SPECTRUM MONITORING FOR OFDM-BASED COGNITIVE RADIO NETWORKS
Detect quickly the reappearance of the primary user within a reception period within an OFDM-based cognitive radio network without requiring received bit decoding
The need of advanced methods and technologies in wireless communications
- Nowadays, static spectrum access is the main policy for wireless communications.
- Under this policy, fixed channels are assigned to licensed users or primary users (PUs) for exclusive use while unlicensed users or secondary users (SUs) are prohibited from accessing those channels even when they are available.
- The idea of cognitive radios (CRs) was proposed in order to have efficient utilization for the RF spectrum.
- Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique employed in many wireless systems/standards which has proven to be a reliable and effective transmission method. OFDM is a preferred modulation technique for cognitive networks.
- Accordingly, it would be beneficial to establish a spectrum monitoring technique that is suitable for OFDM based cognitive radios.
- It is an object of the present invention to address limitations within the prior art relating to spectrum monitoring during receiver reception and more particularly to spectrum monitoring for OFDM-based cognitive wireless networks.
New efficient method and system for Cognitive Radio Spectrum monitoring
- The invention incorporates a spectrum monitoring algorithm named “energy ratio” for Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radios by which the primary user reappearance can be detected during the secondary user transmission (Fig. 1), (Fig. 2).
- The proposed technique reduces the frequency with which spectrum sensing must be performed and greatly decreases the elapsed time between the start of a primary transmission and its detection by the secondary network.
- This is done by sensing the change in signal strength over a number of reserved OFDM sub-carriers so that the reappearance of the primary user is quickly detected.
- Moreover, the OFDM challenges such as power leakage, Narrow Band Interference (NBI), and Inter-Carrier Interference (ICI) are investigated and their effects are studied for the proposed technique.
- Both analysis and simulation show that the energy ratio algorithm can effectively and accurately detect the appearance of the primary user (Fig. 3).
- Technology developed by Walaa Hamouda and Ali Abdelmohsen (Department of Electrical and Computer Engineering, Concordia University).
- Improved efficiency of OFDM-based cognitive radio (polling frequency and primary user reappearance detection latency).
- High immunity to frequency-selective fading channels for both single and multiple receive antenna systems.
- Simulation results indicate that the detection performance is superior than the receiver statistics method, however, with increased complexity.
Spectrum sharing in wireless communications.
Walaa Hamouda, Professor, Department of Electrical and Computer Engineering
Prof. Hamouda received his B.Sc (Telecommunications & Electronics) from Ain Shams University, Cairo, Egypt, M.A.Sc. and Ph.D. degrees from Queen’s University, Kingston, Canada in 1998 and 2002, both in Electrical and Computer Engineering. From 1994 to 1996, he worked as a system engineer for Siemens R&D, Cairo, Egypt. During his Ph.D study, Dr. Hamouda received many fellowships and scholarships including Ontario Graduate scholarships (OGS) and Queen’s graduate fellowship, Queen’s graduate award, IEEE Student Conference Award (ICC2001), and outstanding-engineering award (Siemens). In July 2002, Dr. Hamouda joined the Department of Electrical and Computer Engineering at Concordia University as an assistant professor where he is now a Full Professor. From Sept. 2008-May 2009, he was the Associate Chair for Department of Electrical and Computer Engineering, Concordia University. His current research interests are wireless communications, cognitive radios, ad hoc networks, cross-layer design, MIMO communications, power-line/smart-grid communications.