CN104104485B - A kind of D2D data transmission method - Google Patents

Abstract

This application discloses a kind of D2D data transmission method, this method realizes that D2D is transmitted using ascending resource, and the subframe and re-transmission period used in D2D transmitting procedures D2D data transfers is controlled, avoid using the subframe sent shared by D2D transmission control information to base station to carry out data transmission, simultaneously, limit and retransmit that the HARQ processes used are identical with the HARQ processes just passed, clashed during avoiding transmitting D2D data again between UE with the re-transmission of cellular system.The present invention can reduce the influence to cellular system, it is adaptable in the cellular communication system for introducing D2D technologies while D2D transmission is effectively realized.

Description

A D2D data transmission method

technical field

The present invention relates to mobile communication technology, in particular to a D2D (Device to Device) data transmission method.

Background technique

In the existing LTE system, the data transmission between two user equipments (UEs) is realized through the transfer of the network side. The UE at the sending end first sends the communication data to the network side, and then the network side sends the data to the network side. forwarded to the receiving end UE.

In practical applications, there is an application scenario where the distance between the UE at the sending end and the UE at the receiving end is relatively close. The communication data between them still needs to be transmitted on the network side before being sent to the other party. Obviously, this will lead to a decrease in network resource utilization efficiency and an increase in control signaling.

Aiming at the problems in the above scenarios, the D2D technology is currently proposed. An important concept of this technology is that communication data can be directly transmitted between two UEs, without the need for a transfer on the network side. The introduction of D2D technology can reduce the load on the network side and reduce the data transmission delay. In addition, due to the close distance between two UEs, it can effectively reduce the transmit power of the UE, reduce the interference to other users, and achieve the purpose of energy saving. In order to distinguish it from this D2D transmission technology, the original transmission mode is referred to as cellular transmission hereinafter.

In order to ensure the controllability of the network, the D2D transmission technology of centralized control on the network side can be adopted. In this technology, the network side has the ability to control the entire D2D transmission process, that is, the network side controls the establishment, maintenance and release process of the D2D transmission through control signaling, and the service data is directly transmitted between the two UEs. The D2D transmission centrally controlled by the network side is shown in Fig. 1 .

Since the system introduces the D2D technology, the base station is only responsible for the transmission control of the control signaling, and the service data is directly transmitted between the UEs, while the existing cellular transmission method is suitable for direct communication between two network element entities (such as between the base station and the UE). ) not only transmits and receives data, but also transmits and receives corresponding control signaling. Therefore, the cellular transmission method cannot be directly used in the D2D technology.

A data transmission method suitable for a cellular communication system incorporating D2D technology has not yet been proposed.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a D2D data transmission method, which is applicable to a cellular communication system that introduces D2D technology.

In order to achieve the above object, the technical scheme proposed by the present invention is:

A D2D data transmission method, comprising:

a. The base station notifies the user equipment UE accessing the network of the preset D2D retransmission period T in advance, wherein, when the system loopback time RTT is 10ms, the T is equal to the product of n and Z; when the system loopback time RTT When the RTT is not 10ms, the T is greater than the product of n and Z, n is a natural number greater than or equal to 2, and Z is the duration of a wireless frame;

b. When D2D data transmission needs to be performed between two user equipments, UE1 at the sending end selects a subframe t1 from the currently available uplink subframes for the initial transmission of the D2D data, and according to the retransmission period T and The subframe t1 determines the uplink subframe t4 used to transmit data to the receiving end UE2 again, wherein, according to the HARQ timing preset by the system, the uplink HARQ process corresponding to the subframe t1 corresponds to the uplink HARQ process corresponding to the subframe t4 The uplink HARQ process is the same;

c. The UE1 uses the uplink HARQ process corresponding to the subframe t1 to send the D2D data to the receiving end UE2 in the subframe t1;

d. After receiving the D2D data, the UE2 reports the corresponding control information to the base station in the uplink subframe t2, where the uplink subframe t2 is an uplink subframe located at least d milliseconds after the subframe t1; Said d is the preset processing delay coefficient;

e. The base station performs processing according to the received control information, and sends authorization information corresponding to the processing result to the UE1 and UE2 in the downlink subframe t3;

f. When the UE1 determines that it needs to transmit data to the UE2 according to the received authorization information, the UE1 uses the uplink HARQ process corresponding to the subframe t4 to send a corresponding The data.

To sum up, the D2D data transmission method proposed by the present invention uses uplink resources to realize D2D transmission, and controls the subframe and retransmission period used for D2D data transmission during the D2D transmission process, avoiding the use of sending D2D transmission to the base station. The subframe occupied by the control information is used for data transmission, and at the same time, the HARQ process used for the limited retransmission is the same as the HARQ process for the initial transmission, so as to avoid conflicts with the retransmission of the cellular system when D2D data is transmitted between UEs again. In this way, the D2D transmission can be effectively realized, and the impact on the cellular system can be reduced. Therefore, the present invention is applicable to a cellular communication system that introduces D2D technology.

Description of drawings

FIG. 1 is a schematic diagram of D2D transmission under centralized control on the network side;

Figure 2 is a schematic diagram of a network in which D2D transmission and cellular transmission occur in parallel;

FIG. 3 is a schematic flow chart of Embodiment 1 of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention will use uplink resources to perform D2D transmission. At the same time, considering that D2D transmission requires the network side to control the establishment, maintenance and release process of the transmission, that is to say, in D2D transmission, the UE needs to communicate with the base station, so it may happen that the UE needs to communicate with the base station in the same subframe In the case of communication between two network elements, for example, the UE needs to receive D2D data sent by the sending UE in the same subframe, and at the same time, it also needs to send control information (such as ACK/NACK and other UCI information) for D2D data transmission to the base station. However, according to the existing system, it is impossible for the UE to transmit and receive data with different network elements on the same subframe. Therefore, it is necessary to consider avoiding the occurrence of the above-mentioned situation when performing D2D data transmission.

In addition, when performing uplink data transmission, the system will set a Hybrid Automatic Repeat Request (HARQ) sequence, and set the corresponding process according to the sequence. In this way, according to the HARQ sequence, it can be determined that each process transmits in a different wireless frame. According to the existing cellular system, the process used for the retransmission of uplink data needs to be the same as the process used for the previous initial transmission. In this way, when performing D2D data transmission, it needs to be considered to avoid using the same subframe for D2D data retransmission and cellular retransmission.

Based on the above considerations, the core idea of the present invention is: when using uplink resources for D2D transmission, control the subframe and retransmission period of D2D data transmission, avoiding the use of sending ACK/NACK and other D2D transmission control information to the base station. At the same time, the procedure adopted by the limited retransmission is the same as that of the initial transmission, so as to avoid collision with the retransmission of the cellular system during retransmission.

FIG. 3 is a schematic flowchart of Embodiment 1 of the present invention. As shown in FIG. 3 , the D2D data transmission method implemented in this embodiment mainly includes:

Step 301, the base station notifies the user equipment UE accessing the network of the preset D2D retransmission period T in advance.

Here, in order to avoid conflicts between D2D data retransmission and cellular communication, the D2D retransmission cycle T needs to be specially set. Specifically, when the system loopback time RTT is 10ms, the T needs to be set to the product of n and Z; Wherein, n is a natural number greater than or equal to 2, and Z is the duration of a wireless frame; when the system round-trip time RTT is not 10ms, the T needs to be greater than the product of the n and the Z.

Step 302. When D2D data transmission is required between two user equipments, UE1 at the sending end selects a subframe t1 from the currently available uplink subframes for the initial transmission of the D2D data, and according to the retransmission period T and the subframe t1 to determine the uplink subframe t4 used to transmit data to the receiving end UE2 again.

In this step, it is necessary to select one of the currently available uplink subframes (that is, uplink subframes not used for cellular communication) for the initial transmission of D2D data, so as to ensure that the subframes occupied by sending data to the base station will not be used For data transmission, that is, the UE will not communicate with the base station at the same time on the subframe used for D2D transmission, so that the D2D transmission will not conflict with the cellular communication, and avoid affecting the cellular communication.

Moreover, in this step, when subframe t4 is determined, it is necessary to make the uplink HARQ process corresponding to subframe t4 the same as the uplink HARQ process corresponding to subframe t1 according to the HARQ timing preset by the system. In this way, by restricting the retransmission of D2D data to adopt the same process as the initial transmission, it is possible to avoid using the process for retransmission of the cellular system when retransmitting D2D data, that is, to avoid conflicts between D2D transmission and retransmission of the cellular system.

Specifically, the HARQ timing preset by the system may be the same as that of the existing LTE system, which will not be repeated here.

Step 303, the UE1 uses the uplink HARQ process corresponding to the subframe t1 to send the D2D data to the receiving end UE2 in the subframe t1.

Here, the specific method of using the uplink HARQ process to send data is the same as that of the existing system, and will not be repeated here.

Step 304: After receiving the D2D data, the UE2 reports corresponding control information to the base station in the uplink subframe t2, which is an uplink subframe located at least d milliseconds after the subframe t1.

Here, considering the processing delay at the UE side, the uplink subframe t2 needs to be set as an uplink subframe at least d milliseconds after the subframe t1. The d is a preset processing delay coefficient. In practical applications, its specific value needs to be set according to the data processing delay after the UE receives the data, so that UE2 has enough data processing time before sending the control information . Preferably, the d value can be set to 4ms.

Specifically, the control information may include ACK/NACK information.

Further, according to the uplink HARQ timing, the uplink HARQ process corresponding to the subframe t2 can be made the same as the uplink HARQ process corresponding to the subframe t1. Using the same process can make D2D transmission independent of cellular transmission, and will not multiplex subframes with cellular communication, reducing the impact on the cellular system.

Step 305, the base station processes the received control information, and sends authorization information corresponding to the processing result to the UE1 and UE2 in the downlink subframe t3.

Here, the specific determination method of the subframe t3 may be the same as that of the existing LTE system, that is, the authorization timing requirement of the LTE system is met, and details are not repeated here.

What needs to be explained here is that when D2D data transmission is required, the base station needs to notify the data sending end and receiving end of the subframe for D2D data transmission and the allocated uplink resource information (that is, authorize). In practical applications, The base station needs to notify the grant information to the sending end and the receiving end, ie, UE1 and UE2, in subframe t3.

In this step, the specific methods of processing the control information and sending the authorization information are known to those skilled in the art and will not be repeated here.

Step 306: When the UE1 judges that it needs to transmit data to the UE2 according to the received authorization information, the UE1 uses the uplink HARQ process corresponding to the subframe t4 to send the data to the UE2 in the subframe t4 corresponding data.

Here, the data that UE1 needs to transmit to UE2 may be retransmitted data or newly transmitted data.

In this step, as mentioned above, the uplink HARQ process corresponding to subframe t4 is the same as the uplink HARQ process corresponding to subframe t1. Therefore, it can be ensured that the D2D data transmission between UE1 and UE2 will not use the retransmission subframe of cellular communication. frame, that is to ensure that the direct D2D data transmission between UE1 and UE2 will not conflict with cellular communication.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. A D2D data transmission method, comprising: a. The base station notifies the user equipment UE accessing the network of the preset D2D retransmission period T in advance, wherein, when the system loopback time RTT is 10ms, the T is equal to the product of n and Z; when the system loopback time RTT When the RTT is not 10ms, the T is greater than the product of n and Z, n is a natural number greater than or equal to 2, and Z is the duration of a wireless frame; b. When D2D data transmission needs to be performed between two user equipments, UE1 at the sending end selects a subframe t1 from the currently available uplink subframes for the initial transmission of the D2D data, and according to the retransmission period T and The subframe t1 determines the uplink subframe t4 used to transmit data to the receiving end UE2 again, wherein, according to the HARQ timing preset by the system, the uplink HARQ process corresponding to the subframe t1 corresponds to the uplink HARQ process corresponding to the subframe t4 The uplink HARQ process is the same; c. The UE1 uses the uplink HARQ process corresponding to the subframe t1 to send the D2D data to the receiving end UE2 in the subframe t1; d. After receiving the D2D data, the UE2 reports the corresponding control information to the base station in the uplink subframe t2, where the uplink subframe t2 is an uplink subframe located at least d milliseconds after the subframe t1; Said d is the preset processing delay coefficient; e. The base station processes the received control information, and sends authorization information corresponding to the processing result to the UE1 and UE2 in the downlink subframe t3; f. When the UE1 determines that it needs to transmit data to the UE2 according to the received authorization information, the UE1 uses the uplink HARQ process corresponding to the subframe t4 to send a corresponding The data. 2. The method according to claim 1, wherein the subframe t3 in step e meets the authorization timing requirements of the LTE system. 3. The method according to claim 1, wherein, according to the HARQ timing, the uplink HARQ process corresponding to the subframe t2 is the same as the uplink HARQ process corresponding to the subframe t1. 4. The method of claim 1, the control information comprising ACK/NACK information. 5. The method according to claim 1, wherein the d is 4ms.