The need for dynamic spectrum has become a necessity as a result of the indirect contribution of the conventional allocation spectrums band policy. In this article we will cover spectrum bands, their applications, and emerging technology.
About the Spectrum Bands
The radio spectrum bands are uniquely divided into fixed number of distinct frequency channels in which different wireless communication services are allocated corresponding sections of the radio spectrum bands.
There are many studies which showed that the spectrum usage carried out at different geographical locations had a significant portion of the licensed radio spectrum bands. Particularly, TV spectrum bands are not efficiently deployed, whereas the licensed radio spectrum bands utilization varies from around 15% to 85%, indicating important disparities in the deployment of the radio bands.
This concludes that the conventional allocation spectrum bands policy has inadvertently contributed to the spectrum scarcity, therefore the need for dynamic spectrum access has become a necessity.
New Policies for Spectrum Bands
For the reasons mentioned above, new rules/policies have been proposed to allow unlicensed users to access undeployed portions of the spectrum which has become known as TV white spaces (TVWS), in which transmission on its frequencies is conducted without interference with the incumbent TV transmitters and wireless microphones transmissions; TVWS comprises the Very High Frequency (VHF) band between 30 –300 MHz and Ultra-High Frequency (UHF) band between 470 – 960 MHz that are not deployed by primary users in specific time and location.
The fundamental function of TVWS (also referred to as cognitive radio) is spectrum sensing to detect absence/presence of a primary user in a licensed spectrum band I.e., identifying and accessing spectrum holes without compromising primary user’s transmission.
About Spectrum Sensing & Its Applications
Spectrum sensing falls under two categories, 1) transmitter detection: aimed to determine if primary user is using TV spectrum band. 2) receiver detections: dedicated to detecting existence of primary receivers even when primary transmitter is deploying the spectrum.
The applications of TVWS technology are various including Secured Private Network, Smart Grid, Video Surveillance, Wi-Fi/3G/4G range extension Agriculture Technology, Maritime Communication, Internet-of-Things (IoT), and Rural Internet. This later is the most promising area of application where delivery of broadband in rural areas becomes widely accessible. TVWS work pretty much in the same way as conventional Wi-Fi, however TVWS uses radio frequencies that have high power enabling it travel long distances with high ability to penetrate walls, trees, and obstacles in general, and this means that TVWS requires very few numbers of access points to cover the same area. The excellent obstacle penetration and range characteristics explains why this technology is called “Super Wi-Fi.”
Wifi Vs. TVWS
Current Wi-Fi devices operate at power level of 40 or 100 milliwatts, at this same power level TVWS proves to need about 16X fewer access points in the UHF part of TVWS (600 MHz) to provide the same coverage as Wi-Fi in 2.4 GHz frequency. So with the same access point number which offers four times the range, we can actually achieve sixteen times the area coverage with TVWS.
As for access controls, TVWS has another key difference compared to traditional Wi-Fi is that their devices gain managed access to undeployed TV channels by communicating their exact spatial location to a database which is in charge of providing the list of channels along with operating parameters like duration, power, and geographic boundaries. TVWS devices are instructed to use only channels delivered by an authorized white space database, allowing them to use this spectrum more intelligently over time.
Companies that are innovating in this sector are likely to be eligible for several funding programs including government grants, and SR&ED.
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