COGNITIVE RADIO
Cognitive (or smart) radio networks like xG’s xMaxsystem are an innovative approach to wireless engineering in which radios are designed with an unprecedented level of intelligence and agility. This advanced technology enables radio devices to use spectrum (i.e., radio frequencies) in entirely new and sophisticated ways. Cognitive radios have the ability to monitor, sense, and detect the conditions of their operating environment, and dynamically reconfigure their own characteristics to best match those conditions.
Using complex calculations, xMax cognitive radios can identify potential impairments to communications quality, like interference, path loss, shadowing and multipath fading. They can then adjust their transmitting parameters, such as power output, frequency, and modulation to ensure an optimized communications experience for users.
Using complex calculations, xMax cognitive radios can identify potential impairments to communications quality, like interference, path loss, shadowing and multipath fading. They can then adjust their transmitting parameters, such as power output, frequency, and modulation to ensure an optimized communications experience for users.
Cognitive radio definition
There are likely to be a variety of different views of what exactly what a cognitive radio may be. Accordingly a definition of a cognitive radio may be of use in a number of instances.
A cognitive radio may be defined as a radio that is aware of its environment, and the internal state and with a knowledge of these elements and any stored pre-defined objectives can make and implement decisions about its behaviour.
In general the cognitive radio may be expected to look at parameters such as channel occupancy, free channels, the type of data to be transmitted and the modulation types that may be used. It must also look at the regulatory requirements. In some instances a knowledge of geography and this may alter what it may be allowed to do.
In some instances it may be necessary to use a software defined radio, so that it can reconfigure itself to meet the achieve the optimal transmission technology for a given set of parameters. Accordingly Cognitive radio technology and software defined radio are often tightly linked.
Cognitive radio history
There have been many factors that have lead to the development of cognitive radio technology. One of the major drivers has been the steady increase in the requirement for the radio spectrum along with a drive for improved communications and speeds. In turn this has lead to initiatives to make more effective use of the spectrum, often with an associated cost dependent upon the amount of spectrum used. In addition to this there have been many instances where greater communications flexibility has been required. Along the way, there have been several significant milestones along the road to develop cognitive radio technology.
One example that exemplified the need for flexible communications occurred in the Netherlands in 2000 when a fireworks factory exploded killing 23 people, destroying much of the town and injuring more than a thousand people. While dealing with this catastrophe, the emergency services (fire, medical, police, etc) experienced real communications difficulties because they all had different communications systems and were unable to communicate with the other services.
Another major emergency was the 9-11 terrorist attacks in the USA. Again communications difficulties were experienced.
While often a variety of radios would be needed for intercommunications, this would not be viable for small groups of people, and reconfigurable radios would have enabled far more effective communications to be achieved.
With spectrum becoming a more scarce resource many radio regulatory bodies started to look at how it might be more effectively used.
In the UK a report by Professor Cave was published in 2002 detailing the possibility of selling spectrum dependent upon the bandwidth required. This cognitive radio technology would lend itself to this approach of spectrum management as it would be able to utilise areas that were temporarily free and thereby maximise the use of particular areas.
Similarly others had been working on the possibility of self configuring radios. In fact the term "Cognitive Radio" was coined by Joseph Mitola while he was writing his doctoral thesis on the topic in 2002.
Intelligence and flexibility
Work is under way to determine the best methods of developing a radio communications system that would be able to fulfil the requirements for a CR system. Although the level of processing required may not be fully understood yet, it is clear that a significant level of processing will be needed. The radio will need to determine the occupancy of the available spectrum, and then decide the best power level, mode of transmission and other necessary characteristics. Additionally the radio will need to be able to judge the level of interference it may cause to other users. This is an equally important requirement for the radio communications system if it is to operate effectively and be allowed access to bands that might otherwise be barred.
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