Capacity of UWB Impulse Radio with single-user reception in Gaussian noise and dense multipath

In this letter, we derive the capacity of ultra-wideband impulse radio (IR) systems employing optimal single-user reception. The environment in which the evaluation is set is that of a dense multipath and equal energy levels for interfering users, where multiple-access interference can be modeled as Gaussian. The investigation covers both binary and$M$-ary pulse position modulation approaches, employing either hard or soft decoding, and is targeted to low-signal-to-noise ratio/low-power environments where IR is supposed to work.