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Summary: International Journal of Wireless Information Networks, Vol. 10, No. 4, October 2003 (© 2004)
Conditions and Performance of Ideal RAKE Reception
for Ultra-Wideband Signals in Lognormal Fading Channels
J. Zhang,1,2
R. A. Kennedy,1
T. D. Abhayapala1
In this paper, the conditions and performance of ideal RAKE reception for time hopping Ultra-
Wideband (UWB) investigated. Owing to the complex propagation phenomena and specific
structure of UWB signals, new problems relevant to the operation of RAKE receivers arise. This
motivates us to reconsider the conditions under which a RAKE receiver can work effectively with
negligible interference between fingers. Key findings are that the conditions not only relate to the
property of time hopping codes, but also modulation methods. An analytical technique is introduced
to derive explicit expressions of RAKE performance for various combining methods for a lognor-
mal fading channel. Numerical results show that RAKE reception can largely improve the per-
formance, and equal gain combining has comparable performance to maximum ratio combining.
KEY WORDS: Ultra-wideband; RAKE receiver; lognormal distribution.
1. INTRODUCTION
In the last few years, there has been a rapidly grow-
ing interest in Ultra-Wideband (UWB) systems [14].
Combined with spread spectrum techniques, especially
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