Who would have guessed that my idea from the spring days in 1999 would open an entirely new research field with more than 30,000 articles published within our IEEE community alone by the end of 2014? Products have been built around it, and the 3rd Generation Partnership Project (3GPP) has adopted some of it in its mobile standards specifications. As of 2014, the findings outlined in this manuscript are of almost historic dimension but they shed some light into the early developments in this field. Whilst the majority of the community until today still considers 2-hop networks, in 2003 I had already considered the most generic case of multiple stages of relaying, with each stage being composed of arbitrary clusters of cooperating antennas. A further strength of this work is that it contains Shannon capacity calculus as well as outage and error rate performance analysis in a single manuscript. Finally, I have introduced the only non-iterative approach to waterfilling so far available in the literature.

Mischa Dohler is Professor in Wireless Communications at King's College London, Head of the Centre for Telecommunications Research, co-founder & member of the Board of Directors of the smart city pioneer Worldsensing, Fellow and Distinguished Lecturer of the IEEE, and Editor-in-Chief of the Transactions on Emerging Telecommunications Technologies.