Capacity of MIMO broadcast channels in cognitive radio networks

This paper investigates the sum rate capacity of MIMO broadcast channels (MIMO-BCs) in cognitive radio (CR) networks. An efficient algorithm is proposed for selecting a set of users to achieve a high sum rate capacity of the system. With the above algorithm, the sum rate capacity of MIMO-BCs in CR networks with average interference power constraints and transmit power constraints is derived. We formulate the capacity as a multi-constraint optimization problem and develop efficient algorithms to solve the problem in its equivalent form. Finally, numerical simulations are conducted to corroborate our theoretical results in Rayleigh fading environments. It is shown that the proposed method is capable of achieving a large sum rate capacity with a very low complexity.