Comparison of different Combining methods and Relaying Techniques in Cooperative Diversity

An ad-hoc network with a sender, a destination and a third station act-ing as a relay is analyzed. The channels are modeled containing thermal noise, Rayleigh fading and path loss. Different combining methods and diversity protocols are compared. The amplify and forward protocol shows a better performance than the decode and forward protocol, unless an error correcting code is simulated. To combine the incoming signals the channel quality should be estimated as well as possible. Information about the average quality shows nice benefits, and a rough approximation about the variation of the channel quality increases the performance even more. What-ever combination of diversity protocol and combining method is used second level diversity is observed. The relative distances between the relay and the stations has a large effect on the performance.The aim of this project was to study the characteristics and utility of relaying in future wireless systems. The focus was mainly on the cooperative principles and relay selection in the case of mobile multihop relay structures. This project also included the study of IEEE 802.16j, the multihop relay specification for 802.16 or Wimax standard. It was an interesting assignment to study the practical realization of a concept that has evolved over a couple of years. I studied some relevant research papers (listed in the references section), modeled some simulation scenarios based on the results of these papers and gained a invaluable insight on some of the topics.