Space-time coding for impulse radio

Impulse radio (IR) ultrawide band systems have well documented advantages for low-power peer-to-peer and multiple access communications. Space-time (ST) coding on the other hand, has gained popularity as an effective means of boosting rates and performance. Existing IR transmitters rely on a single antenna, while ST coders have so far focused on digital linearly modulated transmissions. In this paper, we develop an orthogonal ST coding scheme for the analog nonlinearly (pulse-position) modulated multi-antenna IR system. We show that the resulting analog noncoherent detector is equivalent to an existing digital ST decoder possessing maximum likelihood optimality. Simulations testing peer-to-peer and multi-access IR scenarios confirm considerable increase in both bit-error-rate performance and number of users that can be accommodated, when wedding ST coding with IR.