Performance Evaluation of Virtual MIMO Schemes for the UL OFDMA Based Systems

In this paper we propose and assess the performance of virtual MIMO or relay-assisted cooperative schemes designed for the UL OFDMA based systems. We consider the use of an antenna array at the base station and a single antenna at both the mobile terminal and relay. The proposed cooperative schemes emulate a MIMO channel with 2 transmit and M receive antennas. Two types of relays are considered: amplify-and-forward and selective decode-and-forward. We derive the instantaneous normalized capacities and both the outage capacities and bit error rate are compared against the non-cooperative SISO and SIMO systems, considering different scenarios. The proposed relay-assisted schemes are suited for existing and for the future broadband wireless systems to increase the system capacity and coverage.