Distributed Relay Selection Scheme in Decode-and-Forward Cooperative Systems

Author(s):  
Yinsheng Li ◽  
Q. T. Zhang
Author(s):  
Dinh-Thuan Do ◽  
Minh-Sang V. Nguyen

Objective: In this paper, Decode-and-Forward (DF) mode is deployed in the Relay Selection (RS) scheme to provide better performance in cooperative downlink Non-orthogonal Multiple Access (NOMA) networks. In particular, evaluation regarding the impact of the number of multiple relays on outage performance is presented. Methods: As main parameter affecting cooperative NOMA performance, we consider the scenario of the fixed power allocations and the varying number of relays. In addition, the expressions of outage probabilities are the main metric to examine separated NOMA users. By matching related results between simulation and analytical methods, the exactness of derived formula can be verified. Results: The intuitive main results show that in such cooperative NOMA networks, the higher the number of relays equipped, the better the system performance can be achieved. Conclusion: DF mode is confirmed as a reasonable selection scheme to improve the transmission quality in NOMA. In future work, we will introduce new relay selections to achieve improved performance.


Author(s):  
Jyh-Horng Wen ◽  
Jheng-Sian Li ◽  
Hsiang-Shan Hou ◽  
Cheng-Ying Yang

Cooperative system is a tendency in the future communications because it provides a spatial diversity to improve the system performance. This work considers the cooperative communication systems in Fixed DF Mode. The scenario includes multiple source stations, multiple relay stations and multiple destination stations. For the whole system, the maximum throughput approaching is the major purpose. Hence, to select the relay stations for signal transmission could be the important scheme to achieve the optimal system performance. With the exhaustive search method, easily to realize, the optimal selection scheme could be found with a highly complicated calculation. In order to reduce the computational complexity, a relay selection scheme is proposed. With different situations of the communication systems, the performances evaluations obtained with both the proposed algorithm and the exhaustive search method are given for comparison. It shows the proposed algorithm could provide a solution approaches to the optimal one. It could apply the proposed scheme to the practical without a delay because of long-time calculation.


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