CN101483892A - Switching command sending method and base station - Google Patents

Abstract

The invention discloses a method for sending a handover command, which is applied to a long-term evolution system. The method includes: a source base station sends first handover information to a terminal, and the first handover information is a target base station whose change cycle exceeds a preset value information; when it is confirmed that the terminal needs to initiate handover, the source base station sends a handover command to the target base station; the source base station receives the handover response returned by the target base station, and according to the handover response of the target base station, transfers the first Second handover information is sent to the terminal, the second handover information is target base station information whose change period is less than or equal to a preset value. The embodiment of the present invention also provides a base station. By adopting the technical solution of the embodiment of the present invention, the content of the first handover information and the second handover information is clarified, so that in the LTE system, the method of sending handover information in two steps becomes an operable technical solution, which improves the method and ensures Handover information can be delivered to the terminal in a timely, reliable and complete manner.

Description

A method for sending handover command and base station

technical field

The invention relates to the communication field, in particular to a method for sending a handover command and a base station.

Background technique

With the development of communication technology, the requirements for network quality are increasing day by day, one of which is to realize the smooth handover of terminals (User Equipment, UE) between different cells

In wireless networks such as Global System For Mobile Communication (GSM), UE handover between different cells is controlled by Radio Network Controller (RNC). In Long Term Evolution (LTE) networks There is no RNC in the network, and the handover control is completed by the base station (Base Station, BS or NodeB).

The source base station manages the source cell, and the target base station manages the target cell. The UE is currently in the source cell. When the source base station decides to handover the UE to the target cell according to the measurement reports of the UE and the source base station, it will directly exchange information with the target base station through the X2 interface. , complete the resource preparation of the target cell; then send a handover command to notify the UE to switch to the target cell; after the handover is successful, the target base station notifies the source base station to release the radio resources of the source cell. In addition, the source base station needs to transmit the unsent data to the target base station, and update the node relationship between the user plane and the control plane.

From the handover process described above, in order to ensure the success rate of handover, it is a very important factor to promptly and reliably notify the UE to initiate the handover. Several methods for improving the reliability of handover command sending have been discussed in the LTE proposal, but no consensus has been reached. In the R2-075066 proposed by Texas Instruments at the 3gpp 60th RAN2 meeting, a method of sending handover commands in two steps is proposed. The main idea of this proposal is that after the source base station completes the handover decision, while sending the handover request to the target base station, Send some existing handover information of the source base station to the UE, and send the incomplete handover command to the UE with a low-order modulation and coding scheme after receiving the handover confirmation from the target base station. However, the proposal does not specify the content of the message sent at each step.

In the traditional 3G handover process, the entire message of the handover command sent by the source base station to the UE comes from the handover confirmation content returned by the target base station. The current LTE base station is also based on this assumption during the handover process, that is, the source base station must first send a handover command to the target base station, and the handover information can only be obtained after the handover confirmation returned by the target base station. The above scheme of sending the handover command in two steps does not propose the specific content of the handover information sent in the first step, nor does it point out how to obtain this information. Therefore, according to the current way for LTE base stations to obtain handover information, the above technical solution is not an operable one. Technical solutions.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a method for sending a handover command and a base station, realize two-step sending of the handover command, and ensure that the handover command is sent to the terminal in a timely, reliable and complete manner.

An embodiment of the present invention provides a method for sending a handover command, which is applied to a long-term evolution system, and the method includes:

The source base station sends first handover information to the terminal, where the first handover information is target base station information whose change period exceeds a preset value;

When it is confirmed that the terminal needs to initiate a handover, the source base station sends a handover command to the target base station;

The source base station receives the handover response returned by the target base station, and sends second handover information to the terminal according to the handover response of the target base station, where the second handover information is a change period less than or equal to a preset value Target base station information.

An embodiment of the present invention also provides a base station, which is set in a long-term evolution system, and is characterized in that it includes:

a storage unit, configured to store first handover information, where the first handover information is target base station information whose change cycle exceeds a preset value;

A handover command unit, configured to send a handover command to the target base station when it is known that the terminal needs to initiate a handover;

a receiving unit, configured to receive a handover response from the target base station after the handover command unit sends the handover command;

a sending unit, configured to send the first switching information stored in the storage unit to the terminal, and send second switching information to the terminal according to the switching response received by the receiving unit, wherein the second switching information is target base station information whose change period is less than or equal to a preset value.

By adopting the technical solution of the embodiment of the present invention, the content of the first handover information and the second handover information is clarified, so that in the LTE system, the method of sending handover information in two steps becomes an operable technical solution, which improves the method and ensures Handover information can be delivered to the terminal in a timely, reliable and complete manner.

Description of drawings

FIG. 1 is a schematic flowchart of a method for sending a handover command in Embodiment 1 of the present invention;

Figure 2 shows the scene where the terminal switches between the HNodeB and the macro cell;

Figure 3 shows the scene where the terminal is handed over between cells at both ends of the tunnel;

FIG. 4 is a schematic structural diagram of a base station in Embodiment 2 of the present invention.

Detailed ways

The present invention will be described in detail below.

First, the content of the handover command message sent by the base station to the terminal is divided into two categories, one of which is information with a lower frequency of change, such as uplink and downlink configuration information, uplink and downlink bandwidth, and random access parameters (such as: Random sequence format, root sequence index, zero correlation region length, high-speed identification, random access transmission power setting, cell identification), etc., these information will not change before the base station is reconfigured or before the base station is restarted, that is, the change period is longer than that of the base station reconfiguration The configuration or restart interval; or other information that may change before the base station is reconfigured or restarted, but the change period exceeds a preset value (for example, one minute). These information with a lower frequency of change are hereinafter referred to as the first handover information. The other type is information with a relatively high frequency of change, such as C-RNTI Cell Radio Network Temporary Identifier (C-RNTI), time-frequency resource configuration for random access, and dedicated sequences for random access, etc. The information, that is, the information whose changing period is less than or equal to a preset value (for example, one minute), and the information whose changing frequency is relatively high is hereinafter referred to as the second switching information. The preset value of the change cycle can be set from tens of seconds to several hours according to the average number of users in the cell. If the number of users is large, the preset value is low (that is, the period is short), and if the number of users is small, the preset value is high.

When the target base station sends the handover confirmation to the source base station, the two types of information can be contained in two containers respectively, and the container containing the first handover information contains version information, or can also contain the valid time limit of the version information.

The source base station of the first handover information can be obtained through the following two methods:

1) During the first or last handover service process between the source base station and the target base station, when the source base station receives the handover confirmation message from the target base station, if there is a container containing the first handover information in the handover confirmation message, then the first handover information Save it locally.

2) After the target base station is reconfigured or restarted, the target base station judges whether the first handover information has been updated, and if the first handover information has been updated, the target base station actively sends the updated first handover information and new version information to neighboring The base station (including the source base station), after the source base station receives the new version information, updates the locally stored old version information of the target base station, and replaces the locally stored original first handover information of the target base station with the updated first handover information.

FIG. 1 is a schematic flowchart of a method for sending a handover command in Embodiment 1 of the present invention.

The concrete process of this technical scheme is as follows:

Step 1a, the source base station makes a handover decision according to the measurement report, confirms that the terminal needs to initiate a handover, and the source base station checks whether there is first handover information of the target base station to which the terminal wants to handover. If the source base station stores the first handover information, the source base station sends the first handover information stored by the source base station to the terminal while sending a handover request to the target base station.

Step 1b, when the source base station sends a handover request to the target base station, the handover request includes the version number of the first handover information of the target base station saved by the source base station, and the target base station checks whether the first handover information is invalid after receiving the handover request.

Step 2, if the content of the first handover information is updated, the target base station will include a container carrying the new first handover information when sending the handover confirmation to the source base station. Otherwise, the handover confirmation message only needs to include the second handover information.

Step 3, the source base station receives new first handover information and saves it. If the source base station receives new first handover information, it will resend new first handover information and second handover information to the terminal.

Wherein, step 1a and step 1b can be sent in parallel. Step 1a can adopt a high-level confirmation mechanism to achieve higher reliability. In step 3, low-order modulation and a hybrid automatic repeat request (Hybrid Automatic Repeat Request, HARQ) scheme may be used to ensure reliability.

On the user plane, in order to avoid data loss during handover, after the handover process on the signaling is completed, the target base station will notify the mobility management entity/user plane entity (Mobility Management Entity, MME/User Plane Entity, UPE) to send the gateway to The user plane path of the base station is transferred from the source base station to the target base station. At the same time, the source base station successively forwards the data packets for the user received by itself during the handover period to the target base station through the user plane tunnel of the X2 interface.

In addition, step 1a can also be executed in advance before the handover decision. It has certain significance in some special scenarios where the handover target base station is clearly known. For example, in the following home base station (HomeNodeB, HNodeB) scenario: the network already knows that the mobile terminal will definitely go to a certain macro cell after leaving the HNodeB. When to advance specifically, another threshold can be set on the base station side (it can be triggered by the content of the UE's measurement report, or it can be measured by the base station itself). That is, before the handover standard is not reached, the threshold for triggering the early sending of the handover information message may have been reached. This will also help to improve the reliability of handover command delivery.

Examples of HNodeB application scenarios:

Scenario 1, Figure 2 shows a scenario where a terminal switches between the HNodeB and the macro cell.

In this scenario, the source base station is the HNodeB, and the target base station is the base station covering the macro cell. Since there are few macro cells adjacent to the HNodeB, the terminal is basically fixed in the cell to which the HNodeB belongs and the macro cell. During the daily interaction or the last handover interaction, the two base stations may store the first handover information sent in advance by the other side. When HNodeB decides to switch the terminal to the target base station, it sends the first handover information to the terminal in advance, and the terminal can do some handover preparations. When the terminal receives the second handover information, the terminal starts to perform handover to the target base station.

Scenario 2, Figure 3 shows a scenario where a terminal is handed over between cells at both ends of the tunnel.

In this scenario, the source base station and the target base station are respectively base stations covering the cells at both ends of the tunnel, and the cells at both ends of the tunnel are fixed, so both base stations can store the first handover information sent in advance by the other side. When the terminal is handed over at both ends of the tunnel, once the handover is decided, the source base station may send the first handover information of the target base station to the terminal in advance. When sending the handover request to the target base station, the handover request includes version information of the first handover information. When the source base station receives the handover confirmation from the target base station, it detects whether there is a new version of the first handover information, if there is a new version of the information, it is updated locally, and at the same time, it sends the received handover response message to the terminal.

Scenario 3: Handover between macro cells. In addition to the above two scenarios, the handover of the terminal in the macro cell may be relatively unfixed. The source base station may set whether to send such information in advance according to the timeliness of the target base station in sending the first handover information in advance. If the handover confirmation message sent by the target base station does not provide such information, then the source base station combines the locally stored handover information with the content of the received handover information confirmation message from the target base station, sends it to the terminal, and resets the valid value of the locally stored handover information. time limit.

In the above technical solution, by dividing the content of the handover information, the base stations belonging to some adjacent cells are used to notify the terminal of the handover content with a low frequency of change, that is, the first handover information is stored in the source base station. Once the source base station makes a handover decision , it is found that the first handover information of the target base station is stored in the source base station, then this part of handover information can be sent to the terminal in advance, so that the terminal can prepare handover in advance. At the same time, on the one hand, sending part of the handover information in advance can win more sending time for the second handover information; on the other hand, the content of the second handover information is reduced, thereby increasing the modulation and coding scheme (Modulation and Coding Scheme, MCS); On the other hand, the high-level confirmation mechanism can be used to ensure the reliability of the first switching information, which not only ensures the reliability of signaling transmission, but also does not bring delay, and the overhead is relatively higher than other reliability. The solution (for example, using a low-order MCS to send handover signaling that is not split or multiple HARQ processes to send handover signaling that is not split) is also relatively small. In addition, in the case of failure to send the second handover information, the terminal can analyze the target cell to be handed over according to the received first handover information, so as to prevent the terminal from selecting a cell that has not been prepared for handover, resulting in handover failure.

FIG. 4 is a schematic structural diagram of a base station in Embodiment 2 of the present invention.

A base station, set in a long-term evolution system, for sending handover commands, including:

The storage unit 401 is configured to store first handover information, where the first handover information is target base station information whose change cycle exceeds a preset value;

A handover command unit 402, configured to send a handover command to the target base station when it is confirmed according to the measurement report that the terminal needs to initiate a handover;

The receiving unit 403 is configured to receive a handover response from the target base station after the handover command unit sends the handover command;

The sending unit 404 is configured to send the first switching information stored in the storage unit to the terminal, and send the second switching information to the terminal according to the switching response received by the receiving unit, wherein the second switching information is a change period Target base station information less than or equal to a preset value.

Further, the above receiving unit is also configured to receive updated first handover information from the target base station when the first handover information of the target base station is changed;

The storage unit is further configured to update the stored first switching information according to the updated first switching information received by the receiving unit.

Further, the above sending unit also includes:

A judging subunit, configured to judge whether a predetermined trigger threshold is reached;

The sending subunit is configured to send the first switching information to the terminal when the judging subunit judges that a predetermined trigger threshold is reached.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be realized by means of software plus a necessary hardware platform, and of course all can be implemented by hardware, but in many cases the former is better implementation. Based on this understanding, all or part of the contribution made by the technical solution of the present invention to the background technology can be embodied in the form of software products, and the computer software products can be stored in storage media, such as ROM/RAM, magnetic disks, optical disks, etc. , including several instructions to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute the methods described in various embodiments or some parts of the embodiments of the present invention.

The above are only specific implementations of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements and modifications can also be made without departing from the principles of the present invention. These improvements and modifications should also be made. It is regarded as the protection scope of the present invention.

Claims (22)

1. A method for sending a handover command, applied in a long-term evolution system, characterized in that the method comprises: The source base station sends first handover information to the terminal, where the first handover information is target base station information whose change period exceeds a preset value; When it is confirmed that the terminal needs to initiate a handover, the source base station sends a handover command to the target base station; The source base station receives the handover response returned by the target base station, and sends second handover information to the terminal according to the handover response of the target base station, where the second handover information is a change period less than or equal to a preset value Target base station information. 2. The method according to claim 1, wherein the target base station information whose change period exceeds a preset value includes: target base station information that does not change until the source base station is reconfigured or restarted. 3. The method according to claim 1, wherein the target base station information whose change period exceeds a preset value includes: before the source base station is reconfigured or restarted, the target base station information whose change period is greater than a preset value. 4. The method according to claim 3, further comprising: The preset value of the change period is set according to the average number of users in the cell covered by the target base station. 5. The method according to claim 4, wherein the setting the preset value of the change period according to the average number of users of the cell covered by the target base station comprises: As the average number of users in the cell covered by the target base station increases, the preset value of the change period decreases. 6. The method according to claim 1, wherein the first handover information includes: uplink and downlink configuration information, uplink and downlink bandwidth, and random access parameters. 7. The method according to claim 6, wherein the random access parameters include: random sequence format, root sequence index, zero correlation region length, high-speed identification, random access transmission power setting and cell identification. 8. The method according to claim 1, wherein the second handover information includes: a cell radio network temporary identifier (C-RNTI) assigned by the target base station. 9. The method according to claim 8, wherein the second handover information further includes: a random access dedicated sequence, an effective termination time of the random access dedicated sequence, and updated first handover information. 10. The method according to claim 1, characterized in that before the source base station sends the first handover information to the terminal, it further comprises: During the first or last handover service process with the target base station, the source base station receives a handover confirmation message from the target base station, and if the handover confirmation message contains the first handover information, the source base station The base station stores the first switching information. 11. The method according to claim 1, characterized in that before sending the first switching information to the terminal, it further comprises: When the first handover information of the target base station is changed, the source base station receives updated first handover information from the target base station, and updates locally stored first handover information. 12. The method according to claim 1, characterized in that after the source base station sends a handover command to the target base station, the method further comprises: When the first handover information of the target base station is changed, the handover response carries the updated first handover information of the target base station, and the source base station updates locally stored first handover information according to the handover response. 13. The method according to claim 12, wherein the switching response includes two containers, the first container carries the updated first switching information, the second container carries the second switching information, and the The first container also carries updated version information of the first switching information. 14. The method according to claim 13, wherein the first container also carries the valid time limit of the version information of the updated first switching information. 15. The method according to claim 11 or 12, wherein the updating the locally saved first switching information comprises: replacing the old version information in the locally stored first handover information with the new version information in the updated first handover information from the target base station, and replacing the locally stored first handover information with the updated first handover information . 16. The method according to claim 1, wherein before the source base station sends the first handover information to the terminal, it further comprises: During the first or last handover service process with the target base station, when the source base station receives a handover confirmation message from the target base station, when the handover confirmation message includes a predetermined trigger gate for sending the first handover information time limit, storing the predetermined trigger threshold for sending the first handover message. 17. The method according to claim 16, wherein the sending the first switching information to the terminal comprises: When the predetermined trigger threshold for sending the first switching information is reached, the first switching information is sent to the terminal. 18. The method according to claim 17, wherein the arrival of the predetermined trigger threshold for sending the first handover information is before it is confirmed that the terminal needs to initiate handover. 19. The method according to claim 17, characterized in that when it is confirmed that the terminal needs to initiate handover, the predetermined trigger threshold for sending the first handover information is reached. 20. A base station, set in a long term evolution system, characterized in that it comprises: a storage unit, configured to store first handover information, where the first handover information is target base station information whose change cycle exceeds a preset value; A handover command unit, configured to send a handover command to the target base station when it is known that the terminal needs to initiate a handover; a receiving unit, configured to receive a handover response from the target base station after the handover command unit sends the handover command; a sending unit, configured to send the first switching information stored in the storage unit to the terminal, and send second switching information to the terminal according to the switching response received by the receiving unit, wherein the second switching information is target base station information whose change period is less than or equal to a preset value. 21. The base station according to claim 20, characterized in that, The receiving unit is further configured to receive updated first handover information from the target base station when the first handover information of the target base station is changed; The storage unit is further configured to update the stored first switching information according to the updated first switching information received by the receiving unit. 22. The base station according to claim 20, wherein the sending unit comprises: A judging subunit, configured to judge whether a predetermined trigger threshold for sending the first handover message is reached; The sending subunit is configured to send the first handover information to the terminal when the judging subunit judges that a predetermined trigger threshold for sending the first handover message has been reached.

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