CN1802002A - Multi-cell fast switching method - Google Patents

Abstract

The invention discloses a multi-cell fast handover method, comprising the following steps: Step A: sending a handover application message with a handover target cell code list to a MSC (Mobile Switching Center) by a source BSC (base station controller); Step B: The MSC sends handover requests to the BSCs of all cells in the list at the same time, and each BSC establishes radio channel resources according to the handover requests; Step C: If the radio channel resources are successfully established, then send a handover request confirmation message to the MSC; the MSC selects the first received The cell corresponding to a handover request acknowledgment message is used as the target cell of the handover, and a handover command message is sent to the source BSC to perform the handover operation. By using the method of the invention, the speed and success rate of cell switching can be improved.

Description

A multi-cell fast handover method

technical field

The invention relates to the field of mobile communication, in particular to a method for fast handover of multiple cells.

Background technique

In the mobile communication system, when the call of the mobile station is established, the communication quality will be degraded due to the movement of the mobile station during the communication period. big. In order to obtain better communication quality, the mobile station can switch to a new base station cell, and use the wireless channel of the new cell for conversation.

The current switching process under normal conditions is shown in Figure 1, and the specific steps are as follows:

a: When the signal of the mobile user meets the handover conditions during the conversation, the source BSC (base station controller) sends a handoff application message (Handoff Required) with the code list of the handover target cell to the MSC (mobile switching center);

b: MSC sends a Handoff Request message (Handoff Request) to the destination BSC, and the destination BSC allocates wireless channel resources;

c: After the destination BSC successfully establishes the wireless channel resource, it sends a Handoff Request Acknowledge message (Handoff Request Acknowledge) to the MSC;

d: The MSC sends a handoff command message (Handoff Command) to the source BSC to notify the mobile station to start handover;

e: The source BSC sends a handover start message (HandoffCommenced) to the MSC;

f: After the mobile station successfully captures the wireless channel resources established by the target BSC, it sends a Handoff Complete message (Handoff Complete) to the MSC through the target BSC;

g: MSC sends a clear command (Clear Command) to the source BSC to release the wireless channel resources of the source;

h: The source BSC sends a clear complete message (Clear Complete) to the MSC to notify the MSC that the release of the source end is complete.

In some cases, such as interference in the air channel, unstable wireless signal, etc., the wireless channel resources may not be established on the destination side. At this time, the MSC will sequentially select cells of other BSCs for handover attempts. The process is shown in Figure 2, and the specific steps are:

a: When the signal of the mobile user meets the handover conditions during the conversation, the source BSC (base station controller) sends a handoff application message (Handoff Required) with the code list of the handover target cell to the MSC (mobile switching center);

b: MSC sends a handover request message (Handoff Request) to the destination BSC1, and the destination BSC allocates wireless channel resources;

c: BSC1 returns a handover failure message (HandoffFailure) to MSC;

d: The MSC sequentially selects the cell BSC2 of other BSCs to send a handover request message (HandoffRequest);

e: After the destination BSC2 successfully establishes the wireless channel resource, it sends a Handoff Request Acknowledge message (Handoff Request Acknowledge) to the MSC;

f: MSC sends a handover command message (Handoff Command) to the source BSC to notify the mobile station to start handover;

g: The source BSC sends a handover start message (HandoffCommenced) to the MSC;

h: After the mobile station successfully captures the wireless channel resources established by the target BSC2, it sends a Handoff Complete message (Handoff Complete) to the MSC through the target BSC2;

i: MSC sends a clear command (Clear Command) to the source BSC to release the wireless channel resources of the source;

j: The source BSC sends a clear complete message (Clear Complete) to the MSC to notify the MSC that the release of the source end is complete.

Through the above handover process, when at least one of the cell lists carried in the handover application message (Handoff Required) can complete the handover process, the continuity of the call can be guaranteed.

The existing system finds a target cell that can be handed over successfully through sequential attempts. It usually takes a few seconds to more than ten seconds to complete the switching.

There are following defects in the existing system: when the user makes a phone call while taking a high-speed bus or a high-speed train, this switching occurs frequently, because the coverage of a location cell usually only has one or two square kilometers. When the handover occurs, the information of multiple cells is carried in the handover application message. If the handover of the first cell fails, the MSC system will try the second cell, but at this time the mobile station may be far away from the current serving BSC, that is, the source BSC. long distance. If the distance is large enough, the time from sending the handover request message to the BSC returning the handover failure message is long enough, and the mobile station may be dropped, resulting in interruption of the call. If the number of failed cells is more, for example, both the first cell and the second cell return a handover failure message, and the third cell returns a handover request confirmation message, then the probability of disconnection due to time delay will be greater.

Contents of the invention

The invention provides a method for fast multi-cell switching, which improves switching speed and success rate by sending switching request messages in parallel.

The present invention comprises the following steps:

Step A: the source BSC (base station controller) sends a handover application message with the code list of the handover destination cell to MSC (mobile switching center);

Step B: The MSC sends handover requests to the BSCs of all the cells in the list simultaneously, and each BSC establishes radio channel resources according to the handover requests;

Step C: If the wireless channel resources are successfully established, then send a handover request confirmation message to the MSC; the MSC selects the cell corresponding to the first received handover request confirmation message as the target cell of the handover, and sends a handover command message to the source BSC to carry out Toggle action.

According to above-mentioned method of the present invention, also comprise following steps:

Step D: After the handover is completed, the BSC of the target cell sends a handover completion message to the MSC.

According to above-mentioned method of the present invention, also comprise following steps:

Step E: The MSC sends a clear command to the source BSC, and the source BSC sends a clear complete message to the MSC after releasing the radio channel resources.

According to the method of the present invention, if the cell reporting the handover request confirmation message is not selected by the MSC, the MSC sends a channel release command to the BSC that has not selected the target cell, and the corresponding BSC releases channel resources and returns a release success message to the MSC.

According to the above method of the present invention, in the step C, if the establishment of the wireless channel resource fails, a handover request failure message is sent to the MSC.

According to the above method of the present invention, if the MSC receives handover request failure messages sent back by BSCs of all the cells in the handover destination cell code list, the cell handover procedure is terminated.

By adopting the method of the invention, the speed and success rate of cell switching can be improved.

Description of drawings

FIG. 1 is a flow chart of channel switching under normal conditions in the prior art;

Fig. 2 is a flow chart of channel switching failure of a certain destination BSC in the prior art;

Fig. 3 is a flow chart of channel switching in the present invention.

Detailed ways

When the signal of the user meets the handover condition during the call, the source BSC provides the MSC with a list of several destination BSC cells, and the MSC sends a Handoff Request message (HandoffRequest) to each corresponding BSC in parallel according to the destination cell list, and processes the first one. Received Handoff Request Acknowledgment message (HandoffRequest Acknowledge), as shown in Figure 3, the target BSCs corresponding to the target cell list sent by the source BSC to the MSC are BSC1, BSC2, and BSC3 respectively, and the specific operation steps are as follows:

a: The source BSC sends a handover application message (HandoffRequired) with the code list of the handover target cell to the MSC;

b: MSC sends a Handoff Request message (Handoff Request) to each relevant destination BSC1, BSC2, and BSC3 at the same time according to the destination cell list;

c: The target BSC1 and the target BSC2 send a handover request confirmation message to the MSC after successfully establishing the wireless channel resource, and return a handoff failure message (Handoff Falure) to the MSC after the target BSC3 fails to establish the wireless channel resource;

d: BSC1 first reports the handover request acknowledgment message (Handoff Request Acknowledge), MSC selects the cell corresponding to this message as the handover target cell, sends a handover command message (Handoff Command) to the source BSC, and notifies the mobile station to start handover;

e: The source BSC sends a handover start message (Handoff Commenced) to the MSC to start the handover;

f: MSC sends a clear message (Clear Command) to the unselected BSC2;

g: BSC2 returns a clear completion message (ClearComplete) to MSC after releasing the wireless channel resources;

h: After the mobile station successfully captures the wireless channel resources that the target BSC1 has established, the target BSC1 sends a Handoff Complete message (Handoff Complete) to the MSC;

i: MSC sends a clear command (Clear Command) to the source BSC to release the wireless channel resources of the source;

j: The source BSC sends a clear complete message (ClearComplete) to the MSC after releasing the resource at the source end.

K: If in step c, the MSC receives handover failure messages from all the BSCs in the code list of the handover destination cell, the MSC stops the handover process.

Using the parallel trial method of the present invention, a handover command can be initiated after a trial period (from Handoff Request to Handoff Request Ack or Handoff Failure), thereby shortening the handover time and avoiding interruption of calls caused by untimely handover.

Claims (6)

1. A multi-cell fast handover method, comprising the following steps: Step A: the source BSC (base station controller) sends a handover application message with the code list of the handover destination cell to MSC (mobile switching center); Step B: The MSC sends handover requests to the BSCs of all the cells in the list simultaneously, and each BSC establishes radio channel resources according to the handover requests; Step C: If the wireless channel resources are successfully established, then send a handover request confirmation message to the MSC; the MSC selects the cell corresponding to the first received handover request confirmation message as the target cell for handover, and sends a handover command message to the source BSC to perform Toggle action. 2. The method according to claim 1, further comprising the steps of: Step D: After the handover is completed, the BSC of the target cell sends a handover completion message to the MSC. 3. The method of claim 2, further comprising the steps of: Step E: The MSC sends a clear command to the source BSC, and the source BSC sends a clear complete message to the MSC after releasing the radio channel resources. 4. The method according to claim 1, characterized in that: if the cell reporting the handover request acknowledgment message is not selected by the MSC, the MSC sends a channel release command to the BSC that has not selected the target cell, and the corresponding BSC releases the channel resources and then sends a channel release command to the MSC. Return release success message. 5. The method according to claim 1, characterized in that: in the step C, if the wireless channel resource establishment fails, a handover request failure message is sent to the MSC. 6. The method according to claim 5, wherein the MSC terminates the cell handover process if it receives handover request failure messages from all the BSCs in the handover destination cell code list.

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