OFDM AF FG Relaying as an Energy Efficient Solution for the Next Generation Mobile Cellular Systems

We analyzed the bit error rate (BER) and ergodic capacity performance improvement of dual-hop OFDM amplify and forward (AF) relay system with fixed gain (FG) at relay station (R), all attained through ordered subcarrier mapping (SCM) at R. In previous works we showed that in the region of small values of average signal-to-noise ratios (SNRs) on hops best-to-best SCM (BTB SCM) scheme should be applied, while in the region of medium and high values of average SNRs on hops, BER performance improvement is achieved by implementing best-to-worst SCM (BTW SCM) scheme. In this paper we analyzed a new solution, where in the assumed relay system with BTB SCM, one or more subcarriers having the lowest SNRs on each hop are omitted. Furthermore, we examined power balance of the system implementing SCM through comparison of BER performance expressed as a function of power transmitted per subcarrier, with BER performance of the ordinary OFDM AF FG relay system, as well as with the performance in case of direct transmission between source of information (S) and destination terminal (D). OFDM based relay systems are already included in IMT-Advanced standards, and all the obtained BER and ergodic capacity results have confirmed that OFDM AF FG relay system with appropriate SCM scheme implemented at Journal of Green Engineering, Vol. 3, 147–165. c © 2013 River Publishers. All rights reserved. 148 E. Kocan and M. Pejanovic-Djurisic R station represents very interesting and energy efficient solution for the next generation mobile cellular systems.