Research On Relay Selection Technique In Radio Relay Network

1. IntroductionWith the development of modern telecommunication technologies and thepopularity of wireless terminals, the way people access to network services hasgradually changed. More and more new technologies, new software released, whichattracted more customers using the network services through mobile terminals. At themean time, the requirements from the users about data rate and the quality of serviceare also rising, which has become a key topic of researchers recently.In recent years, scholars major on wireless communication have put forward anumber of new ideas, like diversity technique. Among the diversity techniques,multiple-input multiple-output antenna technology (MIMO) is a representative one. Itcould greatly improve the power and spectral efficiency of the system. However, dueto the size and volume of the mobile terminals, and the complexity of the system,MIMO technology has not been widely used in the mobile communication system.Later, a new spatial diversity technique has been proposed, namely cooperativecommunication technology. The information transmitted by the information sourceand the cooperative node at the same time, the sink receives two signalssimultaneously, so we can achieve a space diversity effect. Currently, a number ofacademic studies have demonstrated that cooperative communication technology canenhance the performance of the network. And the research of this paper is focused onit.In cooperative communication techniques, how to choose a relay node is a keyissue.In this paper, we compared several classic relay selection algorithms, chose andimproved the Min-Max algorithm from the classic algorithms, gave a relay selectionalgorithm based on equivalent channel energy gain parameter.2. Relay selection algorithm based on equivalent channel energy gainFirstly, we consider a simple model which fixed source and destination node,select a best relay node from several relay nodes. After simulation experiments, wechoose the program which choose the maximum equivalent channel energy gainminimum relay node. It ensures the best outage probability performance.Secondly, we expend this algorithm to a larger network. We proposed a strategyin which every user in the cell will get a relay node, and will act as a relay node toother users as well. With the application of this strategy, we can expand the coveragearea of the system, reduce system construction costs, reduce outage probability under the same SNR conditions and improve system performance.Although existing algorithms can already achieve the above functions, but theproposed algorithm still has certain advantages. First, the algorithm facilitatesaccessing to the data, we just need to listen to the RTS and CTS signals. Second, withrespect to the outage probability criteria algorithm, our algorithm has a lowercomputational complexity. Third, source node transmits OFDM signals, witch switchthe serial data to parallel data, can be a good fight against inter symbol interference,reduce the effect of fading.3. Simulation results analysisFirstly, we do the simulation about the classical maximum and minimumalgorithm. And the result confirmed that we can reduce the outage probability of thetelecommunication system by distributing cooperative relay node for the usersreasonably. But it is very important to choose a good relay selection algorithm.Because the performance of the random relay selection strategy is worse than thedirectly transmit strategy refers to the outage probability parameter.Then, we do the simulation about the algorithm which based on the equivalentchannel energy gain parameter proposed in this paper. We put forward five differentprograms aiming to find a best way to use the equivalent channel energy gainparameter. This program will allow the system to obtain the minimum outageprobability under the same SNR conditions. By the simulation in the simple model,we proved that the program which chooses the maximum equivalent channel energygain minimum relay node performs best in the five programs.Finally, we do the simulation about the strategy proposed in this paper whichapplied to a large network system. The simulation result shows that the relay selectionprotocol based on equivalent channel energy gain can greatly reduce the systemoutage probability and outperforms the directly transmit system.