CN106162694B

CN106162694B - Method and apparatus for supporting coverage extension and service continuity

Info

Publication number: CN106162694B
Application number: CN201510167721.6A
Authority: CN
Inventors: 邓云; 林晓翔; 刘勇; 李栋
Original assignee: Alcatel Lucent SAS
Current assignee: Alcatel Lucent SAS
Priority date: 2015-04-09
Filing date: 2015-04-09
Publication date: 2020-06-19
Anticipated expiration: 2035-04-09
Also published as: CN106162694A

Abstract

The invention discloses a method and a device for supporting coverage extension and service continuity in a relay station, wherein the relay station is used for receiving signaling and data from a remote user and transmitting the signaling and data from the remote user to a base station, and the method comprises the following steps: the relay station has the S1-AP function and receives a registration request from the remote user, and sends S1-AP signaling of the remote user encapsulated in RRC signaling to a base station or sends S1-AP signaling to the base station through a data radio bearer; or the relay station receives the registration request from the remote user and sends NAS signaling of the remote user registration request encapsulated in RRC signaling to the base station; or receive RRC signaling from a remote user through the PC5 interface and transmit the RRC signaling to the base station over the first data radio bearer. Based on the scheme, not only the expansion of the coverage range is supported, but also the continuity of the service is supported.

Description

Method and apparatus for supporting coverage extension and service continuity

Technical Field

The present invention relates to a wireless communication network, and more particularly, to a method and apparatus for supporting coverage extension and service continuity in a wireless communication network.

Background

Proximity services (ProSe) direct communication was introduced in LTE-a of REL 12. User Equipment (UE) supporting ProSe direct communication can operate in two resource configuration modes: 1) scheduled resource allocation (i.e., mode 1); and 2) UE-autonomous resource selection (i.e., mode 2). If the UE which is not in the network coverage area needs to carry out the ProSe direct communication, only the autonomous resource selection of the UE can be used; if UEs within network coverage are to perform ProSe direct communication, scheduled resource allocation or UE autonomous resource selection may be used.

In REL13, a relay station (UE-NW RN: UE to Network relay node) between the user equipment and the Network is introduced to support coverage extension. Fig. 1 shows a schematic diagram of a UE-NW RN between a user equipment and a network.

An enhanced UE may act as a UE-NW RN between the user equipment and the network with a Uu interface to the serving eNB and a PC5 interface to remote users (outside the network coverage). The UE-NW RN may communicate unicast data (uplink and downlink) or multicast data between the remote user and the network.

Fig. 2 shows a schematic diagram of the user plane architecture of a UE-NW RN, according to TS 23.303. But for the UE-NW RN, the architecture of the control plane has not yet determined, e.g., whether the eNB is aware of the remote UE served by the UE-NW RN.

A simple solution is that the remote users served by this UE-NW RN are transparent to the base station, i.e. the base station is not aware of the presence of the remote users. This solution does not require changes to the existing control plane architecture. Specifically, the UE-NW RN learns the requirements of the remote user through the PC5 interface and then initiates a corresponding service request or connection request to the base station for the remote user. The UE-NW RN exchanges uplink and downlink data for remote users with the base station. During this process, the base station is not aware of the presence of the remote user.

As shown in fig. 3, this solution does not support service continuity when the remote user moves from the coverage of the UE-NW RN to the coverage of the cell.

If the base station does not know the existence of the remote user, when the remote user enters the coverage area of the cell, the remote user initiates a random access process to access the network, the base station reestablishes a data radio bearer for the service of the remote user, and the ongoing service of the remote user is interrupted. This is unacceptable to the user experience.

Disclosure of Invention

In light of the foregoing understanding of the background and the problems with the prior art, it would be advantageous to provide a method and apparatus for supporting coverage extension and service continuity.

According to a first aspect of the present invention, there is provided a method for supporting coverage extension and service continuity in a relay station for receiving signaling and data from a remote user and transmitting the signaling and data from the remote user to a base station, the method comprising any one of: A. the relay station has S1-AP function and receives a registration request from the remote user, the relay station transmits S1-AP signaling of the remote user encapsulated in RRC signaling to the base station; the relay station has S1-AP function and receives a registration request from the remote user, and the relay station sends S1-AP signaling to the base station through a data radio bearer; the relay station receives a registration request from the remote user, and the relay station sends NAS signaling of the remote user registration request encapsulated in RRC signaling to the base station; the relay station receives RRC signaling from the remote user through a PC5 interface and transmits the RRC signaling to the base station through a first data radio bearer.

According to an embodiment of the present invention, said a further comprises: the remote user 'S S1-AP signaling encapsulated in RRC signaling has the remote user' S identity;

according to an embodiment of the present invention, the S1-AP signaling of the remote user encapsulated in RRC signaling is an initial user message, and the initial user message includes NAS signaling of a registration request.

According to an embodiment of the present invention, the C further comprises: the remote user's NAS signaling encapsulated in RRC signaling has the remote user's identity; the remote user's NAS signaling encapsulated in RRC signaling comprises a registration request.

According to an embodiment of the present invention, the B further includes: sending a data radio bearer request to the base station to establish a data radio bearer between the base station and the relay station.

According to an embodiment of the present invention, the B further includes: transmitting an initial user message to the base station over the established data radio bearer.

According to an embodiment of the invention, said D further comprises: receiving an RRC connection request from the remote user;

establishing a first data radio bearer with the base station to transmit the RRC connection request to the base station; and establishing a second data radio bearer with the base station to transmit the service data of the remote user.

According to a second aspect of the present invention, there is provided an apparatus for supporting coverage extension and service continuity in a relay station for receiving signaling and data from a remote user and transmitting the signaling and data from the remote user to a base station, the apparatus comprising any one of: a first S1-AP function unit for making the relay station S1-AP function and receiving a registration request from the remote user, the relay station transmitting S1-AP signaling of the remote user encapsulated in RRC signaling to the base station; or a second S1-AP function unit for making the relay station S1-AP function and receiving a registration request from the remote user, the relay station transmitting S1-AP signaling to the base station through a data radio bearer; or an RRC encapsulating unit for causing the relay station to receive a registration request from the remote user, the relay station transmitting NAS signaling of the remote user encapsulated in RRC signaling to the base station; or an RRC simplifying unit for causing the relay station to receive RRC signaling from the remote user through a PC5 interface and to transmit the RRC signaling to the base station through a data radio bearer.

According to an embodiment of the present invention, the first S1-AP function further comprises the remote user 'S1-AP signaling encapsulated in RRC signaling having the remote user' S identity; the remote user' S1-AP signaling encapsulated in RRC signaling is an initial user message that contains NAS signaling for registration requests.

According to an embodiment of the present invention, the RRC encapsulating unit further includes: the remote user's NAS signaling encapsulated in RRC signaling has the remote user's identity; the remote user's NAS signaling encapsulated in RRC signaling comprises a registration request.

According to an embodiment of the present invention, the second S1-AP functional unit further includes: a bearer establishing unit for sending a data radio bearer request to the base station to establish a data radio bearer between the base station and the relay station; and an initial user message transmission unit for transmitting an initial user message to the base station on the established data radio bearer.

According to an embodiment of the present invention, the RRC simplifying unit further includes: an RRC receiving unit for receiving an RRC connection request from the remote user; a first bearer establishing unit, configured to establish a first data radio bearer with the base station to transmit the RRC connection request to the base station; and the second bearing establishing unit is used for establishing a second data radio bearing with the base station so as to transmit the service data of the remote user.

According to a third aspect of the present invention, there is provided a method for remote user reselection of a relay station supporting coverage extension and service continuity, wherein the remote user has access to a source relay station, the method comprising: the remote user reselects a target relay station when a first condition is met, wherein the first condition is at least one of the following: the channel quality between the source relay station and the base station is lower than a first preset channel quality threshold; the capability of the source relay station is below a capability threshold; the source relay station informs the remote user to reselect a target relay station; the channel quality between the source relay station and the remote user is lower than a second preset channel quality threshold; the channel quality between the remote user and the target relay station is higher than the channel quality between the remote user and the source relay station by a predetermined offset.

According to an embodiment of the present invention, the method further comprises the remote user monitoring a discovery channel or a synchronization channel transmitted by a potential target relay station; the remote user determining one of the potential target relay stations as a target relay station if the potential target relay stations satisfy a second condition, the second condition being any one of: a channel quality between a potential target relay station and the remote user is not below a second channel quality threshold; the channel quality between a potential target relay station and the remote user is higher than the channel quality between the remote user and a source relay station by a predetermined offset.

According to an embodiment of the present invention, the method further comprises the remote user monitoring a discovery channel or a synchronization channel transmitted by a potential target relay station; if the potential target relay station does not satisfy the second condition, the remote user sends a message to continue searching for a potential target relay station; and the remote user determining a target relay station based on feedback from potential target relay stations in response to the message sent by the remote user.

According to a fourth aspect of the present invention, there is provided a method for a user equipment handover supporting coverage extension and service continuity, the method comprising: when a third condition is met, the user equipment is switched from the base station to a target relay station, wherein the third condition is at least any one of the following conditions: the channel quality between the user equipment and the base station is below a third channel quality threshold; the user equipment receives a message from a base station for switching to a target relay station; wherein the user equipment moves from within the coverage of the base station to outside the coverage of the base station.

According to an embodiment of the present invention, the method further comprises the step of searching and decoding a discovery channel and/or a synchronization channel transmitted by a potential target relay station by the user equipment.

According to an embodiment of the present invention, the method further comprises the user equipment monitoring a discovery channel and/or a synchronization channel of a potential target relay station according to a timer; if the channel quality between the potential target relay station and the user equipment is not lower than a third channel quality threshold, the user equipment determines one of the potential target relay stations as the target relay station.

According to an embodiment of the present invention, the method further comprises the user equipment monitoring a discovery channel of a potential target relay station according to a timer; if the channel quality between the potential target relay station and the user equipment is lower than a third channel quality threshold, the user equipment sends a message to search for the potential target relay station; and the user equipment determines the target relay station according to the feedback from the potential target relay station responding to the message sent by the user equipment.

According to an embodiment of the present invention, further comprising when the timer expires, the user equipment continuing to re-search and decode other discovery channels and/or synchronization channels; or the far user equipment stops searching for the target relay station.

According to a fifth aspect of the present invention, there is provided an apparatus for remote user reselection of a relay station supporting coverage extension and service continuity, wherein the remote user has access to a source relay station, the apparatus comprising: a selecting unit, configured to reselect a target relay station by the remote user when a first condition is satisfied, where the first condition is at least any one of: the channel quality between the source relay station and the base station is lower than a first preset channel quality threshold; the capability of the source relay station is below a capability threshold; the source relay station informs the remote user to reselect a target relay station; the channel quality between the source relay station and the remote user is lower than a second preset channel quality threshold; the channel quality between the remote user and the target relay station is higher than the channel quality between the remote user and the source relay station by a predetermined offset.

According to an embodiment of the present invention, the remote user further comprises a monitoring unit, configured to monitor a discovery channel or a synchronization channel transmitted by a potential target relay station; a first determining unit, if potential target relay stations meet a second condition, the remote user determining one of the potential target relay stations as a target relay station; a second determining unit for sending a message to the remote user to continue searching for a potential target relay station if the potential target relay station does not satisfy the second condition; and the remote user determining a target relay station based on feedback from potential target relay stations in response to the message sent by the remote user; wherein the second condition is at least any one of: a channel quality between a potential target relay station and the remote user is not below a second channel quality threshold; the channel quality between a potential target relay station and the remote user is higher than the channel quality between the remote user and a source relay station by a predetermined offset.

According to a sixth aspect of the present invention, there is provided an apparatus for supporting coverage extension and service continuity for user equipment handover, the apparatus comprising: switching means for switching the user equipment from a base station to a target relay station when a third condition is satisfied, wherein the third condition is at least one of: the channel quality between the user equipment and the base station is below a third channel quality threshold; the user equipment receives a message for switching to a target relay station from the base station; wherein the user equipment moves from within the coverage of the base station to outside the coverage of the base station.

According to an embodiment of the present invention, the base station further includes a first searching and decoding unit, configured to search and decode a discovery channel and/or a synchronization channel transmitted by a potential target relay station by the user equipment.

According to an embodiment of the present invention, the method further includes monitoring, by the ue, a discovery channel and/or a synchronization channel of a potential target relay station according to a timer; a determining unit, configured to determine, by the user equipment, one of the potential target relay stations as a target relay station if a channel quality between the potential target relay station and the user equipment is not lower than a third channel quality threshold; if the channel quality between the potential target relay station and the user equipment is lower than a third channel quality threshold, the user equipment sends a message to continuously search for the potential target relay station; the user equipment determines a target relay station according to feedback from potential target relay stations in response to the message sent by the user equipment.

According to an embodiment of the present invention, the ue further comprises a second searching and decoding unit, wherein when the timer expires, the ue continues to search and decode other discovery channels and/or synchronization channels again; or the user equipment stops searching for the target relay station.

The scheme of the control plane architecture of the UE-NW RN provided by the invention not only can support the expansion of the coverage range, but also can support the continuity of the service even if a remote user moves from the coverage range of the relay station to the coverage range of the cell.

In addition, the scheme of the invention also provides a flexible scheme for selecting and reselecting the relay station so as to ensure the continuity of the service.

Drawings

Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments thereof, which proceeds with reference to the accompanying drawings.

Figure 1 shows a schematic diagram of a UE-NW RN between a user and a network;

fig. 2 shows a schematic diagram of a user plane architecture of a UE-NW RN;

figure 3 shows a schematic diagram of a remote user moving towards a cell coverage area;

fig. 4 shows a schematic diagram of a UE-NW RN with S1-AP encapsulated in RRC signaling;

FIG. 5 shows a schematic diagram of a UE-NW RN with a base station as the S1-AP generation;

figure 6 shows a schematic diagram of a UE-NW RN with NAS signaling encapsulated in RRC signaling;

figure 7 shows a schematic diagram of a UE-NW RN with enhanced RRC functionality;

FIG. 8 shows a schematic diagram of a remote user access procedure based on the architectures shown in FIG. 4, FIG. 5 and FIG. 6;

FIG. 9 is a schematic diagram illustrating a remote user access procedure based on the architecture shown in FIG. 7;

FIG. 10 is a schematic diagram of a remote user service set-up process based on the architecture shown in FIG. 7;

FIG. 11 shows a relay station handoff scenario diagram for a remote user;

FIG. 12 shows a flow chart of remote user switching;

FIG. 13 shows another flow chart of remote user switching;

FIG. 14 shows another schematic diagram of a remote user switching scenario; and

FIG. 15 shows yet another schematic diagram of a remote user switching scenario.

Detailed Description

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof. The accompanying drawings illustrate, by way of example, specific embodiments in which the invention may be practiced. The illustrated embodiments are not intended to be exhaustive of all embodiments according to the invention. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. It should be noted that although the steps of methods of the present invention are depicted in the drawings in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results, but rather that the steps described herein can be performed in an order that varies. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step decomposed into multiple step executions.

Fig. 4 shows a schematic diagram of a UE-NW RN with S1-AP (S1Application Protocol) encapsulated in RRC signaling. S1-AP is used for signaling interaction between the base station and the mobility management entity in the existing network. The UE-NW RN410 in fig. 4 may be used to support coverage extension and service continuity and to receive signaling and data from remote users 400 and to transmit signaling and data from remote users 400 to the base station 420. The UE-NW RN410 has S1-AP functionality and receives a registration Request (Attach Request) from the remote user 400, and the UE-NW RN410 sends S1-AP signaling (or simply S1 signaling) of the remote user 400 encapsulated in RRC signaling to the base station 420. Only partial S1-AP functionality may be present in the UE-NW RN410 as shown in fig. 4. A base station in the long term evolution system needs to support a complete S1-AP function, such as supporting service establishment and paging for a certain UE, supporting overload control, etc., where the UE-NW RN410 is only an enhanced UE and does not need to have a complete S1-AP function, such as not supporting overload control.

The S1-AP signaling for remote user 400 encapsulated in RRC signaling may have the identity of remote user 400 so that base station 420 can recognize that the S1-AP signaling is from remote user 400. The remote user 400 sends information including a registration request and the like to the UE-NW RN410 by direct communication.

The S1-AP signaling of remote user 400 encapsulated in RRC signaling is an initial user message that contains nas (non Access stratum) signaling of the registration request.

Fig. 5 shows a schematic diagram of a UE-NW RN when the base station acts as S1-AP proxy. The UE-NW RN510 in fig. 5 may be used to support coverage extension and service continuity and to receive signaling and data from remote users 500 and transmit signaling and data from remote users 500 to base station 520. UE-NW RN510 has S1-AP functionality and receives a registration request from remote user 500, and UE-NW RN510 sends a data radio bearer request to base station 520 to establish a data radio bearer between base station 520 and UE-NWRN 510. UE-NW RN510 sends S1-AP signaling to base station 520 over the data radio bearer. UE-NW RN510 transmits an initial user message to base station 520 on the established data radio bearer. The UE-NW RN510 as shown in fig. 5 may have S1-AP functionality, the base station 520 may act as S1-AP proxy, i.e. if the base station 520 receives S1 signaling for the remote user 500 from the MME 530, the base station 520 sends the signaling to the UE-NW RN510 over the data radio bearer; if base station 520 receives S1 signaling from UE-NW RN510 for remote user 500, base station 520 sends the signaling to MME 530.

Fig. 6 shows a schematic diagram of a UE-NW RN with NAS signaling encapsulated in RRC signaling. The UE-NW RN610 in fig. 6 may be used to support coverage extension and service continuity and to receive signaling and data from remote users 600 and transmit signaling and data from remote users 600 to base station 620. UE-NW RN610 receives the registration request from remote user 600 and UE-NW RN610 sends NAS signaling encapsulating the registration request for remote user 600 in RRC signaling to base station 620.

The NAS signaling of remote user 600 encapsulated in RRC signaling may have the identity of the remote user so that base station 620 can recognize whether the S1-AP signaling is from remote user 600 or from UE-NW RN610 itself.

The NAS signaling of remote user 600 encapsulated in RRC signaling contains the registration request.

Fig. 7 shows a schematic diagram of a UE-NW RN with enhanced RRC functionality. The UE-NW RN710 in fig. 7 may be used to support coverage extension and service continuity and to receive signaling and data from remote users 700 and transmit signaling and data from remote users 700 to base station 720.

The UE-NW RN710 receives RRC signaling from the remote user 700 through the PC5 interface and sends the RRC signaling to the base station 720 through the first data radio bearer.

Specifically, the UE-NW RN710 receives an RRC connection request from the remote user 700. A first data radio bearer is established between the UE-NW RN710 and the base station 720 to transmit the RRC connection request to the base station 720. A second data radio bearer may be established between UE-NW RN710 and base station 720 to transport traffic data for remote user 700. In the architecture of fig. 7, the UE-NW RN710 may act as an RRC proxy for the remote user 700, i.e., may interact RRC signaling with the base station 720 for the remote user 700.

In fig. 4-6, remote users 400, 500, and 600 do not have an RRC layer (which is RRC-enabled and does not need to be provided when the remote users access the network through the UE-NW RN), remote users 400, 500, and 600 transmit NAS signaling to UE-NW RNs 410, 510, and 610, respectively, and then UE-NW RNs 410, 510, and 610 transmit NAS signaling to the network using different mechanisms.

Remote user 700 in fig. 7 has an RRC layer, i.e., a Simplified RRC (S-RRC: Simplified RRC) between remote user 700 and UE-NW RN710, for example. The UE-NW RN710 in fig. 7 may act as an RRC proxy that receives an RRC connection request from the remote user 700 and then sends RRC signaling (of the remote user 700) to the network via a Data Radio Bearer (DRB). Since the base station 720 does not need to configure all the radio parameters of the remote user 700, such as the parameters of the physical layer and the parameters of the layer 2, etc., the configuration of the parameters in the RRC signaling of the remote user 700 can be simplified, referred to as simplified RRC in the present invention, which is used for signaling with a network device, such as a base station, for interacting with the remote user 700, it should be understood by those skilled in the art that the UE-NWRN710 as a user equipment still has the conventional RRC function to interact with the network device, such as the base station, for its own RRC signaling, so that the RRC function of the UE-NW RN710 in fig. 7 is enhanced as a whole.

Fig. 8 shows a schematic diagram of a remote user access procedure based on the architectures shown in fig. 4, 5 and 6.

In step S801, the remote user 800 discovers the UE-NW RN 810. The remote user 800 learns of the UE-NW RN810 through direct discovery.

In step S802, the UE-NW RN810 completes the network registration procedure.

In step S803, the remote user 800 sends a registration request to the UE-NW RN 810.

The remote user 800 transmits NAS signaling and some other necessary parameters, such as NAS signaling of registration Request (Attach Request), and selected Public land mobile Network identity (PLMN ID) to the UE-NW RN810 through direct communication.

How the UE-NW RN810 passes the NAS signaling and non-NAS signaling of the remote user 800 to the base station 820 is a problem to be solved. NAS signaling has different types and lengths. In addition to the registration request, other NAS signaling is typically encrypted over the air as per current specifications. In addition to NAS signaling, there is some other information, such as the selected PLMN ID of remote user 800, which is necessary to register with the network selected by remote user 800. When the remote user 800 completes the registration process and the remote user wants to perform a service, the remote user needs to notify the network of a Temporary identity (TMSI) so that the base station 810 can find a correct Mobility Management Entity (MME) for the remote user 800.

In step S804, the UE-NW RN810 needs to send a registration request for the remote user 800 to the network. There may be different solutions for how the registration request is sent according to the architecture described above.

Scheme 1: this NAS signaling is carried in RRC signaling of the UE-NW RN810 (as in step S804 of fig. 8), or the UE-NW RN810 has a partial S1-AP functionality, which can generate S1-AP signaling, such as an Initial user Message (Initial UE Message) of the remote user, so that the Initial user Message of the remote user can be carried in RRC signaling. This solution corresponds to the architecture shown in fig. 4 and the architecture shown in fig. 6.

Scheme 2: the UE-NW RN810 sends an initial user message to the base station 820 (as in steps S804A to S813A of fig. 8). A new Data Radio Bearer (DRB) is established between the UE-NW RN810 and the base station 820 to forward S1 signaling. This solution corresponds to the architecture as shown in fig. 5.

Scheme 3: UE-NW RN810 acts as an RRC Proxy (RRC Proxy) for remote user 800. The remote user 800 sends an RRC message, such as an RRC connection request, RRC connection setup complete, etc., to the UE-NW RN810 through the PC5 interface (i.e., the interface for direct communication). The UE-NW RN800 sends these RRC messages to the base station 820 over a Data Radio Bearer (DRB). The RRC may be a simplified RRC since the base station 820 does not directly control the remote user nor does it need to configure parameters such as PUCCH/PUSCH/PDSCH for the remote user. A schematic flow diagram of this scheme 3 is shown in fig. 9.

In step S805, after the base station 820 receives the NAS registration request of the remote user 800, the base station needs to select an MME according to the PLMN ID selected by the remote user. The initial user message is then sent to the MME 840.

If scheme 1 is employed in step S804, the UE-NW RN810 needs to send the selected PLMN ID of the remote user to the base station 820 so that the base station 810 can select an MME for the remote user 800.

In step S806, the MME840 sends a create session request to the SGW/PGW850 serving the remote user.

In step S807, the SGW/PGW850 sends a create session response to the MME 840.

In step S808, the MME840 sends an Initial context setup request (Initial context setup request) to the base station 820.

In step S809, after the base station 820 receives the initial context setup request, it can obtain the Quality of Service (QoS) of the default bearer and the NAS PDU of the remote user. For scenario 2 (i.e., S1-MME terminates UE-NW RN), the base station 820 needs to forward the initial context setup request to UE NW RN810 (modify S1-AP UE ID in the message without the rest of the message changing). For scenario 1, the base station 820 may only need to send NAS signaling of registration acceptance of the remote user to the UE-NWRN 810.

In step S810, the UE-NW RN810 sends a registration accept message to the remote user 800.

In step S811, the remote user 800 sends a registration complete message to the UE-NW RN 810.

In step S812, the UE-NW RN810 sends a registration complete message to the base station 820.

In step S813, the base station 820 sends an initial context setup response to the MME840, which may carry a registration complete message.

In step S814/S815, the MME840 may inform the SGW/PGW850 to modify, for example, part of the parameters of the default bearer such as (identification of EPS bearer, eNodeB base station address, etc.).

For the architecture shown in fig. 5, a new DRB is established between the UE-NW RN810 and the base station 820 to forward S1 signaling, the corresponding steps are as follows:

in step S804A, the UE-NW RN810 sends a setup service request to the base station 820, the service request being for transmission of S1 interface signaling. The UE-NW RN810 may send a setup service request to the base station 820 through RRC signaling or NAS signaling. In this embodiment, it is assumed that the S-GW and P-GW serving UE-NW RN810 are located within base station 820. If the SGW/PGW is not located in the base station, corresponding modifications are needed in fig. 8.

In step S805A, the P-GW of UE-NW RN810 (and the S-GW) located within base station 820 sends a create service request to MME830, the request containing an identification of the service to be established and the corresponding quality of service parameters QoS.

In step S806A, the MME830 sends a bearer establishment request to the base station 820.

In step S807A, the base station 820 receives the bearer establishment request, configures corresponding parameters, such as corresponding DRB identifier and layer 2 and layer 1 parameters corresponding to the DRB, and the base station 820 sends RRC connection reconfiguration to the UE-NW RN810, so as to notify the UE-NW RN810 of the DRB parameters that need to be established.

In step S808A, the UE-NW RN810 applies the configuration parameters sent by the base station, and sends an RRC connection reconfiguration complete to the base station 820.

In step S809A, the base station 820 transmits a bearer establishment response to the MME 830.

In step S810A, the UE-NW RN810 sends direct signaling to the base station 820 to transport NAS signaling to the MME. Here NAS signaling refers to traffic management response.

In step S811A, the base station 820 sends a direct transfer message to the MME830 to transmit NAS signaling of a traffic management response to the MME 830.

In step S812A, the MME830 sends a create traffic response to the S-GW/P-GW within the base station 820.

In step S812A, the UE-NW RN810 sends an initial UE message to the base station 820 through the established DRB. The initial UE message contains a registration Request (Attach Request) for the remote user 800. Note that, before sending the initial UE message, the UE-NW RN810 needs to send S1 setup request to the base station 820 through the established DRB in order to establish the S1 interface.

Fig. 9 shows a schematic diagram of a remote user access procedure based on the architecture shown in fig. 7.

For the architecture shown in fig. 7, a dedicated DRB is established between the base station and the UE-NW RN to transport RRC signaling between the remote user and the base station. The UE-NW RN acts as an RRC proxy for the remote user. Some RRC signaling may be simplified because the base station does not need to configure all radio parameters for the remote user.

Steps S901 and S902 of fig. 9 are similar to steps S801 and S802 of fig. 8, and are not described again here.

In step S903, the remote user 900 sends an RRC connection request to the UE-NW RN910 through direct communication.

In step S904, the UE-NW RN910 establishes an E-RAB (referred to as DRB between RN and base station) with the network to transmit RRC signaling of the remote user 900.

In step S905, the UE-NW RN910 transmits an RRC connection request to the base station 920 via the DRB.

In step S906, the base station 920 replies RRC connection setup to the UE-NW RN910 via DRB.

In step S907, the UE-NW RN910 sends RRC connection setup to the remote user 900.

In step S908, the remote user 900 sends an RRC connection setup complete to the UE-NW RN 910.

In step S909, the UE-NW RN910 sends RRC connection setup complete to the base station 920 via the DRB.

In step S910, the base station 920 transmits an initial user message to the MME 940.

In step S911, the MME940 replies to the base station with an initial context setup request message.

In step S912, a DRB is established between the base station 920 and the UE-NW RN910 to transmit traffic of the remote user 900.

In step S913, the base station 920 transmits an RRC connection reconfiguration message to the UE-NW RN 910.

In step S914, the UE-NW RN910 sends an RRC connection reconfiguration message to the remote user 900.

In step S915, the remote user 900 sends an RRC connection reconfiguration complete message to the UE-NW RN 910.

In step S916, the UE-NW RN910 sends an RRC connection reconfiguration complete message to the base station 920 via the DRB.

In step S917, the base station 920 transmits an initial context setup response to the MME 940.

Since the UE-NW RN is still a user equipment, both relay functionality and complexity are supported based on the architecture shown in fig. 9.

Fig. 10 shows a schematic diagram of a service set-up procedure of a remote user based on the architecture shown in fig. 7.

In step S1001, the remote user equipment 1000 successfully completes the registration process, i.e., the registration process of the remote user 900 shown in fig. 9, for example.

Specifically, in step S1003, after the UE-NW RN1010 receives the RRC connection request from the remote user 1000 through the direct link (Sidelink), i.e., the PC5 interface, it forwards the RRC connection request to the base station 1020 through the DRB.

In step S1004, after the base station 1020 receives the RRC connection request via the DRB, the base station 1020 knows that the RRC connection request is from the remote user 1000. It allows access for remote user 1000 and sends RRC connection setup to UE-NWRN1010 through DRB. The RRC connection setup may not include information of physical layer parameters.

In step S1010, after the base station 1020 knows the QoS of the service that the remote user needs to establish through the initial context setup request, the base station 1020 sets up a corresponding dedicated DRB for the UE-NW RN1010, so that the UE-NW RN1010 can forward the data of the remote user 1000.

In step S1011, the base station 1020 transmits the RRC connection reconfiguration to the UE-NW RN1010 through the DRB.

In step S1011A, the base station 1020 may need to reconfigure direct communication resources for downlink transmission of the UE-NW RN1010 to the remote user 1000 according to the QoS of the traffic.

Step S1011 and step S1011A may also be performed in parallel.

Fig. 9 is a flowchart illustrating a registration procedure between the remote user 900 and the network and fig. 10 is a flowchart illustrating steps of fig. 10 similar to those in fig. 9, so that further description is omitted here.

With reference to fig. 4, an exemplary apparatus for supporting coverage extension and service continuity in a UE-NW RN410 of the present invention includes a first S1-AP function unit for making the UE-NW RN 410S 1-AP capable and receiving a registration request from the remote user, the UE-NW RN410 transmitting S1-AP signaling of the remote user encapsulated in RRC signaling to a base station 400. The first S1-AP functional unit may further include: the S1-AP signaling of remote user 400 encapsulated in RRC signaling has the identity of remote user 400; the S1-AP signaling of remote user 400 encapsulated in RRC signaling is an initial user message that contains NAS signaling for the registration request.

In connection with fig. 5, the present invention provides yet another exemplary apparatus for supporting coverage extension and service continuity in a UE-NW RN510, the apparatus comprising a second S1-AP functional unit for enabling the UE-NW RN510 to have S1-AP functionality and to receive a registration request from a remote user 500, the UE-NW RN510 signaling S1-AP to a base station 520 over a data radio bearer. The second S1-AP functional unit further includes: a bearer establishing unit for sending a data radio bearer request to the base station 520 to establish a data radio bearer between the base station 520 and the UE-NW RN 510; and an initial user message transmission unit for transmitting the initial user message to the base station 520 over the established data radio bearer.

In connection with fig. 6, the present invention also provides an exemplary apparatus for supporting coverage extension and service continuity in a UE-NW RN610, the apparatus comprising an RRC encapsulating unit for causing the UE-NW RN610 to receive a registration request from a remote user 600, the UE-NW RN610 transmitting NAS signaling of the remote user 600 encapsulated in RRC signaling to a base station 620. The RRC encapsulating unit may further include: the NAS signaling of remote user 600 encapsulated in RRC signaling has the identity of remote user 600; the NAS signaling of remote user 600 encapsulated in RRC signaling contains the registration request.

In connection with fig. 7, the present invention also provides an exemplary apparatus for supporting coverage extension and service continuity in a UE-NW RN710, the apparatus comprising an RRC simplifying unit for causing the UE-NW RN710 to receive RRC signaling from a remote user 700 over a PC5 interface and to send the RRC signaling to a base station 710 over a data radio bearer. The RRC simplifying unit may further include: an RRC receiving unit for receiving an RRC connection request from the remote user 700; a first bearer establishing unit, configured to establish a first data radio bearer with the base station 720 to transmit the RRC connection request to the base station 720; a second bearer establishing unit, configured to establish a second data radio bearer with the base station 720 to transmit the service data of the remote user 700.

Based on the scheme for supporting coverage extension and service continuity, once a remote user accesses the network and performs service through the UE-NW RN, the base station can learn of the presence of the remote user. If a remote user moves from the coverage of the UE-NW RN to the coverage of a cell and attempts to access the network directly, the base station can identify the remote user. The base station can modify the transmission path of the ongoing service so that the ongoing service is not interrupted and the user experience is improved.

Fig. 11 shows a relay station handoff scenario diagram for a remote user. As shown in fig. 11, a remote user 1100 is currently communicating with the core network through a UE-NW RN1110, and the remote user 1100 needs to find other ways to access the core network, such as other UE-NW RNs.

Fig. 12 shows a flow chart of remote user switching. Fig. 12 provides an exemplary method for remote user reselection relay station to support coverage extension and service continuity, where the remote user in fig. 12 has access to the source relay station.

In step S1201, handover of the UE-NW RN1110 is triggered.

When a first condition is met, the remote user reselects the target relay station, wherein the first condition is at least one of the following conditions:

the channel quality between the source relay station (e.g., UE-NW RN1110) and the base station (e.g., base station 1120) is below a first preset channel quality threshold; or the capability of the source relay is below a capability threshold, e.g., when the remaining energy or power of the UE-NW RN1110 is below a certain threshold; or

The source relay station informs the remote user 1100 to reselect the target relay station; or

The channel quality between the source relay station and the remote user 1100 is lower than a second preset channel quality threshold, for example, when the channel quality between the source relay station and the remote user is poor; or the channel quality between remote user 1100 and the target relay station (e.g., UE-NWRN1111) is higher than the channel quality between remote user 1100 and the source relay station by a predetermined offset.

When the channel quality between the source relay station and the base station is lower than a first preset channel quality threshold, or the capability of the source relay station is lower than a capability threshold, the source relay station needs to inform a remote user to search for a potential target relay station so as to switch a service transmission path. The base station or source relay station may also need to inform the remote user of the potential target relay stations to switch traffic transmission paths for other reasons.

In step S1202, the remote user 1100 monitors a discovery channel or a synchronization channel transmitted by a potential target relay station. A timer may be applied in searching for a potential target relay station. The timer duration may be configured by the base station or pre-configured by the protocol. The synchronization channel includes at least a physical direct link broadcast channel or a direct link synchronization signal.

In step S1203, if the potential target relay station satisfies a second condition, the remote user determines one of the potential target relay stations as the target relay station (e.g., selects the one with the best channel quality or selects the one with the most energy), where the second condition may be any one of the following:

the channel quality between the potential target relay (e.g., UE-NW RN1111) and the remote user 1100 is not below a second channel quality threshold (which may be pre-configured by the protocol);

the channel quality between the potential target relay (e.g., UE-NW RN1111) and the remote user 1100 is higher than the channel quality between the remote user 1100 and the source relay (e.g., UE-NW RN1110) by a predetermined offset (which may be pre-configured by the protocol).

If the potential target relay station does not satisfy the second condition, in step S1204, the remote user 1100 sends a message to continue looking for other potential target relays. For example, remote user 1100 may send a message indicating "i are looking for a relay station".

In step S1205, the remote user 1100 determines a target relay station according to feedback from other potential target relay stations in response to the message sent by the remote user 1100 and establishes a connection with the target relay station.

If the remote user 1100 still does not find a relay station that meets the criteria, the remote user 1100 checks whether the timer has expired, and if the timer has expired, the remote user 1100 may stop searching for relay stations as shown in fig. 12 and may continue to monitor other discovery channels and/or synchronization channels as shown in step S1206A of fig. 13. If the timer has not expired, the remote user 1100 may return to step S1202 or step S1204 to continue searching for a relay station. The synchronization channel includes at least a physical direct link broadcast channel or a direct link synchronization signal. The time reference of the potential target relay station detected by the remote user may not be consistent outside the network coverage, and the remote user may search for the potential target relay station at a certain time reference first, and then search for the potential target relay station at another time reference after the timer expires.

With reference to fig. 12 and 13, the present invention further provides an apparatus for reselecting a relay station by a remote user supporting coverage extension and service continuity, wherein the remote user has access to a source relay station, the apparatus comprising: a selecting unit, configured to reselect a target relay station by the remote user when a first condition is satisfied, where the first condition is at least any one of: the channel quality between the source relay station and the base station is lower than a first preset channel quality threshold; the capability of the source relay station is below a capability threshold; the source relay station informs the remote user to reselect a target relay station; the channel quality between the source relay station and the remote user is lower than a second preset channel quality threshold; the channel quality between a remote user and the target relay station is higher than the channel quality between the remote user and the source relay station by a predetermined offset.

The apparatus as described above may further include a monitoring unit for monitoring a discovery channel or a synchronization channel transmitted by the potential target relay station by the remote user; a first determining unit, if the potential target relay station satisfies the second condition, the remote user determines one of the potential target relay stations as the target relay station; a second determining unit, configured to send a message to the remote user to continue searching for a potential target relay station if the potential target relay station does not satisfy the second condition; and the remote user determining a target relay station based on feedback from potential target relay stations in response to the message sent by the remote user; wherein the second condition is at least any one of: a channel quality between a potential target relay station and the remote user is not below a second channel quality threshold; the channel quality between a potential target relay station and the remote user is higher than the channel quality between the remote user and a source relay station by a predetermined offset.

The concept of the exemplary scheme shown in fig. 12 is also applicable to the scenario when the remote user 1300 moves away from the connected UE-NW RN1310 of the current cell towards another cell as shown in fig. 14.

Two thresholds can also be configured for better service continuity. For example, when the channel quality of the PC5 interface is below threshold a, the remote user starts looking for the target UE-RN and prepares for a handoff, and once the measured channel quality of the PC5 interface with the target UE-NW RN is above threshold b, the remote user performs a handoff to the target UE-NW RN.

FIG. 15 shows yet another schematic diagram of a remote user switching scenario. In fig. 15, a remote user 1400 moves from within the coverage of a cell to outside the coverage of the cell. Based on the scenario and the scenario similar to the scenario, the present invention provides a scheme for supporting coverage extension and service continuity for user equipment handover, and the main concept of the scheme is as follows:

and when a third condition is met, the user equipment is switched from the base station to the target relay station, wherein the third condition is at least any one of the following conditions:

the channel quality between the user equipment 1400 and the base station 1420 is below a third channel quality threshold

A value (the threshold may be configured by the base station, or pre-configured by the protocol);

the user equipment 1400 receives a message for handover to the target relay station from the base station 1420;

wherein the ue 1400 moves from the coverage of the base station 1420 (cell under the jurisdiction) to outside the coverage of the base station.

Specifically, the scheme further includes that the user equipment 1400 searches and decodes a discovery channel and/or a synchronization channel transmitted by the potential target relay station, and a timer may be applied in the searching for the potential target relay station.

The user equipment 1400 monitors the discovery channel and/or the synchronization channel of the potential target relay station according to the timer;

if the channel quality between the potential target relay and the user equipment 1400 is not below the third channel quality threshold, the user equipment 1400 determines one of the potential target relays (e.g., the UE-NW RN1410) as the target relay.

If the channel quality between the potential target relay and the user equipment 1400 is below the third channel quality threshold, the user equipment 1400 sends a message to find the potential target relay, and the user equipment 1400 determines the target relay according to feedback from the potential target relay in response to the message sent by the remote user.

If the ue 1400 still does not find a qualified target relay, the ue 1400 checks whether the timer expires (expires), and if so, the ue 1400 continues to search and decode other discovery channels and/or synchronization channels again; or stop searching for the target relay station. If not, the user equipment 1400 may monitor discovery channels or synchronization channels of other relays and may also continue to transmit signals seeking relays.

In a scenario based on the scenario shown in fig. 15, the user equipment does not inform the base station that it will switch to the coverage of the UE-NWRN and be served by the UE-NW RN. When the ue moves out of the coverage of the base station, the base station releases the RRC connection and S1 connection of the ue, which may cause the core network to release all information of the ue, such as IP address, service information, etc. For the user equipment this may result in a long service interruption. To further address this issue, once the user equipment has found a suitable UE-NW RN, the user equipment may send a message to the base station that the user equipment will switch to the UE-NW RN, upon which the base station may release the RRC connection and S1 connection of the user equipment, while the base station may inform the MME that the user equipment will be served by the UE-NW RN, thereby prompting the PGW not to release the information of the user equipment. When the user equipment accesses the network via the UE-NW RN, the PGW may serve the user equipment, which ensures continuity of the service of the user equipment. Optionally, once the user equipment finds the suitable UE-NW RN, the user equipment may send a message to the base station that the user equipment will switch to the UE-NW RN, based on which the base station may not release S1 connection of the user equipment, and when the user equipment accesses the network via the UE-NW RN, the base station switches the traffic path of the user equipment to the Uu interface between the base station and the UE-NWRN, which also ensures the continuity of the traffic of the user equipment.

In a scenario based on fig. 15, the present invention provides an apparatus for user equipment handover supporting coverage extension and service continuity, the apparatus comprising: switching means for switching the user equipment from a base station to a target relay station when a third condition is satisfied, wherein the third condition is at least one of: the channel quality between the user equipment and the base station is below a third channel quality threshold; the user equipment receives a message for switching to a target relay station from the base station; wherein the user equipment moves from within the coverage of the base station to outside the coverage of the base station.

The apparatus may also include a first search decoding unit for the user equipment to search and decode a discovery channel and/or a synchronization channel transmitted by a potential target relay station. Monitoring means for monitoring, by the user equipment, a discovery channel and/or a synchronization channel of a potential target relay station according to a timer; a determining unit, configured to determine, by the user equipment, one of the potential target relay stations as a target relay station (e.g., with the best channel quality or the most energy) if the channel quality between the potential target relay station and the user equipment is not lower than a third channel quality threshold; if the channel quality between the potential target relay station and the user equipment is lower than a third channel quality threshold, the user equipment sends a message to continuously search for the potential target relay station; the user equipment determines a target relay station according to feedback from potential target relay stations in response to the message sent by the user equipment. A second searching and decoding unit, when the timer is overtime, the user equipment continuously searches and decodes other found channels and/or synchronous channels again; or the user equipment stops searching for the target relay station.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Furthermore, it will be obvious that the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. Several elements recited in the apparatus claims may also be implemented by one element. The terms first, second, etc. are used to denote names, but not any particular order.

Claims

1. A method in a relay station for supporting coverage extension and traffic continuity, the relay station for receiving signaling and data from a remote user and transmitting signaling and data from the remote user to a base station, the method comprising any of:

A. the relay station has S1-AP function and receives a registration request from the remote user, the relay station sends S1-AP signaling of the remote user encapsulated in RRC signaling to the base station, wherein the S1-AP signaling of the remote user encapsulated in the RRC signaling is an initial user message, and the initial user message contains NAS signaling of the registration request; or

B. The relay station has an S1-AP function and receives a registration request from the remote user, and sends S1-AP signaling to the base station through a data radio bearer, wherein the S1-AP signaling is an initial user message, and the initial user message contains NAS signaling of the registration request; or

C. The relay station receives a registration request from the remote user, and the relay station sends NAS signaling of the remote user registration request encapsulated in RRC signaling to the base station; or

D. The relay station receives RRC signaling from the remote user through a PC5 interface and transmits the RRC signaling to the base station through a first data radio bearer.

2. The method of claim 1, wherein a further comprises:

the S1-AP signaling of the remote user encapsulated in RRC signaling has an identification of the remote user.

3. The method of claim 1, wherein C further comprises:

the remote user's NAS signaling encapsulated in RRC signaling has the remote user's identity;

the remote user's NAS signaling encapsulated in RRC signaling comprises a registration request.

4. The method of claim 1, wherein B further comprises:

sending a data radio bearer request to the base station to establish a data radio bearer between the base station and the relay station.

5. The method of claim 4, wherein B further comprises:

transmitting an initial user message to the base station over the established data radio bearer.

6. The method of claim 1, wherein D further comprises:

receiving an RRC connection request from the remote user;

establishing a first data radio bearer with the base station to transmit the RRC connection request to the base station;

and establishing a second data radio bearer between the base station and the remote user to transmit the service data of the remote user.

7. An apparatus for supporting coverage extension and service continuity in a relay station for receiving signaling and data from a remote user and transmitting the signaling and data from the remote user to a base station, the apparatus comprising any one of:

a first S1-AP function unit for making the relay station S1-AP capable and receiving a registration request from the remote user, the relay station sending S1-AP signaling of the remote user encapsulated in RRC signaling to the base station, wherein the S1-AP signaling of the remote user encapsulated in RRC signaling is an initial user message, the initial user message including NAS signaling of the registration request; or

A second S1-AP function unit for enabling the relay station to have S1-AP functionality and to receive a registration request from the remote user, the relay station sending S1-AP signaling to the base station over a data radio bearer, wherein the S1-AP signaling is an initial user message, the initial user message including NAS signaling of the registration request; or

An RRC encapsulation unit for causing the relay station to receive a registration request from the remote user, the relay station transmitting NAS signaling of the remote user encapsulated in RRC signaling to the base station; or

An RRC simplification unit for causing the relay station to receive RRC signaling from the remote user through a PC5 interface and to transmit the RRC signaling to the base station through a data radio bearer.

8. The apparatus of claim 7, wherein the first S1-AP functional unit further comprises:

9. The apparatus of claim 7, wherein the RRC encapsulating unit further comprises:

10. The apparatus of claim 7, wherein the second S1-AP functional unit further comprises:

a bearer establishing unit for sending a data radio bearer request to the base station to establish a data radio bearer between the base station and the relay station; and

an initial user message transmission unit for transmitting an initial user message to the base station over the established data radio bearer.

11. The apparatus of claim 7, wherein the RRC simplification unit further comprises:

an RRC receiving unit for receiving an RRC connection request from the remote user;

a first bearer establishing unit, configured to establish a first data radio bearer with the base station to transmit the RRC connection request to the base station;

and the second bearing establishing unit is used for establishing a second data radio bearing with the base station so as to transmit the service data of the remote user.

12. The method of claim 1, further comprising a method for the remote user to reselect a relay station to support coverage extension and service continuity, wherein the remote user has access to a source relay station, the method for the remote user to reselect a relay station to support coverage extension and service continuity comprising:

the remote user reselects a target relay station when a first condition is met, wherein the first condition is at least one of the following:

the channel quality between the source relay station and the base station is lower than a first preset channel quality threshold;

the capability of the source relay station is below a capability threshold;

the source relay station informs the remote user to reselect a target relay station;

the channel quality between the source relay station and the remote user is lower than a second preset channel quality threshold;

the channel quality between the remote user and the target relay station is higher than the channel quality between the remote user and the source relay station by a predetermined offset.

13. The method for the remote user reselection relay station for supporting coverage extension and service continuity according to claim 12, further comprising

The remote user monitors a discovery channel or a synchronization channel sent by a potential target relay station;

the remote user determines one of the potential target relay stations as a target relay station if the potential target relay stations satisfy a second condition, the second condition being any one of

A channel quality between a potential target relay station and the remote user is not below a second channel quality threshold;

the channel quality between a potential target relay station and the remote user is higher than the channel quality between the remote user and a source relay station by a predetermined offset.

14. The method of claim 13, further comprising the step of reselecting a relay station for the remote user to support coverage extension and service continuity

if the potential target relay station does not satisfy the second condition, the remote user sends a message to continue searching for a potential target relay station; and

the remote user determines a target relay station based on feedback from potential target relay stations in response to the message sent by the remote user.

15. The method of claim 1, further comprising a method for user equipment handover supporting coverage extension and service continuity, the method for user equipment handover supporting coverage extension and service continuity comprising:

when a third condition is met, the user equipment is switched from the base station to a target relay station, wherein the third condition is at least any one of the following conditions:

the channel quality between the user equipment and the base station is below a third channel quality threshold;

the user equipment receives a message from a base station for switching to a target relay station;

wherein the user equipment moves from within the coverage of the base station to outside the coverage of the base station.

16. The method for handover of a user equipment supporting coverage extension and service continuity according to claim 15, further comprising

The user equipment searches and decodes discovery channels and/or synchronization channels transmitted by potential target relay stations.

17. The method for handover of a user equipment supporting coverage extension and service continuity according to claim 16, further comprising

The user equipment monitors a discovery channel and/or a synchronization channel of a potential target relay station according to a timer;

if the channel quality between the potential target relay station and the user equipment is not lower than a third channel quality threshold, the user equipment determines one of the potential target relay stations as the target relay station.

18. The method for handover of a user equipment supporting coverage extension and service continuity according to claim 16, further comprising

The user equipment monitors a discovery channel of a potential target relay station according to a timer;

if the channel quality between the potential target relay station and the user equipment is lower than a third channel quality threshold, the user equipment sends a message to search for the potential target relay station; and

the user equipment determines a target relay station according to feedback from potential target relay stations in response to the message sent by the user equipment.

19. The method for handover of a user equipment supporting coverage extension and service continuity according to any one of claims 17 or 18, further comprising

When the timer is overtime, the user equipment continues to search and decode other discovery channels and/or synchronous channels again; or the user equipment stops searching for the target relay station.

20. The apparatus of claim 7, further comprising means for the remote user reselection relay station supporting coverage extension and service continuity, wherein the remote user has access to a source relay station, the means for the remote user reselection relay station supporting coverage extension and service continuity comprising:

a selecting unit, configured to reselect a target relay station by the remote user when a first condition is satisfied, where the first condition is at least any one of:

the capability of the source relay station is below a capability threshold;

21. The apparatus of claim 20, wherein the means for the remote user reselection of relay stations to support coverage extension and service continuity further comprises

A monitoring unit for monitoring a discovery channel or a synchronization channel transmitted by a potential target relay station by the remote user;

a first determining unit, if potential target relay stations meet a second condition, the remote user determining one of the potential target relay stations as a target relay station;

a second determining unit for sending a message to the remote user to continue searching for a potential target relay station if the potential target relay station does not satisfy the second condition; and the remote user determining a target relay station based on feedback from potential target relay stations in response to the message sent by the remote user;

wherein the second condition is at least any one of:

22. The apparatus of claim 7, further comprising a means for user equipment handover to support coverage extension and service continuity, the means for the remote user to support coverage extension and service continuity to reselect a relay station comprising:

switching means for switching the user equipment from a base station to a target relay station when a third condition is satisfied, wherein the third condition is at least one of:

the user equipment receives a message for switching to a target relay station from the base station;

23. The apparatus of claim 22, wherein the means for the remote user reselection of relay stations to support coverage extension and service continuity further comprises

A first searching and decoding unit, configured to search and decode, by the user equipment, a discovery channel and/or a synchronization channel transmitted by a potential target relay station.

24. The apparatus of claim 23, wherein the means for the remote user reselection of relay stations to support coverage extension and service continuity further comprises

Monitoring means for monitoring, by the user equipment, a discovery channel and/or a synchronization channel of a potential target relay station according to a timer;

a determining unit, configured to determine, by the user equipment, one of the potential target relay stations as a target relay station if a channel quality between the potential target relay station and the user equipment is not lower than a third channel quality threshold; if the channel quality between the potential target relay station and the user equipment is lower than a third channel quality threshold, the user equipment sends a message to continuously search for the potential target relay station; the user equipment determines a target relay station according to feedback from potential target relay stations in response to the message sent by the user equipment.

25. The apparatus of claim 24, wherein the means for the remote user reselection of relay stations to support coverage extension and service continuity further comprises

A second searching and decoding unit, when the timer is overtime, the user equipment continuously searches and decodes other found channels and/or synchronous channels again; or the user equipment stops searching for the target relay station.