Subcarrier pairing and relay assignment with improved user fairness in a multi-user cooperative OFDM system

Abstract

We consider a joint relay selection and subcarrier allocation problem that minimizes the total system power for
a multi-user, multi-relay and single source cooperative OFDM
based two hop system. The system is constrained to all users
having a specific subcarrier requirement (user fairness). However no specific fairness constraints for relays are considered. To ensure the optimum power allocation, the subcarriers in two hops are paired with each other. We obtain an optimal subcarrier allocation for the single user case using a similar method to what is described in [1] and modify the algorithm for multiuser scenario. Although the optimality is not achieved in multiuser case the probability of all users being served fairly is improved
significantly with a relatively low cost trade off.