DEVELOPMENT OF A DFT-PRECODING SCHEME FOR SPATIALLY MULTIPLEXED 4G WIRELESS COMMUNICATION SYSTEM WITH DIFFERENT MIMO CONFIGURATIONS

Abstract

Broadband multiple-input multiple output (MIMO) communication systems using spatial multiplexing are facing multi-stream interference (MSI) from the transmit antennas and intersymbol interference (ISI) due to the time-dispersive nature of the channel. Appropriate detection requires the minimization of both sources of interference, usually at the receiver. Orthogonal frequency division multiplexing (OFDM) is a well-known technique employed in the 4th Generation (4G) communication system that can eliminate ISI, and therefore MSI remains the major source of interference in a MIMO-OFDM system. Removal can be realized at the transmitter utilizing channel state information (CSI) in the frequency domain. In most practical cases, no signal processing at the sub-carrier (frequency domain) level is possible and MSI removal (equalization) has to be done in time domain. In this research, a MIMO-OFDM system was developed as a 4G system connected to a spatial multiplexing convergence layer. A DFT-precoding scheme was presented for removing MSI in frequency selective channels under assumption of perfect CSI at the transmitter that is still benefiting from the OFDM ability to remove ISI. The receiver architecture employs the Minimum Mean Square Error (MMSE) equalization with minimal channel coding. The performance of the system was evaluated using different bandwidth configurations as proposed in the 4G specification, and three different modulation schemes, namely, QPSK, 16QAM and 64QAM. The result shows that the bit error rate performance of the system improves as the bandwidth increases. The data throughput of the system also increases as the antenna configuration at the transmitter and receiver increases from 𝑁=2 to 𝑁=8