Cooperative-Diversity in Wireless Networks

One major limitation of wireless systems is the fading channel that exists between users and the base station. When a user’s channel realization is bad, it may be unable to communicate with the base station. To overcome this problem, many different forms of diversity have been studied including: spatial, temporal, and frequency diversity. Recently, there has been an increasing popularity in a specific form of spatial diversity, namely cooperative diversity. Spatial diversity relies on the principle that multiple antennas located a sufficient distance apart experience independent fading channels. Unlike the traditional form of spatial diversity where a user has access to a physical array of different antennas, cooperative diversity is based off the relay channel model where different users share their individual antennas. In particular, information is transmitted from source to destination both directly and through relays in the network; thus the relays and source act as a virtual antenna array. Within this report, we present multiple cooperative-diversity protocols and analyze their performance via the diversity-multiplexing tradeoff curves.