Delay Diversity Methods for Parallel OFDM Relays

Relays form a distributed antenna system that can be used for extending the coverage of wireless OFDM networks in a cost-efficient manner. We consider a general network where Nr parallel relay nodes (RNs) amplify and forward signals from a base station (BS). Multipath fading is beneficial for OFDM transmission as it increases frequency selectivity which can be exploited by forward error control coding. When relays apply linear or cyclic delay diversity methods [1] to create longer multipath channels, dependence on the propagation environment is reduced. In this paper, we summarize relaying protocols and explain how they facilitate the delay diversity methods. We aim at providing maximum diversity gain, but how it translates to performance gain depends on used coding scheme.