  Radio map in general refers to the geographical signal power spectrum
density, formed by the superposition of concurrent wireless transmissions, as a
function of location, frequency and time. It contains rich and useful
information regarding the spectral activities and propagation channels in
wireless networks. Such information can be leveraged to not only improve the
performance of existing wireless services (e.g., via proactive resource
provisioning) but also enable new applications, such as wireless spectrum
surveillance. However, practical implementation of radio maps in wireless
communication is often difficult due to the heterogeneity of modern wireless
networks and the sheer amount of wireless data to be collected, stored, and
processed. In this article, we provide an overview on the state-of-the-art
techniques for constructing radio maps as well as applying them to achieve
efficient and secure resource management in wireless networks. Some key
research challenges are highlighted to motivate future investigation.
