Performance of an Interleaved Spread Spectrum OFDM System over Multipath Fading Channels 1 Performance of an Interleaved Spread Spectrum OFDM System over Multipath Fading Channels

In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) system and investigate its performance over frequency selective multipath fading channels. The purpose is to exploit frequency diversity capabil-ity, develop an efficient spectrum spreading algorithm and improve the system performance over frequency selective multipath fading channels. At transmitter, a spectrum spread ISS-OFDM signal is generated by employing OFDM modulation and interleaving tech-niques. At the receiver, two solutions including serial demodulation and parallel demodulation for diver-sity combing are proposed, in which the received sig-nals are combined by using a maximum ratio combin-ing (MRC) technique. The simulation indicates that higher frequency diversity is achieved, and the Bit Error Rate (BER) and Peak-to-Average Power Ratio (PAR) performances of the proposed ISS-OFDM sys-tem over frequency selective multipath fading chan-nels are improved significantly as compared with the conventional OFDM systems. Another unique char-acteristic is that the spectrum spreading factor and diversity order provided by the system are reconfig-urable to achieve cognitive communications