Diversity gain in Wireless Communications

crixus

What is meant by achieving "full diversity gain over Rayleigh fading channel"?

marcusl

crixus: you have not provided the context for this quote, the type of system involved, nor even a complete sentence, so my response will be very generic.

A Rayleigh channel is a communications channel (path) consisting of a large number of multipath reflections of random amplitude and phase. Temporal fluctuations in the received signal strength have a Rayleigh statistical distribution. It is seen in an urban area when the transmitter is a cellphone that is moving (walking or traveling in a car), for example.

Diversity is a method to either mitigate or exploit the multipath propagation. The simplest form is switching from an antenna whose signal has temporarily faded to one elsewhere that is receiving a strong signal. There are more sophisticated electronic and signal coding diversity approaches, as you might imagine. In a MIMO system, the independent propagation paths are exploited so that (conceptually, anyway) each carries a different data stream, increasing system capacity and data throughput. Indoor IEEE 802.16 wireless LAN computer routers work this way. The gain obtained in all these cases is called diversity gain.

crixus

Thanks for replying. In fact I was able to figure out. Like if we have a MISO system with each antenna transmitting same symbol then diversity gain would be 1. However if I have multiple receive antennas then diversity gain would be L = no of independent fading paths. Thus "full diversity gain" is achieved in the latter case.