Adaptive RAKE Receivers with Subspace-Based Hadamard-Hermite Template Design for UWB Communications

Craig J. MITCHELL  Giuseppe ABREU  Ryuji KOHNO  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E88-A   No.9   pp.2327-2338
Publication Date: 2005/09/01
Online ISSN: 
DOI: 10.1093/ietfec/e88-a.9.2327
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Ultra Wideband Systems)
Category: RAKE Receiver
Keyword: 
ultra wideband,  RAKE receiver,  multipath,  orthogonal Hermite pulses,  

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Summary: 
In this paper we present a novel method for improving RAKE receiver reception in UWB systems. Due to the fact that practical pulses that can be produced for UWB-IR (Ultra Wideband-Impulse Radio) may occupy a longer time than the typical multipath resolution of the actual UWB channel, multiple channel components may arrive within this typical pulse width. Performance degradation may occur due to the resulting intrapulse (overlapping received pulses) interference. We here propose an adaptive, pilot aided RAKE receiver for UWB communications in the multipath environment. The proposed system estimates the actual received signal with intrapulse interference in each RAKE finger using projections onto a Hadamard-Hermite subspace. By exploiting the orthogonality of this subspace it is possible to decompose the received signal so as to better match the template waveform and reduce the effects of intrapulse interference. By using the projections onto this subspace, the dimension of the received signal is effectively increased allowing for adaptive correlator template outputs. RAKE receivers based on this proposal are designed which show significant performance improvement and require less fingers to achieve required performance than their conventional counterparts.