signalling and security inter-node signalling for mobility between access networks, tracking area list management, gateway selection, roaming, authentication, and bearer management functions. The core network 104 also includes a home subscriber server ( “HSS” ) 116. The HSS 116 maintains a database of network subscribers. The interaction between the MME 114 and HSS 116 in an embodiment is as follows: The MME informs the HSS 116 of the location of a mobile station managed by the HSS 116. The HSS 116 sends, to the MME, all the data needed to support services to the mobile subscriber. Exchanges of data between the MME 114 and the HSS 116 may occur when the mobile subscriber needs a particular service, when the subscriber wants to change some data associated with their subscription, or when some parameters of the subscription are modified.

The system 100 has many components that are not depicted in FIG. 1, including other eNBs, other UEs, wireless infrastructure, wired infrastructure, and other devices commonly found in LTE networks. Example implementations of the UEs include any device capable of LTE communication, such as a smartphone, tablet, laptop computer, and non-traditional devices (e.g., household appliances or other parts of the “Internet of Things” ) .

FIG. 2 illustrates a basic (computing device) hardware architecture found in the devices depicted in FIG. 1 (include the UEs and devices of the core network 104) . The devices may have other components as well, some of which are common to all of the devices and others that are not. The hardware architecture depicted in FIG. 2 includes logic circuitry 202, memory 204, transceiver 206, and one more antennas represented by antenna 208. Each of these elements is communicatively linked to one another via one or more data pathways 210. Examples of data pathways include wires, conductive pathways on a microchip, and wireless connections.

The term “logic circuitry” as used herein means a circuit (atype of electronic hardware) designed to perform complex functions defined in terms of mathematical logic. Examples of logic circuitry include a microprocessor, a controller, or an application-specific integrated circuit. When the present disclosure refers to a computing device carrying out an action, it is to be understood that this can also mean that logic circuitry integrated with the computing device is, in fact, carrying out the action.

Possible implementations of the memory 204 include: volatile data storage； nonvolatile data storage； electrical memory； magnetic memory； optical memory； random access memory ( “RAM” ) ； cache memory； and hard drives.

One context for the various techniques described herein is as follows. Assume that one or more remote UEs are paired with a relay UE, and that the remote UEs move together with the paired relay UE (as would typically be the case if the remote UEs are wearables) . When the remote UE moves the connection between the remote UE and the relay UE remains relatively constant. This scenario is illustrated in FIG. 3A and FIG. 3B, in which a first UE 302, acts as a relay UE for two remote UEs –a second UE 304 and a third UE 306, and the UEs move from a source cell 308 (controlled by a source eNB 310) to a second cell 312 (controlled by a target eNB 314) . Note that two remote UEs are shown only for the sake of simplicity. There may, in fact, be only one remote UE or more than two remote UEs.

According to an embodiment, an enhanced group handover procedure is provided. Turning to FIG. 4, an embodiment of the procedure will now be described. In this description, there is a remote UE 402, a relay UE 404, a source eNB 406, a target eNB 408, and an MME 410, whose functions and architecture are the same as those depicted in the previous figures. Although only one remote UE is shown, the techniques apply to multiple remote UEs as well.

Step 1a. As an optional step, the remote UE 402 sends a measurement report containing information ( “measurement report information” ) to the connected relay UE 404 or the eNB 406. The measurement report information sent from the remote UE 402 includes at least one of the following: the Uu link measurement result (e.g., reference signal received power ( “RSRP” ) measurement of serving cell and/or neighbour cell) , the PC5 link measurement result (e.g., RSRP measurement) measured by the remote UE 402. Optionally, the remote UE 402 could send measurement report information to the connected relay UE 404 via PC5 control plane signalling. Optionally, the data packet of measurement report includes an adapter or RRC layer information indicating the message type, i.e. indicating that the message is a measurement report message or the message shall be combined. Possible ways of sending the remote UE’s measurement report to the relay UE or eNB are described in more detail below under Technical Consideration 1. Optionally, the remote UE 402 determines whether to send a measurement report based on the following:

1) If bidirectional UE to network relay (i.e., both uplink ( “UL” ) and downlink ( “DL” ) transmission between the UE 402 and the network (e.g., one of the eNBs) is relayed by the relay UE 404) is used and eNB scheduled mode (i.e., mode 3) is not used in PC5, the remote UE’s Uu link measurement results do not need to be sent to the relay UE 404 or to the eNB.

2) If unidirectional UE to network relay (e.g., DL paging or system information or data is received directly from the eNB by the remote UE 402) or eNB scheduled mode (i.e., mode 3) is used in PC5, the remote UE’s Uu link measurement results need to be sent to the relay UE 404 or the eNB.

In addition, when the remote UE 402 is connected with the relay UE 404, the remote UE 402 determines whether to start the Uu link measurement and/or reporting based on the PC5 link quality (i.e., PC5 RSRP measurement result) between the remote UE 402 and the connected relay UE 404. For example, if the PC5 link quality is below a threshold, the remote UE 402 could start to measure the Uu link quality of serving cell and/or neighbour cells. The PC5 link quality threshold could be configured by the eNB (e.g., the serving eNB) . Alternatively, the remote UE 402 determine whether to start the Uu link measurement and/or reporting based on the measurement configuration information received from the eNB or the relay UE 404.

Optionally, the relay UE 404 could obtain the relay type (i.e., bidirectional or unidirectional) of the remote UE 402 by the information received from the remote UE 402. The eNB (e.g., the source eNB 406) could obtain the relay type (i.e., bidirectional or unidirectional) of the remote UE 402 by the information received from the remote UE 402 or relay UE 404.

Opionally, the remote UE determines whether to initiate group handover before sending the measurement report. If the remote UE determines to initiate group handover, the remote UE sends the measurement report to the relay UE. Possible ways of determining whether to initiate group handover are described below in more detail below under Technical Consideration 2.

Step 1b. The relay UE 404 sends a measurement report to the source eNB 406. At least one of the following is contained in the measurement report sent from the relay UE. In one embodiment, the items noted as “mandatory” will be in the report, while the ones noted as “optional” may not be:

1) the Uu link measurement result measured by the relay UE 404, mandatory；

2) the PC5 link measurement result measured by the relay UE 404, optional；

3) the Uu link measurement result measured by the remote UE 402 which is received from the remote UE 402, optional；

4) the PC5 link measurement result measured by the remote UE 402 which is received from the remote UE 402, optional；

5) a list of identity of the remote UE 402 which performs group handover with the relay UE 404, optional.

More specifically, if the relay UE 404 has received the measurement report information from the remote UE 402 in step 1a, the relay UE 404 could relay the received measurement report information to the eNB. Optionally, the relay UE 404 could parse the received measurement report information from the remote UE 402. Optionally, the relay UE 404 could combine one or more remote UE 402’s measurement report information and relay UE’s measurement report information into one RRC message and send it to the eNB. The relay UE 404 may send the measurement report to the source eNB 406 via measurement report RRC message or new defined RRC message, e.g. combined measurement report message or group measurement report message. Optionally, the data packet of measurement report sent by the relay UE includes an adapter or RRC layer information indicating that it is a combined message. Or the relay UE 404 could relay measurement report information of remote UE (s) individually to the eNB. Possible ways of sending the remote UE’s measurement report to the eNB are described in more detail below under Technical Consideration 1.

Optionally, the relay UE 404 may determine which remote UE (s) shall perform group handover with the relay UE 404 before sending the measurement report to the source eNB. Possible ways of doing this are described below in more detail below under Technical Consideration 2.

Step 2. The source eNB initiates handover preparation procedure for the relay UE 402 and remote UE (s) .

Optionally, the source eNB determines whether group handover could be performed for the relay UE and remote UE (s) . Optionally, if group handover could be performed for the relay UE and remote UE (s) , the source eNB determines which remote UE (s) shall perform group handover along with the relay UE 404. Possible ways of doing this are described below in more detail below under Technical Consideration 2. The eNB could initiate handover preparation procedure individually for the relay UE 404 and remote UE 402, i.e., send individual X2 handover request message to the target eNB.

Alternatively, the source eNB could initiate group handover preparation procedure to the target eNB, i.e., send X2 group handover request message to target eNB, if the target eNB of remote UE 402 is the same as relay UE’s target eNB. More specifically, at least one of the the following information is contained in the group handover request message: handover request information for the relay UE/remote UE, corresponding relay UE/remote UE identity, a list of remote UE identity. The relay UE/remote UE identity could be eNB X2AP ID, or ProSe layer ID or unique identity of remote UE 402 in the scope of relay UE 404. The group handover request message could be the X2 handover request message or new defined X2 message.

Step 3. After performing admission control for the relay UE 404 and the remote UE 402, the target eNB sends handover request ACK to the source eNB 406 for the accepted relay UE 404 and remote UE (s) .

Similar to what occurred in Step 2, the target eNB 410 could send handover request ACK individually for the relay UE 404 and remote UE 402. Alternatively, the target eNB 410 could combine the handover request ACK messages for the relay UE 404 and remote UE 402 into one X2 message, e.g., handover request ACK message or new defined X2 message.

At least one of the the following information is contained in the combined handover request ACK message in an embodiment: handover request ACK information for the relay UE/remote UE, corresponding relay UE/remote UE identity, a list of remote UE identities (e.g., the identity of remote UE that performs group handover along with the relay UE) . The relay UE/remote UE identity could be in the form of an eNB X2AP ID, ProSe layer ID, or the unique identity of the remote UE in the scope of relay UE.

Step 4. The source eNB 406 transmits a handover command message to the relay UE 404 and/or remote UE (s) . Various embodiments of this step are as follows:

The source eNB 406 could send the handover command message for the remote UE 402 directly to the remote UE 402, or the source eNB 406 could send the handover command message for the remote UE 402 via the relay UE 404.

The source eNB 406 could combine one or more remote UE’s handover command and relay UE’s handover command into one RRC message and send it to the relay UE 404. At least one of the following information is contained in the combined handover command, according to an embodiment: handover command information for the relay UE/remote UE, corresponding relay UE/remote UE identity, a list of remote UE identities. Optionally, the data packet of handover command sent by the source eNB 406 includes an adapter or RRC layer information indicating that it is a combined message. The source eNB 406 may send the handover command to the relay UE 404 via handover command RRC message or new defined RRC message, e.g. combined handover command message or group handover command message. Then, the relay UE 402 sends the remote UE’s handover command to the corresponding remote UE. Or the relay UE 404 could relay the remote UE’s handover command individually to the corresponding remote UE (remote UE 402 and other remote UEs not shown) . Possible ways of sending a remote UE’s handover command to the remote UE from the source eNB 406 are described below in more detail below under Technical Consideration 1.

After the relay UE receives relay UE and/or remote UE (s) ’s handover command, the relay UE 404 could determine which remote UE (s) is accepted by the target eNB 408. For the remote UE (s) not accepted by the target eNB 408, the relay UE 404 sends PC5 link release to the corresponding remote UE. Then, the corresponding remote UE may communicate directly with the eNB or reselect another relay UE.

Step 5. Remote UE and/or relay UE perform synchronisation and random access with the target cell (the cell controlled by the target eNB 408) .

Optionally, if the remote UE’s UL data is directly transmitted to the target eNB 408, or the remote UE use eNB scheduled resource mode (i.e., mode 3) in PC5 communication, the remote UE performs random access with the target cell. Otherwise, the remote UE does not perform random access with the target cell.

Step 6a. As an optional step, the remote UE 402 sends a RRC reconfiguration complete containing information ( “RRC reconfiguration complete information” ) to the connected relay UE 404 or the eNB 406. The remote UE 402 could send the RRC reconfiguration complete message directly to the target eNB 408, or the remote UE 402 could send the RRC reconfiguration complete to the target eNB 408 via the relay UE 404. Optionally, the remote UE 402 could send RRC reconfiguration complete information to the connected relay UE 404 via PC5 control plane signalling. Optionally, the data packet of RRC reconfiguration complete sent by the remote UE 402 includes an adapter or RRC layer information indicating the message type, i.e. indicating that the message is a RRC reconfiguration complete message or the message shall be combined. Possible ways of sending the remote UE’s RRC reconfiguration complete to the relay UE or eNB are described in more detail below under Technical Consideration 1.

Step 6b. Relay UE send RRC reconfiguration complete message to the target eNB 408. Various embodiments of this step are as follows:

If the relay UE 404 has received the RRC reconfiguration complete information from the remote UE 402, the relay UE 404 could relay the received RRC reconfiguration complete information to the target eNB 408. Optionally, the relay UE 404 could parse the received RRC reconfiguration complete information from the remote UE 402. Optionally, the relay UE 404 could combine one or more remote UE’s RRC reconfiguration complete information and relay the combined information (the combined RRC reconfiguration complete information of the remote UEs) in one RRC message and send it to the target eNB 408. Optionally, the relay UE 404 determine which remote UE (s) have completed the RRC reconfiguration before sending the RRC reconfiguration complete to the target eNB 408. The relay UE 404 may send the RRC reconfiguration complete to the target eNB 408 via RRC reconfiguration complete RRC message or new defined RRC message, e.g. combined RRC reconfiguration complete message or group RRC reconfiguration complete message. Optionally, the data packet of RRC reconfiguration complete sent by the relay UE includes an adapter or RRC layer information indicating that it is a combined message. In an embodiment, the RRC reconfiguration complete message sent by the relay UE 404 includes one or more of the following: RRC reconfiguration complete information for the relay UE, RRC reconfiguration complete information for the remote UE, corresponding relay UE identity, corresponding remote UE identity, a list of remote UE identities of the remote UEs which completed the RRC reconfiguration. Or the relay UE could relay remote UE’s RRC reconfiguration complete information individually to the eNB. Possible ways of sending remote UE’s RRC reconfiguration complete information to the eNB are described below in more detail below under Technical Consideration 1.

Steps 7-8. The target eNB initiates path switch procedure to the MME for the relay UE and remote UE. Various embodiments of this step are as follows:

The target eNB 408 could initiate path switch procedure individually for the relay UE 404 and remote UE 402 (each other remote UE not shown) , i.e., send individual S1 path switch request messages to the MME 410. Alternatively, the target eNB could initiate group path switch procedure to the MME, if the MME of remote UE is the same as relay UE’s MME. More specifically, at least one of the the following information is contained in the group path switch request message: path switch request information for the relay UE/remote UE, corresponding relay UE/remote UE identity. The relay UE/remote UE identity could be MME S1AP ID, or ProSe layer ID or unique identity of remote UE in the scope of relay UE. The group path switch request message could be the S1 path switch request message or a newly defined S1 message.

Step 9. The target eNB 408 sends a UE context release message to the source eNB 406.

Similar to what occurred in step 3, the target eNB 408 could send a UE context release message individually for the relay UE 404 and the remote UE 402 (and for other remote UEs, if applicable) . Alternatively, the target eNB 408 could combine the UE context release messages for the relay UE and remote UE into one X2 message, e.g., UE context release message or newly defined X2 message.

At least one of the the following information is contained in the combined UE context release message, in an embodiment: UE context release information for the relay UE/remote UE, corresponding relay UE/remote UE identity, and a list of remote UE identities. The relay UE/remote UE identity could be eNB X2AP ID, or ProSe layer ID or unique identity of remote UE in the scope of relay UE.

According to an embodiment, if an X2 handover procedure cannot be used, the source eNB initiates an S1 handover procedure for the remote UE and the relay UE, which is illustrated in FIG. 5. The components of FIG. 5 include a remote UE 502, a relay UE 504, a source eNodeB 506, a target eNodeB 508, and an MME 510.

In the S1 handover procedure, three handover related messages may need to be delivered between the remote UE/relay UE and the eNB, including the measurement report, handover command, and RRC reconfiguration complete, which is the same as X2 handover procedure. Processing and transferring RRC messages/S1 messages are the same as the RRC messages/S1 messages in X2 handover procedure too.

Step 1a. As an optional step, the remote UE 502 sends a measurement report containing information ( “measurement report information” ) to the connected relay UE 504 or the source eNB 506. The measurement report information sent from the remote UE 502 includes at least one of the following: the Uu link measurement result (e.g., reference signal received power ( “RSRP” ) measurement of serving cell and/or neighbour cell) and the PC5 link measurement result (e.g., RSRP measurement) measured by the remote UE 502. Optionally, the remote UE 502 could send measurement report information to the connected relay UE 504 via PC5 control plane signalling. Optionally, the data packet containing the measurement report includes adapter or RRC layer information indicating the message type, i.e., indicating that the message is a measurement report message or that the message is to be combined. Possible ways of sending the remote UE’s measurement report to the relay UE or eNB are described in more detail below under Technical Consideration 1. Optionally, the remote UE 502 determines whether to send a measurement report based on the following:

1) If bidirectional UE to network relay (i.e., both uplink ( “UL” ) and downlink ( “DL” ) transmission between the UE 502 and the network (e.g., one of the eNBs) is relayed by the relay UE 504) is used and eNB scheduled mode (i.e., mode 3) is not used in PC5, the remote UE’s Uu link measurement results do not need to be sent to the relay UE 504 or to the eNB.

2) If unidirectional UE to network relay (e.g., DL paging or system information or data is received directly from the eNB by the remote UE 502) or eNB scheduled mode (i.e., mode 3) is used in PC5, the remote UE’s Uu link measurement results need to be sent to the relay UE 404 or the eNB.

In addition, when the remote UE 502 is connected with the relay UE 504, the remote UE 502 determines whether to start the Uu link measurement and/or reporting based on the PC5 link quality (i.e., PC5 RSRP measurement result) between the remote UE 502 and the connected relay UE 504. For example, if the PC5 link quality is below a threshold, the remote UE 502 could start to measure the Uu link quality of serving cell and/or neighbour cells. The PC5 link quality threshold could be configured by the eNB (e.g., the serving eNB) . Alternatively, the remote UE 502 determines whether to start the Uu link measurement and/or reporting based on the measurement configuration information received from the eNB or the relay UE 504.

Optionally, the relay UE 504 could obtain the relay type (i.e., bidirectional or unidirectional) of the remote UE 502 by the information received from the remote UE 502. The eNB (e.g., the source eNB 506) could obtain the relay type (i.e., bidirectional or unidirectional) of the remote UE 502 by the information received from the remote UE 502 or relay UE 504.

Step 1b. The relay UE 504 sends a measurement report to the source eNB 406. At least one of the following is contained in the measurement report sent from the relay UE. In one embodiment, the items noted as “mandatory” will be in the report, while the ones noted as “optional” may not be:

1) the Uu link measurement result measured by the relay UE 504, mandatory；

2) the PC5 link measurement result measured by the relay UE 504, optional；

3) the Uu link measurement result measured by the remote UE 502 which is received from the remote UE 502, optional；

4) the PC5 link measurement result measured by the remote UE 502 which is received from the remote UE 502, optional；

5) a list of identity of the remote UE 502 which performs group handover with the relay UE 504, optional.

More specifically, if the relay UE 504 has received the measurement report information from the remote UE 502 in step 1a, the relay UE 504 could relay the received measurement report information to the eNB. Optionally, the relay UE 504 could parse the received measurement report information from the remote UE 502. Optionally, the relay UE 504 could combine one or more remote UE 502’s measurement report information and relay UE’s measurement report information into one RRC message and send it to the eNB. The relay UE 504 may send the measurement report to the source eNB 406 via measurement report RRC message or new defined RRC message, e.g. combined measurement report message or group measurement report message. Optionally, the data packet of measurement report sent by the relay UE includes an adapter or RRC layer information indicating that it is a combined message. Or the relay UE 504 could relay measurement report information of remote UE (s) individually to the eNB. Possible ways of sending the remote UE’s measurement report to the eNB are described in more detail below under Technical Consideration 1.

Optionally, the relay UE 504 may determine which remote UE (s) shall perform group handover with the relay UE 504 before sending the measurement report to the source eNB. Possible ways of doing this are described below in more detail below under Technical Consideration 2.

Step 2-5. The source eNB initiates handover preparation procedure for the relay UE 504 and remote UE (s) .

Optionally, the source eNB determines whether group handover could be performed for the relay UE and remote UE (s) . Optionally, if group handover could be performed for the relay UE and remote UE (s) , the source eNB determines which remote UE (s) shall perform group handover along with the relay UE 504. Possible ways of doing this are described below in more detail below under Technical Consideration 2. The S1 signalling during the S1 handover preparation procedure could be sent individually for the relay UE and the remote UE. Alternatively, combined S1 signalling during the S1 handover preparation procedure could be send for the relay UE and the remote UE if group handover is use.

Step 6. The source eNB 506 transmits a handover command message to the relay UE 504 and/or remote UE (s) . Various embodiments of this step are as follows:

The source eNB 506 could send the handover command message for the remote UE 502 directly to the remote UE 502, or the source eNB 506 could send the handover command message for the remote UE 502 via the relay UE 504.

The source eNB 506 could combine one or more remote UE’s handover command and relay UE’s handover command into one RRC message and send it to the relay UE 504. At least one of the following information is contained in the combined handover command, according to an embodiment: handover command information for the relay UE/remote UE, corresponding relay UE/remote UE identity, a list of remote UE identities. Optionally, the data packet of handover command sent by the source eNB 506 includes an adapter or RRC layer information indicating that it is a combined message. The source eNB 506 may send the handover command to the relay UE 504 via handover command RRC message or new defined RRC message, e.g. combined handover command message or group handover command message. Then, the relay UE 504 sends the remote UE’s handover command to the corresponding remote UE. Or the relay UE 504 could relay the remote UE’s handover command individually to the corresponding remote UE (remote UE 502 and other remote UEs not shown) . Possible ways of sending a remote UE’s handover command to the remote UE from the source eNB 506 are described below in more detail below under Technical Consideration 1.

After the relay UE receives relay UE and/or remote UE (s) ’s handover command, the relay UE 504 could determine which remote UE (s) is accepted by the target eNB 408. For the remote UE (s) not accepted by the target eNB 508, the relay UE 504 sends PC5 link release to the corresponding remote UE. Then, the corresponding remote UE may communicate directly with the eNB or reselect another relay UE.

Step 7. Remote UE and/or relay UE perform synchronisation and random access with the target cell (the cell controlled by the target eNB 408) .

Step 8a. As an optional step, the remote UE 502 sends a RRC reconfiguration complete containing information ( “RRC reconfiguration complete information” ) to the connected relay UE 504 or the eNB 506. The remote UE 502 could send the RRC reconfiguration complete message directly to the target eNB 408, or the remote UE 502 could send the RRC reconfiguration complete to the target eNB 408 via the relay UE 504. Optionally, the remote UE 502 could send RRC reconfiguration complete information to the connected relay UE 504 via PC5 control plane signalling. Optionally, the data packet of RRC reconfiguration complete sent by the remote UE 502 includes an adapter or RRC layer information indicating the message type, i.e. indicating that the message is a RRC reconfiguration complete message or the message shall be combined. Possible ways of sending the remote UE’s RRC reconfiguration complete to the relay UE or eNB are described in more detail below under Technical Consideration 1.

Step 8b. Relay UE send RRC reconfiguration complete message to the target eNB 408. Various embodiments of this step are as follows:

If the relay UE 504 has received the RRC reconfiguration complete information from the remote UE 502, the relay UE 504 could relay the received RRC reconfiguration complete information to the target eNB 508. Optionally, the relay UE 504 could parse the received RRC reconfiguration complete information from the remote UE 502. Optionally, the relay UE 504 could combine one or more remote UE’s RRC reconfiguration complete information and relay the combined information (the combined RRC reconfiguration complete information of the remote UEs) in one RRC message and send it to the target eNB 508. Optionally, the relay UE 504 determine which remote UE (s) have completed the RRC reconfiguration before sending the RRC reconfiguration complete to the target eNB 508. The relay UE 504 may send the RRC reconfiguration complete to the target eNB 508 via RRC reconfiguration complete RRC message or new defined RRC message, e.g. combined RRC reconfiguration complete message or group RRC reconfiguration complete message. Optionally, the data packet of RRC reconfiguration complete sent by the relay UE includes an adapter or RRC layer information indicating that it is a combined message. In an embodiment, the RRC reconfiguration complete message sent by the relay UE 504 includes one or more of the following: RRC reconfiguration complete information for the relay UE 504, RRC reconfiguration complete information for the remote UE 502, corresponding relay UE identity, corresponding remote UE identity, a list of remote UE identities of the remote UEs which completed the RRC reconfiguration. Or the relay UE 504 could relay the remote UE’s RRC reconfiguration complete information individually to the eNB. Possible ways of sending remote UE’s RRC reconfiguration complete information to the eNB are described below in more detail below under Technical Consideration 1.

Step 9. The target eNB 508 sends a handover notify to the MME 510 to inform it that remote UE 502 and/or relay UE 504 has completed the handover procedure. The S1 signalling handover notify could be sent individually for the relay UE 504 and the remote UE 502. Alternatively, combined S1 signalling could be sent for the relay UE 504 and the remote UE 502 if group handover is used.

Step 10-11. The MME 510 initiates a UE context release procedure with the source eNB 506. The S1 signalling during the UE context release procedure could be sent individually for the relay UE 504 and the remote UE 502. Alternatively, combined S1 signalling could be sent for the relay UE and the remote UE if group handover is use.

Technical Consideration 1: Ways to deliver the remote UE’s handover related message between the remote UE and the source/target eNB via the relay UE, according to various embodiments.

In Options 1 -3) , described below, the handover related messages of one or more remote UEs and the relay UE’s handover related message could be combined in one RRC message by the eNB or relay UE and transferred between the relay UE and the eNB.

Option 1) Using hop by hop RRC. The radio protocol stack between the remote UE and the eNB in this embodiment is illustrated in FIG. 6, which depicts a remote UE 602, a relay UE 604, and an eNB 606. Note that there may be an adapter layer between the packet data convergence protocol ( “PDCP” ) layer and the radio link control ( “RLC” ) layer in the remote UE and relay UE. The adapter layer in the remote UE/relay UE/eNB is optional.

According to an embodiment, for the downlink (i.e., handover command message in the handover procedure) , the RRC layer in the eNB 606 generates a RRC message for the relay UE 604, which contains at least one of the following: handover command for remote UE, handover command for relay UE, corresponding remote UE identity, relay UE identity, a list of remote UE identities. Optionally, after PDCP process, the RRC message is delivered from PDCP layer to the adapter layer. The adapter layer adds an adapter layer header for the data packet. The adapter layer header contains at least one of the following: relay UE indication, relay UE identity, radio bearer identity of the relay UE. And then, the handover command message is transmitted to the relay UE.

After the relay UE 604 receives the combined handover command message from the eNB 606, the RRC layer in the relay UE parse the RRC message and obtains relay UE/remote UE’s handover command and identity the corresponding relay UE/remote UE. Then, the relay UE 604 deliver the remote UE’s handover command to the corresponding remote UE’s PC5 RRC entity. The remote UE’s PC5 RRC entity in the relay UE generates PC5 control plane signalling containing the remote UE’s handover command based on the remote UE’s handover command received from the eNB and sends it to the remote UE 602.

For the uplink (i.e., measurement report/RRC reconfiguration complete message in the handover procedure) , the remote UE generates and sends PC5 control plane signalling containing measurement report/RRC reconfiguration complete information to the relay UE via PC5. After receiving PC5 control plane signalling, the relay UE parses the PC5 signalling. If the PC5 signalling is related to measurement report/RRC reconfiguration complete, the relay UE’s RRC layer in the Uu interface generates a new RRC message, which contains at least one of the following: measurement report/RRC reconfiguration complete information for remote UE/relay UE, corresponding remote UE/relay UE identity/identities, a list of remote UE identities. Then, the relay UE 604 sends the combined RRC message to the eNB.

Option 2) Using end to end RRC. The radio protocol stack between the remote UE and the eNB according to an embodiment is illustrated in FIG. 7, which depicts a remote UE 702, a relay UE 704, and an eNB 706. Note that PDCP layer may exist above RLC layer. The adapter layer in the remote UE/relay UE/eNB is optional.

For the downlink (i.e., handover command message in the handover procedure) , the adapter layer or the RRC layer below the adapter layer in the eNB 706 combine the handover commands of one or more remote UEs and that of the relay UE, corresponding remote UE/relay UE identities, and/or remote UE/relay UE’s bearer identities, and/or message type information. The message type information indicates it is a combined message. In this way, the eNB 706 sends the combined messages to the relay UE 704 via one RRC message. After the relay UE 704 receives the combined message, the adapter layer or the RRC layer in the relay UE 704 obtains the relay UE/remote UE’s handover command message and sends remote UE’s handover command message to the corresponding remote UE.

For the uplink (i.e., measurement report/RRC reconfiguration complete message in the handover procedure) , the remote UE 702 sends measurement report/RRC reconfiguration complete message to the relay UE 704. Optionally, the remote UE 702 indicates the message type (i.e., whether this message needs to be combined, or measurement report, or RRC reconfiguration complete) to the relay UE 704 in the adapter layer. After the relay UE 704 receives one or more remote UE’s measurement report/RRC reconfiguration complete message, the adapter layer or the RRC layer in the relay UE 704 combines the handover commands of one or more remote UEs and that of the relay UEs, corresponding remote UE/relay UE identies, and/or remote UE/relay UE’s bearer identities, and/or message type information. In this way, the relay UE 704 sends the combined relay UE/remote UE’s messages to the eNB 706 via one RRC message.

Option 3) Using end to end RRC. In this embodiment, the radio protocol stack between the remote UE and the eNB is illustrated in FIG. 8, which depicts a remote UE 802, a relay UE 804, and an eNB 806.

Compared with Option 2, the functionality of the adapter layer in the remote UE and relay UE in FIG. 7 is replaced by RRC layer in FIG. 8. In the Uu interface between the relay UE and eNB, the adapter layer does not exist, and the functionality of adapter layer is implemented in the RRC layer instead.

Option 4) Using end to end RRC. The radio protocol stack between the remote UE and the CN in this embodiment is illustrated in FIG. 9, which depicts a remote UE 902, a relay UE 904, an eNB 906, and a core network ( “CN” ) 908. In this option, the RRC messages of the one or more remote UEs and that of the relay UE are not combined in one RRC message and transferred between relay UE and eNB. Instead, the remote UEs’ RRC messages are relayed individually between the remote UE and the eNB.

Technical Consideration 2: How to determine whether remote UE could perform group handover along with the relay UE, according to various embodiments？

a) Using group handover related subscription information as a criterion

In an embodiment, group handover related subscription information contains at least one of the following: the related relay UE identity, the related remote UE identity/identities, group handover authorization indication, and an authorized PLMN list for group handover.

In this embodiment, the group handover related subscription information is stored in the HSS or UE. The HSS could send this information to the MME. The eNB could obtain the group handover related subscription information from the MME. The relay UE could obtain the group handover related subscription information from the eNB or remote UE.

b) Using group handover capability as a criterion

In this embodiment, the eNB could obtain the relay UE/remote UE’s group handover capability from the relay UE/remote UE or from the relay UE/remote UE’s MME. The relay UE could obtain the connected remote UE’s group handover capability from the remote UE or the eNB.

c) Using group handover intention as a criterion

In this embodiment, the remote UE could send group handover intention to the relay UE, e.g., during PC5 link setup procedure, or based on the request of the relay UE. Alternatively, a remote UE could send group handover intention to the eNB. Alternatively, the relay UE could obtain the group handover intention of the remote UE (s) from the eNB.

d) Using radio link quality as a criterion

In this embodiment, for example, if bidirectional UE to network relay is used and UE autonomous selection mode (i.e., mode 4) is used in PC5, the PC5 link quality measured by the remote UE or relay UE and the Uu link quality measured by the relay UE are used. If unidirectional UE to network relay or eNB scheduled mode (i.e., mode 3) is used in PC5, the Uu link quality measured by remote UE, the PC5 link quality measured by the remote UE or relay UE, and the Uu link quality measured by the relay UE are used.

Unless otherwise noted herein, the group handover decision could be made by one or more entities, including 1) a remote UE； 2) the relay UE； and 3) the source eNB. Optionally, after the eNB determines whether the remote UE could perform group handover or which remote UE(s) could perform group handover, the eNB could provide the results of this determination to the relay UE. Unless otherwise noted herein, the group handover decision could be made according to one or more of the criterion specified in a) -d) .

It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from their spirit and scope. For example, the steps of the methods described here could be reordered in ways that will be apparent to those of skill in the art.

Claims

A method for performing a group handover in a wireless network, the method comprising:

receiving a combined handover command from a source wireless cell；

transmitting a handover command to a first remote user equipment, , wherein the handover command is based at least in part on information contained in the combined handover command.
The method of claim 1, further comprising:

accessing a target wireless cell；

receiving a radio resource control reconfiguration complete from the first remote user equipment indicating that the first remote user equipment has completed a reconfiguration for the handover；

generating a combined radio resource control reconfiguration complete message indicating that the first remote user equipment and the relay user equipment have completed a reconfiguration for the handover； and

transmitting the combined radio resource control reconfiguration complete to the target wireless cell .
The method of claim 1, wherein the radio resource control reconfiguration complete message is transmitted in a data packet that includes adapter or RRC layer information indicating whether the reconfiguration complete message is to be combined.
The method of claim 1, further comprising:

receiving a measurement report from the first remote user equipment.
The method of claim 4, wherein the measurement report is transmitted in a data packet that includes adapter or RRC layer information indicating whether the measurement report is to be combined.
The method of claim 4, wherein the measurement report includes at least one of: Uu link measurement result and a PC5 link measurement result.
The method of claim 4, further comprising

generating a combined measurement report that includes information from the first remote user equipment’s measurement report and a measurement report for the relay user equipment； and

transmitting the combined measurement report to the source wireless cell.
The method of claim 4, wherein receiving the measurement report comprises receiving the measurement report via PC5 control plane signaling.
The method of claim 1, wherein the handover command message includes at least one of: a handover command for the first remote user equipment or the relay user equipment, the identity of the first remote user equipment or the relay remote user equipment, and a list that includes the identities of the first remote user equipment and the relay user equipment.
The method of claim 1, further comprising parsing the handover command message to obtain a first handover command and an identity the first remote user equipment and a second handover command and an identity of the relay user equipment.
The method of claim 10, further comprising delivering the first handover command to the first remote user equipment and the second handover command to the relay user equipment.
The method of claim 1, wherein the combined radio resource control reconfiguration complete includes at least one of the following: radio resource control reconfiguration complete information of a relay user equipment, the first remote user equipment, and a list of the identities of the relay user equipment, and the first remote user equipment.
In a wireless telecommunications network, a method for performing a group handover, the method comprising:

on a node of source cell of the wireless network, transmitting a combined handover command to a first user equipment, wherein the combined handover command includes the handover command information for both the first user equipment and a second user equipment；

on the node of the destination cell, receiving, from the first user equipment, a combined radio resource control reconfiguration complete message that includes reconfiguration complete information for both the first user equipment and the second user equipment.
The method of claim 13, further comprising:

on a node of source cell of the wireless network, receiving a combined measurement report message from the first user equipment,

wherein the combined measurement report includes measurement result information from one or both the first user equipment and the second user equipment.
The method of claim 13, wherein a data packet containing the combined handover command or the combined radio resource control reconfiguration complete message or the combined measurement report message includes adapter or RRC layer information indicating that it is a combined message.
The method of claim 16, wherein the combined measurement report includes at least one of: Uu measurement result information and the PC5 measurement result information.
A method for carrying out a group handover in a wireless network, the method comprising:

receiving group handover information regarding a first user equipment, a second user equipment, and a third user equipment, wherein the first user equipment acts as a relay user equipment for the second user equipment and the third user equipment；

determining, based on the received group handover information, whether or not to conduct a group handover of the first user equipment, the second user equipment, and the third user equipment from a source cell to a target cell；

based on the determination, carrying out the group handover of the first user equipment, the second user equipment, and the third user equipment.
The method of claim 17, wherein the group handover information comprises group handover subscription information that includes at least one of the following: the identity of the first user equipment, the identities of both of the second and third user equipment, a group handover authorization indication for the first user equipment, a group handover authorization indication for the second user equipment and an authorized public land mobile network list.
The method of claim 17, wherein the group handover information comprises a group handover capability of the first user equipment, the second user equipment, and the third user equipment.
The method of claim 17, wherein the group handover information comprises at least one of the following: a group handover intention of the first user equipment, a group handover intention of the second user equipment, and a group handover intention of the third user equipment.
The method of claim 17, wherein the group handover information comprises measurement result as measured by one or more of the first user equipment, the second user equipment, and third user equipment.
The method of claim 17, wherein receiving the group handover information comprises receiving the group handover information from the first user equipment or the second user equipment.
The method of claim 17, wherein receiving the group handover information comprises receiving the group handover information from an eNB or a core network that supports the wireless network.
A method for performing a group handover in a wireless network, the method comprising:

forming a message on a remote user equipment that is in communication with a relay user equipment； and

transmitting the message to the relay user equipment in a data packet that includes information indicating whether the message is to be combined.
The method of claim 24, wherein the message is a radio resource control reconfiguration complete message.
The method of claim 24, wherein the message is a measurement report.
The method of claim 24, wherein the information is adapter layer information.
The method of claim 24, wherein the information radio resource control layer information.
The method of claim 24, wherein the message is sent via PC5 control signaling.
A computing device configured to carry out any one of claims 1 through 28.
A non-transitory computer-readable medium having stored thereon computer-executable instructions for carrying out any one of claims 1 through 28.