A Resource Allocation Algorithm in Full Duplex D2D Communication System

Huang Wei1,2, Ke Wentao1, Zhang Haibo3, Yang Xiong1, Liang Yunjin1

(1. Chongqing Key Laboratory of Mobile Communication Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065;

2. Army Chongqing Military Representative Bureau in Chengdu Regional Military Representative Office, Chengdu 610036, Sichuan; 3. Broadband Mobile Communication Mobilization Center, Chongqing University of Posts and Telecommunications, Chongqing 400065)

applies full-duplex technology to D2D (Device-to-Device) communication, which can increase the throughput of D2D users In turn, the system throughput is improved, but self-interference caused by full-duplex communication is inevitable. Considering that multiple D2D user pairs can share the same cellular user resources, co-channel interference will occur between the D2D user pairs. Aiming at this problem, under the premise of normal user communication in the system, a resource allocation algorithm based on point coloring in graph theory is proposed. This algorithm limits the co-channel interference between D2D user pairs within an acceptable range, and uses the point coloring algorithm in graph theory to coordinate the resources between D2D user pairs and cellular users to maximize system throughput. The simulation results show that, compared with the traditional half-duplex D2D communication, the algorithm effectively improves the communication quality of D2D users and increases the system capacity of the entire cellular network.

D2D communication; full duplex; multi-sharing mode; resource allocation

Chinese Library Classification Number: TN929.5

A

DOI: 10.16157/j.issn.0258-7998.2016112.024 _

0 Chinese citation format: Huang Wei, Ke Wentao, Zhang Haibo, etc. A resource allocation algorithm in a full-duplex D2D communication system[J]. Application of Electronic Technology, 2016, 42(12): 93-96.

English citation format: Huang Wei,Ke Wentao, Zhang Haibo, et al. A multi-sharing resource allocation scheme for full-duplex D2D communications underlaying cellular networks[J].Application of Electronic Technique, 2016, 42(12): 93-96.

0 Introduction

As one of the key candidate technologies for 5G communication, D2D communication ^{[1, 2]} can increase spectrum utilization by multiplexing cellular user spectrum resources and reduce base station load. D2D communication is used for communication between short-distance terminals, and when full-duplex communication is used for short-distance communication, terminal performance will be greatly improved, so full-duplex technology is used in D2D communication.

The current research on resource allocation mostly focuses on half-duplex D2D communication ^[3-5] . In recent years, with the maturity of self-interference cancellation technology, experts and scholars have begun to study full-duplex D2D communication. Literature [6] proposed a simple full-duplex D2D communication protocol, which improves bandwidth efficiency and system throughput. Literature [7] proposed a resource allocation scheme based on interference-constrained areas, and the results showed that the D2D link throughput in full-duplex D2D communication is close to twice that of half-duplex. The literature [8] aims to maximize the system throughput and proposes a full-duplex resource allocation scheme with graph coloring in graph theory, but the literature does not consider the impact of self-interference. Document [9] aims to maximize the number of D2D users, and proposes a solution for multiple D2D pairs to multiplex the resources of a single cellular user, but this solution does not involve co-channel interference between D2D users. Literature [10] proposed a heuristic algorithm based on ensuring the quality of service for cellular users, but the complexity is too great.

To solve the above problems, this article aims at the full-duplex communication scenario to solve the resource allocation problem of multiple pairs of D2D users multiplexing the same cellular user resources.A resource allocation algorithm supporting full-duplex D2D communication is proposed. Under the premise of ensuring the quality of service for cellular users and D2D users, this algorithm allocates resources to D2D users through the midpoint coloring theory of graph theory.

1 System model

As shown in Figure 1, assuming that D2D reuses cellular user uplink resources, there are K D2D user pairs and N cellular users are randomly distributed in the cell.

where, 1≤i≤N, 1≤j≤K, and l∈{1, 2}.

If the uplink resources of the i-th cellular user are multiplexed by the j-th pair of D2D users, the signal-to-interference and noise ratio (SINR) of the l-th D2D user in the j-th pair of D2D links can be obtained:

Among them, formula (9) indicates that a D2D pair can only multiplex the channel resources of one cellular user.

2 Resource allocation algorithm based on graph coloring theory

In order to solve the above problems, this paper considers from the perspective of graph theory, and transforms the D2D resource allocation problem into a point coloring problem in graph theory.

Constructs an interference graph G=(V, E) according to the relationship of the same frequency interference between D2D user pairs. Each node in set V represents a D2D user pair in the cell, and set E represents a connected D2D user pair的边。 The side. If there is intolerable interference between the D2D user pair x and the D2D user pair y, an edge is used to connect the x and y nodes; otherwise, no connection is made.

If there is a connection between two points in the interference graph, it indicates that the same frequency interference between the corresponding D2D communication pairs is large, and the same cellular resource cannot be reused. Otherwise, it is a potential reusable resource. After completing the construction of the interference graph, the graph will be dot-colored. The coloring function is denoted as π, and the number of point coloring is denoted as τ, and the coloring points are arranged in descending order of the fixed point degree. The pseudo code of the algorithm is shown below.

Based on graph coloring resource allocation algorithm:

3 Simulation analysis

In order to facilitate the implementation,This paper simulates the proposed algorithm in a single cell scenario, and the simulation parameters are shown in Table 1.

As can be seen from Figure 2, when the base station receives increased interference, the total throughput of D2D users also increases, and the number of D2D communication pairs continues to increase. When the self-interference cancellation is 95 dB, the half-duplex (HD) mode performs better than the full-duplex (FD); when the self-interference cancellation is 105 dB and 110 dB, the full-duplex D2D communication mode performs better.

Figure 3 shows the relationship between the interruption probability of a single D2D link communication and the interference received by the base station. Compared with half-duplex D2D communication users, each full-duplex D2D user will experience greater interference.

Figure 4 shows the change trend of system throughput with self-interference. Since the throughput of the half-duplex system is not affected by self-interference, it remains unchanged. The graph coloring resource allocation algorithm used in this paper effectively coordinates the co-frequency interference caused by multiple D2D users being able to reuse the same cellular resource. Compared with the traditional single multiplexing mode, this algorithm improves the throughput of the system.

Figure 5 shows the influence of the increase of the D2D logarithm in the system on the average number of D2D participating in multiplexing. Using the algorithm in this paper makes the number of D2D users that can reuse cellular user resources in the system more than half the number of half-duplex D2D links, thereby effectively reducing co-channel interference. Therefore, a reasonable use of the full-duplex D2D communication mode will bring certain benefits.

4 Conclusion

The many-to-one D2D communication mode in the cellular system can make full use of the limited spectrum resources, thereby increasing the system throughput, but the interference generated in the system will also be more serious. The algorithm proposed in this paper can effectively allocate resources to D2D users through the graph coloring algorithm under the QoS constraints of the quality of service of all users in the system, and control the co-channel interference between D2D users within an acceptable range, thereby improving system performance. Throughput. However, this research does not involve power optimization, so further research is needed on the power control of users in the system.

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