The Importance Of Diversity In Wireless Communication

Introduction

In wireless transmission the signal quality suffers severe degradations due to effects like fading caused by multipath propagation. To reduce such effects, diversity can be used to transfer the different samples of the same signal over essentially independent channels [1]. There are several approaches to implement diversity in a wireless transmission investigated by researchers. Multiple antennas can be used to achieve space diversity [2]. The advantages of multiple-input multiple-output (MIMO) systems have been widely acknowledged, to the extent that certain transmit diversity methods like Alamouti signaling [2] have been incorporated into wireless standards. Although transmit diversity is clearly advantageous on a cellular base station, but it may not be practical for certain other scenarios like wireless sensor networks, mobile ad-hoc networks etc. Specifically, due to size, cost, power or hardware limitations, a wireless agent may not be able to support multiple transmit and receive antennas [3].

Cooperative communication systems exploit the spatial diversity gains inherent in multiuser wireless systems without the

By relaying each other’s data, multiple independent copies of the data are received at the destination. Processing of multiple independent copies of the signal reduces the probability of error. In the cooperative communication, diversity acquired at destination improves the channel reliability and saves resources.Diversity in Communication is an effective way to tackle fading and improve reliability. Diversity is obtained over time and frequency by means of coding and interleaving. It can also be obtained via repeated transmission. Cooperative transmission through relaying is also a way to achieve diversity. User cooperative transmission is a special case of cooperative transmission where users act as relays to help each