Dynamic Spectrum Leasing for Cognitive Radio Networks—Modelling and Analysis

Abstract

Incentive based dynamic spectrum leasing (DSL) has been suggested as a type of cognitive radio (CR) based communication in which the legacy network allows the cognitive radio nodes to utilize its spectrum for their communication in exchange for cooperative relaying services. The key objective of this chapter is to investigate the design space of a DSL empowered large scale CR network (CRN) collocated with a point-to-point primary communication link. The ultimate design objective is to improve both the network level energy efficiency and the spectral efficiency through the exploitation of cooperation gains rendered by the proposed optimally dimensioned DSL mechanism. This chapter presents a DSL scheme where the CRs cooperatively relay the data of the primary network for a duration of time. As a reward for the cooperation, the CRs are granted exclusive access to the primary spectrum for some time. To harness maximum gains in terms of energy efficiency (EE) for the primary network while maintaining its required quality of service and spectral efficiency (SE) of the CR network, a comprehensive model of DSL is presented. To this end, an accurate quantification of the random locations of the CR nodes and the optimal division of leasing time between the primary and secondary activities are two crucial factors. In this chapter, we consider a large scale cognitive random network. The spatial dynamics are modeled by using point process theory from stochastic geometry. Mutual agreement of the primary and secondary nodes on the leasing time division is studied using a game theoretic framework. The analysis indicates that DSL enables the primary to attain its required transmission rate and from 20 up to 50 % of the total leasing time is also reserved for the secondary activity. It is shown that the bargaining powers of the primary and secondary networks strongly dictate the proportion of cooperation and leasing time. Further, the EE of DSL based on the network geometry and optimal leasing time is analytically characterized. The simulation results reveal that DSL operation under such considerations can be significantly more energy efficient as compared to direct communication. A closer look helps to ascertain that DSL with a sparse secondary network can serve to be more than 10 times energy efficient while maintaining the same time-rate product as compared to direct communication for low CR densities. Hence DSL based communication enables the primary to communicate at its desired transmission rate and quality in an energy efficient manner and also enables the CR network to exploit the licensed spectrum for its own communication. In short, DSL is a useful technique for improving the efficiency of wireless communication with direct application to future networks.