DSA: empty TV spectrum bands can support broadband expansion

Thursday 26 November 2015 | 16:43 CET | Background
Update: 28 November 2015 | 22:27 CET

The Dynamic Spectrum Alliance (DSA) sees shared spectrum use playing a key role in improving broadband access in rural Africa and Asia for the four billion unconnected. A large amount of the UHF spectrum reserved for TV is not used there and could be employed to support broadband services. The opportunities are significant,  Prof. H Nwana, Executive Director of the DSA, told Telecompaper.

The Dynamic Spectrum Alliance is a global industry group that lobbies for efficient use of spectrum. The group counts around 50 members, including the charter members BSkyB, Facebook, Google, Interdigital, Mediatek, Microsoft and NICT. Other members include equipment makers Aruba Networks, Broadcom and Ruckus Wireless.

Nwana worked previously as head of spectrum policy at UK regulator Ofcom and helped organise spectrum auctions. He was also a key impetus behind Ofcom's TV White Spaces (TVWS) policy.

Dynamic Spectrum Sharing is an umbrella term for a different approach to spectrum, Nwana said in a phone interview. The static allocation of spectrum licences leads to inefficiency, in part due to the need to use different frequencies in adjacent cells of a network. Local variations in demand and capacity also have an impact.

The idea of dynamic sharing can be applied in any number of frequency ranges, but the UHF spectrum for TV is particularly relevant. The frequencies offer good propagation characteristics and most importantly, the spectrum is widely available.

TV band nearly empty

Those TV bands are nearly empty in many developing countries. In Africa, 82 percent of countries have less than 19 terrestrial TV channels, according to Nwana. Some have as little as two or three channels. A single multiplex suffices for 19 SD channels, meaning much of the band, i.e. hundreds of MHz, is left empty. Nevertheless, the spectrum must be reserved for broadcast services under designations agreed at the ITU.

The previous World Radio Conference in 2012 decided that shared access would be left up to individual countries to decide. Nwana advises the governments of a number of African countries on their spectrum policies. He said it was not justified to try and import policies from OECD countries. Africa has a completely different geography - it is very large - and ARPU is just a few dollars. Affordability and accessibility are the two biggest challenges, after power challenges of course, and so a different type of spectrum policy is needed.

Income distribution

The top 1 billion people in the world earn an average USD 29,000 per year and can spend an average USD 205 per month on telecom services. The bottom 1 billion earn an average USD 540 per year and can spend just USD 2.25. Mobile operators in Africa often generate half their revenue from just 8-10 percent of their base stations and as much as 80 percent of revenue from less than 30 percent of the network. This suggests much of the network is loss-making and there is little incentive to expand coverage.

Nwana suggested that the best way to develop broadband in rural Africa is competition, including competition within the 3GPP ecosystem and between mobile operators and standards. He cited the example of LTE-450 to serve rural areas in Sweden, which could be a solution for Africa as well. Competition between ecosystems will also be needed, Nwana said, noting the mobile industry alone does not have the answer to bringing universal broadband to Africa.

This poses the 3GPP ecosystem against networks based on Licensed Shared Access in broadcast spectrum. The case for sharing is further strengthened by the fact that the primary application is still under-developed, leaving room to grow the commercial value of the spectrum.

TV landscape

Nwana is helping lead the digital switchover in his native Cameroon and advising on it in several other countries. As part of the switch from analogue to digital broadcasting, these countries are looking to develop their own media sectors, with local content production and the equally important local advertising networks. The new industry is working to serve regional differences and local languages.

Satellite is less suitable for serving these regional and local viewers with local content. Cameroon is aiming for 80 percent of the territory covered by digital terrestrial TV services, and Nigeria targets 85 percent. Satellite is the option only for very remote regions where terrestrial networks are not viable.

Wi-Fi in the middle and last mile

With the TV and content ecosystem still in development, there is room for broadband to play a role in the same frequency bands. If the UHF spectrum is used both for broadcast and broadband, the whole system could be viable sooner.

The roll-out scenario for shared spectrum use includes a major role for Wi-Fi. 2G is suitable for calls and messaging, as it has the lowest costs for roll-out, helped by open standards based network equipment. Keeping access affordable is a major challenge, said Nwana.

When 3G and 4G become too expensive for internet, Wi-Fi offers the best alternative as a near-universal standard. Wi-Fi can be used for the last 100-500 meters to deliver broadband. In addition to 'normal’ Wi-Fi in the 2.4 and 5.0 GHz bands, a third version is possible, Wi-Fi in UHF spectrum. The IEEE standardised this in 2012 as 802.11af.

11af Wi-Fi is developed for low spectrum and long distances, up to a few kilometers. The commercial production of supporting Wi-Fi chipsets is expected to start in the course of 2016. Once these are available, end-user devices supporting all three Wi-Fi bands can be developed.

802.11af Wi-Fi will also play a role in ‘middle mile access’, for connectivity at distances of 2-10 km. Notably all devices will be listed in a central database that keeps track of which channels are available. This is important because 'white space' spectrum would be different in every location.

The backhaul for the base stations used can run over microwave systems and if available, fibre. Nwana is advising many countries to deploy fiber to all population centres with at least 20,000 residents.

Major industry players like Facebook and Alphabet (Google) will also play a role, Nwana expects. Both companies support the DSA and are exploring a variety of technologies to expand internet access. Facebook is testing drones, while Alphabet is working with stratosphere balloons in its Project Loon. When it comes to challenges such as connecting rural Nigeria with rural Cameroon, fibre will not be the answer, Nwana noted. He noted that Google and Facebook are lobbying at the WRC-15 for more spectrum. The aim is for a decision at WRC-19 so the services can start soon after.

There are also commercial and pre-commercial projects underway in Asia for shared spectrum use. After the devastating hurricane in the Philippines in November 2013, a TVWS network was used. The equipment was dropped near the severely damaged provincial capital Tacloban and was operational within a few hours. They're now building a network with Wi-Fi in TV White Spaces for educational purposes.

A broader perspective

The Dynamic Spectrum Alliance recently announced a cooperation agreement with the Wireless Broadband Alliance, the industry group supporting licence-free wireless technologies such as Wi-Fi. In addition to the 802.11af standard mentioned above, 802.11ah and 802.22 are also being proposed by the FCC and Ofcom for filling in TV White Spaces.

Also active is the WhiteSpace Alliance (WSA), an industry group with a different make-up and aims than the DSA. While the DSA focuses on efficient spectrum use and key aspects of spectrum policy and regulation, the WSA is developing applications to deliver broadband access in shared spectrum. The two work together on an informal basis.

The Dynamic Spectrum Alliance aims to set up an ecosystem for developing countries, but also has priorities for mature markets. This with an eye on the impending ‘spectrum crunch’, as the exploding demand for connectivity, both for more devices and higher bandwidths, outpaces the available spectrum. 

The Singapore government is also picking up on the idea of shared use. According to Nwana, only 6 percent of spectrum in Singapore is used efficiently, despite it being one of the most densely populated and wealthy countries in the world. How much added value shared use can bring is a question Nwana left for commercial businesses to consider. 

‘TV White Spaces’ is a term developed by regulators such as Ofcom and the FCC. In the UK and US, the focus is on increased capacity. While it was difficult to get TVWS off the ground in the UK, tests in Scotland and Wales will be continued in 2016. Ofcom has opened a public consultation on the final set of TVWS regulations, which should come into effect early in 2016. Shared use is already allowed in the US and being tested in Virginia. 

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