Relay-based deployment concepts for wireless and mobile broadband radio

In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and coverage extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to Working Group 4 of the Wireless World Research Forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.