Performance Analysis of Differential Detection Transmit Diversity

Abstract

Mobile communication is going through a constant improvement and it has improved a lot in past few years. It has evolved from the 1G systems of the past to the present phase which is 4G. With the passage of time the demand for improved systems increases and hence there needs for the system to be improved. For improvement in the capacity of the system MIMO systems are employed. Work has been done on a 2x1 transmit diversity system and after that there has been a lot work done in this direction. This is the base for WCDMA systems. Transmit diversity systems increase the diversity gain of the system but it does not waste the bandwidth for it. It uses the spatial parameter for this diversity gain. This 2x1 transmit diversity scheme works well if there is perfect channel information available at the receiver. In order to estimate the channel pilot symbols are to be transmitted, i.e. the receiver knows the pilot symbols and also the time when the transmitter sends these symbols. The pilot symbols are to be transmitted at regular intervals but even then there are errors in channel approximation. This requires extra hardware at both transmitter and the receiver sides. So in order to remove this limitation differential detection scheme is proposed in which there is no need for channel information. In order to exploit the advantages of differential detection and transmit diversity a scheme was proposed using BPSK modulation. In this thesis simulation results for BER Vs SNR have been compared using BPSK, DPSK and QPSK modulations for this combined scheme. Comparisons of the BER performance have been done between 2x1 transmit diversity scheme and with the combined scheme. The comparisons have been done under multipath fading.