All-digital impulse radio for MUI/ISI-resilient multiuser communications over frequency-selective multipath channels

Impulse radio (IR) is an ultra-wideband system with attractive features for baseband asynchronous multiple access (MA), multimedia services, and tactical wireless communications. Implemented with analog components, the continuous-time IRMA model utilizes pulse-position modulation (PPM) and random time-hopping codes to alleviate multipath effects and suppress multiuser interference (MUI). We introduce a novel continuous-time multiple input multiple output (MIMO) PPM-IRMA scheme, and derive its discrete-time equivalent model. Relying on a time-division-duplex access protocol and orthogonal user codes, we design composite linear and non-linear receivers for the downlink. The linear step eliminates MUI deterministically and accounts for frequency-selective multipath, while a maximum likelihood (ML) receiver performs symbol detection