Power control and scheduling for interfering links

In a wireless network, co-channel interference among links can significantly deteriorate the performance. Power control and link scheduling provide mechanisms to manage interference. Transmission power consumption is critical to the lifetime of a wireless device. For the sake of conserving power, our goal is to manage the interference to meet the system performance requirement most efficiently. The objective is to find a transmission strategy that minimizes the power consumption while maintaining a prespecified average data rate on each link. We model the problem as a convex optimization and attempt to get a solution from its dual. Unlike previous work which assumed a linear relationship between instantaneous data rate on a link and signal to interference plus noise ratio, we use a logarithmic relation as suggested by the Shannon capacity formula. The dual problem is solved sequentially using a combination of a "difference of convex function (DC) program" and a dual computational method. We find that the optimization of power control can be decoupled from link scheduling. Any power allocation solving the dual problem is a candidate for a component of the optimal solution, and we call it a transmission mode. Our analysis shows that an appropriate time-sharing among these transmission modes, which achieves the required average data rate, is an optimal strategy. Simple numerical examples suggest that when the interference is low, the best policy is to transmit on all the links simultaneously with appropriate power control. As the interference becomes severe, the best policy is to schedule the links in a TDMA manner.