Techniques for controlling transmit power and the amount of overlapping in a quasi-orthogonal system are described. A base station for a sector receives transmissions from terminals in that sector and neighbor sectors and determines performance metrics (e.g., overall throughput) and/or QoS metrics (e.g., minimum data rate) for the terminals in the sector. The base station updates an overlapping factor based on the performance metrics and updates a QoS power control parameter based on the QoS metrics. The overlapping factor indicates the average number of overlapping transmissions sent simultaneously on each time-frequency block usable for data transmission. The QoS power control parameter ensures that the terminals in the sector can achieve minimum QoS requirements. A power control mechanism with multiple loops is used to adjust the transmit power of each terminal. The overlapping factor and QoS power control parameter are updated by two of the loops.