Multipath diversity reception of wireless multiple access time-hopping digital impulse radio

The performance of multiple access spread spectrum time-hopping digital impulse radio with pulse position data modulation under multipath propagation conditions is analytically investigated. To simplify the mathematical complexity associated with derivation of the SNR, we assume independent identically distributed random delay for each arriving path of each user. Specifically, the multipath arrival times are uniformly distributed over one frame period. This assumption along with restricting the time-hopping range to a fraction of a frame duration leads to a closed form solution of SNR. Using this result, the degradation factor due to multiple access interference in the presence of multipath is derived and curves for two special cases of exponentially decaying and flat multipath channels are sketched. To investigate the more realistic delay spread profiles, we show simulation results for exponentially decaying and flat multipath channels with deterministic multipath arrival times.