Zero Forcing and Minimum Mean Square Error Equalization for OFDM-CDMA Multiuser Detection in Multipath Fading Channels
Fang‐Biau Ueng, Hsuan-Fu Wang, Riche Chang, Li‐Der Jeng · 2006
This paper introduces four block joint detection (JD) receivers which combining the orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA) techniques, i.e., OFDM-CDMA receiver. The performance of the OFDM-CDMA receiver with orthogonal and non-orthogonal spreading sequences is investigated in mobile radio channels. The sequences considered as spreading codes are orthogonal Walsh-Hadamard, Orthogonal Gold, Gold and maximim length sequences or m-sequences. The JD algorithms for the OFDM-CDMA receiver are Zero Forcing Block Linear Equalizer (ZF-BLE), Minimum Mean Square Error Block Linear Equalizer (MMSE-BLE), with and without decision feedback (DF). Time-domain equalization does not require DFT or FFT operations and can be used to compensate the channel fading effect. Hence for hardware implementation, the time domain interpretation can lead to a more efficient structure when compared with the frequency domain approach. The bit error rate (BER) performance comparisons of different spreading codes and equalizers are shown in the simulations.