Computational Complexity and Performance of RAKE Receivers with Channel Estimation for DS-UWB

Hiroyuki SATO  Tomoaki OHTSUKI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E88-A   No.9   pp.2318-2326
Publication Date: 2005/09/01
Online ISSN: 
DOI: 10.1093/ietfec/e88-a.9.2318
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Ultra Wideband Systems)
Category: RAKE Receiver
Keyword: 
DS-UWB,  MRC-RAKE,  MMSE-RAKE,  MRC-RAKE-Equalizer,  the computational complexity,  the accuracy of channel estimation,  

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Summary: 
In this paper, we evaluate the computational complexity and the performance of the RAKE receivers for the Direct Sequence--Ultra Wideband (DS-UWB) with considering the accuracy of channel estimation in a multipath channel. As RAKE receivers for DS-UWB, we consider the maximal-ratio combining (MRC)-RAKE, the minimum mean square error (MMSE)-RAKE, and the MRC-RAKE-Equalizer that is the MRC-RAKE followed by a liner equalizer. Generally, if the channel estimation is perfect, as the number of fingers or taps increases, the performance of each receiver is improved, however the computational complexity of each receiver increases. In practice, the channel estimation is not perfect. The channel estimation error makes their performances degraded. Therefore, the performances of the RAKE receivers depend on the accuracy of channel estimation. Consequently, we evaluate the computational complexities and the Bit Error Rates (BERs) of MRC-RAKE, MMSE-RAKE, and MRC-RAKE-Equalizer with considering the accuracy of channel estimation for DS-UWB. We show that the accuracy of channel estimation affects the BER of each receiver significantly. We also show that when the accuracy of channel estimation is high, MRC-RAKE-Equalizer can achieve the better BER than MMSE-RAKE with less computational complexity, while MMSE-RAKE can achieve the better BER than MRC-RAKE-Equalizer when the accuracy of channel estimation is low.