Research On Relay Selection Algorithm In Cooperative Wireless Networks

As the mobile channel with multi-path fading and Doppler frequency shift are seriously hindered the channel capacity and service quality improvement, how to effectively against multi-path fading in mobile channel has been a hot broad research problem. Cooperative diversity came into being, it makes use of neighbor nodes around each other mutually transfer information to form a virtual MIMO, this method can good use of space resources, increase the channel capacity. But how effective use and management of the surrounding neighborhood nodes to cooperative transmission and how to choose a collaborative user, become a key issue in collaborative communication.This thesis focus on how to selection collaborative communication nodes (relay nodes) carried out researching, and focus on the analysis of the BER. Thesis is divided into five chapters, the main contents are as follows:In the first chapter, it mainly described the current developments on mobile communications, the problems faced and the thought of Cooperative Diversity's background. In the second chapter,it introduced the key technologies of Cooperative and system model, the key technologies includes transmit diversity, receive diversity, and relay forward means, in this thesis used decoding and forward (decode and-forward, DF) mode, at the terminal used a maximal ratio combining (MRC) reception mode. Cooperative Diversity model introduces two hop parallel and serial models. In the third Chapter the two relay selection of ideas based on threshold was proposed, one method was chose the relay nodes which is the largest SNR and above the threshold; the other method is chose the relay node which the bit error rate is minimum and above the threshold;the best chosen relay nodes was combined with the directly link that the source node to destination node at the destination, and analyzed the different number of relay nodes and threshold value system's effects. The chapter four is based on the previous chapter, proposed the automatic retransmission request (ARQ) idea, adopt Cross-layer design idea which combined the physical layer cooperative diversity techniques and data link layer automatic retransmission request. By observing the simulation results, it can be obtained that automatic requests retransmission collaborative communications, improved the system reliability significantly. In the chapter five,a summary of the thesis was made, and make a prospect on the development of collaborative communication. In each parts of this thesis, there are the corresponding Monte Carlo simulation and the corresponding parameters were analyzed.It is worth mentioned that the content of this thesis is a doctoral research fund project (doctoral category, number 20092125110006) "ARQ collaborative digital relay system cross-layer design" of the sub-topics.