Abstract

Mobile devices are advancing every day, creating a need for higher bandwidth. Because both the bandwidth and spectrums are limited, maximizing the utilization of a spectrum is a target for next-generation technologies. Government agencies lease different spectrums to different mobile operators, resulting in the underutilization of spectrums in some areas. For some operators, limited licensed spectrums are insufficient, and using others’ unused spectrums becomes necessary. The unlicensed usage of others’ spectrums is possible if the licensed users are not using the spectrum, and this gives rise to the idea of cognitive radio networks (CRNs). In CRN architecture, each user must determine the status of a spectrum before using it. In this chapter, we present the complete architecture of CRN, and we additionally discuss other scenarios including the applications of the CRN. After the Federal Communications Commission (FCC) declared the 5 GHz band unlicensed, Wi-Fi, LTE, and other wireless technologies became willing to access the band, leading to a competition for the spectrums. Because of this, ensuring that the spectrum is fairly shared among different technologies is quite challenging. While other works on DSRC and Wi-Fi sharing exist, in this chapter, we discuss LTE and Wi-Fi sharing specifically.