In this paper, we investigate the problem of primary receiver protection in a cell-based network after the presence of the primary transmitter has been detected by cognitive radio. Since the primary transmitter may unicast, multicast or broadcast data to receivers anywhere in the cell, our goal is to protect the entire cell so the received SINR anywhere in the cell is maintained above the target QoS constraint. We formulate the problem using network optimization, and investigate an iterative algorithm for solving the problem. A solution based on partial sampling of monitoring points in the view angles of individual secondary transmitters is then investigated. Numerical results show the benefits of the proposed solution.