Analysis of ISI for an IR UWB symbol-differential autocorrelation receiver

The interframe (IFI) and intersymbol interference (ISI) of a symbol-differential autocorrelation receiver (SD-ACR) for an impulse radio ultra wideband (IR UWB) system in a multipath channel is evaluated. The system can be modelled as a nonlinear filter with respect to the input data sequence. The filter´s coefficients are random variables for which we derive an accurate statistical description up to the second moments. The analysis shows the presence of a bias term, that makes the optimum decision threshold different from zero. The results obtained in this paper provide a good understanding of the performance degradation due to ISI and IFI and they show the impact on system design. Analytical results, confirmed by simulations point out a new concept for the pulse positioning within the symbol interval, and the transmission of one pulse per symbol emerges as the optimum choice for the single user case. Simulated results for the noise-free ideal environment confirm the influence of the system parameters in terms of BER and provide a measure of the achievable bit rate as a function of the channel RMS delay spread.