Understanding TV White Space

By John Rothgeb and Julie Langou

Do you remember Analog TV?

Old fashioned analog TV broadcast needed 6 MHZ bandwidth for each channel. Originally the frequencies between 54 MHZ and 806 MHZ were allocated for the licensed TV broadcasts of 69 VHF and UHF Channels. Digital TV broadcasts require a fraction of the bandwidth which had been required by analog broadcasts. So after we switched from analog to digital TV, blank white spaces appeared in the TV band on frequency charts. The white spaces on the charts represented the unused frequencies in the TV spectrum. Consequently these unused frequencies are referred to as TV white spaces (TVWS). At the present time TVWS frequencies in the VHF (54-216 MHz) and UHF (470-698 MHz) bands are available for unlicensed use at locations where spectrum is not being used by licensed services, such as television broadcasting. To find available TVWS frequencies for your location go here. In general the more rural locations have less broadcast TV and more available TVWS frequencies.

Bandwidth or bandwidth, that is the question?

There is bandwidth and then there is bandwidth. When I use the term bandwidth I am referring to a section of the frequency spectrum expressed in HZ, such as AM Radio Band, FM Radio Band, TV Band, Short Wave Band, etc… Carrier signals these different frequency bands are used for transmitting information. The information is encoded onto the carrier signal at the transmitter and decoded at the receiver. When the information is digital the data transfer rate, expressed in bits per second (bps), is used to describe the speed of the connection. In computer networks, bandwidth is often used when referring to data transfer rate. Whenever you see bandwidth expressed bps it refers to a digital data transfer rate. For example, in California the maximum data rate transfer of an Internet connection must be 6 Mbps or greater to be considered broadband Internet.  So another meaning for the term bandwidth is the speed of your internet connection

What White Space is available?

In wireless communications a carrier frequency is used to transmit information. The information is encoded onto the carrier signal at the transmitter and decoded at the receiver. The carrier frequency is analog. The encoded information may be analog or digital. The portion of the frequency spectrum that is used for the transmission of a carrier signal is called the bandwidth. Old fashioned analog TV broadcast required 6 MHZ bandwidth for each channel and the frequencies between 54 MHZ and 806 MHZ were originally allocated for licensed TV broadcasts.
  • Channel 1 used the bandwidth from 54 MHZ to 60 MHZ.
  • Channel 2 used the frequency range from 60 to 66 MHZ and so forth.

A carrier frequency  bandwidth of only 1.5 MHZ is required for the transmission of a TV channel that is digitally encoded onto the carrier signal. So when we switched from analog TV to digital TV there was a lot of bandwidth freed up in the frequency range between 54 And 806 MHZ. This unused bandwidth in the is called TV white space (TVWS).  At the present time TVWS frequencies in the VHF (54-216 MHz) and UHF (470-698 MHz) bands are available for unlicensed use at locations where spectrum is not being used by licensed services, such as television broadcasting. To find available TVWS frequencies for your location go here. In general the more rural locations have less broadcast TV and more available TVWS frequencies.

Stop calling White Space Super Wi-Fi,  I am already too confused with Wireless, Wifi ….

Wi-Fi is wireless but not all wireless is Wi-Fi. Ok not sure this helps wither!
Wireless = No Wire – and that’s it – using any frequency
My car beeper is wireless, but have you try getting Internet from it! So I guess you get it, Wireless means nothing except no wire. But no wire means those device needs a radio frequency to communicate.
Satellite connection has no wire, so it is wireless, my cell phone has no wire, so it is wireless, my Wi-Fi router has no wire, so it is wireless.
The term Wireless Internet could mean different wireless technologies operating on any frequency. The term wireless broadband usually refers to Internet over cellular networks such as 3G, 4G, LTE, etc…
Wi-Fi = Wireless device using 2.4 and 5.8 GHZ frequency
All Wi-Fi devices are built to very specific specifications so that any Wi-Fi device will work on any Wi-Fi network anywhere in the World. The term Wi-Fi is a registered trademark and has a very specific meaning. Only Wi-Fi products that complete Wi-Fi interoperability testing may use the “Wi-Fi CERTIFIED” trademark. Wi-Fi networks operate in narrow frequency bands at 2.4 and 5.8 GHZ.
Satellite Internet is off course wireless and is not Wi-Fi.
Super Wi-Fi” = TV White Space = Wireless device using 54 to 678 MHZ frequency = longer-distance wireless Internet access
Unfortunately the term “Super Wi-Fi” has been coined to apply to TVWS networks which operate in a totally different frequency band, 54 to 678 MHZ, and do NOT interoperate with any of the billions of Wi-Fi devices in use today. Any user wishing to connect over a future TVWS network will need entirely new equipment.
The term “Super” is also inappropriate. The TVWS frequencies are limited to a peak data rate of 29 Mbps while Wi-Fi systems are being designed to operate at peak rates of 1 Gbps. TVWS only advantage is that it has better connectivity and in some situations that may be the deciding factor. Also if TVWS networks can cover larger areas with fewer access points than required by WI-Fi systems, there may be some savings in equipment costs. For more information on this subject go to http://gigaom.com/2013/03/17/white-spaces-networks-are-not-super-nor-even-wi-fi.

Wouldn’t it be great if we could use the TV spectrum to supply free Internet to rural areas?

One of the most promising applications for TVWS is to provide broadband Internet to rural communities. The TVWS frequencies are lower than the frequencies generally used for the Internet so the data rate capabilities are lower; however, the TV frequencies work better over irregular terrain. They will kind of bend around hills and can go through/around trees and buildings. They will give you better connectivity. That’s why the TV guys chose these frequencies in the first place. If you can think back to when you where using an old fashion TV antenna to receive broadcast TV you have an idea of the potential capability. And the digital performance is better than analog performance. Broadcast TV is free but it no longer exists in rural areas.

WHITE SPACE just deployed California

The first commercial application of TVWS in the U.S. is coming to El Dorado County in Northern California. Internet provider Cal.net is partnering with network equipment provider Carlson to bring this region’s residents something more than dial-up. Preliminary information is that the monthly service will cost users $54.95 per month with speeds of around 2 to 4 mbps. The service is being provided under a temporary license from the FCC and is currently only available in the vicinity of Swansboro.

 

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