IMT-advanced relay standards [WiMAX/LTE Update]

There are two candidates for IMT-Advanced (4G) standards, LTE-Advanced by 3GPP and 802.16m by IEEE. This article focuses on relay architectures in 16m and LTE-A, and discusses design principles and trade-offs leading to decisions in each standards group. Basically, 16m relay and LTE-A Release 10 relay are very similar technologies where the relay is essentially an orthogonal frequency-division multiple access base station with a wireless backhaul link. However, some open issues, such as mobility, power saving, multihop architecture, transparent relaying, multi-arrier transmission, and cooperative transmission, are still left as challenges for engineers and researchers. This article provides insights to both relay standards that could be helpful for readers to fully comprehend practical ways of incorporating relays into 4G wireless broadband networks.