Low-complexity receiver structure with sub-Nyquist analog to digital sampling rate for pulsed-OFDM ultra wideband communication systems
Pulsed orthogonal frequency division multiplexing (pulsed-OFDM) is a simple frequency spreading technique that has been proposed to design low-complexity high performance multi-carrier ultra wideband (UWB) communication systems. A typical receiver for this system samples the received signal at Nyquist rate capturing all diversity branches. In this paper, we propose an alternate complexity-reduced receiver structure that uses analog to digital converters (ADC) with the sampling rate equal to a fraction of the Nyquist rate. We show that the output of the ADC in this case is a subset of the original diversity branches and contains complete information for all sub-carriers. Simulation results show that this technique outperforms the receiver with full rate sampling and selection diversity combining with considerable reduction in the complexity and power consumption. We also examine the possibility of enhancing the performance of the receiver by applying a subset selection algorithm based on the training sequences at the beginning of the every data packet. Simulation results in Rayleigh fading channel shows that the enhancement is negligible and we can adopt reduced-complexity receiver without selection algorithm.