Abstract: Relay transmission plays an important role in future cellular communication system as well as wireless ad hoc and sensor networks ,this is because of its several benefits, such as it increase the system capacity, it extend the radio range and to reduce network infrastructure. In this paper we propose a PDF based relay selection method for dual hop networks. Here the relay selection on the basis of PDF, check each signal and select the best one so it increases the system capacity, reduce interferences and increase diversity. Interferences can be avoided with the help of adaptive filters .Here use only the reactive approach that means, concentrate only the relay to destination section, so it reduces the complexity of the system, and it also decreases the error rate.

Keywords: Average Fairness, Cooperative Diversity, Cumulative Distribution Function (CDF), Outage Probability, Relay Selection.