IoT devices (wireless sensors, actuators, computer devices) produce large volume and variety of data and the data produced by the IoT devices are transient. In order to overcome the problem of traditional IoT architecture where data is sent to the cloud for processing, an emerging technology known as fog computing is proposed recently. Fog computing brings storage, computing and control near to the end devices. Fog computing complements the cloud and provide services to the IoT devices. Hence, data used by the IoT devices must be cached at the fog nodes in order to reduce the bandwidth utilization and latency. This chapter discusses the utility of data caching at the fog nodes. Further, various machine learning techniques can be used to reduce the latency by caching the data near to the IoT devices by predicting their future demands. Therefore, this chapter also discusses various machine learning techniques that can be used to extract the accurate data and predict future requests of IoT devices.

Emerging of Cognitive Radio (CR) technology has provided optimistic solution for the dearth of spectrum by improving the spectrum utilization. The opportunistic use of the spectrum is enabled by spectrum sensing which is one of the key functionality of CR systems. To perform the interference free transmission in a cognitive radio networks, an important part for unlicensed user is to identify a licensed user with the help of spectrum sensing. Recently, the Cooperative Spectrum Sensing has been widely used in the literature where various scattered unlicensed users collaborate with each other to make the final sensing decision. This overcome the hidden terminal problem and also improve the overall reliability of the decisions made about the presence or absence of a licensed user. Each unlicensed user send the sensing results to the base station for final decision. However there exist some nodes which do not provide the correct sensing results to maximize their own profit which can highly degrade the CR network functionality. In this paper, a trust aware model is proposed for detection of misbehaving nodes such that their sensing reports can be filter out from the final result. The performance evaluation of the proposed scheme is done by checking its robustness and efficiency against various possible attacks.