Multiple antennas and relay can improve spectral efficiency of a network. Half duplex relay channels employing decode-and-forward and total power constraint are considered in this work. The resource includes power and time for the receive and transmit stages of the relay. Resource allocation algorithm is designed in order to maximize an achievable rate. The source and the relay nodes are assumed to have partial channel state information (CSI) obtained through finite-rate feedback from relay and/or destination. The full-blown problem is stated and the result of a special case of orthogonal transmission is presented. The transmitters use the simple power on/off precoding with constant number of on-beams while the precoding matrices are chosen according to quantization on Grassmann manifolds. An earlier analytical result on finite rate feedback is employed in the resource allocation algorithm. The complicated expressions of the achievable rates and the non-convexity of the problem make the optimal resource allocations hard to obtain and analyze. Iterative and near optimal resource allocation algorithm is presented. Numerical results are provided to show the benefits of finiterate feedback by comparison of the achievable rates of the relay channel, two-hop transmission and the direct transmission.
['Jun Xiao', 'Youjian Liu', 'Wen Gao', 'An Liu']
Resource allocation for MIMO orthogonal relay channels with finite-rate feedback