Cache-Enabled in Cooperative Cognitive Radio Networks for Transmission Performance

The proliferation of mobile devices that support the acceleration of data services (especially smartphones) has resulted in a dramatic increase in mobile traffic. Mobile data also increased exponentially, already exceeding the throughput of the backhaul. To improve spectrum utilization and increase mobile network traffic, in combination with content caching, we study the cooperation between primary and secondary networks via content caching. We consider that the secondary base station assists the primary user by pre-caching some popular primary contents. Thus, the secondary base station can obtain more licensed bandwidth to serve its own user. We mainly focus on the time delay from the backhaul link to the secondary base station. First, in terms of the content caching and the transmission strategies, we provide a cooperation scheme to maximize the secondary user’s effective data transmission rates under the constraint of the primary users target rate. Then, we investigate the impact of the caching allocation and prove that the formulated problem is a concave problem with regard to the caching capacity allocation for any given power allocation. Furthermore, we obtain the joint caching and power allocation by an effective bisection search algorithm. Finally, our results show that the content caching cooperation scheme can achieve significant performance gain for the primary and secondary systems over the traditional two-hop relay cooperation without caching

Spectrum-aware data replication in intermittently connected cognitive radio networks

Abstract—The opening of under-utilized spectrum creates an opportunity for unlicensed users to achieve substantial per-formance improvement through cognitive radio techniques. In cognitive radio ad-hoc networks, with node mobility and low node density, the network topology is highly dynamic and end-to-end connection is hard to maintain. We propose data replication techniques to address these problems and improve data access performance in such intermittently connected cognitive radio network. Although data replication has been extensively studied in traditional disruption tolerant networks, existing techniques cannot be directly applied here since they do not consider the effects of primary user appearance on data replication. In this paper, we formulate spectrum-aware data replication as an optimization problem which tries to maximize the average data retrieval probability, subject to storage and time constraints. Since the problem is hard to solve based on mixed integer programming, we further design a distributed replication scheme based on the metric of replication benefit. Extensive simulations based on synthetic and realistic traces show that our scheme out-performs existing schemes in terms of data retrieval probability in various scenarios. I