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Journal of Green Engineering- Special Issue - Cognitive Radio and the Application to Green Communications: Technical, Economic, and Regulatory Viewpoints (Paperback)
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Journal of Green Engineering- Special Issue - Cognitive Radio and the Application to Green Communications: Technical, Economic, and Regulatory Viewpoints (Paperback)
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Demand for wireless data exchange is perpetually increasing,
leading to pressure on deployed wireless capacity. As systems
enhance their spectral efficiency to attempt to address this,
evermore complex processing techniques are being employed. Such
techniques increase power consumption, leading to greater heat
output from processers in network elements and increasing powered
cooling. Moreover, the requirement for wideband linearity of radio
frequency circuitry in state-of-the-art OFDM systems, twinned with
high transmission power capability on the network side and the
inefficiencies of components when operating at such limits, leads
to greater inefficiency hence further heat power output and the
need for greater cooling. All of these ingredients significantly
affect the power consumption of communications equipment. Indeed,
merely considering raw transmission power, the Shannon-Hartley
theorem implies that necessary transmission power increases
exponentially with required capacity. Such power consumption issues
can be mitigated through cognitive radio (CR) techniques. The use
of greater bandwidths through CR and in some cases the aggregation
of bandwidths, as well as the opportunistic use of spectrum of more
appropriate propagation characteristics or with better interference
management, can reduce necessary transmission power for devices and
systems. Moreover, CR techniques may achieve greater
spatial/temporal awareness of connectivity options and their
inherent power consumptions, as well as the power consumptions of
chosen radio access characteristics. They might be able to use this
awareness to dynamically switch to connections that better manage
loads and interference, or might be able to minimize the power
consumption of radio frequency circuitry through switching radio
access technique given a required traffic load. At a simpler level,
they may be able to appropriately select nearer connectivity
options minimizing path loss/shadowing hence necessary transmission
power, in consideration of experienced/predicted traffic loads and
channel characteristics. Such capabilities are particularly
relevant considering that, at least in terms of the transmission
power to from-the-socket power consumption ratio, lower power
equipment such as wireless LAN access points achieves far better
efficiency than higher-power equipment such as macro-cell base
stations. This manifestation is not only because of favorable path
loss characteristics, but also because of the better efficiencies
of the lower power components in such access points. CR might also
assist in making other areas of life more environmentally friendly.
The application of CR to intelligent transportation, for example,
facilitating the sharing of information in a timely manner and with
appropriate data rates among vehicles and between vehicles and
roadside infrastructure through enhancing the capabilities of
systems such as IEEE 802.11p, could lead to the better management
of traffic signals and better collaborative automated management of
traffic speeds, limiting unnecessary vehicular start/stop cycles
and greatly reducing the burning of fossil fuels. Moreover, the
presence of CR capability in a wide range of future machines will
facilitate those machines talking to each other more ubiquitously
than today. Such machine-to-machine communications could greatly
enhance the energy efficiency of everyday living. One example of
this is smart grids and smart homes, facilitating the usage of
energy locally, only when needed, and catering for the integration,
better prediction of and capitalization from renewable resources.
Among other benefits, such solutions would decrease wastage in the
home through better management of appliances and heating/cooling
options.
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