Date:24 April 2013
When South Africans talk to each other, the mobile phone is their medium of choice. But when it comes to going online, for many users – particularly in outlying areas – mobile suffers because of poor coverage. The solution: TV signals
The explosion in cellphone use has brought telecommunications to even the most far-flung corners of our country. There is, however, one significant area that lags: broadband. Rural areas are trailing their city-slicker cousins because they are denied high-speed broadband.
That could all be changing, though, thanks to some lateral thinking involving an unlikely source: the TV signal spectrum. TV White Space (TVWS), those slices of the spectrum between existing signals, is being touted as the breakthrough in bridging the digital divide. It will, supporters say, bring broadband to the backwoods at a reasonable cost.
Information and communication technology specialists at the Council for Scientific and Industrial Research are leading the development of this wireless technique. The CSIR’s Meraka Institute, whose focus is ICT, was initially allocated a test licence by the Independent Communications Authority. Then, on 25 March, a trial was finally launched in Cape Town, involving 10 Western Cape schools. The initiative comes in the wake of the government’s identification of broadband as a key social and economic driver.
In the first trial, the 10 schools will be connected to base stations at Stellenbosch University’s Tygerberg Hospital Medical School. Partners include Google, the Wireless Access Providers’ Association, the Tertiary Education and Research Network (TENET) and eSchools. The networks will use Google’s spectrum database to determine white space availability. A second project for TV white space trials is planned in Limpopo near the University of Limpopo’s Mankweng/ Turfloop Campus from April next year.
In principle, the technology works, of course. The trials are essentially being conducted to see how well the technology can co-exist with licensed spectrum holders – more to the point, whether it will interfere with them.
“What we refer to as TV white spaces are unused spectra in the TV spectrum bands between 470 MHz and 790 MHz in Region 1 of the International Telecommunications Union (ITU) at a specific geographical location,” says Dr Ntsibane Ntlatlapa, manager: networks and media at the CSIR. (Region 1 consists largely of Europe, Africa, the Middle East, the former Soviet Union and Mongolia.)
White space technology’s low-power signal has better propagation characteristics than the currently used, much higher, GHz frequency bands, Ntlalapa says. Furthermore, automated control of the white space would allow the number and exact frequency of unused spectrum to vary from location to location and also with time. “Mobile broadband has become very competitive,” says Ntlatlapa. “This is a much more cost effective way to get broadband to people. The whole concept is at the research level across the world.”
With current mobile technologies, there is no real incentive for operators to move away from the cash cow – the big urban or commercial areas. “Innovation is really needed in the rural areas, which will always be left behind if efforts are not made to improve their infrastructure, as well as to provide them with opportunities to keep abreast of developments,” says Ntlatlapa. TV white space spectrum devices, he says, deliver improved wi-fi-like systems for broadband and are based on a combination of spectrum sensing, geolocation and beacon techniques for interference avoidance.
Paradoxically, it’s the smaller populations of outlying areas that make them particularly suited to TV white space. Simply, lower population density means more unoccupied TV spectrum.
According to the Wireless Access Providers’ Association, it’s been a long road involving several years of lobbying for more progressive and efficient spectrum management. Association chairman Christopher Geerdts is reported as saying that the organisation’s members are at the forefront of delivering broadband access to rural communities across South Africa, with most of them using licence exempt frequencies, but these heavily used frequencies are not viewed as a sustainable solution. The TVWS initiative, says Geerdts, vastly increases the scope of what they can achieve.
Right now, the spectrum is fixed. But dynamic spectrum management will make it more efficient. “Of course, for dynamic spectrum management, you need access a database of users. That is the enabler. We are engaged right now in building a database for South Africa,” says Ntlatlapa.
Kenya is said to be the only other African country to have the same level of involvement in exploring white spaces. Botswana is also interested, Ntlatlapa says.
Meanwhile, the CSIR will co-ordinate the trials, conduct research and evaluate the technical parameters and performance of the technology in the South African context. Its findings will help point the way towards a regulatory framework for this technology in South Africa. The organisation is also hoping to create and stimulate opportunities for industry in related fields and to develop technology in collaboration with industry.
Need to know: Television White Spaces
By international convention, wireless transmissions are each allocated a specific part of the broadcast spectrum so that they don’t interfere with each other. Given the limited number of TV broadcasters, there are significant slices of unused spectrum – White Spaces – between individual TV signals. With the migration from analogue to digital TV signals, access to this spectrum will become much easier to manage and automate, opening the door to allocate the unused spectrum for other uses.
But there’s more to it than just spectrum availability. Because these signals are at ultrahigh frequencies, they have the ability to be broadcast long distances and to pass through solid bodies; they don’t need line-of-sight to the signal tower. Those characteristics are useful for transmission in cities as well as in rural areas. At this stage only the US has codified regulations on TVWS. Google supported its first white space trial in the US in 2010, and has recently launched a spectrum database for public comment period with the FCC. The UK is working on similar regulations. Developing countries are, understandably, watching with interest. (Source: WAPA.)