Research On Opportunistic Transmission Techniques For Two-Way Amplify-and-forward Relaying Systems

The channel fading affects the transmission reliability and effectiveness in wireless communication system. Relay technology which can effectively mitigate the negative effects of different kinds of fading in wireless channels, expand the coverage of wireless communication system, increase the system capacity and improve the transmission reliability and effectiveness, has been included in some mainstream wireless standards, e.g., LTE-A and IEEE 802.16 m. It overcomes the spectral efficiency loss in the traditional one-way relaying system, and therefore has become the hotspot in the field of wireless communication ever since it was proposed. For an in-depth understanding of the outage probability and diversity gain performance in various two-way amplify-and-forward(AF) relaying scenarios, this paper studies opportunistic transmission techniques in such systems. The main contributions of this paper are summarized as follows:1. In multiuser two-way relaying system with TDBC(Time Division Broadcast) protocol, two joint antenna-user selection schemes are proposed, i.e., the optimal selection scheme and its suboptimal counterpart. Implementation steps are given for both schemes, and the performance is validated by simulations. The optimal scheme provides better performance, while the suboptimal scheme is characterized by its simplicity and robustness to the channel estimation errors. Furthermore, the performance gap between the two schemes is small.2. This paper studies the application of the beamforming technology in two-way AF relay system, moreover, outage probability and diversity gain are derived in asymmetric two-way AF relaying system. In multi-user and multi-relay two-way AF relaying system, considering the impact of antenna correlation, a low-complexity two-stage joint relay and user selection scheme is proposed. Firstly, according to the channel state information between relays and users, the best relay for each user is selected, forming a relay-user pair. Then with the aim to optimize the system outage probability, the optimal relay-user pair is selected to communication with the base station. This scheme’s outage probability and diversity order are given and the simulations validate the analysis in this paper.