Cooperation in cognitive cellular heterogeneous networks

Abstract

A recent drive by mobile network operators to mitigate the network capacity crunch and to improve indoor coverage involves the development of cellular heterogeneous networks. Cellular heterogeneous networks consist of the existing macrocells plus shorter range cells referred to as small cells. Coexistence of macrocells and small cells sharing the same spectrum represents a special case of cognitive networking, where small cells and their users can be viewed as secondary users, whereas the macrocell and its users act as the primary legacy users. Unlike the traditional listen-before-talk concept in cognitive radio spectrum sensing, this chapter presents techniques for utilizing inherent Radio Link Control (RLC) messages and feedback information in existing cellular systems. It develops a more-advanced cognitive approach that takes into account actual primary user's interference tolerance and facilitates more efficient spectrum sharing. The chapter first introduces the idea of implicit cooperation through the use of inherent feedback information in cellular heterogeneous networks. Explicit cooperation is then discussed in the chapter before introducing the concept of cooperation in hybrid-access cellular heterogeneous networks as well as in dense enterprise femtocell deployments. The chapter concludes by summarizing the most recent trend of integrated access between both cellular and wireless local area network (WLAN) interfaces at small cells for traffic offloading and for improving network capacity.