Capacity enhancement of cognitive wireless networks with 7-distance spectrum usage policy

How much information can one transmit over a randomly distributed ad hoc network of n secondary devices, overlaid with m primary devices? Such a network model is referred to as cognitive wireless network (CWN) and our paper addresses the above question by characterizing its throughput capacity. Although a handful of research efforts related to throughput capacity exist in the area of CWNs, most of these solutions under-explore the capacity analysis. Their analysis particularly indicates that secondary devices can realize only a less or no gain on throughput capacity, in comparison to classical ad hoc networks, when the primary devices are densely placed in the network. Our detailed investigation shows that this unsatisfying capacity figure is due to the unrealistic assumptions and inefficient allocation of wireless spectrum for secondary devices, while formulating the capacity analysis. By resolving the issues in existing research efforts, we enhance the throughput capacity of secondary devices in CWN and at the heart of our analysis lies a novel spectrum usage policy known as γ-distance spectrum usage policy for secondary devices. In contrast to classical ad hoc networks, our results stipulate that when primary devices are densely placed in the network with an i.i.d inactive period of Poff, cognitive wireless network can realize an aggregate throughput capacity of W Poffγ√(m)off/γ √(n/log n) under the constraint Poffγ√(m)off/γ >; 1. This is in fact an interesting result which claims that by judiciously allocating the traffic of secondary devices in the licensed and unlicensed spectrum bands, one can enhance the throughput capacity of cognitive wireless networks.