Interference management for multi-user cooperative relaying networks

Abstract

Background & Objectives: As the electromagnetic spectrum resource is becoming highly scarce, improving spectral efficiency is becoming extremely important for the development of future wireless communication systems. Integrating cooperative relaying techniques into wireless communication systems sheds new light on better spectral efficiency. By taking advantage of the broadcast nature of wireless communications, cooperative transmission can be used in improving communication reliability, and enhancing power and spectrum efficiency. Moreover, comparing to other emerging techniques that could achieve similar performance advantages, such as multiple-input multiple-output (MIMO) technique, cooperative communication is superior in hardware feasibility and deployment flexibility. The important advantages of cooperative communication make it one of the promising techniques for future wireless communication systems. Recently, many cooperative communication schemes have been included in different cellular standards, such as WiMAX and LTE-Advanced. However, the promised throughput and diversity gain may be lost in the presence of interferences, and hence, interference management is very important for exploiting the benefits of cooperation. This requires the need to find proper methods to prevent the interference problems, which is the main target of our current research. Methods: In this study we introduce an efficient cooperative communications scheme which maximizes the received signal-to-noise ratio (SNR) while keeping the interference levels below a certain threshold. The introduced scheme is based on two relay selection methods: max (link 2) which is based on maximizing the SNR of the second hop, and max (e2e) which aims to maximize the end-to-end SNR of the relayed link. In this method, the perfect decoding-and-forward (DF) relaying protocol is used by the relays, and the maximum ratio combining (MRC) receiver is used to combine the direct and the best selected relay links. We derive exact closed form expressions for the probability density function (PDF) of the SNR, outage probability, average capacity, and average bit error probability for the introduced cooperative schemes. Results & Conclusion: Simulations are used to validate the analytical results and an agreement is observed. The results confirm the advantage of the introduced cooperation schemes in enhancing the wireless communication system and in interference management.