BER sensitivity to mistiming in ultra-wideband impulse radios - part II: fading channels

We investigate timing tolerances of ultra-wideband (UWB) impulse radios. We quantify the bit-error rate (BER) sensitivity to epoch timing offset under different operating conditions, including frequency-flat fading channels, dense multipath fading channels, multiple access with time hopping, and various receiver types including sliding correlators and RAKE combiners. For a general correlation-based detector, we derived in Part I unifying expressions for the decision statistics as well as BER formulas under mistiming, given fixed channel realizations. In Part II, we provide a systematic approach to BER analysis under mistiming for fading channels. The BER is expressed in terms of the receiver´s energy capture capability, which we quantify under various radio operating conditions. We also develop the optimal demodulator in the presence of timing offset and show a proper design of the correlation-template that is robust to mistiming. Through analyses and simulations, we illustrate that the reception quality of a UWB impulse radio is highly sensitive to both timing acquisition and tracking errors.