CN101035364A

CN101035364A - Switching method from 3G cell to 2G cell and network side device

Info

Publication number: CN101035364A
Application number: CNA2007100388197A
Authority: CN
Inventors: 高良柱; 刘霞玲
Original assignee: Shanghai Huawei Technologies Co Ltd
Current assignee: Shanghai Huawei Technologies Co Ltd
Priority date: 2007-03-30
Filing date: 2007-03-30
Publication date: 2007-09-12

Abstract

The invention relates to the wireless communication field, disclosing a 3G cell-to-2G cell switching method and the network side equipment, making the network side able to connect the unconnected course with the connected course to implement NACC's solution. After determining target cell for UE, the network side equipment records the corresponding relation between the mark of the target cell and the UE; after obtaining the SI/PSI of the target cell by the unconnected course, it finds the corresponding UE in the corresponding relation according to the mark of the target cell and sends the obtained SI/SPI to the UE; and the determination of target cell of UE can be triggered by measurement report of UE and it can make blind switching according to the network planning information.

Description

Switching method from 3G cell to 2G cell and network side equipment

Technical Field

The present invention relates to the field of wireless communications, and in particular, to a handover technique.

Background

Mobile communication systems have been developed rapidly since they have been able to satisfy the demand of people for communication at any time and place. Global System for mobile communication (GSM) is widely used in The global area as one of The schemes for The Second Generation mobile communication (2G). Wideband Code Division Multiple Access (WCDMA for short) is one of the three mainstream standards of the 3rd Generation (3G for short), inherits the characteristics of high GSM standardization degree and good openness, has good compatibility and interoperability with GSM networks, and is one of the development trends of future mobile communication.

All mobile communication systems, including GSM systems of 2G networks and WCDMA systems of 3G networks, handover is an essential important function. Because the coverage area of a base station is limited, as a User Equipment (UE) moves, the radio connection between the UE and the network must be transferred from one cell to another cell in order to maintain continuity of communication, which is handover.

The purpose of switching is to continue to maintain the conversation of the UE when the serving cell changes, to switch channels under the condition of larger interference of the current serving cell or channel, and to purposefully adjust the handover algorithm, and also to play a role in adjusting the cell boundary and the network structure, defining the switching direction, reducing the traffic congestion of the cell, and the like. In both GSM and WCDMA systems, a process of performing service handover is defined.

For the handover From the 3G Cell to the 2G Cell, a Cell Change Order (CCO) technology may be adopted, and Network-Assisted Cell Change (NACC) is an enhancement of the CCO technology, and its main idea is to first obtain System Information (SI)/Packet System Information (PSI) of a target Cell through a radio access Network Information Management (RIM) process (hereinafter referred to as "or" in the present invention), and bring the System Information/Packet Information to the UE in a Cell Change Order From uplink (Cell Change From Utran) message. Since the UE obtains the system message of the target cell through network assistance, the UE does not need to read the system message in the target cell access process, thereby reducing the time for changing from the 3G cell to the 2G cell, as shown in fig. 1.

It is not easy to find that the key of the NACC technology is to obtain the SI/PSI of the target cell, and one existing scheme is shown in fig. 2, when a Serving Radio Network controller (Services RNC, abbreviated as "SRNC") receives a measurement report of the UE, and determines to transfer the UE to an evolved enhanced data Radio Access Network (GSM EDGE Radio Access Network, abbreviated as "GERAN"), it initiates a RIM request message to a Serving GPRS Support Node (SGSN) to request to obtain the SI/PSI of the target cell. The SGSN forwards the request to a Base Station Subsystem (BSS) of the target cell by using a RIM procedure, and the BSS sends the SI/PSI of the target cell to the SGSN by using the RIM procedure, and forwards the SI/PSI to the SRNC by using an "on-demand" (e.g., single report) or an "on-modification" (e.g., multiple reports) of the SGSN. The SGSN forwards the message to the SRNC over the Iu interface. Wherein, if multiple reports are available, the SRNC can terminate the report through a TERMINATION/END message flow.

The inventors of the present invention have found that since the acquisition of SI/PSI is UE triggered, i.e. connection oriented. The RIM procedure for acquiring the SI/PSI of the target cell is connectionless (sent via Iu interface message "Direct Information Transfer", which is a connectionless message), and therefore, the NACC scheme cannot be really implemented.

Disclosure of Invention

The main technical problem to be solved by the embodiments of the present invention is to provide a method for switching from a 3G cell to a 2G cell and a network side device, so that a network side can associate a connectionless process with a connectionless process to implement a NACC scheme.

In order to solve the above technical problem, an embodiment of the present invention provides a handover method from a 3G cell to a 2G cell, including the following steps:

after network side equipment determines a target cell for User Equipment (UE), recording the corresponding relation between a target cell identifier and the UE;

the network side equipment acquires system information SI or grouped system information PSI of a target cell through a connectionless process, finds corresponding UE from the recorded corresponding relation according to the identification of the target cell, and sends the acquired SI or PSI to the UE;

and the UE is switched from the 3G cell to the 2G cell according to the acquired SI or PSI.

The embodiment of the present invention further provides a network side device, including:

means for determining a target cell for a UE;

a module for recording the corresponding relation between the target cell identification and the UE after the target cell is determined for the UE;

means for acquiring SI or PSI of a target cell through a connectionless procedure;

a module for finding out the corresponding UE from the recorded corresponding relation according to the identification of the target cell;

and sending the acquired SI or PSI to a corresponding UE.

Compared with the prior art, the implementation mode of the invention has the main differences and the effects that:

after the network side equipment determines a target cell for the UE, the corresponding relation between the target cell identification and the UE is recorded. And after the SI/PSI of the target cell is acquired through a connectionless process, the corresponding UE is found from the recorded corresponding relation according to the identification of the target cell, and the acquired SI/PSI is sent to the UE. Although the acquisition of the SI/PSI is connection-oriented, and the process for acquiring the SI/PSI of the target cell is connectionless, the connection process and the connectionless process are linked through the common target cell information, the switching process from the 3G cell to the 2G cell is perfected, and the scheme of NACC is really realized.

Drawings

Fig. 1 is a schematic illustration of NACC signaling flow according to the prior art;

FIG. 2 is a schematic diagram of a NACC implementation according to the prior art;

fig. 3 is a flowchart of a handover method from a 3G cell to a 2G cell according to a first embodiment of the present invention;

fig. 4 is a schematic diagram of a network-side device structure according to a third embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A first embodiment of the present invention relates to a method for handover from a 3G cell to a 2G cell, in this embodiment, a connectionless process used by a network side device to acquire SI/PSI is an RIM process, and a specific flow is shown in fig. 3.

In step 310, the UE reports a measurement report and triggers a cell change. Specifically, when the UE moves from the 3G cell to the 2G cell, the UE needs to perform cell change, and therefore, the UE reports a measurement report to the network side device RNC to notify the network side of a neighboring cell with better received signal quality.

Then, step 320 is entered, and the RNC records the corresponding relationship between the target cell id and the UE. Specifically, after receiving the measurement report reported by the UE, the RNC determines whether to perform cell change and a target cell for the change according to the measurement report. After the target Cell of the UE is determined, a corresponding relationship between a target Cell identifier and the UE is recorded, for example, a Global Cell identifier (CGI) is used to record the target Cell and the corresponding UE. The target cell id in this embodiment is not limited to the CGI, and may be a customized private cell id in the system, as long as the target cell id is information that can uniquely identify a cell in the system.

Next, step 330 is entered, and the RNC acquires the SI/PSI of the target cell through RIM procedure. Specifically, the RNC sends a connectionless message "DIRECT information transmission" to the SGSN, the connectionless message content containing a RIM request message requesting to obtain the SI/PSI of the target cell. After receiving the request of the RNC, the SGSN uses the RIM process to forward the request to the BSS of the target cell, the BSS of the target cell uses the RIM process to send a 'RAN INFORMATION' message to the SGSN, the message contains the SI/PSI of the target cell, and the SGSN sends the RIM message containing the SI/PSI of the target cell to the RNC through the 'DIRECT INFORMATION TRANSFER' message.

Then, step 340 is entered, and the RNC finds the corresponding UE from the recorded corresponding relationship according to the identifier of the target cell. Specifically, because the RIM message carries the identification information of the cell, such as the CGI of the cell, after acquiring the SI/PSI by the RIM process, the RNC can determine which cell's SI/PSI corresponds to the acquired SI/PSI. Then, the RNC may find the corresponding UE from the recorded correspondence according to the CGI of the cell.

For example, in step 320, after receiving the measurement report of the UE1, the RNC determines that the target cell for the UE1 is cell a, and the recorded corresponding relationship is that the CGI of the cell a corresponds to the UE 1. Then, in step 340, since the RIM message carries the CGI of the cell a, the RNC may learn that the obtained SI/PSI is the SI/PSI of the cell a, and find the corresponding UE, i.e., UE1, according to the CGI of the cell a.

Next, in step 350, the RNC sends an "CELL CHANGE order rom UTRAN" (cell change from universal mobile telecommunications system terrestrial radio access network) message to the UE, carrying the acquired SI/PSI information of the target cell. And sending the acquired SI/PSI to the UE. For the above case, the RNC sends the SI/PSI of cell A to the UE 1.

The UE receiving the SI/PSI can switch from the 3G cell to the 2G cell based on the obtained SI/PSI, as shown in step 360.

Therefore, although the acquisition of the SI/PSI is connection-oriented, and the RIM process for acquiring the SI/PSI of the target cell is connectionless, the connection process and the connectionless process are linked through the common target cell information (CGI), the handover process from the 3G cell to the 2G cell is perfected, and the NACC scheme is really realized, namely the UE can acquire the SI/PSI of the target cell through network assistance, so that the SI/PSI does not need to be read in the target cell access process, and the time for changing from the 3G cell to the 2G cell is reduced.

In step 370, the SGSN sends an "Iu Release Command" (Iu interface Release Command) message to the RNC, and the RNC returns an "Iu Release Complete" message to the SGSN to Release the Iu interface.

A second embodiment of the present invention relates to a handover method from a 3G cell to a 2G cell, and the present embodiment is substantially the same as the first embodiment except that in the first embodiment, an RNC triggers a cell change after receiving a measurement report of a UE, that is, determines a target cell for the change for the UE. In the present embodiment, the RNC determines the target cell to be changed for the UE according to the network planning information, that is, performs blind handover on the UE. So that handover from a 3G cell to a 2G cell can be flexibly implemented.

A third embodiment of the present invention relates to a network side device, as shown in fig. 4, including a determining module, configured to determine a target cell for a UE; a recording module, configured to record a corresponding relationship between a target cell identifier (e.g., CGI) and the UE after the determining module determines the target cell for the UE; an obtaining module, configured to obtain the SI/PSI of the target cell through a connectionless procedure, such as an RIM procedure; a searching module, configured to find a corresponding UE from the recorded corresponding relationship according to an identifier (e.g., CGI) of the target cell; and a sending module, configured to send the acquired SI/PSI to a corresponding UE.

Because the information of the target cell is both in the connection message (UE-oriented message) and the connectionless message (RIM process message), the association between the connection process and the connectionless process is established through the identifier (such as CGI) of the target cell, so that the NACC scheme can be really implemented, and the handover process from the 3G cell to the 2G cell is perfected.

The determining module may determine the target cell for the UE according to the measurement report after receiving the measurement report of the UE, or may determine the target cell for the UE according to the network planning information, that is, perform blind handover on the UE. So that the present embodiment can be flexibly implemented. The network side device in this embodiment may be an RNC.

In summary, in the embodiments of the present invention, after determining a target cell for a UE, a network side device records a corresponding relationship between a target cell identifier and the UE. And after the SI/PSI of the target cell is acquired through a connectionless process, the corresponding UE is found from the recorded corresponding relation according to the identification of the target cell, and the acquired SI/PSI is sent to the UE. Although the acquisition of the SI/PSI is connection-oriented, and the process for acquiring the SI/PSI of the target cell is connectionless, the connection process and the connectionless process are linked through the common target cell information, the switching process from the 3G cell to the 2G cell is perfected, and the scheme of NACC is really realized.

The determination of the target cell of the UE can be triggered by a measurement report of the UE, and can also be performed with blind handover according to network planning information to determine the target cell for the UE, so that the implementation mode of the invention can be flexibly realized.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

1. A method for handover from a 3G cell to a 2G cell, comprising the steps of:

the network side equipment acquires system information SI or grouped system information PSI of the target cell through a connectionless process, finds corresponding UE from the recorded corresponding relation according to the identification of the target cell, and sends the acquired SI or PSI to the UE;

and the UE is switched from the 3G cell to the 2G cell according to the obtained SI or PSI.

2. The method of claim 1, wherein the network-side device determines a target cell for the UE after receiving the measurement report of the UE.

3. The method of claim 1, wherein the network-side device determines a target cell for the UE according to network planning information.

4. The method of handover from a 3G cell to a 2G cell of claim 1, wherein the target cell identity is a global cell identity (CGI).

5. Method for handover from a 3G cell to a 2G cell according to any of claims 1 to 4, wherein the connectionless procedure is a radio access network information management, RIM, procedure.

6. The method of any of claims 1 to 4, wherein the network side device is a Radio Network Controller (RNC).

7. A network-side device, comprising:

means for determining a target cell for a UE;

means for acquiring SI or PSI of the target cell through a connectionless procedure;

and sending the acquired SI or PSI to a corresponding UE.

8. The network-side device of claim 7, wherein the means for determining the target cell for the UE determines the target cell for the UE after receiving the measurement report of the UE; or,

the module for determining a target cell for the UE determines the target cell for the UE according to network planning information.

9. The network-side device of claim 7, wherein the target cell identifier is a CGI.

10. The network-side device of any one of claims 7 to 9, wherein the connectionless procedure is a RIM procedure.