Pilot-aided Frequency-domain Equalization with Threshold Detection for OFDM-CDMA Down Link Transmissions in A Frequency Selective Fading Channel

Abstract In OFDM-CDMA down link, frequency equalization is necessary at the receiver to restore orthgonality among different users. But the noise enhancement due to orthgonality restoration degrades transmission performance. In this paper, pilot-aided frequency equalization with threshold detection (TD) is presented that can effectively suppress the noise enhancement. There is an optimal threshold that can minimize the bit error rate (BER) for a given received Eb/N0. The average BER performance of OFDM-CDMA down link transmissions using TD equalization is evaluated by computer simulation. It is found that TD equalization using optimum detection threshold can significantly reduce the BER floor and outperforms DS-CDMA with ideal rake combining. The achievable BER performance is also compared with those of ORC, CE, and MMSEC equalization techniques.