Power Allocation for Multi-Antenna Multiple Access Channels in Cognitive Radio Networks

A cognitive radio network is often described as a secondary communication network operating in a frequency band originally allocated to a primary network consisting of one or multiple primary users. A fundamental challenge for realizing such a system is to ensure the quality of service of the primary users as well as to maximize the throughput of the secondary users. In this paper, we consider a sum-rate maximization problem for single-input multiple output multiple access channels (SIMO-MAC) under interference constraints for the primary users as well as a peak transmission power constraint for each secondary user. We apply zero-forcing based decision feedback equalizers to decouple the SIMO-MAC, and develop a capped water-filling algorithm to maximize the sum-rate of the secondary users. We also investigate another scenario where only multiple primary users´ interference constraints are considered. Furthermore, we provide numerical simulations to illustrate the effectiveness of the algorithm.