A new interference model for the IEEE 802.22 cognitive WRAN

The IEEE 802.22 cognitive Wireless Regional Area Networks (WRAN) uses cognitive radio technique to allow Secondary Users (SUs) to opportunistically share the TV bands with TV broadcast service on a non-interfering basis and hence improve the spectrum utilization. WRAN employs Orthogonal Frequency Division Multiplexing (OFDM) technology for transmission and thus is sensitive to inter-carrier interference. So one of the challenging issues in WRAN performance analysis is the interference analysis from SUs. Existing research on interference primarily focuses on the co-channel interference. The study of inter-carrier interference in WRAN has not received considerable attention. In this paper, we design a new interference model for IEEE 802.22 cognitive WRAN that incorporates both the co-channel interference and inter-carrier interference. We first examine the interference in the context of one SU, and then study the aggregate interference in the context of multiple SUs. Existing work on studying the aggregate interference is to derive its probability density function, which is known computationally intensive. In this paper, we investigate the aggregate interference from a new perspective. Instead of deriving the probability density function, we calculate the aggregate interference by estimating the maximum number of interfering SUs. Our results suggest that the maximum number typically ranges from 6 to 10 depending on the network configurations. This finding significantly simplifies the interference estimation process. To verify the new interference model, comprehensive simulations are performed. Results confirm that the inter-carrier interference cannot be ignored especially when a high frequency offset is present. The maximum number of SUs and its effectiveness are also validated.