Time division adaptive retransmission for reducing signal impairments in portable radiotelephones

Multiple-antenna receiving diversity was shown previously to be effective in mitigating the effects of random angular orientation and multipath radio propagation for portable radiotelephones. It is shown that time-division adaptive retransmission used with appropriate antenna configurations can also mitigate these effects. The retransmission configurations require fewer antennas than the receiving diversity configurations for a given improvement in relative signal-to-noise ratio (S/N). Cumulative distributions of S/N were determined for adaptive retransmission and diversity using random orientation and multipath propagation models. Distributions of S/N for systems with two antennas at the portable set and two appropriately polarized antennas at the portable radiotelephone terminal (PORT) are similar to distributions for two-branch selection diversity in the fixed-orientation mobile radio environment. Systems with one portable antenna and two PORT antennas have distributions with slopes similiar to two-branch mobile radio distributions but the distributions for the portables range from 3 to 7 dB worse.