IDMA-OFDM schemes for wireless communication systems

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is a very efficient way of realizing multicarrier modulation. It provides high spectral efficiency thanks to the orthogonality among subcarriers. What’s more, Inter-symbol Interference (ISI) among users can be eliminated by cyclic prefix, and the implementation of OFDM can be simply realized by a pair of IFFT & FFT. However, an uncoded OFDM may not perform well in frequency selective fading channels. Interleave Division Multiple Access (IDMA) can be treated as a special form of CDMA. In IDMA, random interleavers are employed for user specification. With appropriate Forward Error Correction (FEC) coding and low cost iterative Multi-user Detection (MUD), IDMA performs well in fading channels. OFDM-IDMA is a recent proposed wireless communication scheme. The motivation of such a joint-scheme is simply to combine the advantages of both OFDM and IDMA. It is expected that OFDM-IDMA has a good performance over fading channels for multiuser communication system. On top of this, power allocation can be applied to enhance the system performance with different system data rates. In this project, the following issues will be addressed: 1. Software implementation of OFDM-IDMA multiuser system with FEC and QPSK modulation over Rayleigh fading multipath channels 2. Power allocation for supporting different system rates 3. Software implementation of uncoded OFDMA multiuser system with QPSK modulation over Rayleigh fading multipath channels 4. Comparison between OFDM-IDMA and uncoded OFDMA over Rayleigh fading channels 5. Performance evaluation of OFDM-IDMA and uncoded OFDMA when considering Doppler Effect