Adaptive MMSE Rake-Equalizer Receiver Design with Channel Estimation for DS-UWB System

In this paper, a robust adaptive MMSE Rake-equalizer receiver scheme is presented with channel estimation that has been transmitted in Direct Sequence-Ultra Wideband (DS-UWB) system. The DS-UWB has a fine path resolution by transmitting information with ultra short pulses. The Rake receiver is known as a technique that can effectively combine paths with different delays and obtain the path diversity gain. Due to sub-nano seconds narrow pulse and the large transmission bandwidth in the systems, we therefore use equalizer to overcome the resulting ISI and a long delay spread in the characterization of the UWB channel. The proposed receiver structure reduces intense multi-path destruction and severe inter-symbol interference (ISI) by using a combined adaptive Rake and equalizer structure referred to as the MMSE (minimum mean square error) algorithm. Channel information is obtained through the use of a least mean square (LMS) adaptive algorithm on the training sequence of a preamble. The indoor environment is represented by dense multipath channel models proposed by IEEE 802.15.3a. Simulation results show that the new scheme employing the energy of a few paths to obtain better performance than the traditional maximum ratio combining (MRC) Rake receiver. Key-Words: Least mean squares (LMS), minimum mean square error (MMSE), adaptive receiver, direct sequence ultra wideband (DS-UWB)