UC Riverside

We first provide an overview of some of the latest developments in wireless communications using multiple transmitters and multiple receivers. We point out the importance of SNR control in fast random fading environments. For applications where large antenna arrays are not suitable, we introduce the concept of wireless antennas or wireless relays that are distributed between a source and a destination. We propose Hurwitz-Radon space-time code for the wireless relays. Each relay receives a noisy baseband signal simultaneously from the source. The baseband signals (symbols) are not decoded into information bits at the (non-regenerative) relays, but rearranged (i.e., space-time modulated) in their orders, amplitudes and phases according to the Hurwitz-Radon code. The relays do not exchange symbols with each other, but forward the modified sequences of symbols in parallel to the destination. Our study shows that with R relays, a diversity factor around R/2 can be achieved, i.e., the averaged bit error rate is in the order of 1/SNRR2/ as opposed to 1/SNR for a single (regenerative) relay system. More than 10 dB power saving, from the baseline of a single relay system, is possible with eight relays. Issues such as channel estimation, symbol synchronization, medium access protocols and signal processing hardware are also discussed.