A Fast Maximum Likelihood DS-UWB Equalizer
Mohamed Kamoun, L. Mazet, M. de Courville, Pierre Duhamel · 2006
For very large bandwidth systems such as Direct Sequence Ultra Wide Band (DS-UWB)(1), the channel impulse response delay spread is much larger than for traditional CDMA(2) systems. This requires an adaptation of the usual Rake(3) equalization scheme suited for DS-UWB. In this contribution we propose a maximum likelihood equal- ization scheme based on the use of FFT. The main idea is to adopt a block representation of the channel convolution with a block length equal to the spreading sequence duration and exploit pseudo-circulant matrices structure which allows fast FFT diagonalization. A Viterbi decoder using a trellis with a small number of states is applied to perform the ML detection by taking into account the block channel memory. This technique is compared to other known equalization method Rake and DFE(4).