Walsh Hadamard Transform Precoded MB-OFDM: An Improved High Data Rate Ultrawideband System

Abstract

This paper examines the performance improvement to be achieved by preceding the OFDM symbol by the Walsh Hadamard transform (WHT) in a multiband orthogonal frequency division multiplexing (MB-OFDM) ultrawideband system. An upper bound on the probability of error for WHT-MB-OFDM in the Rayleigh fading channel with convolutional coding is derived, and compared to the upper bound for MB-OFDM. For high rate and low constraint length codes, WHT-MB-OFDM is shown to perform better than MB-OFDM. Next, the effect of narrowband interference is studied, and the WHT-MB-OFDM system is shown to perform significantly better than the MB-OFDM system. Finally, a general amplitude probability distribution (APD) function is derived for linearly precoded MB-OFDM systems and the WHT-MB-OFDM system is shown to cause less interference than the MB-OFDM to the co-existing narrowband system