Distributed QoS-Aware Scheduling in Cognitive Radio Cellular Networks

In a cognitive radio cellular network (Cog Cell), it is very common that primary users (PUs) rarely utilize all the assigned frequency bands in the given time period and the locations. The spectral inefficiency caused by the spectrum holes motivated cognitive radio technology (CR) that presents unlicensed secondary users (SUs) an opportunity for using spectrum holes. In this paper, we investigate the QoS-aware scheduling problem defined in [14] in which all SUs will be scheduled to transmit in different time slots in order to guarantee the QoS requirements from PUs. Note also that we plan to integrate the Cog Cell system into the existing environmental monitoring platform to improve the communication efficiency and reliability. Moreover, the data used in the Cog Cell are collected from different sensors deployed in the monitoring field. The main objective here is to minimize the length of the scheduling process in terms of total number of the time slots to admit all SUs a chance to transmit meanwhile the QoS requirements from both PUs and admitted SUs should be guaranteed. This is a very challenging problem and the NP-hardness has been shown in the literature [17]. Due to the limitations of centralized scheme proposed in [13, 14] in which the topology of the Cog Cell and the sensor system has to be known in advance by both PUs and each SUs, we focus on decentralized (distributed) approaches and propose a time efficient scheme to accomplish the QoS-aware scheduling problem. To be our best knowledge, this is the first time to consider distributed scheduling in Cog Cells with applications in the environmental monitoring.