Cognitive and Green Communications

The Communications Research Group has one of the largest academic teams in the UK dedicated to Cognitive Radio (CR) and Cognitive Networking (CN). The field requires 'cross-layer' thinking to maximise the utility of the radio spectrum and can be applied to several layers of the protocol stack.

The big driver for CR has been the obvious success of unlicensed band communications, whose rules enable efficient 'semi-intelligent' assignment of spectral resources and control of interference.

Over the last 10 years or so we have carried out extensive research into radio resource and spectrum management, and have built up significant expertise, centred on the data-link layer, while taking into account physical layer effects and the impact of the network and higher layers on performance.

The Cognitive Radio Lab is expanding rapidly, and is supported by a UK Ministry of Defence Competition of Ideas Project 'Cognitive Routing for Tactical Ad Hoc Networks', which also involves members of the Intelligent Systems Research Group.

CR came to prominence with the publication of the doctoral thesis by Joseph Mitola III in 2000. He used CR as a way of incorporating machine-based learning into software-defined radio. Since then, the definition has been broadened to address the general concept of intelligent assignment of available radio spectrum.

Spectrum is often considered a scarce resource. However, studies commissioned by the UK regulator OFCOM show that up to 90% of spectrum in the 2-10 GHz bands in any geographical area is not used at any time.

CR takes unlicensed band techniques to the next logical stage, identifying spectral 'holes' via wide-band sensing and using them opportunistically. Protocol intelligence and environment awareness allows interference to be controlled and performance of other uses maintained. CR encompasses the following aspects:

Software-defined radio at the physical layer
Multiple access and channel assignment at the data link layer
Intelligent networking at the network layer.

We are ideally placed to explore the cross-layer discipline of CR, and our ongoing activities include CR for heterogeneous systems, with application of game theoretic principles to resource assignment. Over the next few years we will be investigating:

How to perform opportunistic assignment across multiple frequency bands/channels, including the intelligent coexistence and band sharing of heterogeneous nodes and networks. These could include PANs, ad hoc multihop networks, terrestrial MANs, and high altitude platforms.
The ability to cope with legacy systems and nodes with limited intelligence.
The application of game theory and economic principles to perform real-time efficient assignment of the radio spectrum, without necessarily the need to refer to a central authority. This will include dealing with rule breakers.
The integration of routing and topology management with cognitive radio techniques for ad hoc networks, and using them to select the most spectrally efficient path through the network.
Channel selection strategies that take into account traffic type and usage patterns. This will be linked with the emerging field of channel sensing for cognitive radio.
New cognitive MAC layers to cope with new physical layer cooperative diversity techniques.
The impact of antenna directionality (including beamforming) and transmitter power control on cognitive radio terminals.
Development of firmware designs for cognitive radio.

For more details of our current projects in Cognitive Radio, please see the links at the bottom of this page.

Useful Links for Cognitive Radio

Cognitive and Green Communications: Projects

	Coexistence of Heterogeneous Cognitive Radio Systems Members: Pairoj Likitthanasate, David Grace, Paul Mitchell The purpose of this project is to establish how broadband terrestrial and HAPs systems should use the same spectral allocation in order to maximise system capacity and quality of service. read more...
	Cognitive Networking for Heterogeneous Wireless Systems Members: Mohamed Elsokkary and David Grace The purpose of this project is to examine how cognitive networking techniques can be applied to systems of heterogeneous wireless nodes (especially those delivering multicast transmissions), as a way of improving dynamic performance over multi-hop backhaul networks. read more...
	Cognitive Radio and Coexistence for Mixed Terrestrial Multicast Communications Systems Members: Meng fei Yang, David Grace In the future many different types of communications systems may well wish to use the same pooled spectrum. The purpose of this project is to investigate how cognitive radio can be applied to terrestrial multicast-based communication systems of different capabilities. read more...
	Cognitive Radio for Short Range Systems Members: RuoFan Jin, David Grace, Paul Mitchell This project will examine how best to deliver cognitive radio in short range systems. Techniques based on Ultra Wide Band (UWB) and/or Orthogonal Frequency Division Multiplex (OFDM) will be explored, specifically examining how such systems can simultaneously operate in a pooled spectrum environment, while maintaining appropriate QoS for other systems, including primary users. read more...
	Cognitive Radio for ‘Smart’ Building Environments Members: Elizar, David Grace, Paul Mitchell Cognitive Radio (CR) is likely to operate best in indoor or short-range scenarios, where buildings can be used to provide a variable degree of shielding, enhancing frequency reuse. The purpose of this project is to explore an exciting new dimension in the development of CR, namely the benefits it would bring to users and systems operating in ‘smart’ buildings environments. read more...
	Cognitive Routing for Tactical Ad Hoc Networks Members: David Grace, Paul Mitchell, Tim Clarke, Alister Burr, Dave Pearce, Yiming Liu, Andrew Pomfret, Yu Deng, Pairoj Likitthanasate, Jingxin Chen, Danshan Chen, Yi Wang Military and crisis management networks are characterised by their ad-hoc heterogeneous structure. For example, they will contain low-capability sensors, medium-capability nodes for speech/video delivery, or even high-capability 'landmark' nodes with directional antennas which will relay trunked traffic directly to headquarters. This project seeks to improve their scalability, reducing the impact of the node relaying overhead through improved network management and better coordination of the routing, bandwidth assignment, and physical layer transmission methodologies. The ultimate goal is to increase the viable network size by an order of magnitude. read more...
	Cognitive Routing for Wireless Ad Hoc Networks Members: Bo Han, David Grace, Yiming Liu The purpose of this project is to investigate how the impact of relaying can be reduced in wireless ad hoc networks by examining routing strategies and network design that exploit heterogeneous node capabilities, including nodes that are able to assign variable amounts of bandwidth using cognitive radio techniques. read more...
	Energy-Efficient Cognitive Radio Exploiting Antenna Beam-Forming for Ad-Hoc Networks Members: Aizat Ramli, David Grace This project investigates optimum channel allocation and multiple-access techniques for cognitive radio systems employing beam-forming antennas. These antennas can significantly lower the energy requirements of these radio systems, as well as reducing the interference for other users of the radio spectrum. read more...
	Improving Spectrum Usage in Mixed Wireless Systems Through Cognitive Radio Members: Jingxin Chen, David Grace, Paul Mitchell Unassigned radio spectrum below 10GHz is now becoming increasingly scarce, but at the same time studies commissioned by regulators show that large parts of this spectrum are not being used in any specific geographical location. This problem can be solved by Cognitive Radio (CR) techniques, where terminals can dynamically change their transceiver parameters based on interaction with the environment in which they operate, thus using the spectrum in a dynamic manner. read more...
	Reduced Complexity Cognitive Radio Systems Members: Tao Jiang, David Grace, Yiming Liu Researchers are proposing a variety of increasingly complex methods of implementing cognitive radio, which incorporate software defined radio, dynamic spectrum management, and intelligence. The drawback of this complexity is that it is predicted that CR is still years away from implementation. The purpose of this project is to initially take a top level examination of the solutions proposed, to try and understand whether such complexity is justified, and what benefits they bring to overcome the current regulatory constrained spectral assignment process. read more...
	Robust Cognitive Radio Based Bandwidth Assignment for Heterogeneous Wireless Networks Members: Hai Bin Li, David Grace, Paul Mitchell Many cognitive radio schemes being developed today rely on spectrum etiquettes to maintain quality of service for their users, and to control impact on primary users. The purpose of this project is to develop suitable Cognitive Radio (CR) techniques that will deliver increased robustness to interference without the need to wholly rely on spectrum etiquettes to control interference. read more...