Research On Outage Performance Of D2D Relay Communication In Multi-band Cellular Networks

The fifth generation(5G) wireless network in the process of evolution can overcome disadvantages of the existing 4G wireless network. 5G wireless network can achieve higher data transmission rate, better end-to-end performance, better use coverage in hot spot region, lower time delay coverage in dense region, lower power consumption, lower cost and so on. It is to meet QoS of different business that 5G multi band architecture may contain macro cellular cell, a variety of small cells, wireless relay and D2 D network. Therefore, D2 D technology is becoming a hot spot of 5G research. Relevant research shows that cell throughput can be improved when D2 D communication technology is introduced in cellular networks. This thesis focuses on the D2 D relay system of cellular networks and proposes methods of improving outage performance for single relay and multi relay scenarios, respectively.For single relay scenario, it is proposed that taking the base station as a two-way amplify-and-forward relay on the basis of the most basic D2 D relay model, so that the direct link is combined with relay link. Then, D2 D users can receive the target signal in two different time slots. This paper only takes the interference of cellular users to D2 D users into consideration when analyzing outage probability. It is derived that the exact formula of D2 D link outage probability and approximate form at high SNR. Then, this paper proposes a optimal power allocation scheme on the target of minimizing the outage probability. Simulation results show that the strategy proposed can significantly improve the performance of D2 D relay system. The optimal power allocation scheme is superior to equal power allocation.In this paper, the scheme that taking the base station as a two-way decode-and-forward relay is also proposed to further enhance the outage performance of D2 D relay link. Firstly, D2 D relay link is divided into symmetric and asymmetric cases by considering whether the received power of realy is equal.The exact expression of outage probability is obtained by theoretical analysis. Secondly, Effect of noise can be ignored by assuming cellular users are far away from the D2 D link, so that the lower bound of the outage probability can be obtained. The simulation results not only confirm that outage probability of the base station as a DF relay strategy is significantly reduced when compared to traditional D2 D transmission but also show that performance of this strategy is better than that of AF relay when SNR is in a small range.This paper presents a simple theoretical framework for analyzing the performance of D2 D communication systems and taking into account the outage probability of cellular users for multiple relay scenario. The system is divided into two cases of up uplink and downlink band by considering co-channel interference between D2 D users and cellular users. At the same time, the outage probability theory for D2 D and cellular links is analyzed. Then, this paper proposes a shortest path routing(SPR) algorithm based on the target of minimizing outage probability. Simulation results verify accuracy of the outage probability that is derived by theory analysis and demonstrate the change trend of outage performance between the D2 D link and cellular link.