Performance Investigation of Space-Time Coded MIMO-OFDM Systems using Turbo Codes

Abstract

Achieving higher and higher data rates in wireless communications has been one of the issues which is continuously being addressed and research is being carried. There is a growing demand for high speed, spectrally efficient reliable communication especially through wireless media. Because of time varying frequency selective nature of wireless media, providing high speed reliable communication with high spectral efficiency has been one of the biggest challenges of any wireless communication system. Fourth Generation wireless systems (4G) and above are coming up with systems and schemes towards mitigating these challenges. The two key underlying technologies which are prominent players in the physical layer design of 4G wireless systems and are being adopted in 4G wireless standards are MIMO (Multiple Input Multiple Output) and OFDM (Orthogonal Frequency Division Multiplexing). While MIMO can improve capacity of wireless channels and performance through diversity and space-time coding techniques, OFDM improvesspectral efficiency and convert the nature of the channel from frequency selective to frequency flat. The combo MIMO-OFDM together can serve to improve data rates as well as spectral efficiency. In this thesis, an investigation of channel codes such as turbo codes which are capable of achieving very low Bit-Error-Rates (BER) is carried out over MIMO-OFDM system. It is shown that a turbo coded MIMO-OFDM can improve the performance of wireless systems to a greater extent thus paving the way for further enhancement in data rates.