Optimization of transmit power and time slot for multiple secondary users in cognitive radio system (ソフトウェア無線)

概要

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This paper addresses the issues of coexistence for cognitive radio networks. The coexistence considered include the coexistence between primary users (PUs) and secondary users (SUs), as well as the coexistence among SUs. The coexistence issue addresses the sharing of identified spectrum opportunity among SUs. The coexistence issue between SUs and PUs addresses the interference from SUs to PUs. In our previous study, we have introduce the a new parameter named as quality of coexistence (QoC), which is defined as the quality of SU transmission divided by the negative interference to PUs. Assuming the a time slot of spectrum opportunity has been found by multiple SUs, we partition this time slot to multiple SUs to maximize the QoC. This leads to a good spectrum usage among SUs and minimized interference to PUs. In this study we assume that the SUs have multiple antennas and employ fixed transmit power control (fixed-TPC). A procedure for time slot allocation among SU is proposed. Further, by using the approximation of the approximation to the distribution of weighted sum of chi-square random variable (RV) we develop the analytical model for the time slot allocation among SUs. Results show that the the transmit power and time slot can be allocated to achieve the maximum QoC. In a particular scenario the QoC can be increased by 60%. The presented algorithm can be implement in the architecture presented in [1].
2010-02-24