Spectrum sensing as an enabling function for dynamic spectrum access has attracted significant interest from both industry and academia. An enormous amount of research has been carried out for conventional spectrum-sensing techniques, for example, energy detection, matched filtering detection, and cyclostationary feature detection. These existing techniques address challenges for avoiding interference by secondary users. A hybrid spectrum-sensing method to consider both primary and secondary user activities is necessary.

Both the Federal Communications Commission in the US and the Office of Communications in the UK have promoted the TV white space spectrum, in which pioneering work is aimed at putting dynamic spectrum access into practice. This spectrum allocation policy, together with various standards development efforts, such as IEEE 802.22, IEEE 802.11ac, IEEE P1900, and ZigBee, would enable a new range of wireless services such as cognitive sensor networks, as indicated in this paper.

Along with further development of dynamic spectrum access, Zahmati et al. identify the challenge of finding the optimal sensing period upon activities from both primary and secondary users, model the problem in a continuous-time Markov chain system, and test the model with ZigBee radios. For those interested in spectrum sensing for next-generation cognitive radio networks, this paper is definitely worth reading.