CN106888494A - A kind of methods, devices and systems for selecting relaying UE - Google Patents

Abstract

The present invention provides a method for selecting a relay UE among remote UEs, wherein the method includes: a. The remote UE broadcasts or multicasts a relay discovery request message outside the network coverage to the network coverage; b. receiving a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE, where the response message includes the radio access network connection status information of the candidate relay UE and/or the candidate relay UE and its Frequency information used between serving cells; c. According to the response message and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE, from the at least one candidate Selecting a candidate relay UE from among the relay UEs as the relay UE of the remote UE; d. Establishing direct communication with the relay UE, so that the remote UE communicates with the network through the relay UE .

Description

A method, device and system for selecting a relay UE

technical field

The present invention relates to the field of communication technologies, and in particular to a method, device and system for selecting a relay UE.

Background technique

In the prior art, the operator usually needs to pre-deploy a repeater (similar to a small base station in the UE's view) at a selected location, so that a remote UE (User Equipment) located outside the network coverage can pass through the deployed The repeater is used to communicate with the network. This solution requires a huge deployment cost and is extremely inflexible. Once the repeater connected to the remote UE fails, the remote UE will no longer be able to communicate with the network, or, Repeaters must be switched through a complex switching process.

Contents of the invention

The object of the present invention is to provide a method, device and system for selecting a relay UE.

According to an aspect of the present invention, a first device for selecting a relay UE among remote UEs is provided, wherein the first device includes:

The first sending device is used to broadcast or multicast the relay discovery request message to the network coverage outside the network coverage;

The first receiving means is configured to receive a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE, where the response message includes radio access network connection status information and /or frequency information used between the candidate relay UE and its serving cell;

selecting means, configured to select a candidate from the at least one candidate relay UE according to the response message and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE a relay UE serving as a relay UE for the remote UE;

First establishing means, configured to establish direct communication with the relay UE, so that the remote UE communicates with the network through the relay UE.

According to another aspect of the present invention, there is also provided a second device for assisting a remote UE in selecting a relay UE, wherein the second device includes:

A fourth receiving means, configured to receive a relay discovery request message from a remote UE;

The second sending means is configured to feed back a response message corresponding to the relay discovery request message to the remote UE when a predetermined relay condition is satisfied, wherein the response message includes the wireless access of the candidate relay UE Network connection status information and/or frequency information used between the candidate relay UE and its serving cell;

Wherein, the second means also includes the following means for performing operations after the feedback means:

The second establishing means is configured to establish direct communication with the remote UE, and establish a data connection with the cellular network and the core network, so as to serve as a relay UE for the remote UE to allow the remote UE to pass through the intermediate Then the UE communicates with the network.

According to another aspect of the present invention, a method for selecting a relay UE among remote UEs is provided, wherein the method includes:

a. The remote UE broadcasts or multicasts a discovery request message outside the network coverage to the network coverage;

b. Receive a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE, wherein the response message includes radio access network connection status information and/or candidate relay of the candidate relay UE Frequency information used between the UE and its serving cell;

c. Select a candidate relay UE from the at least one candidate relay UE according to the response message and the link quality measured by the remote UE between the remote UE and the at least one candidate relay UE being a relay UE for the remote UE;

d. Establishing direct communication with the relay UE to enable the remote UE to communicate with the network through the relay UE.

According to another aspect of the present invention, a method for assisting a remote UE in selecting a relay UE is provided, wherein the method includes:

A receives a relay discovery request message from a remote UE;

B. When the predetermined relay condition is satisfied, feed back a response message corresponding to the relay discovery request message to the remote UE, wherein the response message includes the radio access network connection status information of the candidate relay UE and/or or frequency information used between the candidate relay UE and its serving cell;

Wherein, after said step B, the method also includes:

X establishes direct communication with the remote UE, and establishes a data connection with the cellular network and the core network, so as to act as a relay UE for the remote UE to enable the remote UE to communicate with the network through the relay UE .

According to another aspect of the present invention, a system for selecting a relay UE is provided, wherein the system includes a remote UE located outside the coverage of the network and a candidate relay UE located within the coverage of the network, the remote UE Including the first device described in the present invention, the candidate relay UE includes the second device described in the present invention.

Compared with the prior art, the present invention has the following advantages: 1) The remote UE can select from at least one candidate relay UE according to the radio access network connection status information and/or frequency information of the at least one candidate relay UE One of the most suitable candidate relay UEs is used as the relay UE of the remote UE; 2) By selecting the candidate relay UE in the RRC connection state as the relay UE, it is avoided that the RRC connection cannot be successfully established after the relay UE is selected. 3) By selecting a candidate relay UE capable of simultaneously using different frequencies for cellular communication and D2D communication as the relay UE, to avoid conflicts between cellular communication and D2D communication in the selected relay UE; 4) The remote UE can determine whether to reselect the relay UE according to the relay monitoring information from the selected relay UE; 5) When the selected relay UE is not suitable to continue as a relay, it can pass the MAC layer Send the relay UE reselection indication information to the remote UE to suggest or notify the remote UE to reselect the relay UE. This reselection mechanism can save a lot of wireless resources, and the remote UE can be no longer suitable for the remote UE as the relay UE. The UE can trigger the reselection mechanism of the relay UE in time.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 is a schematic flowchart of a method for selecting a relay UE according to an embodiment of the present invention;

FIG. 2 is a schematic flowchart of a method for selecting a relay UE according to another embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a system for selecting a relay UE according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a system for selecting a relay UE according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a scenario in which a remote UE selects a relay UE in an example of the present invention;

Fig. 6 is a schematic diagram of the MAC PDU format in the SL-SCH of an example of the present invention;

FIG. 7 is a schematic diagram of an example SL-SCH MAC subheader.

The same or similar reference numerals in the drawings represent the same or similar components.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

FIG. 1 is a schematic flowchart of a method for selecting a relay UE according to an embodiment of the present invention. The method according to the present invention is mainly realized by a remote UE and a relay candidate UE; wherein, the remote UE is used to represent a user equipment located outside the network coverage; wherein the candidate relay UE is used to represent a user equipment located in the network coverage The candidate relay UE should have an interface (such as a PC5 interface) for connecting to a remote UE and an interface (such as a Uu interface) for connecting to its serving cell. For example, FIG. 5 is a schematic diagram of a scenario in which a remote UE selects a relay UE in an example of the present invention, wherein UE1 and UE2 are located within the network coverage of the eNB, and both UE1 and UE2 have a PC5 interface and a Uu interface, and there are Remote UEs, therefore, UE1 and UE2 can be candidate relay UEs.

The method according to this embodiment includes step S101, step S102, step S103, step S04, step S105, step S106 and step S107.

In step S101, the remote UE broadcasts or multicasts a relay discovery request message outside the network coverage to within the network coverage.

Wherein, the relay discovery request message includes any information related to the remote UE's relay discovery request; preferably, the relay discovery request message includes but not limited to: message type, identification information (such as ID) of the remote UE , group identification information (such as group ID) of the remote UE, and the like.

As an example, when the remote UE detects that the remote UE is outside the coverage of the network, and the remote UE wishes to communicate with the network, the remote UE broadcasts a relay discovery request message to the network coverage, so that the relay discovery request Messages are sent to all user devices within network coverage.

As another example, when the remote UE detects that the remote UE is outside the coverage of the network, and the remote UE wishes to communicate with the network, the remote UE multicasts a relay discovery request message to the network coverage, so that the relay A discovery request message is sent to a group of user equipments within the coverage of the network.

It should be noted that, for the sake of simplicity, although only one candidate relay UE is shown in FIG. 1 , those skilled in the art should understand that there may be multiple candidate relay UEs within the coverage of the network.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limiting the present invention. Those skilled in the art should understand that any broadcast or multicast relay discovery from outside the network coverage to within the network coverage The implementation of the request message should be included in the scope of the present invention.

In step S102, the candidate relay UE receives a relay discovery request message from a remote UE.

It should be noted that although only one candidate relay UE is shown in FIG. 1, those skilled in the art should understand that when the remote UE broadcasts a relay discovery request message to the network coverage, all The user equipment will receive the relay discovery request message; when the remote UE multicasts the relay discovery request message to the network coverage, the user equipment belonging to the multicast group within the network coverage will receive the relay discovery request information. It should be further noted that the user equipment that receives the relay discovery request message may not necessarily be a candidate relay UE, and the user equipment that cannot be a candidate relay UE will not respond to the relay discovery request message.

As an example, based on the scenario shown in FIG. 5, in step S101, the remote UE broadcasts a relay discovery request message outside the network coverage to the network coverage; in step S102, UE1 and UE2 within the network coverage receive Relay discovery request message from remote UE.

In step S103, when a predetermined relay condition is met, the candidate relay UE feeds back a response message corresponding to the relay discovery request message to the remote UE.

Wherein, the predetermined relay condition includes any condition for judging whether the user equipment within the coverage area has a relay capability; for example, the predetermined relay condition indicates that when the user equipment within the coverage area has both a PC5 interface and a Uu interface, and When the power of the user equipment is higher than a predetermined threshold, the user equipment has a relay capability. It should be noted that when the predetermined relay condition is not satisfied, no response to the relay discovery request message is required.

Wherein, the response message is used to indicate the response made by the candidate relay UE to the relay discovery request message from the remote UE.

Wherein, the response message includes the radio access network connection status information of the candidate relay UE and/or the frequency information used between the candidate relay UE and its serving cell. Wherein, the radio access network connection state information includes any information used to indicate the radio access network connection state of the candidate relay UE; for example, the radio access network connection state information is used to indicate that the candidate relay UE is in the RRC connection state (RRC_Connected) or idle state (RRC_Idle). Wherein, the frequency information is used to indicate whether the carrier frequency used between the candidate relay UE and its serving cell is the same as the carrier frequency used between the candidate relay UE and the remote UE; The remote UE is connected to the PC5 interface and the Uu interface used to connect to its serving cell, and the frequency information is used to indicate whether the Uu link frequency used by the candidate relay UE is the same as the PC5 link frequency. It should be noted that when the frequency information used between the candidate relay UE and its serving cell needs to be considered in the process of selecting the relay UE, it is assumed that the candidate relay UE can support simultaneous processing of cellular communication and D2D (Device-to- -Device) communication.

Preferably, the response message further includes identification information of the candidate relay UE and the remote UE, such as the ID of the candidate relay UE and the ID of the remote UE. Preferably, the response message further includes information indicating the relay capability of the candidate relay UE, such as backhaul link quality, remaining relay capacity in supported links, and the like.

It should be noted that, the response message may be transmitted in broadcast, unicast or multicast form using the selected or scheduled resource.

It should be noted that although only one candidate relay UE is shown in FIG. 1 , those skilled in the art should understand that when there are multiple candidate relay UEs, the multiple candidate relay UEs will all perform step S103 to feed back a response message to the remote UE.

As an example, based on the scenario shown in FIG. 5, UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response message including UE1's radio access network connection status information, the radio access network connection state information indicates that UE1 is in the RRC connection state; UE2 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, and the response message includes UE2’s wireless Access network connection state information, where the radio access network connection state information indicates that UE2 is in an idle state.

As another example, based on the scenario shown in FIG. 5, UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE. The response message includes the Frequency information, the frequency information indicates that the Uu link frequency used by UE1 is different from the PC5 link frequency; UE2 determines that it meets the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response The message includes frequency information used between UE2 and eNB, and the frequency information indicates that the Uu link frequency used by UE2 is the same as the PC5 link frequency.

As another example, based on the scenario shown in FIG. 5 , UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE. The response message includes UE1's radio access network connection State information and frequency information used between UE1 and eNB, the radio access network connection state information indicates that UE1 is in the RRC connection state, and the frequency information indicates that the Uu link frequency used by UE1 is different from the PC5 link frequency; UE2 determines its Satisfy the predetermined relay conditions, and feed back a response message corresponding to the relay discovery request message to the remote UE. The response message includes the connection status information of the radio access network of UE2 and the frequency information used between UE2 and eNB. The radio access network The network access connection state information indicates that UE2 is in an idle state, and the frequency information indicates that the Uu link frequency used by UE2 is the same as the PC5 link frequency.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limit the present invention. Those skilled in the art should understand that when any predetermined relay condition is met, the remote UE is fed back to the remote UE The implementation of the response message corresponding to the above relay discovery request message should be included in the scope of the present invention.

In step S104, the remote UE receives a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE.

It should be noted that, when there are multiple candidate relay UEs within the coverage of the network to feed back response messages to the remote UE, the remote UE respectively receives the relay information fed back by each candidate relay UE among the multiple candidate relay UEs. Discover the response message corresponding to the request message.

In step S105, the remote UE selects from the at least one candidate relay UE according to the response message and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE A candidate relay UE is used as a relay UE for the remote UE.

Wherein, the link quality is the D2D link quality between the remote UE and the candidate relay UE; when the candidate relay UE is connected to the remote UE through the PC5 interface, the link quality is the PC5 link quality.

As an example, based on the scenario shown in Figure 5, the response message fed back by UE1 includes the radio access network connection status information of UE1, and the radio access network connection status information indicates that UE1 is in the RRC connection state; the response message fed back by UE2 includes UE2's radio access network connection status information, the radio access network connection status information indicates that UE2 is in an idle state; in step S105, the remote UE determines the measured link quality between the remote UE and UE1 and the link quality between the remote UE and UE1 The link quality between UE2 satisfies the predetermined link quality condition (for example, the link quality is higher than the predetermined quality threshold), then the remote UE selects UE1 in the RRC connection state from UE1 and UE2 according to the response message fed back by UE1 and UE2 An intermediate UE as a remote UE. It should be noted that if the relay UE selected by the remote UE is in an idle state, the relay UE needs to initiate a random access procedure to establish an RRC connection, because the random access procedure may fail or the serving base station may refuse to access , these situations will lead to the failure of the relay UE to successfully establish the RRC connection with the serving base station, which makes the remote UE have to reselect the relay UE, which will cause service delay; therefore, preferably, when the link quality meets the predetermined In the case of link quality conditions, the remote UE preferentially selects a candidate relay UE that is currently in the RRC connection state as the relay UE of the remote UE, which can effectively avoid service delays caused by RRC connection failure.

As another example, assume that UE1 and UE2 can support simultaneous processing of cellular communication and D2D communication of different frequencies; based on the scenario shown in Figure 5, the response message fed back by UE1 includes the frequency information used between UE1 and eNB, and the frequency information indicates that UE1 The Uu link frequency used is different from the PC5 link frequency; the response message fed back by UE2 includes the frequency information used between UE2 and eNB, and the frequency information indicates that the Uu link frequency used by UE2 is the same as the PC5 link frequency; In step S105, the remote UE determines that the measured link quality between the remote UE and UE1 and the link quality between the remote UE and UE2 all meet a predetermined link quality condition (for example, the link quality is higher than a predetermined quality threshold ), then the remote UE selects UE1 from UE1 and UE2 that uses a different Uu link frequency and PC5 link frequency as the intermediate UE of the remote UE according to the response messages fed back by UE1 and UE2. It should be noted that the selected relay UE uses different frequencies to perform cellular communication and D2D communication respectively, which can effectively avoid the conflict between cellular communication and D2D communication in the relay UE.

As a preferred solution, the response message fed back by the candidate relay UE also includes the quality of the backhaul link. In step S105, the remote UE based on the quality of the backhaul link of at least one candidate relay UE, the radio access network connection status information and/or or frequency information, and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE, and select a candidate relay UE from the at least one candidate relay UE as the intermediate UE of the remote UE Following UE.

As an example, based on the scenario shown in FIG. 5, when both UE1 and UE2 meet the predetermined link quality conditions, and UE1 and UE2 have similar backhaul link quality (the backhaul link quality in this scenario is Uu link quality ), the remote UE preferentially selects UE1 in the RRC connected state as the relay UE of the remote UE.

It should be noted that when the remote UE does not select a suitable relay UE during this discovery period (for example, the link quality between the candidate relay UE and the candidate relay UE is lower than the predetermined quality threshold), the remote UE will Repeat step S101 to broadcast or multicast the discovery request message again.

It should be noted that the above example is only to better illustrate the response message of the present invention, and the remote UE and the at least one technical solution measured by the remote UE, rather than limiting the present invention, those skilled in the art should It is understood that any implementation of selecting a candidate relay UE from the at least one candidate relay UE as the relay UE of the remote UE according to the link quality between the candidate relay UEs shall be included in this document. within the scope of the invention.

After the relay UE of the remote UE is selected, the remote UE performs step S106, and the relay UE performs step S107, so that the remote UE can communicate with the network through the selected relay UE.

In step S106, the remote UE establishes direct communication with the relay UE, so that the remote UE communicates with the network through the relay UE.

During the establishment of direct communication (direct communication) between the remote UE and the relay UE, cross-authentication and D2D link security setting may be performed between the remote UE and the relay UE first.

Specifically, the remote UE initiates a direct communication request to the relay U1, and establishes direct communication with the relay UE based on the interaction with the relay UE.

In step S107, the relay UE selected by the remote UE establishes direct communication with the remote UE, and establishes a data connection with the cellular network and the core network, so as to serve as the relay UE of the remote UE to make the remote UE The remote UE communicates with the network through the relay UE.

It should be noted that, for the sake of simplicity, FIG. 1 does not show the process of the selected relay UE establishing a data connection with the cellular network and the core network.

After step S107, data transmission is performed between the remote UE and the network through the selected relay UE. The selected relay UE can rebroadcast unicast traffic (including uplink and downlink traffic) between the remote UE and the network.

As a preferred solution, after step S107, the method of this embodiment further includes the following steps: the selected relay UE sends relay monitoring information to the remote UE; the remote UE receives the relay monitoring information from the relay UE , and measure the channel quality between the remote UE and the relay UE according to the relay monitoring information.

Preferably, the relay monitoring information is a discovery message.

Preferably, the selected relay UE periodically sends relay monitoring information to the remote UE, and the remote UE periodically receives the relay monitoring information from the relay UE, and measures the remote UE based on the received relay monitoring information. Channel quality (such as D2D link quality) between the UE and the relay UE.

It should be noted that the remote UE can measure the quality of the link between the remote UE and the relay UE by decoding the relay monitoring information, and learn other information, such as the quality of the backhaul link of the relay UE.

Preferably, the preferred solution further includes the following steps: when it is detected that the channel quality is lower than a predetermined threshold, the remote UE repeats step S101 to re-broadcast or multicast a relay discovery request message to the network coverage to reselect Following UE.

Specifically, when the channel quality between the remote UE and the selected relay UE is detected within a predetermined threshold, the remote UE determines that the relay UE is no longer suitable as a relay between the remote UE and the network, and the remote UE terminates its Serve and release the direct communication connection with the current relay UE, and repeat step S101 to re-broadcast or multicast the relay discovery request message to the network coverage, so as to reselect a relay UE.

In the prior art, operators usually pre-deploy relays (similar to small base stations from the perspective of UEs) at specific locations, so that remote UEs located outside the coverage of the network can communicate with the network through the relays. This solution requires The deployment cost is huge, and once the repeater fails, the remote UE will no longer be able to communicate with the network.

At present, a solution of introducing UE-to-network relay (relay) to support coverage extension has been proposed, that is, a remote UE can select a user equipment within the coverage of the network as the relay UE of the remote UE, so as to communicate with However, in the prior art, when the remote UE selects the relay UE, it only considers whether the link between the remote UE and the relay UE satisfies the conditions, and how to trigger the remote UE to reselect the relay UE is still under study middle. The present invention finds the following problems in the prior art: 1) The remote UE does not consider the radio access network connection status of the candidate relay UE in the process of selecting the relay UE, so the selected relay UE may be idle In this case, the selected relay UE needs to initiate a random access procedure to establish an RRC connection. If the relay UE cannot successfully establish an RRC connection with the serving base station, the remote UE must reselect the relay UE , which will cause service delay; 2) After the relay UE starts serving the remote UE, the link quality between the relay UE and the serving base station may be poor, or due to the limitation of the relay UE itself, the The relay UE continues to act as a remote UE, but the prior art does not support relay UE reselection in these situations.

According to the solution of this embodiment, the remote UE can select a most suitable candidate relay UE from the at least one candidate relay UE according to the radio access network connection status information and/or frequency information of the at least one candidate relay UE to serve as the relay UE for the remote UE; by selecting a candidate relay UE in the RRC connection state as the relay UE, it is possible to avoid the service delay caused by the inability to successfully establish the RRC connection after the relay UE is selected; At the same time, a candidate relay UE for cellular communication and D2D communication with different frequencies is used as a relay UE to avoid conflicts between cellular communication and D2D communication in the selected relay UE; Select a relay UE among the relay UEs. This selection mechanism does not require the operator to pre-deploy the relay, and it is extremely flexible, which greatly saves operating costs, and is especially suitable for geographically inconvenient deployment of relays. disaster area; this embodiment provides a relay UE reselection mechanism, and the remote UE can determine whether to reselect the relay UE according to the relay monitoring information from the selected relay UE, that is, The remote UE can know the state of the relay UE itself (such as power or power, etc.) and/or the link quality between the relay UE and the serving base station through the relay monitoring information, so that the current relay UE is no longer suitable as the remote UE. When relaying the UE, the reselection mechanism of the relay UE can be triggered in time.

Fig. 2 is a schematic flowchart of a method for selecting a relay UE according to another embodiment of the present invention. The method according to this embodiment includes step S101, step S102, step S103, step S04, step S105, step S106, step S107, step S108, step S109, step S110; wherein, the step S101, step S102, step S103, Step S04 , step S105 , step S106 and step S107 have been described in detail with reference to FIG. 1 , and will not be repeated here.

In this embodiment, after step S107, the remote UE and the selected relay UE trigger the operation of reselecting the relay UE by performing steps S108, S109, and S110.

In step S108, when the relay UE reselection trigger condition is met, the relay UE (that is, the candidate relay UE selected as the relay UE) sends the relay UE reselection indication information to the remote UE, wherein The subsequent UE reselection indication information is carried by the MAC layer control information in the direct communication data packet.

Wherein, the relay UE reselection trigger condition includes any condition used to trigger the current relay UE to suggest to the remote UE to reselect its relay UE, such as the current power level is lower than a predetermined power value, and the link quality with the serving base station Below a predetermined threshold, power below a predetermined power value, etc. It should be noted that when the relay UE reselection trigger condition is satisfied, it means that the current relay UE is no longer suitable as the relay UE of the remote UE.

Wherein, the relay UE reselection indication information includes any information used to indicate that the relay UE can be reselected; preferably, the relay UE reselection indication information includes but not limited to: the current relay UE power information, Power information, link quality information with the serving base station, or information that directly indicates that the relay UE is recommended to be reselected (for example, "1" indicates that the relay UE is recommended to be reselected).

Preferably, the relay UE reselection indication information is added to the stuffing bits in the header of the MAC layer control information, and/or, the MAC control element of the MAC layer control information.

For example, Fig. 6 is a schematic diagram of the MAC PDU format in SL-SCH of an example of the present invention, wherein "MAC Control element 1" is a newly added MAC control element, when the relay UE detects that its power is lower than the predetermined power value , the relay UE sends relay UE reselection indication information to the remote UE, and the relay UE reselection indication information is added to "MAC Control element 1" shown in FIG. 6 .

As another example, FIG. 7 is a schematic diagram of an example SL-SCH MAC subheader, where "R" represents a padding bit, and there are four reserved bits in the subheader; when the relay UE detects that its Uu link quality is low When the predetermined threshold is reached, the relay UE sends relay UE reselection indication information to the remote UE, and the relay UE reselection indication information is added to the padding bits shown in FIG. 7 .

For another example, the relay UE adds its Uu link quality to the padding bit of the header of the MAC control information, and adds its current power to the newly added MAC control element in the MAC control information, and sends it to Remote UE.

It should be noted that the above examples are only to better illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Those skilled in the art should understand that any Sending the relay UE reselection indication information, the realization manner that the relay UE reselection indication information is carried by the MAC layer control information in the direct communication data packet shall be included in the scope of the present invention.

In step 109, the remote UE receives MAC layer control information in the direct communication data packet from the selected relay UE, where the MAC layer control information includes relay UE reselection indication information.

Specifically, the remote UE receives the MAC layer control information in the direct communication data packet from the selected relay UE, and extracts the relay UE reselection indication information carried in the MAC layer control information.

For example, in step S108, the relay UE adds the relay UE reselection indication information to the "MAC Control element 1" shown in Figure 6, and sends it to the remote UE through the MAC layer; in step S109, the remote UE receives From the MAC layer control information shown in FIG. 6 of the relay UE, and extract the relay UE reselection instruction information carried by "MAC Control element 1".

For another example, in step S108, the relay UE adds the relay UE reselection indication information to the first padding bit shown in FIG. 7, and sends it to the remote UE through the MAC layer; in step S109, the remote UE receives From the MAC layer control information shown in FIG. 7 of the relay UE, the relay UE reselection indication information carried in the first padding bit is extracted.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limit the present invention. Those skilled in the art should understand that any MAC received in the direct communication data packet from the selected relay UE Layer control information, the implementation manner of relaying UE reselection instruction information included in the MAC layer control information should be included in the scope of the present invention.

In step S110, when it is determined according to the relay UE reselection indication information that a relay UE needs to be reselected, the remote UE repeats step S101 to re-broadcast or multicast a relay discovery request message within the network.

Wherein, the remote UE may determine whether to reselect the relay UE according to the reselection indication information in various ways.

For example, after receiving the relay UE reselection indication information from the relay UE, the remote UE directly determines that the relay UE needs to be selected.

For another example, the remote UE determines whether to reselect the relay UE according to the received relay UE reselection indication information and a predetermined judgment condition (eg, the quality of the D2D link between the remote UE and the relay UE is lower than a predetermined threshold).

For another example, the remote UE determines whether to reselect the relay UE according to the received relay UE reselection indication information and relay monitoring information.

It should be noted that, when the remote UE determines that the relay UE does not need to be reselected, the remote UE does not perform any operation.

It should be noted that the above examples are only to better illustrate the technical solutions of the present invention, rather than limiting the present invention. Those skilled in the art should understand that any When following the UE, the implementation manners in which the remote UE repeats step S101 should be included in the scope of the present invention.

According to the solution of this embodiment, another reselection mechanism for the relay UE is provided. When the selected relay UE is not suitable to continue to be a relay, it can send a relay UE reselection indication to the remote UE through the MAC layer. information to suggest or notify the remote UE to reselect the relay UE. This reselection mechanism can save a lot of radio resources, and the remote UE can trigger the reselection of the relay UE in time when the current relay UE is no longer suitable as the relay UE of the remote UE. selection mechanism; the relay UE reselection indication information may include link quality related information between the relay UE and the serving base station, so that the remote UE can more timely and accurately determine whether to reselect the relay UE.

FIG. 3 is a schematic structural diagram of a system for selecting a relay UE according to an embodiment of the present invention. The system includes a remote UE located out of network coverage and a candidate relay UE located within network coverage; wherein, the remote UE includes a first device for selecting a relay UE, and the first device includes a first sending device 101 , a first receiving means 104, a selecting means 105, and a first establishing means 106; wherein, the candidate relay UE includes a second means for assisting a remote UE in selecting a relay UE, and the second means includes a fourth receiving means 102 , the second sending means 103 and the second establishing means 107. It should be noted that, for the sake of simplicity, only one candidate relay UE is shown in FIG. 3 , and those skilled in the art should understand that there may be multiple candidate relay UEs within the coverage of the network.

The first sending unit 101 of the remote UE is configured to broadcast or multicast a relay discovery request message outside the network coverage to within the network coverage.

Wherein, the relay discovery request message includes any information related to the remote UE's relay discovery request; preferably, the relay discovery request message includes but not limited to: message type, identification information (such as ID) of the remote UE , group identification information (such as group ID) of the remote UE, and the like.

As an example, when the remote UE detects that the remote UE is located outside the network coverage and the remote UE wishes to communicate with the network, the first sending device 101 of the remote UE broadcasts a relay discovery request message to the network coverage, In order to send the relay discovery request message to all user equipments within the network coverage.

As another example, when the remote UE detects that the remote UE is outside the coverage of the network and the remote UE wishes to communicate with the network, the first sending means 101 of the remote UE multicasts the relay discovery request to the network coverage message to send a relay discovery request message to a group of user equipments within network coverage.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limiting the present invention. Those skilled in the art should understand that any broadcast or multicast relay discovery from outside the network coverage to within the network coverage The implementation of the request message should be included in the scope of the present invention.

The fourth receiving module 102 of the candidate relay UE receives a relay discovery request message from a remote UE.

It should be noted that although only one candidate relay UE is shown in FIG. 3 , those skilled in the art should understand that when the first sending device 101 of the remote UE broadcasts the relay discovery request message to the network coverage area, The fourth receiving means 102 in all user equipments within the network coverage will receive the relay discovery request message; when the first sending means 101 of the remote UE multicasts the relay discovery request message within the network coverage, the network The fourth receiving means 102 in the user equipment belonging to the multicast group within the coverage area will all receive the relay discovery request message. It should be further noted that the user equipment that receives the relay discovery request message may not necessarily be a candidate relay UE, and the user equipment that cannot be a candidate relay UE will not respond to the relay discovery request message.

As an example, based on the scenario shown in FIG. 5 , the first sending device 101 of the remote UE broadcasts a relay discovery request message outside the network coverage to the network coverage; the fourth receiving device 102 of UE1 and UE2 within the network coverage Each of the fourth receiving means 102 receives a relay discovery request message from a remote UE.

When the predetermined relay condition is met, the second sending module 103 of the candidate relay UE feeds back a response message corresponding to the relay discovery request message to the remote UE.

Wherein, the predetermined relay condition includes any condition for judging whether the user equipment within the coverage area has a relay capability; for example, the predetermined relay condition indicates that when the user equipment within the coverage area has both a PC5 interface and a Uu interface, and When the power of the user equipment is higher than a predetermined threshold, the user equipment has a relay capability. It should be noted that when the predetermined relay condition is not satisfied, no response to the relay discovery request message is required.

Wherein, the response message is used to indicate the response made by the candidate relay UE to the relay discovery request message from the remote UE.

Wherein, the response message includes the radio access network connection status information of the candidate relay UE and/or the frequency information used between the candidate relay UE and its serving cell. Wherein, the radio access network connection state information includes any information used to indicate the radio access network connection state of the candidate relay UE; for example, the radio access network connection state information is used to indicate that the candidate relay UE is in the RRC connection state (RRC_Connected) or idle state (RRC_Idle). Wherein, the frequency information is used to indicate whether the carrier frequency used between the candidate relay UE and its serving cell is the same as the carrier frequency used between the candidate relay UE and the remote UE; The remote UE is connected to the PC5 interface and the Uu interface used to connect to its serving cell, and the frequency information is used to indicate whether the Uu link frequency used by the candidate relay UE is the same as the PC5 link frequency. It should be noted that when the frequency information used between the candidate relay UE and its serving cell needs to be considered in the process of selecting the relay UE, it is assumed that the candidate relay UE can support simultaneous processing of cellular communication and D2D communication of different frequencies.

Preferably, the response message further includes identification information of the candidate relay UE and the remote UE, such as the ID of the candidate relay UE and the ID of the remote UE. Preferably, the response message further includes information indicating the relay capability of the candidate relay UE, such as backhaul link quality, remaining relay capacity in supported links, and the like.

It should be noted that, the response message may be transmitted in broadcast, unicast or multicast form using the selected or scheduled resource.

It should be noted that although only one candidate relay UE is shown in FIG. 3 , those skilled in the art should understand that when there are multiple candidate relay UEs, the second sending means of the multiple candidate relay UEs 103 will perform operations to feed back a response message to the remote UE.

As an example, based on the scenario shown in FIG. 5, the second sending means 103 of UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response message including UE1's Radio access network connection state information, the radio access network connection state information indicates that UE1 is in the RRC connection state; the second sending device 103 of UE2 determines that it satisfies the predetermined relay condition, and feeds back the information corresponding to the relay discovery request message to the remote UE. A corresponding response message, where the response message includes the radio access network connection state information of UE2, and the radio access network connection state information indicates that UE2 is in an idle state.

As another example, based on the scenario shown in FIG. 5 , the second sending means 103 of UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response message including UE1 The frequency information used between eNB and eNB, the frequency information indicates that the Uu link frequency used by UE1 is different from the PC5 link frequency; the second sending device 103 of UE2 determines that it meets the predetermined relay condition, and feeds back Following the response message corresponding to the discovery request message, the response message includes frequency information used between UE2 and the eNB, and the frequency information indicates that the Uu link frequency used by UE2 is the same as the PC5 link frequency.

As another example, based on the scenario shown in FIG. 5 , the second sending means 103 of UE1 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response message including UE1 The radio access network connection state information and the frequency information used between UE1 and eNB, the radio access network connection state information indicates that UE1 is in the RRC connection state, and the frequency information indicates the Uu link frequency and PC5 link frequency used by UE1 The frequencies are different; the second sending means 103 of UE2 determines that it satisfies the predetermined relay condition, and feeds back a response message corresponding to the relay discovery request message to the remote UE, the response message including the wireless access network connection status information of UE2 and the UE2 The frequency information used with the eNB, the radio access network connection status information indicates that UE2 is in an idle state, and the frequency information indicates that the Uu link frequency used by UE2 is the same as the PC5 link frequency.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limit the present invention. Those skilled in the art should understand that when any predetermined relay condition is met, the remote UE is fed back to the remote UE The implementation of the response message corresponding to the above relay discovery request message should be included in the scope of the present invention.

The first receiving module 104 of the remote UE receives a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE.

It should be noted that when there are multiple candidate relay UEs within the coverage of the network to feed back response messages to the remote UE, the first receiving unit 104 of the remote UE performs operations multiple times to respectively receive each of the multiple candidate relay UEs. Response messages corresponding to relay discovery request messages fed back by candidate relay UEs.

The selection means 105 of the remote UE selects one of the at least one candidate relay UE according to the response message and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE. The candidate relay UE serves as a relay UE for the remote UE.

Wherein, the link quality is the D2D link quality between the remote UE and the candidate relay UE; when the candidate relay UE is connected to the remote UE through the PC5 interface, the link quality is the PC5 link quality.

As an example, based on the scenario shown in Figure 5, the response message fed back by UE1 includes the radio access network connection status information of UE1, and the radio access network connection status information indicates that UE1 is in the RRC connection state; the response message fed back by UE2 includes UE2's Radio access network connection status information, the radio access network connection status information indicates that UE2 is in an idle state; the selection means 105 of the remote UE determines the measured link quality between the remote UE and UE1 and the link quality between the remote UE and UE2 If the link quality between UE1 and UE2 satisfies the predetermined link quality condition (for example, the link quality is higher than the predetermined quality threshold), the selection means 105 of the remote UE selects from UE1 and UE2 the RRC connection according to the response message fed back by UE1 and UE2. The UE1 in the state is an intermediate UE of the remote UE. It should be noted that if the relay UE selected by the selection means 105 is in an idle state, the relay UE needs to initiate a random access procedure to establish an RRC connection. These situations will lead to the failure of the relay UE to successfully establish the RRC connection with the serving base station, which makes the remote UE have to reselect the relay UE, which will cause service delay; therefore, preferably, when the link quality meets In the case of predetermined link quality conditions, the remote UE preferentially selects a candidate relay UE currently in the RRC connection state as the relay UE of the remote UE, which can effectively avoid service delays caused by RRC connection failure.

As another example, assume that UE1 and UE2 can support simultaneous processing of cellular communication and D2D communication of different frequencies; based on the scenario shown in Figure 5, the response message fed back by UE1 includes the frequency information used between UE1 and eNB, and the frequency information indicates that UE1 The frequency of the Uu link used is different from that of the PC5 link; the response message fed back by UE2 includes the frequency information used between UE2 and eNB, which indicates that the frequency of the Uu link used by UE2 is the same as the frequency of the PC5 link; The selection means 105 of the UE determines that the measured link quality between the remote UE and UE1 and the link quality between the remote UE and UE2 all meet a predetermined link quality condition (for example, the link quality is higher than a predetermined quality threshold) , then the selecting means 105 selects UE1 with different Uu link frequency and PC5 link frequency from UE1 and UE2 as the intermediate UE of the remote UE according to the response messages fed back by UE1 and UE2. It should be noted that the selected relay UE uses different frequencies to perform cellular communication and D2D communication respectively, which can effectively avoid the conflict between cellular communication and D2D communication in the relay UE.

As a preferred solution, the response message fed back by the candidate relay UE also includes the quality of the backhaul link, and the selection means 105 of the remote UE is based on the quality of the backhaul link of at least one candidate relay UE, the connection state information of the radio access network and/or frequency information, and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE, and selecting a candidate relay UE from the at least one candidate relay UE as the relay of the remote UE UE.

As an example, based on the scenario shown in FIG. 5, when both UE1 and UE2 meet the predetermined link quality conditions, and UE1 and UE2 have similar backhaul link quality (the backhaul link quality in this scenario is Uu link quality ), the selection means 105 of the remote UE preferentially selects UE1 in the RRC connected state as the relay UE of the remote UE.

It should be noted that during this discovery period, when the remote UE does not select a suitable relay UE (for example, the link quality between the candidate relay UE and the candidate relay UE is lower than the predetermined quality threshold), the remote UE will During this period, step S101 is repeated to broadcast or multicast the relay discovery request message again.

It should be noted that the above example is only to better illustrate the response message of the present invention, and the remote UE and the at least one technical solution measured by the remote UE, rather than limiting the present invention, those skilled in the art should It is understood that any implementation of selecting a candidate relay UE from the at least one candidate relay UE as the relay UE of the remote UE according to the link quality between the candidate relay UEs shall be included in this document. within the scope of the invention.

After the relay UE of the remote UE is selected, the first establishing means 106 of the remote UE performs an operation, and the second establishing means 107 of the relay UE performs an operation, so that the remote UE can communicate with the network through the selected relay UE communication.

The first establishing module 106 of the remote UE establishes direct communication with the relay UE, so that the remote UE communicates with the network through the relay UE.

During the establishment of direct communication (direct communication) between the remote UE and the relay UE, cross-authentication and D2D link security setting may be performed between the remote UE and the relay UE first.

Specifically, the first establishing means 106 of the remote UE initiates a direct communication request to the relay U1, and establishes the direct communication with the relay UE based on the interaction with the relay UE.

The second establishing means 107 in the relay UE selected by the remote UE establishes direct communication with the remote UE, and establishes a data connection with the cellular network and the core network, so as to serve as the relay UE of the remote UE enabling the remote UE to communicate with the network through the relay UE.

After the operation performed by the second establishing means 107, data transmission is performed between the remote UE and the network through the selected relay UE. The selected relay UE can rebroadcast unicast traffic (including uplink and downlink traffic) between the remote UE and the network.

As a preferred solution, after the operation performed by the second establishing means 107, the second device in this embodiment further includes a fourth sending means (not shown in the figure), and the first device further includes a third receiving means (not shown in the figure) . The fourth sending means in the selected relay UE sends relay monitoring information to the remote UE; the third receiving means of the remote UE receives the relay monitoring information from the relay UE, and measures Channel quality between the remote UE and the relay UE.

Preferably, the relay monitoring information is a discovery message.

Preferably, the fourth sending means of the selected relay UE periodically sends the relay monitoring information to the remote UE, and the third receiving means of the remote UE periodically receives the relay monitoring information from the relay UE, and according to The received relay monitoring information measures the channel quality (such as D2D link quality) between the remote UE and the relay UE.

It should be noted that the remote UE can measure the quality of the link between the remote UE and the relay UE by decoding the relay monitoring information, and learn other information, such as the quality of the backhaul link of the relay UE.

Preferably, the first device in this preferred solution further includes a second reselection device (not shown in the figure). When it is detected that the channel quality is lower than the predetermined threshold, the second reselection device of the remote UE triggers the first sending device 101 to repeatedly perform operations to re-broadcast or multicast the relay discovery request message to the network coverage area to reselect Relay UE.

Specifically, when it is detected that the channel quality between the remote UE and the selected relay UE is within a predetermined threshold, the second reselecting device of the remote UE determines that the relay UE is no longer suitable as an intermediate channel between the remote UE and the network. Next, the second reselecting device terminates its service and releases the direct communication connection with the current relaying UE, and triggers the first sending device 101 to repeatedly perform operations to re-broadcast or multicast the relay discovery request message to the network coverage area, to reselect a relay UE.

In the prior art, operators usually pre-deploy relays (similar to small base stations from the perspective of UEs) at specific locations, so that remote UEs located outside the coverage of the network can communicate with the network through the relays. This solution requires The deployment cost is huge, and once the repeater fails, the remote UE will no longer be able to communicate with the network.

At present, a solution of introducing UE-to-network relay (relay) to support coverage extension has been proposed, that is, a remote UE can select a user equipment within the coverage of the network as the relay UE of the remote UE, so as to communicate with However, in the prior art, when the remote UE selects the relay UE, it only considers whether the link between the remote UE and the relay UE satisfies the conditions, and how to trigger the remote UE to reselect the relay UE is still under study middle. The present invention finds the following problems in the prior art: 1) The remote UE does not consider the radio access network connection status of the candidate relay UE in the process of selecting the relay UE, so the selected relay UE may be idle In this case, the selected relay UE needs to initiate a random access procedure to establish an RRC connection. If the relay UE cannot successfully establish an RRC connection with the serving base station, the remote UE must reselect the relay UE , which will cause service delay; 2) After the relay UE starts serving the remote UE, the link quality between the relay UE and the serving base station may be poor, or due to the limitation of the relay UE itself, the The relay UE continues to act as a remote UE, but relay UE reselection in such situations is not supported in the prior art.

According to the solution of this embodiment, the remote UE can select a most suitable candidate relay UE from the at least one candidate relay UE according to the radio access network connection status information and/or frequency information of the at least one candidate relay UE to serve as the relay UE for the remote UE; by selecting a candidate relay UE in the RRC connection state as the relay UE, it is possible to avoid the service delay caused by the inability to successfully establish the RRC connection after the relay UE is selected; At the same time, a candidate relay UE for cellular communication and D2D communication with different frequencies is used as a relay UE to avoid conflicts between cellular communication and D2D communication in the selected relay UE; Select a relay UE among the relay UEs. This selection mechanism does not require the operator to pre-deploy the relay, and it is extremely flexible, which greatly saves operating costs, and is especially suitable for geographically inconvenient deployment of relays. disaster area; this embodiment provides a relay UE reselection mechanism, and the remote UE can determine whether to reselect the relay UE according to the relay monitoring information from the selected relay UE, that is, The remote UE can know the state of the relay UE itself (such as power or power, etc.) and/or the link quality between the relay UE and the serving base station through the relay monitoring information, so that the current relay UE is no longer suitable as the remote UE. When relaying the UE, the reselection mechanism of the relay UE can be triggered in time.

Fig. 4 is a schematic structural diagram of a system for selecting a relay UE according to another embodiment of the present invention. The system includes a remote UE located out of network coverage and a candidate relay UE located within network coverage; wherein, the remote UE includes a first device for selecting a relay UE, and the first device includes a first sending device 101 , the first receiving means 104, the selecting means 105, the first establishing means 106, the second receiving means 109 and the first reselecting means 110; wherein, the candidate relay UE includes the first relay UE for assisting the remote UE to select the relay UE Two means, the second means includes a fourth receiving means 102 , a second sending means 103 , a second establishing means 107 and a third sending means 108 . Wherein, the first sending means 101, the first receiving means 104, the selecting means 105, the first establishing means 106, and the fourth receiving means 102, the second sending means 103, and the second establishing means 107 have been described with reference to Fig. 3 be described in detail and will not be repeated here.

In this embodiment, after the first establishing means 106 and the second establishing means 107 perform operations, the third transmitting means 108 of the candidate relay UE, and the second receiving means 109 and the first reselecting means 110 of the remote UE perform operations to trigger the operation of reselecting the relay UE.

When the relay UE reselection trigger condition is satisfied, the third sending module 108 of the relay UE (that is, the candidate relay UE selected as the relay UE) sends the relay UE reselection indication information to the remote UE, the The relay UE reselection instruction information is carried by the MAC layer control information in the direct communication data packet.

Wherein, the relay UE reselection trigger condition includes any condition used to trigger the current relay UE to suggest to the remote UE to reselect its relay UE, such as the current power level is lower than a predetermined power value, and the link quality with the serving base station Below a predetermined threshold, power below a predetermined power value, etc. It should be noted that when the relay UE reselection trigger condition is satisfied, it means that the current relay UE is no longer suitable as the relay UE of the remote UE.

Wherein, the relay UE reselection indication information includes any information used to indicate that the relay UE can be reselected; preferably, the relay UE reselection indication information includes but not limited to: the current relay UE power information, Power information, link quality information with the serving base station, or information that directly indicates that the relay UE is recommended to be reselected (for example, "1" indicates that the relay UE is recommended to be reselected).

Preferably, the relay UE reselection indication information is added to the stuffing bits in the header of the MAC layer control information, and/or, the MAC control element of the MAC layer control information.

For example, Fig. 6 is a schematic diagram of the MAC PDU format in SL-SCH of an example of the present invention, wherein "MAC Control element 1" is a newly added MAC control element, when the relay UE detects that its power is lower than the predetermined power value , the third sending module 108 of the relay UE sends relay UE reselection indication information to the remote UE, and the relay UE reselection indication information is added to "MAC Control element 1" shown in FIG. 6 .

As another example, FIG. 7 is a schematic diagram of an example SL-SCH MAC subheader, where "R" represents a padding bit, and there are four reserved bits in the subheader; when the relay UE detects that its Uu link quality is low When the predetermined threshold is reached, the third sending module 108 of the relay UE sends relay UE reselection indication information to the remote UE, and the relay UE reselection indication information is added to the stuffing bits shown in FIG. 7 .

For another example, the third sending means 108 of the relay UE adds its Uu link quality to the padding bit of the header of the MAC control information, and adds its current battery power to the newly added MAC control element in the MAC control information, And send to the remote UE through the MAC layer.

It should be noted that the above examples are only to better illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Those skilled in the art should understand that any Sending the relay UE reselection indication information, the realization manner that the relay UE reselection indication information is carried by the MAC layer control information in the direct communication data packet shall be included in the scope of the present invention.

The second receiving module 109 of the remote UE receives MAC layer control information in the direct communication data packet from the selected relay UE, where the MAC layer control information includes relay UE reselection indication information.

Specifically, the second receiving module 109 of the remote UE receives the MAC layer control information in the direct communication data packet from the selected relay UE, and extracts the relay UE reselection indication information carried in the MAC layer control information.

For example, the third sending device of the relay UE adds the relay UE reselection indication information to "MAC Control element 1" shown in FIG. 6, and sends it to the remote UE through the MAC layer; the second receiving device 109 of the remote UE The MAC layer control information shown in FIG. 6 from the relay UE is received, and the relay UE reselection indication information carried by "MAC Control element 1" is extracted.

For another example, the third sending means 108 of the relay UE adds the relay UE reselection indication information to the first padding bit shown in FIG. 7, and sends it to the remote UE through the MAC layer; the second receiving means of the remote UE 109 receives the MAC layer control information shown in FIG. 7 from the relay UE, and extracts the relay UE reselection indication information carried in the first padding bit.

It should be noted that the above examples are only to better illustrate the technical solution of the present invention, rather than limit the present invention. Those skilled in the art should understand that any MAC received in the direct communication data packet from the selected relay UE Layer control information, the implementation manner of relaying UE reselection instruction information included in the MAC layer control information should be included in the scope of the present invention.

When it is determined according to the relay UE reselection indication information that the relay UE needs to be reselected, the first reselection device 110 of the remote UE triggers the first sending device 101 to repeatedly perform operations to re-broadcast or multicast the relay to the network Discovery request message.

Wherein, the first reselection module 110 of the remote UE may determine whether to reselect the relay UE according to the reselection indication information in various ways.

For example, after the second receiving module 109 receives the relay UE reselection indication information from the relay UE, the first reselecting module 110 directly determines that the relay UE needs to be selected.

For another example, the first reselection module 110 of the remote UE determines whether to The relay UE needs to be reselected.

For another example, the first reselection module 110 of the remote UE determines whether to reselect the relay UE according to the received relay UE reselection indication information and relay monitoring information.

It should be noted that, when the remote UE determines that the relay UE does not need to be reselected, the remote UE does not perform any operation.

It should be noted that the above examples are only to better illustrate the technical solutions of the present invention, rather than limiting the present invention. Those skilled in the art should understand that any When following the UE, the implementation manners in which the remote UE repeats step S101 should be included in the scope of the present invention.

According to the solution of this embodiment, another reselection mechanism for the relay UE is provided. When the selected relay UE is not suitable to continue to be a relay, it can send a relay UE reselection indication to the remote UE through the MAC layer. information to suggest or notify the remote UE to reselect the relay UE. This reselection mechanism can save a lot of radio resources, and the remote UE can trigger the reselection of the relay UE in time when the current relay UE is no longer suitable as the relay UE of the remote UE. selection mechanism; the relay UE reselection indication information may include link quality related information between the relay UE and the serving base station, so that the remote UE can more timely and accurately determine whether to reselect the relay UE.

It should be noted that the present invention can be implemented in software and/or a combination of software and hardware. For example, each device of the present invention can be implemented by using an application specific integrated circuit (ASIC) or any other similar hardware devices. In one embodiment, the software program of the present invention can be executed by a processor to realize the steps or functions described above. Likewise, the software program (including associated data structures) of the present invention can be stored in a computer-readable recording medium such as RAM memory, magnetic or optical drive or floppy disk and the like. In addition, some steps or functions of the present invention may be implemented by hardware, for example, as a circuit that cooperates with a processor to execute each step or function.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned. In addition, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A plurality of units or devices stated in the system claims may also be realized by one unit or device through software or hardware. The words first, second, etc. are used to denote names without implying any particular order.

Claims (15)

1. A first device for selecting a relay UE among remote UEs, wherein the first device comprises: The first sending device is used to broadcast or multicast the relay discovery request message to the network coverage outside the network coverage; The first receiving means is configured to receive a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE, where the response message includes radio access network connection status information and /or frequency information used between the candidate relay UE and its serving cell; selecting means, configured to select a candidate from the at least one candidate relay UE according to the response message and the link quality between the remote UE and the at least one candidate relay UE measured by the remote UE a relay UE serving as a relay UE for the remote UE; First establishing means, configured to establish direct communication with the relay UE, so that the remote UE communicates with the network through the relay UE. 2. The first device according to claim 1, wherein the first device further comprises the following means for performing operations after the first establishing means: The second receiving device is configured to receive MAC layer control information in the direct communication data packet from the relay UE, where the MAC layer control information includes relay UE reselection indication information; The first reselecting means is configured to trigger the first sending means to repeatedly execute the operation when it is determined according to the relay UE reselection indication information that the relay UE needs to be reselected. 3. The first device according to claim 2, wherein the relay UE reselection indication information is added to the padding bits in the header of the MAC layer control information, and/or the MAC layer control information information in the MAC control element. 4. The first device according to any one of claims 1 to 3, wherein the first device further comprises the following means for performing operations after the first establishing means: A third receiving device, configured to receive relay monitoring information from the relay UE, and measure the channel quality between the remote UE and the relay UE according to the relay monitoring information; Wherein, the first device also includes: The second reselecting means triggers the first sending means to repeat operations when it detects that the channel quality is lower than a predetermined threshold. 5. A second device for assisting a remote UE in selecting a relay UE, wherein the second device comprises: A fourth receiving means, configured to receive a relay discovery request message from a remote UE; The second sending means is configured to feed back a response message corresponding to the relay discovery request message to the remote UE when a predetermined relay condition is satisfied, wherein the response message includes the wireless access of the candidate relay UE Network connection status information and/or frequency information used between the candidate relay UE and its serving cell; Wherein, the second means also includes the following means for performing operations after the feedback means: The second establishing means is configured to establish direct communication with the remote UE, and establish a data connection with the cellular network and the core network, so as to serve as a relay UE for the remote UE to allow the remote UE to pass through the intermediate Then the UE communicates with the network. 6. The second device according to claim 5, wherein the second device further comprises the following means for performing operations after the second establishing means: The third sending means is configured to send relay UE reselection indication information to the remote UE when the relay UE reselection trigger condition is met, and the relay UE reselection indication information is controlled by the MAC layer in the direct communication data packet information carry. 7. The second device according to claim 6, wherein the relay UE reselection indication information is added to the padding bits in the header of the MAC layer control information, and/or the MAC layer control information information in the MAC control element. 8. The second device according to any one of claims 5 to 7, wherein the second device further comprises the following means for performing operations after the second establishing means: The fourth sending device is configured to send relay monitoring information to the remote UE. 9. A method for selecting a relay UE among remote UEs, wherein the method comprises: a. The remote UE broadcasts or multicasts a discovery request message outside the network coverage to the network coverage; b. Receive a response message corresponding to the relay discovery request message fed back by at least one candidate relay UE, wherein the response message includes radio access network connection status information and/or candidate relay of the candidate relay UE Frequency information used between the UE and its serving cell; c. Select a candidate relay UE from the at least one candidate relay UE according to the response message and the link quality measured by the remote UE between the remote UE and the at least one candidate relay UE being a relay UE for the remote UE; d. Establishing direct communication with the relay UE to enable the remote UE to communicate with the network through the relay UE. 10. The method according to claim 9, wherein, after said step d, the method further comprises: receiving MAC layer control information in the direct communication data packet from the relay UE, where the MAC layer control information includes relay UE reselection indication information; When it is determined according to the relay UE reselection indication information that the relay UE needs to be reselected, the step a is repeated. 11. The method according to claim 10, wherein the relay UE reselection indication information is added to the padding bits in the header of the MAC layer control information, and/or, the MAC layer control information in the MAC control unit. 12. A method for assisting a remote UE in selecting a relay UE, wherein the method comprises: A receives a relay discovery request message from a remote UE; B. When the predetermined relay condition is satisfied, feed back a response message corresponding to the relay discovery request message to the remote UE, wherein the response message includes the radio access network connection status information of the candidate relay UE and/or or frequency information used between the candidate relay UE and its serving cell; Wherein, after said step B, the method also includes: X establishes direct communication with the remote UE, and establishes a data connection with the cellular network and the core network, so as to act as a relay UE for the remote UE to enable the remote UE to communicate with the network through the relay UE . 13. The method according to claim 12, wherein, after step X, the method further comprises: When the relay UE reselection triggering condition is satisfied, the relay UE reselection indication information is sent to the remote UE, and the relay UE reselection indication information is carried by the MAC layer control information in the direct communication data packet. 14. The method according to claim 13, wherein the relay UE reselection indication information is added to the padding bits in the header of the MAC layer control information, and/or, the MAC layer control information in the MAC control unit. 15. A system for selecting a relay UE, wherein the system includes a remote UE located outside the coverage of the network and a candidate relay UE located within the coverage of the network, the remote UE comprising The first device according to any one of claims 5 to 8, wherein the candidate relay UE includes the second device according to any one of claims 5 to 8.