Turbo Coded Single User Massive MIMO
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This work deals with turbo coded single user massive multiple input multiple output (SU-MMIMO) systems, with and without precoding. SU-MMIMO has a much higher spectral efficiency compared to multi-user massive MIMO (MU-MMIMO) since independent signals are transmitted from each of the antenna elements (spatial multiplexing). MU-MMIMO that uses beamforming has a much lower spectral efficiency, since the same signal (with a delay) is transmitted from each of the antenna elements. In this work, expressions for the upper bound on the average signal-to-noise ratio (SNR) per bit and spectral efficiency are derived for SU-MMIMO with and without precoding. We propose a performance index f(N_t), which is a function of the number of transmit antennas N_t. Here f(N_t) is the sum of the upper bound on the average SNR per bit and the spectral efficiency. We demonstrate that when the total number of antennas (N_tot) in the transmitter and receiver is fixed, there exists a minimum value of f(N_t), which has to be avoided. Computer simulations show that the bit-error-rate (BER) is nearly insensitive to a wide range of the number of transmit antennas and re-transmissions, when N_tot is large and kept constant. Thus, the spectral efficiency can be made as large as possible, for a given BER and N_tot.
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