Spectrum sensing techniques for cognitive radio
We consider a system with two networks : a primary (or legacy) network, that owns the spectrum and has full access to it ; and a secondary network, which is allowed to use the primary network's bandwdith, as long as the primary network remains totally unaware of it. The secondary network must use cognitive radio techniques to access to the resource. No information is exchanged between both networks.
The secondary network must detect the unused spectrum. Detecting primary user sis the most efficient way to detect spectrum holes. Several techniques exist for spectrum sensing. They can be classified into three categories:
- Transmitter detection: cognitive radios must have the capability to determine if a signal from a primary transmitter is locally present in a certain spectrum, there are several approaches proposed:
- Marched filter detection
- Energy detection
- Cyclostationary feature detection
- Cooperative detection: refers to spectrum sensing methods where information from multiple cognitive radio users are incorporated for primary user detection.
- Interference based detection.
The training work will consist in studying these techniques, and comparing them. More precisely, the advantages and drawbacks (in terms of requested information, complexity, etc.) of each method will be determined. The performances of spectrum sensing techniques will be evaluated through MatLab or C simulations. This characterization should lead to a set of recommendations. The context of application will be a primary WiMAX network, and a secondary network that may be either based on OFDMA, or on CDMA.
Keywords:
Cognitive radio, spectrum sensing, detection
Requirements:
Telecommunications, signal processing, Matlab and/or C languages.
Good mathematical level.
References:
- D. Cabric, S.M. Mishra and R.W. Brodersen, "Implementation issues of spectrum sensing in cognitive radio", in ASILOMAR Conf., 2004.
- A. Sahai and D. Cabric, "Spectrum sensing: fondamental limits and practical challenges", Tutorial, Dyspan Conf., 2005.
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