Throughput-delay tradeoff for opportunistic spectrum access in cognitive radio networks

The internet of things accelerates the wireless connections of massive devices to provide all kinds of new services, and thus intensifies the spectrum scarcity and access delay. Cognitive radio (CR) technology brings a solution for the issue. As a typical CR scheme, opportunistic spectrum access (OSA) has been addressed widely in the past decade. However, the tradeoff between two key indexes, the throughput of cognitive radio network (CRN) and the delay of secondary user (SU), is rarely mentioned so far, which ignites the authors' work in this paper. Taking into account a channel handoff (CH) based multi-channel OSA scenario, the authors first analyze the opportunistic transmission performance of SU, and model the throughput of CRN as well as the handoff delay of SU. Then, the authors build up a delay-constraint throughput optimization problem, and thus formulate the throughput-delay tradeoff for OSA. Finally, the optimal traffic rates of SU for a good throughput-delay tradeoff are derived according to maximizing the throughput of CRN. Theoretical and simulated results show that to enhance the throughput and to reduce the delay do not conflict always. By well adjusting the traffic rates of SU according to the traffic rates of primary user, the throughput of CRN can be improved while the handoff delay can be kept under a given level. The authors address the tradeoff between the throughput of cognitive radio network and the delay of secondary user (SU) under a reactive channel handoff based opportunistic spectrum access scenario. The handoff blocking-then-reaccess scheme is deeply analyzed. Then the throughput-delay tradeoff is formulated with a delay-constrained throughput optimization problem. The authors' results indicate that it is possible to improve the throughput while making the handoff delay reduced by properly adjusting the traffic rates of SU.image