Combating Shadowing Effects for Systems with Transmitter Diversity by Using Collaboration among Mobile Users

In the current wireless, cellular systems, each mobile station (MS) independently communicates with a base station (BS). In this article we investigate collaboration among MSs where an MS retransmits a signal from the BS to a nearby MS that is in a shadowing or deep fading region relative to the BS. We develop a formula for the outage probability of a non-collaborative system with two transmit antennas and one receive antenna in a lognormal shadowing environment, and compare it with a formula developed for the outage probability of the collaborative system, in which the second transmit antenna is indeed located on another MS. Results of simulating a real system with practical parameters are also presented and compared with the theoretical results. The outage probability of the proposed system is reduced by an order of magnitude over that of the non-collaborative system.