CN1214671C - Method for realizing synchronization between base stations in mobile communication system - Google Patents

Abstract

The invention provides a method for realizing synchronization between base stations in a mobile communication system. This includes: determining the base station with the clock reference source and its corresponding base station group in the system, and there is a stable interface transmission resource between each base station in the base station group and the base station with the clock reference source; in this way, each base station in the base station group can easily The respective synchronization information can be obtained from base stations with clock reference sources through the corresponding interface transmission resources; at the same time, the base stations of non-base station groups can be synchronized through the already synchronized base stations with message transmission resources between the incoming base stations. The present invention simplifies the process of realizing synchronization between base stations; at the same time, the present invention directly realizes the transmission synchronization between base stations through the transmission resources between base stations, saves wireless resources, increases system capacity, and reduces the burden of RNC at the same time, so that RNC can Process other services at a faster speed to improve the communication quality of the mobile communication system.

Description

Method for Realizing Synchronization Between Base Stations in Mobile Communication System

technical field

The invention relates to the technical field of mobile communication, in particular to a method for realizing synchronization between base stations in a mobile communication system.

Background technique

In mobile communication systems, especially in CDMA (Code Division Multiple Access, Code Division Multiple Access) mobile communication systems, achieving good synchronization between base stations can reduce interference, improve system transceiver performance, and increase system capacity.

In the CDMA mobile communication system, especially in the third generation mobile communication system, its working mode is divided into two modes: TDD (Time Division Duplex, Time Division Duplex) and FDD (Frequency Division Duplex, Frequency Division Duplex). In the FDD mode, the NodeB (base station) synchronizes with the RNC (Radio Network Controller) to achieve synchronization between base stations. In the TDD mode, the NodeBs are kept in sync with each other through the direct synchronization process, and it is more commonly used to realize the synchronization between the NodeBs through the air interface. For example, each NodeB monitors the SYNC (synchronization) signal of the surrounding NodeBs, and then according to these signal to adjust its own clock.

At present, the method for realizing synchronization between NodeBs through the air interface is to divide the RNS (Radio Network Subsystem, Radio Network Subsystem) into multiple cell base station groups, and each cell base station group uses a single downlink synchronization code. The synchronization of cell base stations through the air interface specifically includes:

Initial stage: At the beginning of the system, the cell base stations are synchronized with each other:

1) Obtain the reference time of the RNC area: each RNC area has a cell base station with an external synchronization time reference, such as GPS (Global Positioning System) time, and the cell base station is responsible for converting the GPS time into SFN (system frame number) modulo local time;

First, the RNC asks for the reference time from the base station of the cell with an external synchronization time reference; and obtains the reference time sent back by the base station of the reference cell;

Then, RNC adjusts own local clock RFN (RNC FrameNumber, RNC frame number) according to this time, wherein deducts the transmission delay between RNC and this cell base station;

Finally, the RNC adjusts the local clock BFN (base station frame number, Base-station Frame Number) of other cell base stations in the area according to a unified time value, wherein the time adjustment value sent to each cell base station deducts the RNC and the cell Average transmission delay between base stations.

2) Other cell base stations enter the Frequency Acquisition Phase (Frequency Acquisition Phase). In this phase, the cell base stations with external clock references need to continuously send downlink synchronization (SYNC-DL) sequences in each radio frame, and other cell base stations monitor this Signal sequence, when the base station of the cell locks its own frequency within the 50ppb range of the reference frequency, it ends the frequency acquisition phase and notifies the RNC.

3) Initial phase (Initial Phase): the synchronization process of the cell base stations in the RNS area is performed at the beginning of the network;

Let each cell base station send its own SYNC-DL in a continuous radio frame period, and the cell base stations that receive the SYNC-DL signals of other cell base stations report to the RNC the time when they receive the signal and the received S/(N+I) (S, signal power; N, noise power; I, interference power; S/(N+I), signal-to-noise ratio) value; RNC calculates the relative time difference of these cell base stations through a measurement matrix, and determines each cell base station Time adjustment and calibration; in order to ensure the accuracy of synchronization, the above process can be repeated many times.

Stable stage: When the system is stable, adjust the synchronization time of the cell base station, and maintain the synchronization accuracy of the cell in real time;

The RNC regularly compares the SYNC-DL information of neighboring cell base stations reported by each cell base station, and adjusts the corresponding synchronization time according to this information; it is usually required that there should be direct communication between each cell base station and the cell base station with GPS reference clock Or an indirect two-way measurement channel (through the RNC), so that each cell base station can obtain synchronization time update information.

When the mobile communication system adds a cell base station, the RNC notifies the SYNC-DL code and carrier frequency that it needs to monitor according to the position of the new cell base station; the new cell base station reports the locked frequency to the RNC; Calculate the time offset that the new cell should calibrate with the monitoring result reported by the base station of the new cell. Then, the RNC issues a corresponding synchronous transmission plan to the base station of the new cell.

In the prior art, the RNC controls the entire synchronization algorithm, including initial and establishment of connection plans, collection of measurement information, calculation of time accuracy, and support for NBAP (NodeB ApplicationPart, base station application part) signaling. It is also responsible for estimating the accuracy of inter-cell synchronization, and notifying the UE (User Equipment, User Equipemt) of this information during handover. The calculation and planning of the time calibration amount by the RNC are independent, and if it is necessary to improve the clock synchronization accuracy, an updated calibration scheme (that is, determine the frequency, when to send, and when to receive) can be implemented.

Therefore, the method for synchronization between base stations adopted in the prior art not only has a complicated process, but also increases the burden on the mobile communication system, and simultaneously because the RNC is responsible for the control and management of synchronization between base stations, it also greatly increases the burden on the RNC, affecting the RNC's ability to communicate with other users. The processing speed of the business, in today’s increasing RNC functions, if some business functions that can be completed by different network entities are all concentrated in the RNC, it will definitely affect the communication quality of the mobile communication system. Therefore, the functions in the current mobile communication network are relatively The distribution among the various entities is not reasonable.

Contents of the invention

The purpose of the present invention is to provide a method for realizing synchronization between base stations in a mobile communication system, so that the base stations can directly realize synchronization by using the interface between the base stations, so that the function of realizing synchronization of the existing RNC is completed by the base station, thereby making the mobile communication network The distribution of functions and entities in the system is more reasonable.

The purpose of the present invention is achieved like this: the method for realizing synchronization between the base stations in the mobile communication system comprises:

a. Determine the base station with the clock reference source and its corresponding base station group, and there is a stable interface signaling connection between each base station in the base station group and the base station with the clock reference source;

b. Each base station in the base station group sends a transmission delay measurement request to the base station with the clock reference source through a corresponding interface signaling connection, and obtains the transmission delay according to the feedback response of the base station with the clock reference source;

c. Each base station in the base station group sends a synchronization request to the base station with the clock reference source through the corresponding interface signaling connection, and according to the reference clock responded by the base station with the clock reference source, deducts the transmission delay of the base station to obtain the synchronization time ;

d. Each base station in the base station group implements synchronization according to the obtained synchronization time.

Described step d comprises:

d1. The base station calculates a synchronization error according to the obtained synchronization time and the time of the base station;

d2. The base station judges whether the synchronization error is greater than a set threshold for synchronization time adjustment, and if it is greater than the set threshold, execute step d3, otherwise, execute step b;

d3. Adjust the time of the base station accordingly.

Said step d3 also includes:

d31, judging whether the base station that needs clock adjustment is a base station that has been synchronized and provides a synchronous reference clock for base stations outside the base station group, if yes, execute step d32, otherwise, the process ends;

d32. For a base station that has been synchronized and provides a synchronous reference clock for base stations outside the base station group, in addition to clock adjustment, it is also necessary to send a transmission time adjustment message to the base station that uses it as a synchronous reference clock;

d33. The base station adjusts the message according to the received transmission time, and updates the synchronization time through the transmission delay test and node synchronization;

d34. After the synchronization time update process of the base station is completed, notify the base station that provides the reference clock for it.

The method for realizing synchronization between base stations in the described mobile communication system also includes between step a and step b for the synchronization of newly added base stations:

(1) The newly added base station obtains the identification number and address information of the corresponding base station with clock reference source through communication with adjacent base stations, and establishes communication with the base station with clock reference source;

(2) The base station with the clock reference source determines whether to establish synchronization message transmission for the newly added base station according to its own signaling connection;

(3) If the base station with the clock reference source establishes synchronization message transmission for the newly added base station, then perform step b;

(4) If the base station with the clock reference source has no synchronization message transmission established for the newly added base station, then the newly added base station takes the synchronized base station as the base station with the clock reference source, and performs step b.

Described step (1) comprises:

(11) The newly added base station sends a neighboring base station reference information request to the neighboring base station;

(12) The newly added base station receives the response information of the adjacent base station, and the response information includes: the identification number of the adjacent base station, the identification number and address information of the base station with the clock reference source to which the adjacent base station belongs;

(13) The newly added base station sends a synchronization resource request to the base station with the clock reference source according to the obtained identification number and address information of the base station with the clock reference source.

The base station with the clock reference source is a GPS (Global Positioning System) base station.

As can be seen from the above technical solution, the method for realizing synchronization between base stations in the mobile communication system provided by the present invention greatly simplifies the process of realizing synchronization between base stations; at the same time, in the present invention, the transmission resources between base stations are directly used to perform synchronization between base stations. Transmission synchronization saves the process of base station sending downlink synchronization sequence and each base station measuring downlink synchronization sequence, which saves wireless resources and increases system capacity; at the same time, it also saves the processing process of RNC for inter-base station synchronization, reducing the burden on RNC, so that The RNC can process other services at a faster speed, improving the communication quality of the mobile communication system.

Description of drawings

Fig. 1 is the concrete implementation flowchart A of the present invention;

Fig. 2 is the concrete implementation flowchart B of the present invention;

Fig. 3 is a timing diagram of the present invention.

Detailed ways

Concrete implementation of the present invention is described as follows in conjunction with Fig. 1, Fig. 3:

Step 1: Determine a base station with an external clock reference source as a clock reference, this base station is called a G base station, such as a GPS base station; the G base station converts a GPS clock or a clock from other sources into an SFN (system frame number) modulo The local clock BFN (Base Station Frame Number, base station frame number); other base stations can use the BFN of the G base station as a reference to adjust their own clocks.

Step 2: Determine the base station group corresponding to the G base station;

Before other base stations perform clock adjustment, each base station needs to know the transmission delay of data transmission with G base station through IuNB (inter-base station interface), which requires that each base station and G base station must have stable IuNB protocol interface transmission resources and Priority, the base station group composed of base stations with stable IuNB interface transmission resources and priority between G base stations is called T group;

Step 3: Depending on the signaling connection of the allocated IuNB interface, the base station in the T group sends the IuNB delay measurement request "IuNB Transport Time Delay Test Request" signaling to the G base station;

After the G base station receives the request, it sends back the "IuNBTransport Time Delay Test Report" response through the signaling connection on the IuNb interface; the requesting base station can determine the IuNB transmission delay with the G base station according to the response fed back by the G base station;

Step 4: The base stations in the T group send a synchronization request to the G base station to obtain the reference clock;

The base stations in the T group send the "IuNB NodeB Syncronization Request" signaling to the G base station, and the G base station responds to the request through the signaling "IuNB NodeB Syncronization Report". The BFN of the base station, deducting the IuNB transmission delay between it and the G base station, calculates the precise synchronization time;

Step 5: The base stations in the T group judge whether synchronization has been achieved, and if synchronization has been achieved, then perform step 6, otherwise, perform step 8;

Step 6: Determine the synchronization error between the calculated synchronization time and the current synchronization time of the base station;

Step 7: Determine whether the synchronization error is greater than the set threshold that needs to be adjusted for synchronization time. If it is greater than the set threshold, that is, the currently measured IuNB transmission delay with the G base station and the corresponding measured value between the reference clock and the base station currently reserved If there is a large error between them, go to step 8; otherwise, go to step 3;

Step 8: Adjust the synchronization time of the base station to the calculated synchronization time to achieve synchronization with the G base station; cyclic execution of steps 3 to 8 can realize the synchronization and maintenance of synchronization between the base stations in the T group and the G base station .

Through the above process, the synchronization between the base stations in the mobile communication system is realized. However, considering that the mobile communication system is not static after it is established, it is often possible to add new base stations to the system according to the needs of business expansion. For the newly added base stations, use The specific process of realizing the synchronization of the mobile communication system in which the above-mentioned base stations have been synchronized is as follows, see Fig. 2 and Fig. 3:

Step 9: When a new base station joins in the mobile communication system, the newly added base station needs to send a request "IuNB NodeB StatusRequest" about the relevant situation of the neighboring base station to the neighboring base station to obtain the relevant situation of the neighboring base station, It is easy to know whether you are in the T group alone;

Step 10: After receiving the "IuNB NodeB Status Rerquest" signaling from the new base station, the adjacent base station sends its own NodeB identification number, address, and the identification number and address of the G base station in the T group to which it belongs through the "IuNB NodeB Status Report" signal. Order feedback to the newly added base station;

Step 11: The new base station retains the received information, and determines the address of the G base station in the T group with which the new base station can establish communication through the feedback information, and the new base station sends an IuNB synchronization to the G base station according to the G base station address of the T group to which it belongs Resource request "IuNB NodeB SyncronizationResource Request";

Step 12: The G base station judges whether it is possible to establish a stable IuNB transmission resource with the newly added base station according to its own IuNB interface transmission resource situation, if yes, perform step 13, otherwise, perform step 14;

Step 13: The G base station feeds back the corresponding transmission layer address and port number and other resources to the new base station through the "IuNB NodeB Syncronization Resource Report" signaling, and the newly added base station realizes transmission synchronization through the G base station;

Step 14: The G base station feeds back the information that it cannot provide the required transmission resources for the newly added base station through the "IuNB NodeB Syncronization Resource Report";

Step 15: Since the G base station does not establish IuNB synchronization message transmission resources with the newly added base station, the newly added base station does not belong to the T group that the G base station is paired with; The base station realizes transmission synchronization; the base station that has been synchronized and has IuNB synchronization message transmission resources with the new base station is called H base station;

First, the new base station determines the IuNB transmission delay with the H base station through the transmission delay request "IuNB NodeB Transport Time Delay" signaling and the transmission delay response "IuNB NodeB Transport Time Delay Report" signaling; then, through the transmission synchronization request "IuNBNodeB Syncroniztion Request" signaling and transmission synchronization response "IuNB NodeBSyncronization Report" signaling to achieve transmission synchronization between the new base station and the H base station.

The synchronization maintenance process for the newly added base station is shown in FIG. 3 , which is basically the same as the synchronization maintenance process of the base stations in the T group described in steps 6 to 8 above. The timing of the newly added base station is calibrated through the clock reference source of the G base station; the timing calibration is through each base station regularly sending and receiving "IuNB Transport Time Delay Test Request, IuNB Transport TimeReport" and "IuNB NodeB Syncronization Request, IuNB NodeBSyncronization Report" Signaling is implemented, and the base station judges whether there is a large error between its own clock and the reference clock, so as to determine whether clock adjustment is required, and make corresponding adjustments as required.

The synchronization maintenance process of the newly added base station that realizes synchronization through the H base station is implemented by the cooperation of the H base station. That is, when the H base station in the system needs to perform clock adjustment, after its synchronous update process (clock adjustment), it needs to send a synchronization adjustment message "IuNB NodeB Syncronization Adjustment Request" to the base station with itself as the base clock reference source, corresponding When the base station receives the synchronization adjustment message sent by the H base station, the clock is updated synchronously through the transmission delay test and the node synchronization process. The transmission delay test is completed with two signalings: "IuNB Transport Time DelayTest Request" and "IuNB Transport Time Report". , and the node synchronization is completed with "IuNB NodeB Syncronization Request" and "IuNB NodeB Syncronization Report". After the base station transmission synchronization update is completed, it needs to send the "IuNB NodeB Syncronization Adjustment Report" message to the H base station to notify the H base station that the synchronization time has been completed. Adjustment.

Claims (6)

1. A method for realizing synchronization between base stations in a mobile communication system, comprising: a. Determine the base station with the clock reference source and its corresponding base station group, and there is a stable interface signaling connection between each base station in the base station group and the base station with the clock reference source; b. Each base station in the base station group sends a transmission delay measurement request to the base station with the clock reference source through a corresponding interface signaling connection, and obtains the transmission delay according to the feedback response of the base station with the clock reference source; c. Each base station in the base station group sends a synchronization request to the base station with the clock reference source through the corresponding interface signaling connection, and according to the reference clock responded by the base station with the clock reference source, deducts the transmission delay of the base station to obtain the synchronization time ; d. Each base station in the base station group implements synchronization according to the obtained synchronization time. 2. The method for realizing synchronization between base stations in a mobile communication system according to claim 1, wherein said step d comprises: d1. The base station calculates a synchronization error according to the obtained synchronization time and the time of the base station; d2. The base station judges whether the synchronization error is greater than a set threshold for synchronization time adjustment, and if it is greater than the set threshold, execute step d3, otherwise, execute step b; d3. Adjust the time of the base station accordingly. 3. The method for realizing synchronization between base stations in a mobile communication system according to claim 2, wherein said step d3 further comprises: d31, judging whether the base station that needs clock adjustment is a base station that has been synchronized and provides a synchronous reference clock for base stations outside the base station group, if yes, execute step d32, otherwise, the process ends; d32. For a base station that has been synchronized and provides a synchronous reference clock for base stations outside the base station group, in addition to clock adjustment, it is also necessary to send a transmission time adjustment message to the base station that uses it as a synchronous reference clock; d33. The base station adjusts the message according to the received transmission time, and updates the synchronization time through the transmission delay test and node synchronization; d34. After the synchronization time update process of the base station is completed, notify the base station that provides the reference clock for it. 4. The method for synchronizing between base stations in the mobile communication system according to claim 1, characterized in that: for the synchronization of newly added base stations, between step a and step b: (1) The newly added base station obtains the identification number and address information of the corresponding base station with clock reference source through communication with adjacent base stations, and establishes communication with the base station with clock reference source; (2) The base station with the clock reference source determines whether to establish synchronization message transmission for the newly added base station according to its own signaling connection; (3) If the base station with the clock reference source establishes synchronization message transmission for the newly added base station, then perform step b; (4) If the base station with the clock reference source has no synchronization message transmission established for the newly added base station, then the newly added base station takes the synchronized base station as the base station with the clock reference source, and performs step b. 5. The method for realizing synchronization between base stations in a mobile communication system according to claim 4, wherein said step (1) comprises: (11) The newly added base station sends a neighboring base station reference information request to the neighboring base station; (12) The newly added base station receives the response information of the adjacent base station, and the response information includes: the identification number of the adjacent base station, the identification number and address information of the base station with the clock reference source to which the adjacent base station belongs; (13) The newly added base station sends a synchronization resource request to the base station with the clock reference source according to the obtained identification number and address information of the base station with the clock reference source. 6. The method for achieving synchronization between base stations in a mobile communication system according to claim 1, characterized in that: said base station with a clock reference source is a GPS base station.

Images