Friday, October 25, 1996
1504 G. G. Brown Building
The talk presents and discusses two results on the effect of sampling-time jitter at the receiver on the bit error probability in digital modulation over an additive Gaussian noise channel.
The first result is regarding the bit error probability of a digital communication system with mismatched square-root raised cosine filters at the transmitter and the receiver, in which the filters have different roll-off factors; the second is the Taylor series approximation of the bit error probability in the case of matched raised-cosine pulse-shaping filters.
The principal result is that the roll-off factor mismatch incurs intersymbol interference even when the sampling time is perfect and that the mismatch intersymbol interference seems negligible when the signal-to-noise ratio is moderate (around 6 dB) and it grows as the signal-to-noise ratio increases. However, the mismatch loss is within 0.5 dB of the optimum bit error probability at around 1.0E-8.
In the case of the matched square-root raised cosine filters, an approximation formula for the bit error probability is derived. It shows how the factors affect the bit error probability. This formula becomes more accurate for smaller jitter and a bigger roll-off factor.
Sangsin Na is a Professor in the Department of Electronics Engineering, Ajou University, Suwon 442-749, Korea. He received his BS in EE, Seoul National University, MS in ECE, University of Michigan, and his Ph.D. in EE:Systems, Univ. of Michigan.