C30. Enhancement of OFDM modulation and adaptive array beamforming using discrete wavelet transform

Abstract

The adaptive array antenna is combined with OFDM "orthogonal frequency division multiplexing" as multicarrier technique to combat the flat and frequency selective fading effects at high speed wireless communication. It is well known in OFDM that a cyclic prefix (CP) is appended to each symbol in order to mitigate the effect of InterSymbol Interference (ISI). However, this reduces the spectral efficiency. A perfect reconstruction using discrete wavelet transmultiplexer in OFDM transceiver counters the degrading effect of ISI, and also conserves bandwidth. A discrete wavelet transform-based least mean square (WLMS) adaptive beamformer is presented in this paper, this beamformer uses wavelet transform to reduce the signal dimension in wavelet domain for low complexity and denoising. Theoretical analysis and simulations demonstrate this algorithm with better beamforming performance which converges faster than the conventional adaptive beamformer.