Pseudocoherent detection of OOK/PPM signals as zero-delay transmitted-reference signals with bandpass downsampling for UWB communications

We investigate low-complexity ultrawideband (UWB) communication systems such as on-off keying (OOK) transmission with an energy-detection receiver and transmitted-reference (TR) signaling with an autocorrelation receiver (AcR). It is observed that the conventional noncoherent energy detector for OOK signals suffers from a huge performance loss compared with that of the coherent detector, which suggests space of improvement. It is also found that the OOK signaling can be treated as a special case of TR signaling with pulse-amplitude modulation (PAM). Inspired by this observation, we propose a new pseudocoherent detection scheme for OOK transmission, which can also be applied to pulse-position-modulation (PPM) transmission. We also consider the implementation issues of the proposed receiver, such as the high sampling rate requirement. We propose a new scheme named bandpass downsampling (BPDS) to overcome this difficulty. With BPDS, we are able to reduce the sampling rate to one tenth of the Nyquist rate, and yet, it can provide performance with a small degradation. A theoretical analysis is carried out to evaluate the bit-error-rate (BER) performance of the proposed receiver. The numerical results show that the performance of the proposed receiver can drastically be improved from that of the conventional energy detector (CED).