white space (radio)

In telecommunications, white spaces refer to radio frequencies allocated to a broadcasting service but not used locally. National and international bodies assign frequencies for specific uses and, in most cases, license the rights to broadcast over these frequencies. This frequency allocation process creates a bandplan which for technical reasons assigns white space between used radio bands or channels to avoid interference. In this case, while the frequencies are unused, they have been specifically assigned for a purpose, such as a guard band. Most commonly however, these white spaces exist naturally between used channels, since assigning nearby transmissions to immediately adjacent channels will cause destructive interference to both.

In addition to white space assigned for technical reasons, there is also unused radio spectrum which has either never been used, or is becoming free as a result of technical changes. In particular, the switchover to digital television frees up large areas between about 50 MHz and 700 MHz. This is because digital transmissions can be packed into adjacent channels, while analog ones cannot. This means that the band can be compressed into fewer channels, while still allowing for more transmissions.

In the United States, the abandoned television frequencies are primarily in the upper UHF 700-megahertz band, covering TV channels 52 to 69 (698 to 806 MHz). U.S. television and its white spaces will continue to exist in UHF frequencies, as well as VHF frequencies for which mobile users and white-space devices require larger antennas. In the rest of the world, the abandoned television channels are VHF, and the resulting large VHF white spaces are being reallocated for the worldwide (except the U.S.) digital radio standard DAB and DAB+, and DMB.

White-spaces devices

Various proposals, including IEEE 802.11af, IEEE 802.22 and those from the White Spaces Coalition, have advocated using white spaces left by the termination of analog TV to provide wireless broadband Internet access. A device intended to use these available channels is a white-spaces device (WSD). Such devices are designed to detect the presence of existing but unused areas of airwaves, such as those reserved for analog television, and utilize them for White Space Internet signals. Such technology is predicted to improve the availability of broadband Internet and Wi-Fi in rural areas.

Early ideas proposed including GNSS receivers and programming each WSD with a database of all TV stations in an area, however this would not have avoided other non-stationary or unlicensed users in the area, or any stations licensed or altered after the device was made. Additionally, these efforts may impact wireless microphones, medical telemetry, and other technologies that have historically relied on these open frequencies.

Professional wireless microphones have used white space for decades previous to so-called white space devices.

Comparison with Wi-Fi

Like Wi-Fi, TV whitespace is a wireless connection that uses different frequency bands. TV white space operates in 470 MHz to 698 MHz, while Wi-Fi operates in 2.4 and 5 GHz bands. Speed-wise, it really depends on the model of the radio, the vendor, the antenna length, and other factors. New radios can support more than 50 Mbit/s. Wi-Fi, similarly, speed depends on several factors, such as the range, the line of sight, and so on, but they can support up to 1000 Mit/s using the IEEE 802.11ac standard. The range is a crucial difference between Wi-Fi and TV white space. On average, TV white space range is 6 miles, but it can be less or more depending on different aggregates, such as noise, line of site and so on. One of the three main TV white space manufactures, Carlson wireless, advertises that their radios can go up to 24.8 miles. Both have low power consumption - 20 to 100 watts depending on the device, the antenna length, the vendor, and so on. Both technologies meet the government security standards such as FIPS 197 Compliance (Advanced Encryption Standards). While Wi-Fi works great in cities, TV white space works great in rural areas. Graph 1 illustrates the differences between TV white space and Wi-Fi.

By country

Argentina

Microsoft, in a partnership with the communications authority of Argentina, Ente Nacional de Comunicaciones (ENACOM), planned to deliver wireless access to schools in the province of Mendoza on or around August, 2017. Microsoft will borrow the White Spaces hardware to ENACOM technicians, and national satellite operator ARSAT will act as the ISP. No further trial details has been delivered yet.

Canada

In August 2011, Industry Canada, the Canadian ministry for industry, launched a consultation on "Consultation on a Policy and Technical Framework for the Use of Non-Broadcasting Applications in the Television Broadcasting Bands Below 698 MHz"
pdf
. The consultation closed on November 4, 2011. Submissions wer

from a wide range of organisations from the telecoms and broadcast industries.

Kenya

A pilot project by Indigo Telecom/Microsoft and the Kenyan government is reportedly delivering bandwidth speeds of up to 16 Mbit/s to three rural communities, which lack electricity - Male, Gakawa and Laikipia, using a solar-powered network.

Namibia

, a pilot project called Citizen Connect, a collaboration between the Microsoft 4Afrika Initiative, the MyDigitalBridge Foundation, and the MCA-N (Millennium Challenge Account Namibia), is slated to deliver broadband Internet to "twenty-seven schools and seven circuit offices of the Ministry of Education in Omusati, Oshana and Ohangwena", using "TV White Space technology".

Philippines

In 2014, Microsoft worked with the Philippine government to pilot a program for digitizing the management of remote fishermen.

Singapore

After FCC, Singapore Info-communications Media Development Authority is the second regulator in the world to have TV White Space regulated, ahead of UK and Canada. The Singapore efforts were driven mainly by the Singapore White Spaces Pilot Group (SWSPG) founded by the Institute for Infocomm Research, Microsoft and StarHub. The Institute for Infocomm Research subsequently spun off Whizpace to commercialize TV White Space radio using strong IPs that were developed in the institute since 2006.

South Africa

Google, in a partnership with the Independent Communications Authority of South Africa (ICASA)
CSIRMeraka Institute
the Wireless Access Providers Association
WAPA
an
Carlson wireless
delivers wireless access to 10 schools through 3 base stations at the campus of Stellenbosch University’s Faculty of Medicine and Health Sciences in Tygerberg, Cape Town. There was an initial trial that took place within 10 schools in order to deliver affordable internet to the selected schools in South Africa without TV interference, and to spread awareness about future TVWS technologies in South Africa. The trial took place over 10 months, from March 25, 2013 to September 25, 2013.

A second trial involved providing point-to-point Internet connectivity to five rural secondary schools in Limpopo province, with equally good results.

ICASA subsequently issued regulations on the use of television white spaces in 2018. Three temporary TV white space spectrum licenses were issued by ICASA in April 2020, response to the Covid-19 pandemic, in the 470–694 MHz band, to Mthinthe Communications, Levin Global & Morai Solutions.

United Kingdom

Ofcom, the licensing body of spectrum in the UK, has made white-space free to use.

On June 29, 2011, one of the largest commercial tests of white space Wi-Fi was conducted in Cambridge, England. The trial was conducted by Microsoft using technology developed by Adaptrum and backed by a consortium of ISP's and tech companies including Nokia, BSkyB, the BBC
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