Cognitive radio (CR) has been proposed as a solution to the spectrum scarcity problem, which is aggravated by emergence of the bandwidth-demanding high-data-rate and feature-rich wireless applications. The current radio spectrum regulations assign specific bands to particular services and grant licensed bands access to only licensed users, which render the spectrum use inefficient. CR implements dynamic spectrum allocation policies to better exploit the existing spectrum. In a CR network, the intelligent radio part allows unlicensed users (secondary users) to access spectrum bands licensed to primary users, while avoiding interference with them. This means more constraints on the RF/antenna front-end design of the transceiver and necessitates the development of algorithms for sensing the surrounding environment and subsequently controlling the functions of the antenna and RF front end.

The objective of this special issue is to report on the recent advances in the design of antennas and RF front ends for cognitive radio and the development and integration of spectrum sensing and channel modeling algorithms and antenna/RF front-end control. Potential topics include, but are not limited to:

• Frequency-, pattern-, and polarization-reconfigurable antennas
• Wideband/ultrawideband antennas
• Small-size antennas
• MIMO systems for cognitive radio
• Smart antennas/antenna arrays for cognitive radio
• Agile RF front ends
• Modulation and waveform design for cognitive radio
• Spectrum sensing algorithms
• Modeling of spectrum usage
• Simulation tools and test beds for cognitive radio

Before submission authors should carefully read over the journal’s Author Guidelines, which are located at http://www.hindawi.com/journals/ijap/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/submit/journals/ijap/arf/ according to the following timetable: