Energy efficiency of location-aware clustered cooperative beamforming without destination feedback

Energy efficiency of wireless communications has received a lot of attention recently owing to the tremendous energy demands resulting from widely deployed wireless networks and mobile personal devices. In this paper, we propose an energy-efficient cooperative relaying scheme for location-aware clustered relays. Energy efficiency is achieved through a low-overhead timer-based relay selection algorithm and by removing the destination feedback of channel state information (CSI) that is usually required for cooperative beamforming. In order to avoid possible collisions between relay transmissions, we propose a distributed mechanism for the selected relays to appropriately insert guard intervals before their transmissions. We analyse the system energy efficiency considering the energy utilized to obtain CSI, to select best relays and to perform cooperative beamforming. Moreover, we investigate the impacts of the number of available relays, the number of selected relays and the location of relay cluster on energy efficiency. The simulation results reveal that the proposed cooperative relaying scheme achieves higher energy efficiency than direct communication, best relay selection, and all relay selection for relay clusters located close to the source. Independent of relay cluster location, the proposed scheme exhibits significantly higher energy efficiency compared to an existing cooperative relaying scheme.