Power Allocation for Cooperative Broadcast Channel with Shared Channel Quality Indicators

In this paper, cooperative power allocation is investigated in a two-transmitter multi-receiver broadcast multiple input single output (MISO) channel. With shared data information and shared channel quality indication (CQI), rather than sharing the full channel state information (CSI), the two transmitters jointly send information to multiple receivers by fixing the transmit beamforming weights according to Zero Forcing (ZF) principle. The power allocation is then studied to maximize the sum throughput (capacity), which can be modeled as a non-convex optimization problem. Through an application of Karush-Kuhn-Tucker (KKT) conditions, the nonconvex optimization problem is reformulated as a convex one. Then the closed form solution is derived, which takes a form similar to classic water-filling principle but is also combined with an interesting cooperation feature. Moreover, based on the derived solution, an optimal cooperative power allocation algorithm is presented. Finally, numerical simulation results are given to evaluate and demonstrate the performance of the derived joint power allocation scheme.