Abstract
We present a comparison between coherent and noncoherent UWB receivers, under a realistic propagation environment, that takes into account also the effect of path-dependent pulse distortion. As far as coherent receivers are concerned, both maximal ratio combining (MRC) and equal gain combining (EGC) techniques are analyzed, considering a limited number of estimated paths. Furthermore, two classical noncoherent schemes, a differential detector, and a transmitted-reference receiver, together with two iterative solutions, recently proposed in the literature, are considered. Finally, we extend the multisymbol approach to the UWB case and we propose a decision-feedback receiver that reduces the complexity of the previous strategy, thus still maintaining good performance. While traditional noncoherent receivers exhibit performance loss, if compared to coherent detectors, the iterative and the decision-feedback ones are able to guarantee error probability close to the one obtained employing an ideal RAKE, without requiring channel estimation, in the presence of static indoor channel and limited multiuser interference.
Highlights
Ultra-wideband (UWB) systems are based on the transmission of subnanosecond pulses, typically obtained by directly driving an antenna with short electrical pulses
In case of perfect channel estimation and absence of intersymbol and multiuser interference, it is well known [18] that a RAKE receiver is the optimal detection scheme in the sense that it minimizes the probability of error
TR, ITR-maximum likelihood (ML), and differential receivers (DRs) are characterized by really poor performance similar to the MF. Both ITR-ML and DF-DR are capable of achieving bit error rate (BER) similar to the one obtained by employing a RAKE receiver equipped with 10 fingers
Summary
Ultra-wideband (UWB) systems are based on the transmission of subnanosecond pulses, typically obtained by directly driving an antenna with short electrical pulses. A different approach to overcome all the abovementioned disadvantages is based on the use of noncoherent reception techniques These techniques do not require channel estimation and allow to capture a large amount of the received energy, despite distortions and multipath propagation. They represent, a suboptimal solution, if compared to coherent receivers, because of the adoption of a noisy signal as a reference waveform for the demodulation process. In [2], some reception schemes, based on the adoption of energy detectors and orthogonal modulations, are presented All those techniques lead to low-complexity receivers, able, in principle, to capture a large portion of the transmitted energy and less sensible than coherent demodulators to channel variations and synchronization mismatch [15].
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