Conditions and Performance of Ideal RAKE Reception for Ultra-Wideband Signals in Lognormal Fading Channels

Abstract

In this paper, the conditions and performance of ideal RAKE reception for time hopping UltraWideband (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 lognormal fading channel. Numerical results show that RAKE reception can largely improve the performance, and equal gain combining has comparable performance to maximum ratio combining.

Cramer-Rao lower bounds for the time delay estimation of UWB signals

“…This equation can be evaluated numerically by Monte Carlo simulation which requires highly computational complexity. Alternatively, we invoke the Hermite-Gauss quadrature [18], and P e can be accurately approximated by…”

Performance and parameter optimization of UWB RAKE reception with interchip interference

“…The parameter Γ represent the ray decay factor in the IEEE802.11.3a model, and σ is related to the Lognormal distribution of |a |. As comparisons, the performance with clean RAKE output (without ICI), derived in [1], is also shown. It is clear that ICI introduced by a practical TH codes has negligible influence on the mean SEP as is proved by both Gaussian approximation method and the method using mean of φ, and EGC still has comparable performance with MRC.…”

“…INTRODUCTION Since the radiation power of UWB signals is limited to be very low, RAKE reception is a crucial technique for UWB to collect enough power from multipath signals. For a general RAKE receiver based on simple matched filters, a key condition for it to work effectively is that the interchip interference (ICI 1 ) is sufficiently small. Ideal autocorrelation performance of spread spectrum codes is always assumed and utilized to eliminate the ICI.…”

“…For Time-hopping (TH) UWB systems, it is indicated in [1] that not only the property of TH codes but also the modulation method determines whether ICI could be negligible. We suppose a suitable modulation method (such as bipolar modulation) is applied here.…”

“…The property of autocorrelation is highly related to the relationship between the number of chip positions in a frame (N c ) and National ICT Australia is funded by the Australian Government's Department of Communications, Information Technology and the Arts and the Australian Research Council through Backing Australia's Ability and the ICT Centre of Excellence program. 1 We do not explicitly mention inter-symbol interference (ISI) here because ISI can roughly be regarded as ICI in time-hopping systems. Furthermore, in systems with bipolar modulation, the interference from ISI plus ICI could be smaller than that from the pure ICI due to cancellation between antipodal signals.…”