Design, Implementation and optimisation of 4x4 mimo-ofdm transmitter for communication systems

Multiple Input Multiple Output (MIMO) uses multiple antennas at both the transmitter and receiver side. In recent times the demand for the use of MIMO systems has increased due to its capability of robustness against Multipath fading and increasing the Spatial Multiplexing Gain and Spatial Diversity Gain. Orthogonal Frequency Division Multiplexing (OFDM) is one of the best digital modulation schemes, where signal is divided into number of narrow band channels to obtain spectral efficiency and minimizing the Inter Symbol Interference (ISI). Thus, combining MIMO and OFDM technologies will improve spectral efficiency, link reliability and spectral gain.

In this paper, MIMO and OFDM techniques are combined to improve the transmitter performance. Software reference model for 4x4-MIMO-OFDM Transmitter for wireless communication system is designed and modeled in MATLAB as well as the same is implemented in C language. The evaluation of Bit Error Rate (BER) and Signal to Noise Ratio (SNR) performance of the OFDM technique combined with Alamouti Space Time Block Codes (STBC) based on two modulation schemes namely QPSK and 16 QAM over AWGN channels is carried out. The developed system model is implemented in C and performance comparison & optimization are carried out using Real View Development Suite (RVDS) by considering different ARM cores.

Performance metrics such as Mean Square Error (MSE) and Peak Signal-to-Noise Ratio (PSNR) are computed for 4x4-MIMO-OFDM transmitter system and performance of whole system is analysed for QPSK and 16 QAM modulation techniques. BER for QPSK is 10-^2.6 and BER for 16 QAM is 10-^1.5 dB at a fixed SNR of 10 dB. System developed in C is analysed in RVDS. Profiling results shows that ARM cortex family provides better performance in terms of number of cycles estimated to execution of code and code coverage when compared with lower versions of it. The number of estimated cycles in ARM Cortex A9 is reduced by 8.5% when compared to ARM 1136. The work can be further enhanced by using massive MIMO in place of conventional MIMO.