Subcarrier Weighting Scheme in OFDM Receiver with SigmaDelta A/D Converter on Multipath Fading Channels

In OFDM receivers, an analog-to-digital converter must convert a signal with large bandwidth and high resolution. A ΣΔ modulator is a type of A/D converters that has very high resolution. However, it has lower bandwidth than the other types of A/D converters because the quantization noise of the ΣΔ modulator increases in high frequency. Moreover, the oversampling rate of the ΣΔ modulator needs to be decreased for reduction of power consumption. In this paper, performance of an OFDM receiver with the ΣΔ modulator using a subcarrier weighting scheme is investigated. The symbol weighting scheme is used with a soft-decision Viterbi decoder in the receiver, and the symbol on each subcarrier is weighted by a coefficient derived from the output noise spectrum of the ΣΔ modulator. The numerical results obtained through computer simulation show that the BER performance is improved by about 2-3 dB on multipath fading channels.