CN101801039B - Method for reducing delay in multiple base station cooperation - Google Patents

Abstract

A method for reducing time delay in multi-base station cooperation belongs to the method for multi-base station cooperation in the third generation mobile communication long-term evolution project, which solves the problem of excessive time delay in multi-base station cooperation and reduces the waiting time delay of cooperative users. The invention includes: base station forwarding step, data sending step, judging step, positive confirmation step, negative confirmation step, retransmission step and failure processing step. The present invention realizes the consistency of packet data convergence protocol layer data by setting the automatic retransmission request protocol under the general packet wireless service tunnel protocol; when the service base station receives the collaborative user data from the service gateway, it Forwarding the data to the cooperative base station, compared with the existing method, in the method of the present invention, the wired time delay of the newly transmitted data forwarded by the serving base station to the cooperative base station is included in the time delay of the wireless resource allocation process, thus reducing the time delay of the cooperative The sending delay of the user's newly transmitted data.

Description

A method for reducing delay in multi-base station cooperation

technical field

The invention belongs to a method for multi-base station cooperation in the third-generation mobile communication long-term evolution project (3G LTE), and in particular relates to a method for reducing time delay in multi-base station cooperation.

Background technique

The mobile communication network consists of three parts: wireless access network, core network and backbone network. The core network and backbone network mainly provide switching and transmission services for various services; the wireless access network mainly provides access network services for mobile terminals, including multiple nodes, which can be base stations or users; a cell is the management area of a base station , the entire mobile network is composed of many cells. Adding multi-base station cooperation can effectively improve the communication quality of cell edge users. In the access network, in order to realize cooperative joint scheduling of multiple base stations, one or more cooperation modules are added to form one or more cooperation sets, and each cooperation module corresponds to a cooperation set, as shown in FIG. 1 . The cooperation module can be located inside the base station or as an independent node. The main functions of the cooperation module include: joint radio resource management for the base stations participating in the cooperation; maintenance and transmission of control signaling, etc. A wired communication interface is set between the cooperation module and each base station, which is responsible for the interaction of multi-base station cooperation control signaling, but does not perform data information transmission between the cooperation module and the base stations.

For the situation where multiple collaboration sets exist, communication interfaces can be set between different collaboration modules, as shown in FIG. 2 .

The multi-base station cooperative system is introduced as follows: users are divided into cooperative users and ordinary users. The service priority of cooperative users is higher than that of ordinary users. Ordinary users are generally users at the center of a cell, and cooperative users are generally users at the edge of a cell. Base stations and users According to the user's communication quality and other factors, decide whether to use the user as a collaborative user. Each ordinary user belongs to only one serving base station, and each cooperative user belongs to one serving base station and one or more cooperative base stations; the two types of user data only reach the serving base station; ordinary users only receive information from the serving base station; cooperative users receive information at the same time The information sent by the serving base station and the coordinated base station; the serving base station and the coordinated base station can only send data to the cooperative user after receiving the wireless resource allocation result; the cooperative module only performs wireless resource allocation for the data of the cooperative user in the serving base station and the coordinated base station, including Resource allocation for data transmission and retransmission data, and the resource allocation result is sent to the serving base station and the cooperative base station through the wired interface. The serving base station and the cooperative base station send user data according to the wireless resource allocation result; the serving base station and the cooperative base station receive the resource allocation After the result, use the wireless resources not occupied by the cooperative users to allocate wireless resources for the data of ordinary users serving themselves; the resource allocation of ordinary user data is allocated by its serving base station.

It can be found that no matter whether the cooperation module is an independent node of the access network or located in the base station, there will be the following problems: for the cooperation users, since the service gateway (forwarding the user data from the network side to the base station, and the base station forwards it to the user) only Send the user's data to the serving base station. When the cooperation module notifies the serving base station and the cooperative base station of the wireless resource allocation result of the cooperative user data, since the two base stations want to send the cooperative user data at the same time, the cooperative base station has not yet received the coordinated user data. The data cannot be sent immediately at the same time. Therefore, the serving base station needs to forward the cooperative user data to the cooperative base station, and the existence of wired delay between base stations will inevitably increase the waiting delay of the cooperative user.

Contents of the invention

The invention provides a method for reducing time delay in multi-base station cooperation, solves the problem of excessive time delay in multi-base station cooperation, and reduces the waiting time delay of cooperative users.

The present invention only studies downlink multi-base station cooperation. It should be pointed out that all types of nodes include a protocol stack inside, and the protocol stack is a collection of protocol layers, including Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) protocol layer, Media Access Control (MAC) layer , General Packet Radio Service Tunneling Protocol (GTP) layer, data and signaling are processed between each protocol.

A method for reducing delay in multi-base station cooperation of the present invention, the serving base station and the cooperative base station in the wireless access network are equipped with a retransmission timer and a transmission count counter, including the following steps:

1. Base station forwarding steps: the serving base station waits for the data forwarded from the serving gateway, receives the data forwarded by the serving gateway to a specific cooperative user, and forwards the data to the cooperative base station to which the specific cooperative user belongs at the packet data convergence protocol layer; the serving base station The wireless link control protocol layer sends a data status report to the cooperation module; the cooperation module receives and stores the data status report, allocates wireless resources for the data forwarded to a specific cooperative user according to the data status report, and sends the wireless resource allocation result to all The serving base station and the coordinated base station to which the specific coordinated user belongs; the data status report indicates the size of forwarded data;

2. Data sending step: the serving base station and the coordinated base station to which the specific cooperative user belongs receive the wireless resource allocation result, and send the data to the specific cooperative user at the same time (using hybrid automatic repeat request for the first transmission), The serving base station and the cooperative base station to which it belongs set the maximum number of transmissions, the number of transmissions counter is set to one, and the retransmission timer is started;

3. Judgment step: After the specific cooperative user receives the data, perform channel decoding to judge whether the decoding is successful, if yes, go to step 4; otherwise, go to step 5;

4. Positive confirmation step: send a positive confirmation message to the serving base station and the cooperative base station, the serving base station and the cooperative base station judge whether to receive the positive confirmation message, and if so, forward the positive confirmation message to the cooperation module, and the cooperation module will not repeat Transfer data resource allocation, go to step 1; otherwise, the retransmission timer times out, go to step 6;

5. Negative acknowledgment steps: send negative acknowledgment information to the serving base station and the cooperative base station, and the serving base station and the cooperative base station judge whether the negative acknowledgment information is received, and if so, go to step 6; otherwise, the retransmission timer times out, go to step 6 ;

6. Retransmission steps: the serving base station and the cooperative base station judge whether the number of transmissions exceeds the maximum number of transmissions, and if so, go to step 7; otherwise, the serving base station and the cooperative base station send negative confirmation information to the cooperation module, and the cooperation module The data status report allocates wireless resources for the data forwarded to the specific cooperative user, and sends the wireless resource allocation result to the serving base station and the cooperative base station to which the specific cooperative user belongs; When transmitting data wireless resource allocation results, send retransmission data to the specific cooperative user at the same time (using hybrid automatic repeat request for retransmission), restart the retransmission timer, increase the number of transmissions by one, and go to step 3;

7. Failure processing steps: sending fails, canceling data transmission, and starting an automatic retransmission request at the packet data convergence protocol layer.

The method for reducing time delay in multi-base station cooperation is characterized in that:

In the first step, the serving base station and the cooperative base station use the general packet radio service tunneling protocol when forwarding data at the packet data convergence protocol layer, and set the automatic repeat request protocol under the general packet radio service tunnel protocol, the automatic repeat request protocol Ensure that the packet data aggregation protocol layer sequence numbers of the serving base station and the cooperative base station are consistent; the cooperative module allocates resources for the data forwarded to a specific cooperative user in units of logical channels, and all logical channels in the serving base station and all logical channels in the cooperative base station Define the same priority sequence to ensure that each logical channel of the serving base station and the cooperative base station allocates the same size of wireless resources, so as to ensure the complete consistency of the data sent between the cooperative base stations.

The main function of the automatic repeat request protocol is to ensure the data consistency between the serving base station and the cooperative base station. Even if a data forwarding error occurs on the wired link, it will only affect the correctness of the data transmitted by a certain cooperation. The above situation also exists in the method of data forwarding after receiving the wireless resource allocation result, so performance degradation will not be caused. In the case of a data forwarding error, the multi-base station cooperation of the current wrong data can be canceled, and only the serving base station sends data to the cooperative user.

The method for reducing time delay in multi-base station cooperation is characterized in that:

In the second step, the wireless resource allocation results received by the serving base station and the coordinated base station are in units of logical channels, using the same time-frequency wireless resources, modulation and coding schemes.

In the method proposed by the present invention, on the one hand, by setting the automatic repeat request protocol under the general packet wireless service tunneling protocol, the data consistency of the packet data convergence protocol layer of the serving base station and the cooperative base station is realized; on the other hand, the serving base station is in When the cooperative user data is received, the data is forwarded to the cooperative base station at the packet data convergence protocol layer. Compared with the existing method in which the serving base station forwards the cooperative user data after receiving the wireless resource allocation result of the cooperative module, the method of the present invention In the method, the wire delay of newly transmitted data forwarded by the serving base station to the cooperative base station is included in the wireless resource allocation process delay, thereby reducing the transmission delay of the cooperative user's newly transmitted data.

Description of drawings

FIG. 1 is a schematic diagram of a scene of an embodiment of the present invention;

Fig. 2 is a schematic flow chart of the present invention.

Specific implementation

The present invention is further described below in conjunction with embodiment and accompanying drawing.

As shown in Figure 1, an embodiment of the present invention, the system includes the following parts: base station 1 and base station 2, used to send and receive user data and signaling, receive the wireless resource allocation result of the cooperation module, and allocate wireless resources for ordinary users , to forward positive confirmation information, negative confirmation information, etc. from the cooperative users to the cooperation module; a cooperation module, as an independent node of the access network, is used to perform radio resource management on the two base stations participating in the cooperation; 4 users, use For sending and receiving data and signaling, user 1, user 3, and user 4 are common users, and user 2 is a cooperative user; the serving base station of cooperative user 2 is base station 1, and the cooperative base station is base station 2; the serving base station of common user 1 and user 3 is base station 1, and the serving base station of common user 4 is base station 2; the cooperation module and the base station are connected through a wired interface; the base stations are connected through a standard (the standard interface between the base station and the base station, defined as X2). In the figure, a hexagonal frame represents a cell.

For collaborative user 2, the specific steps are shown in Figure 2. Among them, the wired link delay is 3ms, the retransmission timer timing of the cooperative base station and the serving base station is 20ms, and the maximum number of retransmissions is 5 (including the first transmission).

For ordinary users 1, 3, and 4, they only accept data and signaling from the corresponding serving base stations, and only send confirmation information to the corresponding serving base stations; and their downlink wireless resource allocation is implemented by their respective serving base stations.

Claims (3)

1. A method for reducing time delay in multi-base station cooperation, the serving base station and the cooperative base station in the wireless access network are all equipped with a retransmission timer and a number of transmission counter, comprising the following steps: 1. Base station forwarding steps: the serving base station waits for the data forwarded from the serving gateway, receives the data forwarded by the serving gateway to a specific cooperative user, and forwards the data to the cooperative base station to which the specific cooperative user belongs at the packet data convergence protocol layer; the serving base station The wireless link control protocol layer sends a data status report to the cooperation module; the cooperation module receives and stores the data status report, allocates wireless resources for the data forwarded to a specific cooperative user according to the data status report, and sends the wireless resource allocation result to all The serving base station and the coordinated base station to which the specific coordinated user belongs; the data status report indicates the size of forwarded data; 2. Data sending step: the serving base station and the cooperative base station to which the specific cooperative user belongs receive the wireless resource allocation result, and send the data to the specific cooperative user at the same time, and the serving base station and the cooperative base station to which they belong set the maximum number of transmission times, and transmit The number of times counter is set to one, and the retransmission timer is started; 3. Judgment step: After the specific cooperative user receives the data, perform channel decoding to judge whether the decoding is successful, if yes, go to step 4; otherwise, go to step 5; 4. Positive confirmation step: send a positive confirmation message to the serving base station and the cooperative base station, the serving base station and the cooperative base station judge whether to receive the positive confirmation message, and if so, forward the positive confirmation message to the cooperation module, and the cooperation module will not repeat Transfer data resource allocation, go to step 1; otherwise, the retransmission timer times out, go to step 6; 5. Negative acknowledgment steps: send negative acknowledgment information to the serving base station and the cooperative base station, and the serving base station and the cooperative base station judge whether the negative acknowledgment information is received, and if so, go to step 6; otherwise, the retransmission timer times out, go to step 6 ; 6. Retransmission steps: the serving base station and the cooperative base station judge whether the number of transmissions exceeds the maximum number of transmissions, and if so, go to step 7; otherwise, the serving base station and the cooperative base station send negative confirmation information to the cooperation module, and the cooperation module The data status report allocates wireless resources for the data forwarded to the specific cooperative user, and sends the wireless resource allocation result to the serving base station and the cooperative base station to which the specific cooperative user belongs; When transmitting data radio resource allocation results, send retransmission data to the specific cooperative user at the same time, the retransmission data is retransmitted using a hybrid automatic repeat request, restart the retransmission timer, increase the number of transmissions by one, and go to step 3; 7. Failure processing steps: sending fails, canceling data transmission, and starting an automatic retransmission request at the packet data convergence protocol layer. 2. The method for reducing delay in multi-base station cooperation as claimed in claim 1, characterized in that: In the first step, the serving base station and the cooperative base station use the general packet radio service tunneling protocol when forwarding data at the packet data convergence protocol layer, and set the automatic retransmission request protocol under the general packet radio service tunneling protocol; the cooperation module is the The data allocation resource forwarded to a specific cooperative user is in units of logical channels, and all logical channels in the serving base station and all logical channels in the cooperative base station define the same priority sequence. 3. The method for reducing delay in multi-base station cooperation as claimed in claim 1 or 2, characterized in that: In the second step, the wireless resource allocation results received by the serving base station and the coordinated base station are in units of logical channels, using the same time-frequency wireless resources, modulation and coding schemes.

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