CN101932106A - Random access method, user equipment, cell control equipment and system - Google Patents

Abstract

The embodiment of the present invention discloses a random access method, which is used to ensure the success of random access. The method in this embodiment of the present invention includes: receiving a handover request message sent by a source cell, where the handover request message carries information about a UE that needs to be handed over; generating a physical random access channel (PRACH) resource configuration, and each frame of the PRACH resource configuration There is at least one PRACH resource; sending a handover request response message to the source cell, where the handover request response message includes the PRACH resource configuration, and the PRACH resource configuration is used to indicate the PRACH resource used by the UE to send the dedicated preamble sequence. The embodiment of the present invention additionally discloses user equipment, cell control equipment and a system. The embodiment of the present invention can ensure successful random access.

Description

Random access method, user equipment, cell control equipment and system

technical field

The present invention relates to the field of mobile communication, in particular to a random access method, user equipment, cell control equipment and a system.

Background technique

In the Long Term Evolution (LTE, Long Term Evolution) system, due to the mobility of the user equipment (UE, User Equipment), cell switching becomes an essential process of the system. When performing cell switching, the UE needs to be synchronized with the target cell , and the synchronization is realized through the random access process. As an important step in the handover process, the random access process directly determines the handover performance (handover success rate, handover control plane, user plane interruption delay).

Before the UE performs random access, it needs to obtain the physical random access channel (PRACH, Physical Random Access Channel) resource configuration of the target cell first. The PRACH resource generally has 64 configuration indexes, and each configuration index contains a preamble Format parameters, system frame number (SFN, System Frame Number) and subframe number.

In the existing handover process, the target cell indicates that the PRACH resource configuration used by the handover UE to send the dedicated preamble sequence is the default PRACH configuration of the target cell, which includes the SFN of the target cell, but the UE does not know the SFN of the target cell during handover. The SFN of the source cell may be applied to the target cell, causing the target cell to fail to receive the dedicated preamble, resulting in random access failure.

Contents of the invention

Embodiments of the present invention provide a random access method, user equipment, cell control equipment and a system, which are used to ensure successful random access.

The random access method provided by the embodiment of the present invention includes: receiving a handover request message sent by a source cell, the handover request message carrying information of a user equipment UE that needs to be handed over; generating a physical random access channel PRACH resource configuration, the Each frame of PRACH resource configuration has at least one PRACH resource; send a handover request response message to the source cell, where the handover request response message includes the PRACH resource configuration, and the PRACH resource configuration is used to instruct the UE to send PRACH resource used by the dedicated preamble.

The embodiment of the present invention provides a random access method, including: after the source cell sends a handover request message to the target cell and receives a handover request response message from the target cell, receiving a handover command sent by the source cell, the handover command includes a physical random access Incoming channel PRACH resource configuration, the PRACH resource configuration is sent by the target cell to the source cell through a handover request response message, and each frame of the PRACH resource configuration has at least one PRACH resource; The PRACH resource sends a dedicated preamble sequence to the target cell; receives a random access response sent by the target cell.

An embodiment of the present invention provides a cell control device, including: a request message receiving unit, configured to receive a handover request message sent by a source cell, where the handover request message carries information about a user equipment UE that needs to be handed over; a configuration generation unit, configured to generate PRACH resource configuration, each frame of the PRACH resource configuration has at least one PRACH resource; a response message sending unit, configured to send a handover request response message to the source cell, and the handover request response message includes the configuration generating unit A generated PRACH resource configuration, where the PRACH resource configuration is used to indicate the PRACH resource used by the UE to send the dedicated preamble.

The embodiment of the present invention provides user equipment UE, including: a command receiving unit, configured to receive a handover command sent by the source cell after the source cell sends a handover request message to the target cell and receives a handover request response message from the target cell, and the handover The command includes physical random access channel PRACH resource configuration, the PRACH resource configuration is sent by the target cell to the source cell through a handover request response message, and each frame of the PRACH resource configuration has at least one PRACH resource; the sequence sending unit uses The PRACH resource on the frame configured with the PRACH resource received by the command receiving unit is used to send a dedicated preamble sequence to the target cell; the response receiving unit is configured to receive a random access response sent by the target cell.

An embodiment of the present invention provides a communication system, including: a target cell control device, configured to receive a handover request message sent by a source cell control device, and generate a PRACH resource configuration, where each frame of the PRACH resource configuration has at least one PRACH resource, which is sent to The source cell control device sends a handover request response message, the handover request response message includes PRACH resource configuration, and the PRACH resource configuration is used to instruct the user equipment UE to send the PRACH resource used by the dedicated preamble sequence; the source cell control device is used to Sending a handover request message to the target cell control device, the handover request message carrying information about the user equipment UE that needs to be handed over, receiving a handover request response message sent by the target cell control device, and sending a handover command to the user equipment UE, the handover command Including physical random access channel PRACH resource configuration; UE is used to receive the handover command sent by the source cell control device, and use the PRACH resource on the frame of the PRACH resource configuration in the handover command to send a dedicated preamble to the target cell control device, Receive the random access response sent by the control device of the target cell.

It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

After receiving the PRACH resource configuration, the UE uses the PRACH resource on the frame configured by the PRACH resource to send a dedicated preamble sequence to the target cell. Since there is at least one PRACH resource on each frame configured by the PRACH resource, no matter which frame the UE uses The dedicated preamble is sent by the PRACH resources on the network, and the target cell can always receive the dedicated preamble, so as to ensure successful random access.

Description of drawings

FIG. 1 is a schematic diagram of an embodiment of a random access method in an embodiment of the present invention;

FIG. 2 is a schematic diagram of another embodiment of the random access method in the embodiment of the present invention;

FIG. 3 is a schematic diagram of another embodiment of the random access method in the embodiment of the present invention;

FIG. 4 is a schematic diagram of an embodiment of a cell control device in an embodiment of the present invention;

Fig. 5 is a schematic diagram of another embodiment of the cell control device in the embodiment of the present invention;

FIG. 6 is a schematic diagram of an embodiment of user equipment in the embodiment of the present invention;

Fig. 7 is a schematic diagram of an embodiment of a communication system in an embodiment of the present invention.

Detailed ways

Embodiments of the present invention provide a random access method, user equipment, cell control equipment and a system, which are used to ensure successful random access.

Referring to Figure 1, a specific embodiment of the random access method in the embodiment of the present invention includes:

101. Receive a handover request message;

When the source cell detects that the UE needs to be handed over, the source cell sends a handover request message to the target cell. The handover request message carries the information of the user equipment UE that needs to be handed over, and is used to indicate that there is a UE that will be handed over to the target cell.

It should be noted that, in practical applications, the source cell may decide whether to perform cell handover for the UE, or the UE itself may decide whether to perform cell handover.

In this embodiment, the source cell can measure the geographic location of the UE or the signal strength that can be provided to the UE. When the geographic location of the UE is relatively far from the control device of the source cell, or the signal strength that the source cell can provide to the UE is low If it is lower than a certain threshold, the source cell can determine that the UE needs to perform cell handover.

The UE can also measure its own geographical location or the signal strength provided by the source cell. When the geographical location of the UE is far from the control device of the source cell, or the signal strength that the source cell can provide for the UE is lower than a certain threshold, Then the UE may determine that cell handover is required.

It can be understood that, in practical applications, the source cell or the UE has more ways to decide whether to perform handover, which are not specifically limited here.

It should be noted that if the UE decides whether to switch or not, when the UE decides to perform cell switching, the UE will send a switching request to the source cell.

102. Generate a PRACH resource configuration;

When the target cell receives the handover request message and determines that a UE will be handed over to the target cell, the target cell generates a PRACH resource configuration for the UE, and each frame of the PRACH resource configuration has at least one PRACH resource.

103. Send a handover request response message to the source cell.

After generating the PRACH resource configuration, the target cell sends the PRACH resource configuration to the source cell through a handover request response message, and the PRACH resource configuration is used to indicate the PRACH resource that the UE can use when sending the dedicated preamble.

In the embodiment of the present invention, after receiving the PRACH resource configuration, the UE uses the PRACH resource on the frame configured by the PRACH resource to send a dedicated preamble sequence to the target cell. Since there is at least one PRACH resource on each frame configured by the PRACH resource, No matter in which frame the UE uses the PRACH resource to send the dedicated preamble, the target cell can always receive the dedicated preamble, thus ensuring successful random access.

For ease of understanding, another embodiment of the random access method in the embodiment of the present invention is described below, please refer to FIG. 2 for details. Another embodiment of the method of the present invention includes:

201. Receive a handover request message;

This step is basically similar to the content of step 101 described in the embodiment shown in FIG. 1 , and will not be repeated here.

202. Generate a PRACH resource configuration;

When it is determined that a UE will be handed over to the target cell, the target cell generates a PRACH resource configuration for the UE, and each frame of the PRACH resource configuration has at least one PRACH resource.

It should be noted that the PRACH resource configuration generated by the target cell may only be used for handover of the UE into the current cell, without changing the default PRACH resource configuration of the current cell.

For example, in an LTE system, assuming that the default PRACH period of the target cell is 20 milliseconds, there is only PRACH configuration in even frames, and the target cell configures at least one PRACH resource for each frame of the UE-generated PRACH resource, that is, every 10 milliseconds There is a PRACH resource to enable the UE to send a dedicated preamble.

The configuration table of the PRACH resources in this embodiment is shown in Table 1:

Table 1. Configuration table of PRACH resources

In the above PRACH resource configuration table, PRACH Configuration Index indicates the PRACH resource setting index, Preamble Format indicates the preamble format used, SFN is System FrameNumber, indicating the number of the frame containing the PRACH resource, and Subframe number indicates the number of the frame containing the PRACH resource The starting subframe number occupied by the preamble.

If the PRACH period of the target cell is 20 milliseconds, the index of the default PRACH resource configuration of the target cell is 0. From the above table, it can be seen that there are only PRACH resources in the first subframe of the even-numbered frame. When the target cell receives the After receiving a handover request message, it is confirmed that a UE will be handed over to the target cell, and the target cell generates a PRACH resource configuration for the UE. Each frame of the PRACH resource configuration has at least one PRACH resource, which can be selected from the above table The PRACH resource configuration whose SFN is "ANY" can be seen from the above table, taking the index of the generated PRACH resource configuration as 3 as an example, querying the above table shows that there is a PRACH resource in the first subframe of each frame, which can be used Send a dedicated preamble.

It should be noted that Table 1 in this embodiment is a configuration table of PRACH resources in Frequency Division Duplex (FDD, Frequency Division Duplex) mode. It can be understood that, in practical applications, there may also be other modes, For example, in Time Division Duplex (TDD, Time Division Duplex) mode, the content of the specific PRACH resource configuration table is similar, and will not be repeated here.

203. Send a handover request response message;

After the target cell generates the PRACH resource configuration for the UE, the target cell sends the PRACH resource configuration to the source cell through a handover request response message.

204. Receive a dedicated preamble;

After receiving the handover request response message sent by the target cell, the source cell will send a handover command to the UE. The handover command includes PRACH resource configuration, and the UE will use the PRACH resource on the frame configured by the PRACH resource to send a dedicated preamble to the target cell. Since the PRACH resource configuration received by the UE has at least one PRACH resource in each frame, no matter in which frame the UE sends the dedicated preamble, the target cell will receive the dedicated preamble sent by the UE.

The target cell can perform a corresponding random access operation according to the dedicated preamble sequence, and the execution process is common knowledge of those skilled in the art, and the details are not limited here.

205. Send a random access response;

After the target cell receives the dedicated preamble sequence, it can perform the random access process. After the random access is completed, it can send a random access response to the UE. When the UE receives the random access response, the UE successfully completes the cell switch.

206. Release the PRACH resource configuration.

After confirming that the target cell has received the dedicated preamble sent by the UE, it releases the PRACH resource configuration allocated for the UE.

It should be noted that there is no order of steps 205 and 206 in this embodiment of the present invention, and step 205 or 206 may be executed first, or both steps 205 and 206 may be executed at the same time, which is not limited here.

Compared with the aforementioned embodiment shown in FIG. 1, this embodiment increases the process of releasing PRACH resource configuration. In addition to the beneficial effects of the embodiment shown in FIG. 1, this embodiment also has the following beneficial effects, because when After the UE switches into the target cell, the PRACH resource configuration is released, which can save channel resources.

The random access method in the embodiment of the present invention is mainly described above from the perspective of the target cell, and the random access method of the present invention is described below from the perspective of the UE. Please refer to FIG. 3 , another specific example of the embodiment of the present invention include:

301. Receive a switching command;

When the source cell sends a handover request message to the target cell and receives a handover request response message from the target cell, the UE receives a handover command sent by the source cell. The handover request response message sent, and each frame of PRACH resource configuration has at least one PRACH resource.

302. Send a dedicated preamble;

After receiving the handover command, the UE parses the handover command to obtain the dedicated preamble sequence and the PRACH resource configuration of the target cell, and uses the PRACH resource on the frame configured by the PRACH resource to send the dedicated preamble sequence to the target cell.

303. Receive a random access response sent by the target cell.

After the UE sends the dedicated preamble sequence to the target cell, it can receive a random access response from the target cell, and then the UE completes the cell handover.

In this embodiment of the present invention, the PRACH resource used by the UE to send the dedicated preamble sequence to the target cell is generated by the target cell for the UE to switch into the target cell. The target cell can always receive the dedicated preamble on which frame the PRACH resource is used to send the dedicated preamble, so that the UE can be handed over to the target cell successfully.

The above content describes the random access method in the embodiment of the present invention, and the cell control device is described below. Please refer to FIG. 4. An example of the cell control device in the embodiment of the present invention includes:

The request message receiving unit 401 is configured to receive a handover request message sent by the source cell, where the handover request message carries information about the user equipment UE that needs to be handed over;

The configuration generation unit 402 is configured to generate a PRACH resource configuration, and each frame of the PRACH resource configuration has at least one PRACH resource;

The response message sending unit 403 is configured to send a handover request response message to the source cell, where the handover request response message includes the PRACH resource configuration generated by the configuration generation unit 402, and the PRACH resource configuration is used to indicate the PRACH resource used by the UE to send the dedicated preamble sequence.

When the source cell detects that a UE needs to be handed over, the request message receiving unit 401 receives the handover request message sent by the source cell, indicating that a UE will be handed over to the target cell, and the configuration generating unit 402 generates a PRACH resource configuration for the UE, and responds The message sending unit 403 sends a handover request response message to the source cell, where the handover request response message includes PRACH resource configuration.

In the embodiment of the present invention, after receiving the PRACH resource configuration, the UE uses the PRACH resource on the frame configured by the PRACH resource to send a dedicated preamble sequence to the target cell. Since there is at least one PRACH resource on each frame configured by the PRACH resource, No matter in which frame the UE uses the PRACH resource to send the dedicated preamble, the target cell can always receive the dedicated preamble, thus ensuring successful random access.

For ease of understanding, another embodiment of the cell control device in the embodiment of the present invention is described below. Please refer to FIG. 5 for details. Another embodiment of the cell control device in the embodiment of the present invention includes:

The request message receiving unit 501 is configured to receive a handover request message sent by the source cell, where the handover request message carries information about the user equipment UE that needs to be handed over;

The configuration generation unit 502 is configured to generate a PRACH resource configuration, and each frame of the PRACH resource configuration has at least one PRACH resource;

The response message sending unit 503 is configured to send a handover request response message to the source cell, where the handover request response message includes the PRACH resource configuration generated by the configuration generation unit 502, and the PRACH resource configuration is used to instruct the UE to send the PRACH resource used by the dedicated preamble sequence;

A sequence receiving unit 504, configured to receive a dedicated preamble sent by the UE;

an access control unit 505, configured to perform random access according to the dedicated preamble sequence received by the sequence receiving unit 504;

a response sending unit 506, configured to send a random access response to the UE;

The configuration releasing unit 507 is configured to release the PRACH resource configuration generated by the configuration generating unit 502 .

After the source cell detects that the UE needs to be handed over, the request message receiving unit 501 receives the handover request message sent by the source cell, indicating that a UE will be handed over to the target cell, the configuration generating unit 502 generates a PRACH resource configuration, and then responds to the message The sending unit 503 sends a handover request response message to the source cell. After receiving the handover request response message, the source cell sends a handover command to the UE. The handover command includes PRACH resource configuration. Then, the UE sends a dedicated preamble sequence to the sequence receiving unit 504, responding The sending unit 506 sends a random access response to the UE to indicate that the UE has successfully switched into the target cell. Finally, the configuration releasing unit 507 releases the PRACH resource configuration.

For ease of understanding, the following describes each unit of the cell control device in this embodiment with a specific application scenario:

When the source cell detects that the UE needs to be handed over, the source cell sends a handover request message to the target cell to indicate that a UE will be handed over to the target cell, and the request message receiving unit 501 may receive the handover request message from the source cell .

After the request message receiving unit 501 receives the handover request message from the source cell, the configuration generating unit 502 generates a PRACH resource configuration for the UE, and each frame of the PRACH resource configuration has at least one PRACH resource.

It should be noted that the PRACH resource configuration generated by the target cell can only be used for handover of the UE into the current cell, and the default PRACH resource configuration of the current cell will not be changed.

For example, the default PRACH period of the target cell is 20 milliseconds, and the SFN is an even frame. The target cell configures at least one PRACH resource for each frame of the PRACH resource generated by the UE, that is, there is a PRACH resource every 10 milliseconds so that the UE can send Dedicated preamble.

After the configuration generating unit 502 generates the PRACH resource configuration for the UE, the response message sending unit 503 sends the PRACH resource configuration to the source cell through a handover request response message.

After the source cell receives the handover request response message sent by the response message sending unit 503, it will send a handover command to the UE. The handover command includes PRACH resource configuration, and the UE will use the PRACH resource on the frame configured by the PRACH resource to send a dedicated message to the target cell. For the preamble sequence, the sequence receiving unit 504 will receive the dedicated preamble sequence sent by the UE, indicating that the UE can be handed over to the target cell.

After the sequence receiving unit 504 receives the dedicated preamble, the access control unit 505 can perform random access according to the dedicated preamble, and then the response sending unit 506 can send a random access response to the UE.

After the sequence receiving unit 504 confirms receiving the dedicated preamble sequence sent by the UE, the configuration releasing unit 507 may release the PRACH resource configuration allocated for the UE.

The cell control device in the embodiment of the present invention is described above, and the user equipment is introduced below. Please refer to FIG. 6. A specific example of the user equipment in the embodiment of the present invention includes:

The command receiving unit 601 is configured to receive a handover command sent by the source cell, the handover command includes a PRACH resource configuration, the PRACH resource configuration is included in the handover request response message sent by the target cell to the source cell, and each frame of the PRACH resource configuration There is at least one PRACH resource;

The sequence sending unit 602 is configured to use the PRACH resource on the frame configured by the PRACH resource received by the command receiving unit 601 to send a dedicated preamble sequence to the target cell;

The response receiving unit 603 is configured to receive a random access response sent by the target cell.

When the source cell sends a handover request message to the target cell and receives a handover request response message from the target cell, the command receiving unit 601 receives the handover command sent by the source cell, the handover command includes PRACH resource configuration, and then the sequence sending unit 602 uses the The PRACH resource on the frame configured by the PRACH resource sends a dedicated preamble to the target cell.

After receiving the PRACH resource configuration, the UE uses the PRACH resource on the frame configured by the PRACH resource to send a dedicated preamble sequence to the target cell. Since there is at least one PRACH resource on each frame configured by the PRACH resource, no matter which frame the UE uses The dedicated preamble is sent on the PRACH resource on the target cell, and the target cell can always receive the dedicated preamble, so that random access can be successfully performed.

The above embodiment introduces the user equipment, and a communication system is introduced below, please refer to FIG. 7 , a specific example of the communication system in the embodiment of the present invention includes:

The target cell control device 701 is configured to receive the handover request message sent by the source cell control device 702, generate a PRACH resource configuration, each frame of the PRACH resource configuration has at least one PRACH resource, and send a handover request response to the source cell control device 702 message, the handover request response message includes a PRACH resource configuration, and the PRACH resource configuration is used to instruct the user equipment 703 to send the PRACH resource used by the dedicated preamble sequence;

The source cell control device 702 is configured to send a handover request message to the target cell control device 701, the handover request message carrying the information of the user equipment UE that needs to be handed over, receiving the handover request response message sent by the target cell control device 701, and sending the handover request message to the user equipment 703 Send a handover command, where the handover command includes physical random access channel PRACH resource configuration;

The user equipment 703 is configured to receive the handover command sent by the source cell control device 702, use the PRACH resource on the frame configured by the PRACH resource in the handover command to send a dedicated preamble sequence to the target cell control device 701, and receive the preamble sequence sent by the target cell control device 701. Random access response.

In this embodiment, the user equipment 703 sends a dedicated preamble sequence to the target cell control device 701 by using the PRACH resource on the PRACH resource configuration frame generated by the target cell control device 701, and each frame of the PRACH resource configuration has at least one PRACH resource, so no matter in which frame the UE uses the PRACH resource to send the dedicated preamble, the user equipment 703 can always be handed over to the target cell successfully.

Those of ordinary skill in the art can understand that all or part of the steps in the method of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the above-mentioned storage The medium can be read-only memory, magnetic or optical disk, etc.

A random access method, user equipment, cell control equipment and system provided by the present invention have been introduced in detail above. For those of ordinary skill in the art, based on the ideas of the embodiments of the present invention, in terms of specific implementation methods and application scope There will be changes. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (10)

1. an accidental access method is characterized in that, comprising:

The handoff request message that the reception sources sub-district sends, described handoff request message is carried the information of the user equipment (UE) that need switch;

Generate Physical Random Access Channel PRACH resource distribution, have a PRACH resource on each frame of described PRACH resource distribution at least;

Send handover request ack message to described cell-of-origin, described handover request ack message comprises described PRACH resource distribution, and described PRACH resource distribution is used to indicate described UE to send the PRACH resource that special leader sequence uses.

2. accidental access method according to claim 1 is characterized in that, describedly comprises after the cell-of-origin sends handover request ack message:

Receive the special leader sequence that described UE sends;

Carry out access at random according to described special leader sequence;

Send accidental access response to described UE.

3. accidental access method according to claim 2 is characterized in that, comprises after the special leader sequence that described reception UE sends:

Discharge the PRACH resource distribution of described generation.

4. according to each described accidental access method in the claim 1 to 3, it is characterized in that described generation Physical Random Access Channel PRACH resource distribution comprises:

Selecting system frame number parameter is the PRACH resource distribution of ANY from PRACH resource distribution table.

5. an accidental access method is characterized in that, comprising:

After handover request ack message is received to Target cell transmission handoff request message and from Target cell in the cell-of-origin, the switching command that the reception sources sub-district sends, described switching command comprises Physical Random Access Channel PRACH resource distribution, described PRACH resource distribution is sent to the cell-of-origin by handover request ack message by Target cell, has a PRACH resource on each frame of described PRACH resource distribution at least;

Use the PRACH resource on the frame of described PRACH resource distribution to send special leader sequence to Target cell;

The accidental access response that the receiving target sub-district sends.

6. a cell control equipment is characterized in that, comprising:

The request message receiving element is used for the handoff request message that the reception sources sub-district sends, and described handoff request message is carried the information of the user equipment (UE) that need switch;

The configuration generation unit is used to generate the PRACH resource distribution, has a PRACH resource on each frame of described PRACH resource distribution at least;

The response message transmitting element, be used for sending handover request ack message to described cell-of-origin, described handover request ack message comprises the PRACH resource distribution that described configuration generation unit generates, and described PRACH resource distribution is used to indicate described UE to send the PRACH resource that special leader sequence uses.

7. cell control equipment according to claim 6 is characterized in that, described cell control equipment also comprises:

The sequential reception unit is used to receive the special leader sequence that described UE sends;

The access control unit, the special leader sequence that is used for receiving according to described sequential reception unit is carried out at random and is inserted;

The response transmitting element is used for sending accidental access response to described UE.

8. cell control equipment according to claim 7 is characterized in that, described cell control equipment also comprises:

The configuration releasing unit is used to discharge the PRACH resource distribution that described configuration generation unit generates.

9. a user equipment (UE) is characterized in that, comprising:

The order receiving element, be used for after handover request ack message is received to Target cell transmission handoff request message and from Target cell in the cell-of-origin, the switching command that the reception sources sub-district sends, described switching command comprises Physical Random Access Channel PRACH resource distribution, described PRACH resource distribution is sent to the cell-of-origin by handover request ack message by Target cell, has a PRACH resource on each frame of described PRACH resource distribution at least;

The sequence transmitting element is used to use the PRACH resource on the frame of the PRACH resource distribution that described order receiving element receives to send special leader sequence to Target cell;

The response receiving element is used for the accidental access response that the receiving target sub-district sends.

10. a communication system is characterized in that, comprising:

The Target cell control appliance, be used for the handoff request message that the reception sources cell control equipment sends, generate the PRACH resource distribution, has a PRACH resource on each frame of described PRACH resource distribution at least, send handover request ack message to described cell-of-origin control appliance, described handover request ack message comprises the PRACH resource distribution, and described PRACH resource distribution is used to indicate user equipment (UE) to send the PRACH resource that special leader sequence uses;

The cell-of-origin control appliance, be used for sending handoff request message to the Target cell control appliance, described handoff request message is carried the information of the user equipment (UE) that need switch, the handover request ack message that the receiving target cell control equipment sends, send switching command to user equipment (UE), described switching command comprises Physical Random Access Channel PRACH resource distribution;

UE, be used for the switching command that the reception sources cell control equipment sends, use the PRACH resource on the frame of the PRACH resource distribution in the described switching command to send special leader sequence to the Target cell control appliance, the accidental access response that the receiving target cell control equipment sends.

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