COOPERATIVE COMMUNICATION TECHNIQUES IN WIRELESS NETWORKS (ANALYSIS WITH VARIABLE RELAY POSITIONING)

Sammanfattning: Signal transmission in Wireless Networks suffers considerably from many impairments, one of which is channel fading due to multipath propagation. Cooperative communication is a technique which could be employed to mitigate the effects of channel fading by exploiting diversity gain achieved via cooperation between nodes and relays. To achieve transmit diversity, a node would generally require more than one transmitting antenna which is not too common due to the limits in size and complexity of wireless mobile devices. However by sharing antennas with other single-antenna nodes in a multi-user environment, a virtual multi-antenna array is formed and transmit-diversity is accomplished. Subsequently, radio coverage is extended without the need to implement multiple antennas on nodes and increased transmission reliability is achieved. In this scenario, a network containing a sender, a destination and a relay is analyzed. Two cooperative communication schemes which include Amplify and forward and Decode and forward are employed with different combining techniques are investigated and results obtained from simulations with respect to variable relay positioning are presented.