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Stefan Mangold, Swisscom Innovations, Berne Switzerland
stefan.mangold@swisscom.com

Lars Berlemann, Guido R. Hiertz,
ComNets, RWTH Aachen University, Germany
lars.berlemann@ieee.org, hiertz@ieee.org

The popular IEEE 802.11™ standard with its extensions for support of quality of service (802.11e), for dynamic radio resource management (802.11h), and for new types of radio resource measurements (802.11k), is a well suited candidate technology for future cognitive radios. In this tutorial, we describe and evaluate these extensions, and describe how they can be used to build cognitive radios. Cognitive radios coordinate the usage of radio spectrum without involvement of restrictive radio regulation. They operate in spectrum when it is not used by licensed radio systems, and therefore share spectrum with radio systems that have priority access. This is referred to as "vertical sharing." Unused radio spectrum is called a "spectrum opportunity". In the vertical sharing scenario, cognitive radios adapt their transmission schemes such that they fit into the identified spectrum usage patterns of the incumbent radio systems. Note that cognitive radio refers not only to the radio technology: It also requires a revolutionary change in how our spectrum will be regulated. However, with this change and the new cognitive radio approach for open spectrum sharing, it will be difficult to achieve fairness and efficient spectrum sharing. This is particularly challenging in ad hoc mesh networks, where cognitive radio systems rely on their own capabilities not only to maintain connectivity but to increase spectrum efficiency. This horizontal sharing problem in mesh networks is a challenge for cognitive radios, and is in our work approached with spectrum etiquette rules. Spectrum etiquette rules are voluntary rules based on mechanisms like dynamic channel selection, transmission power control, adaptive duty-cycles, or carrier sensing. Details about spectrum etiquette are provided in this tutorial. We then provide insights on cognitive algorithms and reasoning based on machine-understandable languages and logics. The support of quality of service in spectrum sharing scenarios is a challenging problem. Decentralized cognitive algorithms on the basis of spectrum observation for mutual coordination are discussed. The tutorial will be concluded by giving insight into layer 2 aspects of 802.11-based mesh networks, where we specifically discuss the intensified needs for cognitive approaches.

Outline
1. IEEE 802.11™ medium access control
- 802.11e/h/k for flexible spectrum management
2. FCC's notices of proposed rulemaking
- Cognitive radio & unlicensed secondary usage of TV broadcast bands
3. DARPA's Next Generation XG Program
4. Spectrum opportunity identification
5. Spectrum etiquette and reasoning
6. Cognitive Medium Access
- Application of game theory
- Spectrum Load Smoothing
7. Cognitive Algorithms in Future Networks
- Mesh networks (IEEE 802.11s, 802.15.5)

Biography Stefan Mangold:
Stefan Mangold is project leader at Swisscom Innovations, Bern, Switzerland. He is currently working in the project "Cognitive Radio". Before joining Swisscom in April 2005, Dr. Mangold was senior member research staff at Philips Research, NY, USA.

Biography Lars Berlemann:
Lars Berlemann is research assistant at ComNets RWTH Aachen University, Germany. His research interests are cognitive radios, distributed QoS support in spectrum sharing scenarios, spectrum etiquette, and flexible protocol stacks.

Biography Guido R. Hiertz:
Guido R. Hiertz is research assistant at ComNets RWTH Aachen University, Germany. His research interests are QoS support in layer-2 protocols, IEEE 802.11, MBOA Ultra Wideband, and decentralized algorithms for Mesh WLAN & WPAN.