An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern laboratory/office building. The bandwidth of the signal used in this experiment is in excess of 1 GHz, ...which results in a differential path delay resolution of less than a nanosecond, without special processing. Based on the experimental results, a characterization of the propagation channel from a communications theoretic view point is described, and its implications for the design of a UWB radio receiver are presented. Robustness of the UWB signal to multipath fading is quantified through histograms and cumulative distributions. The all RAKE (ARAKE) receiver and maximum-energy-capture selective RAKE (SRAKE) receiver are introduced. The ARAKE receiver serves as the best case (bench mark) for RAKE receiver design and lower bounds the performance degradation caused by multipath. Multipath components of measured waveforms are detected using a maximum-likelihood detector. Energy capture as a function of the number of single-path signal correlators used in UWB SRAKE receiver provides a complexity versus performance tradeoff. Bit-error-probability performance of a UWB SRAKE receiver, based on measured channels, is given as a function of the signal-to-noise ratio and the number of correlators implemented in the receiver.
This paper proposes a space-time selective RAKE (SRAKE) receiver with maximum signal-to-interference-plus-noise ratio (MSINR) for direct-sequence ultra-wideband (UWB) communications in the presence ...of narrowband interference (NBI) and multiple-access interference. For effectively extracting a fixed number of the UWB signal components (fingers) from numerous resolvable paths, four finger selection strategies (FSSs) are considered for the proposed space-time SRAKE receiver, including the optimum FSS (with MSINR), which is not very computationally feasible, and three feasible FSSs: an energy-based FSS (EB-FSS), a constrained energy-based FSS (CEB-FSS), and a hybrid energy-based FSS, which is also a combination of the EB-FSS and CEB-FSS. Through a performance analysis, we show that the performance of the proposed receiver in the presence of NBI not only depends on the power ratio, bandwidth ratio, and relative spectrum location of NBI with respect to the UWB signal, but also on the FSS used. Some simulation results are then presented to show that the proposed space-time MSINR-SRAKE receiver with the preceding FSSs used can provide a larger system capacity and better immunity to strong NBI than the existing time-only SRAKE receivers and space-time SRAKE receivers.
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