Performance of Multi-Hop Whisper Cognitive Radio Networks

In 2003, Federal Communications Commission (FCC) has released a new spectrum policy called ``Interference Temperature model" to improve the channel access opportunities of secondary users. Under this model, the secondary users are allowed to access the licensed spectrum simultaneously with the primary users provided that the interference at the primary receiver meets a certain threshold. We refer the Cognitive Radio Networks that employs this model as ``Whisper CRNs" (since secondary users have to use smaller transmission power to satisfy the interference constraint). In this work, we systematically analyze the performance of whisper CRNs and compare it with the traditional CRNs, where the secondary users are not allowed to transmit when primary users are busy. We aim to answer the fundamental question: what is the performance trade-off by switching to whisper CRNs from traditional CRNs. Based on the performance analysis, we also propose an efficient channel assignment scheme that has a small channel switching overhead. The results show that whisper CRNs can improve the connectivity and end-to-end throughput of secondary users considerably (by more than two times in some scenarios) but at the cost of increasing end-to-end delay. We also show that the node density of secondary users has a significant impact on the performance of whisper CRNs.