CSI assisted and modulation adaptive wireless cooperation for increased spectral efficiency

Cooperative communications is a very important mechanism to provide diversity for devices that are incapable of harboring multiple antennae by emulating MIMO system. Different strategies of cooperation exist such as amplify-and-forward (AF) and decode-and-forward (DF). Although cooperation is a viable means of fighting multi path fading, it inherently induces a reduction in spectral efficiency which is against the need for increased data rate of wireless networks. In this paper, adaptive modulation is applied on existing cooperative protocols (AF and DF) as an approach to compensate for spectral efficiency loss while cooperating. In addition, an approach based on the previously existing ones called CSI directed estimate and forward (CDEF) strategy that utilizes CSI better and results in better BER performance with improved spectral efficiency is proposed. Simulation results also confirm the improvements, highlighting a promising approach to satisfy high data rate demands by current and future wireless networks.