Research On Antenna Selection Technology In Wireless Relay Network Systems

MIMO can increase system’s capacity and spectral eiffciency without improvingtransmit-power and increasing spectral band wide. Relay can extend communicationdistance and combat shadowing, which is introduced into the fourth generation mobilecommunication. Antenna selection technology is brought into the MIMO relay system,which can achieve higher communication rate and quality with the advantages of lowcomplexity and low implementation cost at the same time. Two-way relay technologywhich includes physical layer network coding and analog network coding has moreapplication prospect, with the advantages of high frequency utilization. Two-wayrelay system is received the widespread attention in academic. Because of broadcastcharacteristics of wireless communication transmission, signals are eavesdroppedeasily and secure communication has become the hot spot of research on physical.Therefore, this paper investigates the antenna selection schemes and algorithm，which based on physical layer network coding and analog network coding fortwo-way relay system. This paper also designs the antenna selection algorithm basedon secrecy rate for MIMO relay system.First of all, the paper proposes a joint design scheme of physical network codingand antenna selection scheme for two-way relay physical layer network codingsystem, which optimizes bit error rate(BER) of the system. The proposed schemeemploys the multiple access(MA) and broadcast(BC) minimum distance of theClosest-Neighbor Clustering as the criterion and make the theoretical analysis.Simulation results show that the proposed joint scheme outperforms the existingschemes, e.g. physical network coding scheme or antenna selection scheme only interms of BER.Then, compared to the physical layer network coding，analog network coding is easy for theoretical derivation and realization. To optimize BER of the system, alow-complexity minimum mean squared error antenna selection algorithm is proposed.LMM antenna selection algorithm select antennas at the relay for two-way relayanalog network coding system，which based on traditional antenna selection schemeat the relay for MIMO relay system.Taking situation which receive antenna andtransmit antenna at the relay may be different into account, the proposed algorithmselects the receive-transmit antenna pair according to the simplified expression whichis derived by the closed-form expression of mean squared error (MSE) when onemore receive-transmit antenna pair is added. Simulation results demonstrate that theproposed scheme outperforms the existing selection algorithms and approaches theoptimal algorithm most in terms of MSE and BER.Lastly, the paper considers physical layer security in wireless relay networkcommunication. Based on the MIMO relay system, the paper presents a lowercomplexity antenna selection algorithm which can maximize the secrecy rate ofsystem. Taking situation which receive antenna and transmit antenna at the relay maybe different into account，I proposed the theorem and finished the proof of theorem.The proposed algorithm selects the receive-transmit antenna pairs according to thesimplified expression which is derived by the closed-form expression of secrecy ratewhen one more receive-transmit antenna pair is added. The proposed algorithmapproaches the optimal algorithm with secrecy rate which is demonstrated bysimulation results.