Ten schools in the Cape Town area have been connected to the Internet at speeds of 4 MB/s using unused ultra-high frequency spectrum between 480 MHz and 690 MHz reserved for television broadcasting, says Council for Scientific and Industrial Research (CSIR) Meraka Institute manager Dr Ntsibane Ntlatlapa.
The ten schools are participating in the first trial in South Africa to study the effects of connecting and the potential to connect underserviced regions to the Internet using television white spaces (TVWSes), which comprises the currently unused frequencies reserved for television broadcasting. Unused frequencies vary, depending on regions, channels and time of day.
A second trial will aim to demonstrate the use of TVWSes to connect rural regions in Limpopo.
A possible third trial will involve machine-to-machine communication and possible remote meter reading using TVWS frequencies in a time-division multiplexing format, where different signals are sent at different times, or the study of the functionality and use of TVWS channels with regard to machines only sending signals periodically.
The Meraka Institute is studying several different concepts, including the interference of such TVWS connections with frequencies in use, the use of existing television antennae to connect rural and township residents to the Internet and the effective ranges of TVWS broadband connections, he says.
The Department of Communications has issued a licence to Meraka, which enables the institute to conduct studies of these TVWS frequencies in the Cape Town region.
TVWSes are more abundant in rural areas, owing to fewer television channels broadcasting to these regions; therefore, more TVWSes are available to deliver services.
Further, TVWSes are significantly cheaper to use than 2.6 GHz frequencies because the signal travels farther using the same power for transmission. This may enable easier entry for new users, such as broadband service providers or content distributors, in different regions, says Ntlatlapa.
Much of TVWS research pertains to future applications of the frequencies, specifically to provide channels to distribute education services, to enable egovernance services, including rural municipalities having direct communication channels to residents and rural residents interfacing with the Department of Home Affairs without travelling great dis- tances, and to provide entertainment, broadband Internet access and connectivity to more people in South Africa.
“An antenna is not only a receiver and, with the correct hardware, every house’s antenna can be connected to a base station. However, we have several research projects at Meraka to iron out the details and applicability of different technologies,” he notes.
The purpose of the study, however, is to help the Department of Communication to draw up regulations for the use of TVWSes by licensed operators, he says.
Operators currently lease spectrum, such as that monitored by Meraka, over fixed ranges according to spectrum databases. However, Meraka has conducted several studies on newer technologies, specifically dynamic access and beaconing.
Dynamic access involves base stations searching for unused frequencies and providing services to connected devices on these unused frequencies.
Beaconing searches for channels used by other base stations and, using a complex algorithm, determines how the different channels will be used by base stations should possible interference be probable. A PhD researcher at the CSIR has developed a viable algorithm for this emerging technology.
Further, the capabilities provided by improved connectivity in rural and remote areas should foster the development of more industry and businesses in these regions, he adds.
“There is now a demand for this TVWS spectrum to deliver improved WiFi-like systems for broadband; these devices are known as white space devices. White space devices are based on a combination of spectrum sensing, geolocation and beacon techniques for interference avoidance,” Ntlatlapa notes.
These frequency bands are attractive to potential broadband users owing to the availability of a large amount of spectrum that can be used to provide connectivity, propagation qualities that provide for non-line-of-sight performance and in-building penetration, as well as large coverage areas, thanks to the long-range propagation of the signal at these frequencies.
The Meraka Institute’s research will help the Department of Communication to develop effective regulations for using the TVWS spectrum in South Africa; it may also have future implications for the licensing, use and sharing of spectrum for all telecommunications, he concludes.