Near-optimal spectrum allocation for cognitive radios: A frequency-time auction perspective

Cognitive radio networks (CRN) is a promising technology for the efficient utilization of spectrum resource. However, how to dynamically allocate the spectrum combining with the characteristics of CRN is a crucial challenge for the mechanism design. In this paper, from the perspective of frequency-time characteristics of the spectrum opportunity in CRN and the secondary users´ flexible requirements, we model the dynamic spectrum allocation problem as a knapsack problem and prove that maximizing the social welfare is NP-hard. Therefore, a spectrum auction mechanism is developed to approximate the optimal social welfare, and we prove its approximate ratio. Further, to guarantee the truthfulness, we devise a corresponding payment scheme. In simulation results, we show that no matter how many SUs are in the CRN, our scheme can approximate the maximal social welfare perfectly, and the spectrum utilization can be improved to over 96.5% or even larger.