Performance Analysis of Closed-Loop MIMO system

Abstract

In this paper, it investigate the bit error rate (BER) performance of transmit beamforming using singular value decomposition (SVD) for closed loop multiple-input multiple-output (MIMO) wireless systems with various modulation techniques such as binary phase shift keying (BPSK), quadrature phase-shift keying (QPSK�� and 16- quadrature amplitude modulation (16-QAM) along with convolution encoder and viterbi decoder. Beamforming separates the MIMO channel into parallel subchannels. The beamforming vectors used at the transmitter and the receiver can be obtained by the singular value decomposition (SVD) of the MIMO channel. Signals are transmitting in the direction of the eigenvector corresponding to the largest eigen value of the channel. The transmit beamforming is performed by multiplying the input symbols with beamforming vector (i.e.) unitary matrix and the precoded symbols are transmitted over rayleigh fading channel. At the receiving end the transmitted signals are obtained by performing the receiver shaping by multiplying the received signal with conjugate transpose of the unitary matrix. Furthermore, derive an expression for a capacity of MIMO system and derive expressions for average BER for BPSK and average symbol error rate (SER) for M-QAM. Simulation results displays the diversity performance of the single beamforming when the three modulations are used separately and it shows the proposed SVD-based beamforming with convolution encoder yield the better performance when compare to the other beamforming method.