Space Time Code Design using Quadrature Amplitude Modulation for Multiple Access Channel with Quantized Feedback

Space time block codes for multiple access channels with full diversity and low decoding complexity for any number of transmitters and one receiver with quantized feedback. We provide detail of our scheme for four transmitter and four antennas. Each transmitter sends code word to the receiver at the same time. First propose a codebook design and feedback scheme that combines space time block coding and array processing. To the best of our knowledge this is the first scheme with quantized feedback that can achieve low decoding complexity and full diversity for any number of users when all users transmit at the same time. The QAM Scheme can implement low decoding complexity differential modulation it can be used to increase the bit error rate and signal to noise ratio. The performance of TDMA System in AWGN channel shows that QAM modulation technique has better performance compared to that of QPSK.