Advanced relaying concepts for future wireless networks

Relaying is undoubtedly a key technology for future wireless networks as it can be applied to provide coverage extension and capacity increase in a cost-effective manner. This paper presents an outline of the major advanced relaying concepts that will be part of future systems from the viewpoint of the ARTIST4G European project. These concepts can be divided into three categories, those pertinent to type-1 relays, type-2 relays and moving relays. The characteristics of each of these concepts are presented and the challenges related to their implementation are discussed. Furthermore the paper proposes a set of solutions to address the discussed challenges. For type-1 relays, the paper presents solutions for the allocation of resources to the backhaul and the access links, the inter-relay interference mitigation, and the multi-hop transmission mode. For type-2 relays, our focus is on the design of distributed hybrid automatic repeat request (HARQ) protocols. More specifically, we propose that the conventional HARQ schemes are adapted to exploit the potentially better channel conditions provided by the relays. Moreover distributed turbo coding solutions are introduced for increasing transmission reliability with the aid of relays. Finally, moving relays are presented as an efficient solution to the ever-growing demand for wireless broadband by users within public transportation vehicles. We show that moving relays can very effectively overcome the vehicle penetration loss and boost the achievable capacities of the vehicular users. Overall, we conclude that the presented advanced relaying concepts are very promising and can significantly enhance the user experience in future wireless networks.