CN112994759A

CN112994759A - Cooperative relay D2D communication method based on OFDM

Info

Publication number: CN112994759A
Application number: CN202110153511.7A
Authority: CN
Inventors: 蒋林; 王斌; 王文鼐
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2021-02-04
Filing date: 2021-02-04
Publication date: 2021-06-18
Anticipated expiration: 2041-02-04
Also published as: CN112994759B

Abstract

The invention discloses an OFDM-based cooperative relay D2D communication method, which includes a long-distance D2D pair performing data relay communication through a special D2D pair, the special D2D pair multiplexing multiple resources and serving as a relay device, and using multiple The available resources are used for signal transmission; the frame structure of the communication system is divided into two time slots of equal length. In odd-numbered time slots, the special D2D transmitter can both send signals and receive relay forwarding signals. In even-numbered time slots, special D2D transmitters Based on OFDM, the machine sends its own transmission signal and forwards the relayed signal. The present invention selects the D2D user as the relay device of the long-distance D2D pair, which can effectively solve the problem that the D2D communication cannot be performed due to the distance limitation, and effectively increase the number of D2D accesses in the system; through the OFDM technology, one D2D multiplexing can be fully utilized. In the case of multiple cellular resources, the spectrum utilization efficiency in the system can be effectively improved under the premise of ensuring the special D2D communication quality acting as a relay, which has a wide range of practical value and application prospects.

Description

Cooperative relay D2D communication method based on OFDM

Technical Field

The invention relates to wireless communication, in particular to a cooperative relay D2D communication method based on OFDM.

Background

With the rapid development of information technology and the explosive growth of the number of multimedia smart devices, and the online use of various multimedia applications, and accompanied with high requirements for communication service quality, delay and rate, the existing communication means and communication resources have difficulty in coping with and providing the real demands of users. D2D communication is one of the technical components of the 5G architecture, and is a communication mode in which data transmission can be directly performed between a neighboring device and a device without data forwarding through a base station. As shown in fig. 1, D2D can directly perform short-distance communication for users by multiplexing cellular user resources, thereby greatly reducing the number of data processing and forwarding times of the base station, and greatly increasing the utilization rate of spectrum resources, thereby increasing the total throughput of the system, expanding the network capacity, reducing the power consumption, and ensuring the Qos of user communication.

The communication frequency band used by D2D is a telecommunication authorized frequency band, and the base station can control the transmission power, mode selection and resource reuse of the user. The resource used for D2D communication may be the communication resource of a shared cellular user or may occupy a communication channel alone. In general, there are three modes of communication for D2D: dedicated mode, cellular mode, and shared mode (reuse mode), but shared mode is the most commonly used one, and the shared mode can greatly improve the spectrum utilization efficiency and improve the cell communication capacity.

In the multiplexing mode, the case of multiplexing resources can be classified into a one-to-one multiplexing mode and a many-to-one multiplexing mode. As shown in fig. 2, the users D2D all adopt the multiplexing mode, the users D2D _1 multiplex the resources of the cellular user CUE _1, and the users D2D _2 and D2D _3 jointly multiplex the resources of the cellular user CUE _ 2. Compared with a one-to-one multiplexing mode, the many-to-one multiplexing mode can enable the system to accommodate more communication users, and further improves the spectrum utilization rate of the system. In the many-to-one resource multiplexing mode, the D2D users may be resource multiplexed by grouping, and the grouping may control the interference among the D2D users as little as possible. In the grouping process, some D2D pairs can perform resource multiplexing in a plurality of cellular user resource blocks, but in the actual multiplexing process, one D2D traffic multiplexing one resource block can complete the communication task, thereby causing the waste of the frequency spectrum in the system. The D2D communication can reduce the load of the base station due to its short-distance direct communication, but when the distance between the devices is relatively large, the communication quality of the two devices cannot be guaranteed, and even the two devices may not be connected, which may affect the communication performance of the whole system when there is available resource.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to solve the defects that D2D users cannot directly communicate due to long distance and the problem of frequency waste, and provides a cooperative relay D2D communication method based on OFDM, which improves the access quantity of a system D2D and ensures the communication quality of special D2D users.

The technical scheme is as follows: a cooperative relaying D2D communication method based on OFDM, the long-distance D2D pair carries on the data relay communication through the special D2D pair, the special D2D pair multiplexes a plurality of resources and acts as the relay equipment, utilize a plurality of available resources to carry on the signal transmission based on OFDM; the frame structure of the communication system is divided into two time slots with equal length, in the odd time slot, the special D2D transmitter can send signals and receive relay forwarding signals, and in the even time slot, the special D2D transmitter sends self transmission signals and relay forwarding signals based on OFDM.

Further, the cellular user normally communicates with the base station BS by using an uplink in all time slots, the ordinary direct-connection D2D user normally multiplexes cellular resource communication in all time slots, the long-distance D2D transmitter sends a signal in an odd time slot, and receives a relay forwarding signal in an even time slot; the special D2D acting as a relay performs normal direct communication using one cellular resource in odd slots, receives a relay forwarding signal using another available multiplexing resource, and transmits its own communication signal and the relay forwarding signal in even slots.

Further, the long range D2D transmitter sends information to the special D2D transmitter acting as a relay by multiplexing the special D2D pairs of pairable cellular resources at odd time slots.

Further, the special D2D transmitter acting as a relay uses both cellular resources at the same time in odd slots, communicates normally on one resource, does not transmit on the other resource, receives only signals from the remote D2D user and stores for retransmission in even slots.

Further, the special D2D transmitter acting as a relay simultaneously multiplexes two resource blocks that can be paired for signal transmission based on OFDM in even slots, and transmits signals to the long-distance D2D receiver and the special D2D receiver, respectively, based on OFDM.

Further, the far distance D2D receiver and the special D2D receiver receive the transmitted signal from the special D2D transmitter acting as a relay at even slots.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: the problem that D2D communication cannot be carried out due to distance limitation can be effectively solved by selecting the D2D user as the relay equipment of the long-distance D2D pair, and the access quantity of the system D2D is effectively increased; the OFDM technology can fully utilize the condition that one D2D multiplexes a plurality of cellular resources, and effectively improves the utilization efficiency of the spectrum in the system on the premise of ensuring the communication quality of the special D2D serving as a relay.

Drawings

Fig. 1 is a D2D communication link diagram under an LTE system;

FIG. 2 is a diagram of one-to-one and many-to-one resource reuse scenarios;

FIG. 3 is a diagram of a D2D communication scenario in which a D2D user acts as a relay in the present invention;

FIG. 4 is a diagram illustrating a system information transmission scheduling frame structure according to the present invention;

fig. 5 is a diagram of a communication scenario of OFDM-based cooperative relay D2D in the present invention;

fig. 6 is a general model diagram of a communication scenario of the OFDM-based cooperative relay D2D in the present invention.

Detailed Description

The following detailed description of embodiments of the present invention will be made with reference to the accompanying drawings and examples.

As shown in fig. 3, the D2D pair is used as a relay device, and the D2D pair serving as a relay is called a special D2D pair, so that the intra-system spectrum resources can be effectively utilized and the number of system accessible communications D2D can be increased.

The system frame structure is divided into two time slots with odd-even alternation and equal length, cellular users normally use uplink to communicate with the base station BS in all time slots, common direct-connection D2D users normally multiplex cellular resource communication in all time slots, a long-distance D2D transmitter sends signals in odd time slots, and a long-distance D2D receiver receives relay forwarding signals in even time slots. The special D2D user acting as a relay uses one cellular resource for normal direct communication in odd time slots, uses another available multiplexing resource to receive the relay forwarding signal, and sends the signal's own communication signal and the relay forwarding signal in even time slots, as shown in fig. 4.

As shown in fig. 5, the OFDM-based cooperative relay D2D communication transmission scheme proposed by the present invention is directed to a single cell communication scenario, where multiple cellular users and D2D users exist in a cell, the cellular users preferentially select resources, then the D2D performs resource multiplexing after effective grouping, when the D2D pairs are grouped, one D2D pair may be paired with multiple cellular resources, but in an actual use process, only one cellular resource is specified to be multiplexed by one D2D pair, and OFDM-based cooperative relay D2D communication is proposed in order to improve spectrum utilization. As shown in fig. 6, for analysis of a cooperative relay transmission situation, a cell contains a base station, a pair of long-distance D2D pairs, and two D2D groups, which can be multiplexed by a special D2D pair (D2D _1) serving as a relay at the same time. The long-distance D2D cannot perform normal communication due to distance limitation, the special D2D transmitter acting as a relay receives the signal transmitted by the long-distance D2D transmitter and forwards the signal to the long-distance D2D receiver, and the special D2D pair can also perform normal communication. The dashed lines in the figure represent interfering signals. The following describes the procedure of the present scheme by taking the data transmission of the system in two time slots as an example.

(1) Odd number of time slots

Step 1: remote at odd time slotsThe off-D2D transmitter sends information to the special D2D transmitter acting as a relay by multiplexing the special D2D pairable cellular resources. As shown in FIG. 6, the special D2D pair can multiplex the cellular resources of packet 1 and packet 2 simultaneously, and the long-distance D2D transmitter arbitrarily multiplexes one of the resources for data transmission S₀The special D2D user reuses the remaining one resource for normal signal transmission S₁。

Step 2: the same resource-specific D2D transmitter does not transmit signals at odd slots and long distances, only receives signals from remote D2D users and stores them for retransmission at even slots. The special D2D transmitter receives the signal S transmitted from the long-distance D2D transmitter₀And simultaneously receiving signals sent by other D2D transmitters in the cluster, and dividing the signals by S₀Besides signals, other signals are interference signals.

(2) Even number of time slots

Step 4, the special D2D transmitter which acts as a relay in the even time slot simultaneously multiplexes two resource blocks which can be paired for signal transmission by OFDM technology. Signal S is transmitted to a long-distance D2D receiver and a special D2D receiver respectively through OFDM technology₂And S₃. Through OFDM technology, the special D2D transmitter can utilize the cellular resources of packet 1 and packet 2 simultaneously, and utilize orthogonal resources to transmit signal S without mutual interference₂And S₃To both receivers.

Step 5 the long-range D2D receiver and the special D2D receiver receive the signal transmitted from the special D2D transmitter acting as a relay at even slots. The long-distance D2D receiver and the special D2D receiver are receiving the useful signal S₂And S₃Meanwhile, communication signals of other D2D users (D2D _2 and D2D _3) in the group are received, and the signals can be regarded as interference signals to carry out correct signal reception.

The embodiments of the present invention are described in detail with reference to the prior art, and the description thereof is not limited thereto. The invention is verified by repeated experiments, and obtains more satisfactory effect.

Claims

1. An OFDM-based cooperative relay D2D communication method, characterized in that a long-distance D2D pair performs data relay communication through a special D2D pair that multiplexes multiple resources and acts as a relay device based on OFDM Use multiple available resources for signal transmission; divide the frame structure of the communication system into two time slots of equal length. In odd-numbered time slots, the special D2D transmitter can both send signals and receive relay forwarding signals. In even-numbered time slots, The special D2D transmitter transmits its own transmission signal and retransmits the relay retransmission signal based on OFDM.

2. The OFDM-based cooperative relay D2D communication method according to claim 1, wherein the cellular user normally communicates with the base station BS using the uplink in all time slots, and the normal direct-connected D2D user is normal in all time slots Multiplexing cellular resource communication, the long-distance D2D transmitter sends signals in the odd-numbered time slots, and the long-distance D2D receiver receives the relay-forwarded signals in the even-numbered time slots; the special D2D pair acting as a relay is in the The odd-numbered time slot uses one cellular resource for normal direct-connection communication, uses another available multiplexing resource to receive the relay-forwarded signal, and sends the own communication signal and the relay-forwarded signal in the even-numbered time slot.

3. The OFDM-based cooperative relay D2D communication method according to claim 2, wherein the long-distance D2D transmitter is capable of pairing cellular resource directions by multiplexing the special D2D pair in the odd-numbered time slot. The special D2D transmitter acting as a relay sends the information.

4. The OFDM-based cooperative relay D2D communication method according to claim 3, wherein the special D2D transmitter acting as a relay uses two cellular resources at the same time in the odd-numbered time slots, and in one resource On the other hand, no signal is sent on another resource, and only the signal from the remote D2D user is received and stored for forwarding in the even-numbered time slot.

5 . The OFDM-based cooperative relay D2D communication method according to claim 4 , wherein the special D2D transmitter serving as a relay multiplexes two paired pairs of OFDM-based D2D transmitters simultaneously in the even-numbered time slots. 6 . The resource block transmits the signal, and transmits the signal to the long-distance D2D receiver and the special D2D receiver respectively based on OFDM.

6 . The OFDM-based cooperative relay D2D communication method according to claim 5 , wherein the long-distance D2D receiver and the special D2D receiver receive information from a relay acting as a relay in the even-numbered time slot. 7 . The signal sent by the special D2D transmitter.