Large blocks of underused spectrum lie tantalizingly out of reach, waiting for enabling regulation, administration, and to some extent technology, to accelerate our move towards Digital India. One such category is unused/underused TV spectrum or "TV White Space" (TVWS). Despite growing demand, operators face bleak prospects as they struggle to deliver, starved of spectrum and infrastructure. Their dilemma is how to extend delivery capability without choking on buying spectrum so precious it's like an albatross around their necks, leaving little capital for densifying and extending their networks.
There's a war brewing around wireless broadband trials using TVWS in India, years after completion in other countries. These frequencies are most effective for long-range broadband. Mobile operators are watchful of developments such as Microsoft getting preferential access, triggered by announcements of its partnership with the Education and Research Network (ERNET) for countrywide rural broadband. Equipment suppliers also seem apprehensive of developments that could lead to swathes of spectrum being "unlicensed", reducing markets for their established products for licensed spectrum.
This article aims to clear some of the misinformation to facilitate policies for Digital India.
What is "TV White Space"?
There's confusion and disinformation about what TVWS is. Quite simply, TVWS is unused TV spectrum, or TV bands devoid of TV signals. The meaning derives from the areas on a page without print or pictures. Microsoft calls it "White-Fi", while some call it "super Wi-Fi".
Even bands broadcasting TV programs can have underutilised sections that can carry broadband, as pioneered by researchers at Rice University in Houston, Texas. Rice has a system that uses TV bands for both broadcasting as well as broadband.1 According to researchers, although the 400 to 700MHz band is used for broadcasting TV in many US cities, its capacity is largely underutilised because of alternative ways of accessing TV signals, such as through cable, satellite, or Internet TV. Therefore, incorporating Rice's technology in TV sets or remote equipment could significantly expand the urban reach of "super Wi-Fi", and not restrict it to rural areas.
Is there any TVWS in India? Some say there isn't!
Studies across the country show that over most of it, unused TV spectrum (white space) amounts to 85 to 95 per cent of TV spectrum.2,3,4 Studies, excluding northern India, show that in over a third of the area, a large band - 470 to 585 MHz - is available for alternate use.2,4
An odd controversy has been created about whether this is "white space" or not, precisely because the spectrum is largely unused.5 The convoluted semantics are mystifying, because white space is by definition unused broadcast spectrum. The National Frequency Allocation Plan already designates this band for fixed or mobile wireless, in addition to TV. In other words, without changes in allocation, operators can share TV spectrum on a secondary basis, as in the USA, the UK, and Singapore.
Regarding spectrum usage charges, as with any infrastructure, it is much more beneficial in the public interest to provide affordable services first and to collect government fees and taxes later, than to front-load auction fees and have no services at all (imagine road systems if up-front charges had to be paid for the right to build them). Overall benefits from Digital India, which is impossible in the foreseeable future without low-cost wireless broadband connections to the NOFN and other backbone networks like ERNET, will far exceed cash collections from auctions.
Proponents of auctions suggest that TVWS be reallocated as cellular spectrum and auctioned. Their reasons: (a) The transfer of public property to private operators; (b) Transparency and fairness; and (c) Government collections. This reasoning is false and misleading, because: (a) No transfer is required, as all operators can get secondary access equitably through a consortium approach; (b) This ensures transparency and fairness; and (c) Government collections from productive use will far exceed any auction collections, as evidenced by licence fees: in 2005, estimated auction fees lost until March 2007 were Rs 20,000 crore, whereas actual collections were double, at Rs 40,000 crore; collections by March 2010 were Rs 80,000 crore, in addition to the public benefits of better services.
Should TVWS be used only for 3G & 4G?
Another negative argument is the insistence that TVWS should be auctioned for 3G and 4G. Whereas Digital India needs low-cost wireless broadband, especially for long-distance links in rural India, because of the high cost and difficulty of building and maintaining fibre or wired networks in difficult terrain, and/or in sparsely populated areas. Therefore, access to TVWS needs to be bundled with the National Optic Fibre Network/BharatNet, and other shared backbone networks like ERNET. Policies should permit different network design scenarios including transmission power and purpose. Point-to-point links are needed over long distances in place of fibre or microwave, and broad coverage is needed for contiguous areas like industrial developments, campuses, commercial complexes, or rural communities. At the user end, TVWS could interface through cellular (3G or 4G) or Wi-Fi transceivers.
TVWS does need tight radio filters (unlike Wi-Fi) to minimise interference, the underlying consideration that drives spectrum management. There's also need for varying power specifications depending on the network design and purpose as described above, and policies for unlicensed sharing using geolocation databases, as defined by the US FCC (Federal Communications Commission).
To be most beneficial, it is not important to extract the maximum carrying capacity from TVWS in every location, as in the misplaced number-of-subscribers-linked spectrum policy some years ago. Rather, the objective for Digital India is to use this technology in combination with others for the purposes people need, namely, for affordable broadband wherever they are, while mitigating radiation hazards. This is essential for India to get its basic communications infrastructure.
1. http://news.rice.edu/2015/07/13/rice-tests-wireless-data-delivery-over-active-tv-channels-2/, Jade Boyd, September 5, 2014.
2. IIT-Hyderabad studied TVWS in southern India from 2009, shared findings with the government/other IITs from 2011, and published in 2014: http://link.springer.com/chapter/10.1007/978-3-319-08747-4_3#, Kalpana Naidu et al.
3. http://www.cse.iitd.ernet.in/~vinay/papers/coral13.pdf, Pradeep Kumar et al, June 2013, IIT-Delhi.
4. arXiv:1310.8540v1 [cs.IT], Gaurang Naik et al, 31 October 2013, IIT-Bombay.