Cognitive Radio-based Home Area Networks

A future home area network (HAN) is envisaged to consist of a large number of devices that support various applications such as smart grid, security and safety systems, voice call, and video streaming. Most of these home devices are communicating based on various wireless networking technologies such as WiFi, ZigBee and Bluetooth, which typically operate in the already congested ISM licensed-free frequency bands. As these devices are located in a small physical space (i.e., limited by the size of the house), they might interfere with one another, which causes a severe limitation to the quality-of-service (QoS) such as throughput. These issues are further aggravated in dense cities where the HAN also receives interference from neighboring HANs. Cognitive radio (CR) is seen as one of the most promising technologies to solve these problems and at the same time fulfill the HANs communication needs. CR technology enables the HAN devices to intelligently exploit idle spectrum including licensed spectrum for their communications, avoiding from being interfered as well as causing interference to others (in particular the incumbent user). We study these problems and the appropriateness of CR as a candidate solution.

We start by designing a new communication system for HANbased on CR technology and clustered network topology, called TD-CRHAN. TD-CRHAN aims at sustainably and efficiently supports the ever-rising throughput demand as well as solving the interference issue in HAN. In TD-CRHAN, the achievable throughput is optimized to be just equal or slightly higher than the total network’s throughput demand, instead of being maximized. We then mathematically model the proposed TD-CRHAN where in the model, general expressions of the cooperative spectrum sensing performance parameters are considered. This allows us to analyze the performance of TD-CRHAN for more realistic scenarios where the incumbent user signal-to-noise-ratio (SNR) is not the same at different sensing devices. We provide the performance analysis on the proposed design numerically and through simulation.

As a cognitive radio based network also imposes additional overhead in energy consumption due to spectrum sensing, we then propose an energy efficient cooperative spectrum sensing (CSS) scheme. The scheme is designed based on the proposed TD-CRHAN. In this scheme we also ensure that the throughput demand is kept satisfied efficiently. From the difference in sensing devices’ incumbent user SNR (that is previously considered), we select the optimal sensing devices for CSS with the corresponding sensing time and detection probability, which can be varied from one sensing device to another. We then evaluate the proposed CSS scheme and exhibit the gains obtained in energy- and throughput-efficiency. Finally, we present a sensing device grouping and scheduling scheme for multichannel CSS. In addition to the energy- and throughput-efficiency, this scheme addresses the fairness in spectrum sensing load distribution among the available sensing devices in a HAN. In this work, we consider the fairness objective as to maximize the lifetime of each sensing device to its expected lifetime. In the proposed scheme, we determine the optimal number of channels that should be used for the network and the selected channels. We also determine the optimal number of devices in each sensing group and which devices. Subsequently, we optimally schedule the formed sensing groups to sense the selected channels. We provide the results and the analysis on our proposed scheme to illustrate its performance.