Adaptive Multiple Time-Scale Power Allocation for Spectrum Sharing in DS-CDMA Networks

In this paper, we propose adaptive multiple time- scale power allocation (AMTPA) method for opportunistic spectrum access (OSA) in the uplink of DS-CDMA networks. In AMTPA, the secondary service is facilitated by granting passive access to the power control commands transmitted by the primary network´s base-station. AMTPA manages the secondary service transmission power in two phases, each in different time-scales. In the longer time-scale, Power Allocation Phase adaptively allocates the secondary service transmit power based on the medium-scale variations of the secondary channel, so that the achieved capacity is maximized. Then in the shorter time-scale, power adjustment phase exploits the power control commands transmitted in the primary network to adaptively adjust secondary service transmission power to reduce the effect of the secondary service transmission on the quality-of-service of the primary network. Simulation results show that maintaining a given collision probability constraint, AMTPA makes a significant improvement on the achieved capacity.