WO2011022981A1

WO2011022981A1 - Handoff method and terminal and server for realizing handoff method

Info

Publication number: WO2011022981A1
Application number: PCT/CN2010/072241
Authority: WO
Inventors: 吕永
Original assignee: 中兴通讯股份有限公司
Priority date: 2009-08-28
Filing date: 2010-04-27
Publication date: 2011-03-03
Also published as: CN101646216A

Abstract

A handoff method and a terminal and server for realizing the handoff method are provided, which can furthest ensure the continuity of service when the terminal is carrying out the handoff between wireless access networks. Said handoff method comprises: when the terminal finds out the quality of a current link L1 which has been established is less than a preset value, the terminal establishes a link L2 with the server on another network different from the network where said link L1 is located, or respectively establishes several links L2 with said server on a plurality of other networks different from the network where said link L1 is located, and initiates the same service as that on said link L1 with said server on said link(s) L2, then said terminal selects the link with better quality as the link for said service; thus the continuity of the service between different access networks is maintained.

Description

Switching method and terminal and server for implementing the same

The present invention relates to the field of IP-based communication services, and in particular, to a handover method and a terminal and a server for implementing the same. Background technique

With the development of wireless technology, various wireless access technologies (called RATs) have emerged, and correspondingly generate many wireless networks based on different technologies to meet the diverse communication needs of different users. These wireless networks have different characteristics because of the different wireless access technologies. It is usually impossible to make a network cover all locations, and a network cannot satisfy all the communication needs of a user. But if these networks work together to provide services to users, they can cover most locations and meet most of the user's needs.

In order to utilize the capabilities of multiple wireless networks, at the radio access technology level, a multi-mode terminal appears, that is, a mobile terminal simultaneously supports multiple radio access technologies, thereby providing the user with simultaneous access to multiple wireless networks. The ability to allow the user to simultaneously utilize the services provided by multiple wireless networks.

At the service level, IP technology makes it possible to decouple upper-layer services in mobile terminals from underlying wireless access technologies. Most wireless access networks now support IP transmission technology. For upper layer services, as long as the underlying transport protocol is considered to be IP-based, there is no need to understand the details of the underlying access technology. This makes IP-based service development independent of the underlying wireless access technology, and IP-based communication services can run on all IP-enabled wireless access networks.

However, despite the use of the above-described multimode wireless access terminal and IP-based service technology, the user can simply consume the same service on different wireless access networks, but this approach does not solve the problem of business continuity. For example, when there are two wireless networks N1 and N2, when the user performs VoIP service on the N1 network, the call process is normal; but because of the mobility of the mobile terminal, the user is likely to find that the N1 network is unavailable during the call. At this point, even if the N2 network is available, the user has to disconnect the call in progress and then redial the number on N2 to continue the call. This causes the VoIP service to be interrupted when switching between access networks, which destroys its continuity. Traditional The telecommunication network introduces an IMS network architecture when solving this problem. This network architecture requires interfaces between different radio access networks and coordinates spontaneously during terminal handover. However, in the actual network, the IMS network architecture has not been used on a large scale, and there are still many networks (such as the Internet) that are not traditional telecommunication networks and cannot adopt the IMS network architecture. Summary of the invention

The technical problem to be solved by the present invention is to provide a handover method and a terminal and a server for implementing the same, which can ensure maximum continuity of service continuity when the terminal performs radio access network handover.

In order to solve the above problem, the present invention provides a handover method, including: when a terminal finds that the quality of the currently established link L1 is less than a preset value, and the server on another network different from the network where the link L1 is located Establishing a link L2, or establishing a plurality of links L2 with the server on different networks different from the network where the link L1 is located, and establishing the same with the server on the link L2. The service on the link L1 has the same service, and then the terminal selects the link with the good quality as the service in the link; thus maintaining service continuity between different access networks.

In the method, the step of establishing, on the link L2, the same service as the service on the link L1 with the server includes: the terminal sending a service establishment request to the server on the link L2, and The service establishment request carries the service identifier of the service on the link L1, and after receiving the service establishment request, the server establishes the same service as the service of the link L1 according to the service identifier.

In the foregoing method, after the service is the same as the service on the link L1, the method further includes: the terminal and the server receiving and/or transmitting service data on the link L1, and The service data is received and/or transmitted on the link L2, and the data transmitted on the link L1 and the link L2 is the same.

In the foregoing method, the terminal finds that the quality of the currently established link L1 is less than the preset value, and the terminal determines that the link L1 is determined when one or more of the following parameters are greater than the preset value in the preset time. The quality is less than the preset value: packet loss rate, bit error rate, and transmission delay; and/or, the terminal determines the link L1 when one or more of the following parameters are less than the preset value within the preset time The quality is less than the preset value: wireless signal strength and wireless signal quality. In the above method, after the terminal and the server receive the service data on the link L1 and the link L2, the method further includes: combining the received service data in any of the following manners: (a) according to the two chains The signal strength of the path, only processing the data on the stronger link, discarding the data on the weaker link; (b) mixing the data on the two received links together, removing the duplicated data blocks, leaving The next data block is processed as a unique business data.

In the above method, the step of the terminal selecting the link with the good quality as the service in the link includes: after receiving and/or transmitting data on the link L1 and the link L2 for a period of time, the terminal compares the time The signal quality of each link is selected, and the link with good signal quality is selected, and only the service data is received and/or transmitted on the link.

In the above method, after the mixing step, the method further includes: determining, by the terminal and the server, whether there is a duplicate data block according to a transmission control protocol sequence number of the data block or a user datagram protocol sequence number.

In order to solve the above problem, the present invention further provides a terminal for implementing handover, which includes a determining unit, a link establishing unit, and a link selecting unit, where:

The determining unit is configured to: when it is determined that the quality of the currently established link L1 is less than a preset value, triggering the link establishing unit to establish a new link;

The link establishing unit is configured to: establish, according to the triggering by the determining unit, a link L2 with a server on another network different from the network where the link L1 is located, or a network different from the link L1 Establishing a plurality of links L2 with the server on the other plurality of networks, and establishing the same service as the service on the link L1 with the server on the link L2;

The link selection unit is configured to: select a good quality link from the links L1 and L2 as a link of the service;

Thereby supporting business continuity between different access networks.

In the terminal, the link establishing unit is further configured to: send a service establishment request to the server on the link L2, and carry the service identifier of the service on the link L1 in the service establishment request, so that The server establishes the same service as the service on the link L1.

The terminal further includes: a data transceiver unit configured to: send service data on the link L1 At the same time, the service data is also transmitted on the link L2, and the data transmitted on the two links is the same, and the service data is received on the link L1 and the link L2.

In the terminal, the determining unit determines that the quality of the currently established link L1 is less than the preset value, that is, when one or more of the following parameters are greater than the preset value in the preset time, the link L1 is The quality is less than the preset value: packet loss rate, bit error rate and transmission delay; and/or, the quality of the link L1 is less than the preset when one or more of the following parameters are less than the preset value within the preset time Value: Wireless signal strength and wireless signal quality.

In the terminal, the data transceiver unit is further configured to: after receiving the service data on the link L1 and the link L2, combine the received service data by using any one of the following methods: (a) according to the two links Signal strength, only processing data on stronger links, discarding data on weaker links; (b) mixing data on the two received links together, removing duplicate data blocks, leaving the remaining data The block is processed as a unique business data.

In the terminal, the link selection unit further includes: a comparison module and a selection module: the comparison module is configured to: compare signal quality of each link in the link L1 and the link L2 in a period of time; the selection module The method is set to: select a link with good signal quality according to the signal quality of each link; the terminal only receives and/or transmits service data on the link selected by the selection module.

In order to solve the above problems, the present invention also provides a server for implementing handover, which includes a link establishment unit and a service establishment unit, where:

The link establishing unit is configured to: establish one or more links L2 other than the currently established link L1, and the network where the link L2 is located is different from the network where the link L1 is located;

The service establishing unit is configured to establish, with the terminal, the same service on the link L2 as that on the link L1.

The server further includes: a data transceiving unit configured to receive the service data on the link L1 and the link L2, and combine the received service data in any of the following manners: (a) according to the two chains The signal strength of the path, only processing the data on the stronger link, discarding the data on the weaker link; (b) mixing the data on the two received links together, removing the duplicated data blocks, leaving The next data block is processed as a unique business data. By adopting the technical solution of the present invention, the continuity of the service can be significantly improved. Taking the voice service as an example, according to the prior art, the L1 link is unreliable, and the terminal must first disconnect the L1 link and then establish the L2 link, causing the voice service to be interrupted. After the technical solution of the present invention is used, when the L1 link is still available, the service link is initiated on the L2 link in advance. When the quality of the L1 is insufficient to support the voice service, and the L2 link is stable, The L1 link is disconnected, so that there is no interruption in the voice service. Moreover, the solution of the present invention only needs to modify the service logic of the terminal side and the service logic of the server side, and does not need to change the hardware design, and has no additional requirements for the wireless access network, and is economical to implement. BRIEF abstract

1 is a schematic diagram of establishing a link between a terminal and a server in the prior art;

2 is a schematic diagram of establishing a plurality of links between a terminal and a server through multiple networks according to the present invention; FIG. 3 is a schematic diagram of connecting a terminal of the present invention to a server after switching from the current network to another network; FIG. 4 is a flowchart of the method of the present invention. Preferred embodiment of the invention

The present invention provides a handover method and a terminal and a server for implementing the same, which can maintain service continuity among different access networks, and the multimode terminal finds that the signal of the currently established link L1 is unstable (for example, the signal quality is smaller than the preset). a value L2, establishing a link L2 with a server (such as a service server) on another network different from the network where the link L1 is located, or separately on the other plurality of networks different from the network where the link L1 is located The server establishes a plurality of links L2, and establishes the same service as the service on the link L1 with the server on the link L2, and then the terminal selects a link with good quality as the service among the plurality of links.

The embodiment provides a switching system, including a terminal and a server;

a terminal, configured to establish a link L2 with the server on another network different from the network where the link L1 is located when the signal quality on the established link L1 is less than a preset value, and on the link L2 The server establishes the same service as the service on the link L1, and is also used to select the quality in the two links. Better as a link to the service.

The terminal establishes the same service as the service on the link L1 with the server on the link L2. When the terminal sends a service establishment request to the server, the terminal carries the service identifier of the service. After receiving the service establishment request, the server establishes the same service as the service. Business;

The terminal is further configured to send the service data on the link L1 while transmitting the service data on the link L1, and the data sent on the two links is the same, and is also used to receive the service data on the link L2; It is used to transmit service data on the link L1 while transmitting the service data on the link L1, and the data transmitted on the two links is the same, and is also used to receive the service data on the link L2.

The terminal finds that the quality of the currently established link L1 is less than the preset value. The quality of the link L1 is less than the preset value when one or more of the following parameters are greater than the preset value in the preset time: Packet loss rate , bit error rate and transmission delay; and / or,

The quality of the link L1 is less than the preset value when one or more of the following parameters are less than the preset value within the preset time: wireless signal strength and wireless signal quality.

The terminal and the server receive the service data on the link L1 and the link L2, and are also used to merge the received service data in any of the following manners:

(a) According to the signal strength of the two links, only the data on the stronger link is processed, and the data on the weaker link is discarded;

(b) mixing the data on the two received links, removing duplicate data blocks, and processing the remaining data blocks as unique service data; the terminal and the server according to the TCP of the data block (transmission control) Protocol) Serial number or UDP (User Datagram Protocol) sequence number determines whether it is a duplicate data block.

The terminal selects the link with the better quality as the service in the two links, and after the data is received and/or transmitted on the link L2 for a period of time, the terminal compares the link L1 and the link L2 during the period. The signal quality, if the signal quality of the link L1 is better than the signal quality of the link L2, only the service data is received and/or transmitted on the link L1, if the signal quality of the link L2 is better than the signal of the link L1 Quality then receives and/or transmits traffic data only on the link L2.

The embodiment provides a terminal for implementing handover, which includes a determining unit and a link establishing unit. And a link selection unit, wherein:

The determining unit is configured to: when it is determined that the signal quality on the currently established link L1 is less than a preset value, trigger the link establishing unit to establish a new link;

Thereby supporting business continuity between different access networks.

Preferably, the link establishing unit is further configured to: send a service establishment request to the server on the link L2, and carry the service identifier of the service on the link L1 in the service establishment request, so that the The server establishes the same service as the service on the link L1;

Preferably, the terminal further includes: a data transceiver unit configured to: transmit service data on the link L1 while transmitting service data on the link L2, and send the same data on the two links, and Traffic data is received on link L1 and link L2.

Preferably, the determining unit determines that the quality of the currently established link L1 is less than the preset value, that is, the quality of the link L1 is less than when the one or more of the following parameters are greater than the preset value in the preset time. Default value: packet loss rate, bit error rate, and transmission delay; and/or, when one or more of the following parameters are less than the preset value within the preset time, the quality of the link L1 is less than a preset value: Wireless signal strength and wireless signal quality.

Preferably, the data transceiver unit is further configured to: after receiving the service data on the link L1 and the link L2, combine the received service data in any of the following manners: (a) according to the signals of the two links Intensity, only processing data on stronger links, discarding data on weaker links; (b) mixing data on the two received links together, removing duplicate data blocks, leaving the remaining data blocks Processing as a unique business data.

Preferably, the link selection unit further includes: a comparison module and a selection module: the comparison module is configured to: compare signal quality of each link in the link L1 and the link L2 in a period of time; The selection module is configured to: select a link with good signal quality according to the signal quality of each link; the terminal receives and/or transmits service data only on the link selected by the selection module.

The embodiment provides a server for implementing handover, which includes a link establishing unit and a service establishing unit, where:

Preferably, the server further includes: a data transceiving unit configured to receive the service data on the link L1 and the link L2, and combine the received service data in any of the following manners: (a) according to The signal strength of the two links, only processing the data on the stronger link, discarding the data on the weaker link; (b) mixing the data on the two received links together to remove duplicate data blocks , the remaining data blocks are processed as unique business data.

This embodiment provides a handover method for maintaining service continuity between different access networks. As shown in FIG. 4, the method includes the following steps:

Step 101: The terminal T establishes a service link L1 with the server on the network N1, and initiates the service 8. At this point, the business data between the T and the server is transmitted through L1. On the server, each S has a unique identifier SID, and terminal T also has this SID;

Step 102: The terminal T detects the link quality of the link L1, and based on a certain criterion, if the link quality of the L1 is found to be insufficient, the search for the backup network begins.

The foregoing method for determining the quality of the link may be based on a statistical characteristic of the IP packet, such as one or more parameters of the packet loss rate, the bit error rate, the transmission delay, and the like being greater than a preset value within a preset time; The terminal may detect that the quality of the wireless link of the link is unstable within a preset time, that is, one or more of the following signals are less than a preset value within a preset time: wireless signal strength or wireless signal quality. Wait.

Step 103: The terminal T discovers the standby network N2, establishes a service link L2 with the server on the N2, and sends a service establishment request on the L2, where the service establishment request includes the service on the L1. S SID (service identifier), in this way requesting the server to initiate service S on L2;

Step 104: After receiving the service establishment request, the server establishes a service S with the terminal on the link L2 according to the SID contained therein, and returns an acknowledgement response to the terminal; while the data of the service S is sent on the L1, Sending on L2, and starting to receive the service data uploaded by L2; Step 105: After receiving the acknowledgment response from the server, the terminal 确定 determines that the service S on the link L2 is successfully established, and sends the S service data on the link L1. Also transmitting on link L2, and starting to receive data uploaded by L2;

Step 106: The terminal and the server can receive data on both L1 and L2, and the two channels of data are actually homologous, so the two channels of data can be combined, and the manner of combining can be one way. Any of the following:

(a) According to the signal strength of the two links, only the data on the stronger link is processed, and the data on the weaker link is discarded; for example, the signal on the link L1 is stronger than the link L2 at a certain moment. The signal then processes the received data on link L1, and at the next moment the signal on link L2 is stronger than the signal on link L1, then the received data on link L2 is processed.

(b) mixing the data on the two received links together, removing duplicate data blocks, and processing the remaining data blocks as unique service data; terminal T and server may be based on TCP UDP of the data block The serial number determines whether it is the same data block.

Combining the received data in the above manner can obtain a part of the gain;

Step 107: After receiving and/or transmitting data on the link L2 for a period of time, the terminal T may select a link with a better link quality as a chain used by the service S according to the link quality of the link L1 and the link L2. If the signal quality of L1 is better than the signal quality of L2, the terminal T may terminate the reception and/or transmission on L2 and return to the initial state. If the signal quality of L2 is better than the signal quality of L1, the terminal T may The link to L1 is disconnected, and only the service data is received and/or transmitted on link L2.

Therefore, regardless of the result of the terminal handover, the service S can be guaranteed to be continuous.

Applications

The following describes the present invention by taking a VoIP service on a dual-mode terminal supporting EVDO and WIFI as an example. When the quality of the EVDO network is degraded, the terminal needs to switch to the WIFI network. In the above, how to ensure business continuity by adopting the solution of the present invention. The server in this example is a VOIP service server.

Step 1: The terminal establishes a service session with the remote server on the EVDO network. During the process of establishing the service link, the remote server assigns a unique service identifier SID to the VoIP session and backs up the SID on the terminal.

The process of establishing a session is as follows: first, one or several Socket channels are established as a transmission link by using EVDO, and then a session process is established with the above remote server.

The above establishment session process may adopt an approach similar to the existing SIP protocol or H.323 protocol. After the session is successfully established, relevant voice and signaling data are transmitted on the transmission link. During the session establishment process, the remote server assigns the VoIP service a unique identifier SID, which may be globally unique, such as a URI, or may be unique on the server, such as an integer of a certain length. And after the session is successfully established, the SID is backed up on the terminal.

Step 2: During the service execution process, the terminal detects the link quality, and based on a certain criterion, finds that the quality of the service link on the established EVDO is unstable, and starts to search for the standby WIFI network.

The process of the above terminal searching for a standby WIFI network includes two cases. The first type is that the WIFI module is in the closed state before the terminal looks for the standby network. At this time, the terminal first opens the WIFI module, and then searches for a suitable network according to some preset manner. In another case, the WIFI module is located when the terminal is looking for the standby network. The status is turned on, and an alternate network is available. In this case, the existing alternative network can be used.

Step 3: The terminal establishes a second transmission link with the remote server on the alternative WIFI network, and establishes the same VoIP service with the remote server as the EVDO network on the transmission link, and the second transmission chain The voice and signaling data transmitted on the road is the same as the voice and signaling data transmitted on the first transmission link;

The process of establishing a session is as follows: First, establish one or several Sockets through the WIFI network. The channel acts as a transport link and then establishes a session with the remote server described above.

The above establishment session process may adopt an approach similar to the existing SIP protocol or H.323 protocol. After the session is successfully established, relevant voice and signaling data are transmitted on the transmission link. During the session establishment process, the terminal first needs to send a session establishment request to the server, and sends the previously backed up SID to the server in the request message;

Step 4: After the session is successfully established, the server and the terminal perform a "send and merge" operation on the relevant transmission link.

The sending and combining means that the server determines the corresponding VoIP service according to the SID uploaded by the terminal in the session establishment request, and the voice and signaling data generated by the VoIP service are previously transmitted with the terminal through the EVDO network (usually this transmission) The link includes one or more socket links), and is also sent on the newly established transmission link established through the WIFI network; the terminal establishes the signaling and voice data generated by the VoIP service before establishing the EVDO network with the server. The transmission link (usually this transmission link includes one or more socket links) is also sent on the newly established transmission link established through the WIFI network;

Step 5: The server and the terminal perform the reception and merge. Receiving a merge means that the server and the terminal are both

Receiving VoIP service data on the transmission link established by the EVDO network, receiving VoIP service data on the transmission link established by the WIFI network, and merging the received data;

Step 6: For the data received on the newly established transmission link, both the server and the terminal should monitor the quality of the transmission link according to certain criteria to determine whether the link is stable.

The criterion may be based on statistical characteristics of the IP packet, such as packet loss rate, bit error rate, transmission delay, etc., or may be the quality of the radio link detected by the terminal, such as wireless signal strength, wireless signal quality, and the like.

Step 7: When the quality of the transmission link on the WIFI network is better than the quality of the transmission link on the EVDO network, or when the transmission link on the EVDO network continues to deteriorate so that it cannot be used, the terminal initiates the server with the server. Link switching "Operation.

The above "link switching" operation means that the terminal disconnects the transmission link on the EVDO network, and

The data received on the transmission link on the WIFI network is used as data received by the VoIP service; after discovering the interruption of the transmission link on the EVDO network, the server also selects the data received on the transmission link on the WIFI network as the VoIP. The data received by the business. Industrial applicability

By adopting the technical solution of the present invention, the continuity of the service can be significantly improved. Taking the voice service as an example, according to the prior art, the L1 link is unreliable, and the terminal must first disconnect the L1 link and then establish the L2 link, causing the voice service to be interrupted. After the technical solution of the present invention is used, when the L1 link is still available, the service link is initiated on the L2 link in advance. When the quality of the L1 is insufficient to support the voice service, and the L2 link is stable, the network link is broken. The L1 link is opened, so that there is no interruption in the voice service. Moreover, the solution of the present invention only needs to modify the service logic of the terminal side and the service logic of the server side, and does not need to change the hardware design, and has no additional requirements for the wireless access network, which is economical to implement.

Claims

Claim

1. A switching method, comprising:

When the terminal finds that the quality of the currently established link L1 is less than a preset value, the terminal establishes a link L2 with the server on another network different from the network where the link L1 is located, or is different from the network where the link L1 is located. A plurality of links L2 are respectively established on the other plurality of networks with the server, and the same service as that on the link L1 is established with the server on the link L2, and then the terminal selects a link. Medium quality good as the link of the service;

Thereby maintaining business continuity between different access networks.

2. The method of claim 1 wherein:

The steps of establishing the same service as the service on the link L1 with the server on the link L2 include:

The terminal sends a service establishment request to the server on the link L2, and carries the service identifier of the service on the link L1 in the service establishment request, after the server receives the service establishment request, according to the service Identifies the establishment of the same service as the service of link L1.

3. The method according to claim 2, wherein after establishing the same service as the service on the link L1, the method further comprises: the terminal and the server receiving the sum on the link L1 Z or transmitting service data, and receiving and/or transmitting service data on the link L2, and the data transmitted on the link L1 and the link L2 are the same.

4. The method of claim 1 wherein:

The terminal finds that the quality of the currently established link L1 is less than a preset value, which means:

When the one or more of the following parameters are greater than the preset value in the preset time, the terminal determines that the quality of the link L1 is less than a preset value: a packet loss rate, a bit error rate, and a transmission delay; and/or,

The terminal determines that the quality of the link L1 is less than a preset value when one or more of the following parameters are less than the preset value within the preset time: the wireless signal strength and the wireless signal quality.

5. The method of claim 3, wherein:

After the terminal and the server receive the service data on the link L1 and the link L2, the method further includes: combining the received service data by using any one of the following methods: (a) According to the signal strength of the two links, only the data on the stronger link is processed, and the data on the weaker link is discarded;

(b) Mixing the data on the two received links together, removing duplicate data blocks, and processing the remaining data blocks as unique business data.

6. The method of claim 3, wherein:

The step of the terminal selecting the link with the good quality as the service in the link includes: after receiving and/or transmitting data on the link L1 and the link L2 for a period of time, the terminal compares the links during the period Signal quality, selecting a link with good signal quality, receiving and/or transmitting service data only on the link.

7. The method of claim 5, wherein after the mixing step, the method further comprises:

The terminal and the server determine whether there is a duplicate data block according to the transmission control protocol sequence number of the data block or the user datagram protocol sequence number.

8. A terminal for implementing handover, comprising: a determining unit, a link establishing unit, and a link selecting unit, wherein:

Thereby supporting business continuity between different access networks.

9. The terminal of claim 8, wherein:

The link establishing unit is further configured to: send a service establishment request to the server on the link L2, and carry the service identifier of the service on the link L1 in the service establishment request, so that the server establishes and The service of the same service on the link L1.

10. The terminal of claim 9, further comprising:

a data transceiving unit, configured to: transmit service data on link L1 while transmitting service data on link L2, and transmit the same data on both links, and on link L1 and link L2 Receive business data.

11. The terminal of claim 8, wherein:

The determining unit determines that the quality of the currently established link L1 is less than the preset value: the quality of the link L1 is less than the preset value when one or more of the following parameters are greater than the preset value within the preset time : packet loss rate, bit error rate and transmission delay; and / or,

12. The terminal of claim 10, wherein:

The data transceiver unit is further configured to: after receiving the service data on the link L1 and the link L2, combine the received service data in any of the following manners:

According to the signal strength of the two links, only the data on the stronger link is processed, and the data on the weaker link is discarded;

13. The terminal of claim 8, wherein: the link selection unit further comprises: a comparison module and a selection module:

The comparison module is configured to: compare the signal quality of each link in the link L1 and the link L2 in a period of time;

The selection module is configured to: select a link with good signal quality according to signal quality of each link;

The terminal receives and/or transmits service data only on the link selected by the selection module.

14. A server for implementing handover, comprising a link establishment unit and a service establishment unit, wherein:

The link establishing unit is configured to: establish another one with the terminal other than the currently established link L1 a link or a plurality of links L2, where the network where the link L2 is located is different from the network where the link L1 is located; the service establishing unit is configured to: establish the same link with the terminal on the link L2 The same business on the L1 business.

15. The server of claim 14, further comprising:

The data transceiver unit is configured to receive service data on both the link L1 and the link L2, and combine the received service data in any of the following manners: