Beyond interference avoidance: On transparent coexistence for multi-hop secondary CR networks

This paper explores the so-called "transparent coexistence" paradigm for spectrum sharing between primary and secondary nodes in a multi-hop network environment. Although such paradigm has been studied in the information theory and communications communities, it is not well understood in the wireless networking community, particularly for multihop networks. Under this paradigm, a secondary network is allowed to use the same spectrum simultaneously with the primary network as long as their activities are "transparent" (or "invisible") to the primary network. Such transparency can be accomplished through a systematic interference cancellation (IC) by the secondary nodes without any impact on the primary network. This paper offers an in-depth study of this paradigm in a multi-hop network environment and addresses issues such as channel selection, IC to/from primary network, and IC within the secondary network. Through a rigorous modeling and formulation, we develop an optimization problem under this paradigm with the objective of maximizing secondary user's throughput. Through simulation results, we show that such paradigm offers significant improvement to a multi-hop network in terms of spectrum efficiency and throughput performance as compared to the prevailing interference-avoidance paradigm.