Performance loss minimization in cooperative networks based on quantized channel feedback

In wireless networks, having channel state information (CSI) at some central node is essential for most resource allocation problems. We turn our attention to the uplink transmission in a cellular network where the cell users are assisted by a single relay; our goal is to maximize sum rate over the users. Understanding that assuming perfect CSI is a purely theoretical construct, we investigate the scenario where only quantized CSI (QCSI) is available at a central node. Here we design quantization levels which minimize the performance loss in terms of loss in sum rate due to quantization in the network. Next, assuming a finite capacity for the CSI feedback link, we argue that the performance loss may be further reduced through proper bit allocation, i.e., quantization of different links with different precision. We further show that for any given network, there is always savings in terms of CSI bits required as long as optimal bit allocation is deployed. Finally, we propose a lower bound on performance loss achieved through optimal bit allocation.