Spectrum white open

Television spectrum currently owned by Doordarshan, once vacated post digitisation, can be used for connecting rural India


Ankita Lahiri | February 25, 2016 | New Delhi

A cheap broadband solution for the last mile connectivity is lying unutilised with the government, which so far has been reluctant to use. But with several successful pilots underway, ‘white space’ technology can soon emerge as one of the best solutions for cheap broadband connectivity for rural India, something that the national optical fibre network (NOFN) project initiated in 2011 has so far failed to achieve. The project which aimed to provide broadband connectivity to two lakh gram panchayats (GPs) has been able to connect, according to the December 2015 data, only 32,272 GPs with a roll out of 76,624 km fibre network. NOFN was later renamed as BharatNet in early 2015.

So what is white space?

It is the television spectrum that is currently owned by Doordarshan, which will be vacated once digitisation is completed in India. This spectrum can then be used for broadband, especially in areas where physical terrain is an obstacle. To test the potential of this technology, the government has granted experimental licenses to four institutes.

“The transition from analog to digital television is resulting in an opportunity for reallocation of the spectrum that is being used by analog television systems. There is an ongoing global effort to release this spectrum under innovative licensing regimes with an objective to encourage state-of-the-art wireless solutions at low costs to the end users,” explained Abhay Karandikar, professor, department of electrical engineering at the Indian Institute of Technology (IIT) Bombay.

The white space trials

Four institutes – three IITs (Delhi, Hyderabad and Bombay) and ERNET (Education and Research Network) – have been given the experimental license by wireless planning and coordination (WPC) wing of the department of telecommunication, which have been conducting trials using this technology. While ERNET is conducting experiments in five schools in Srikakulam in Andhra Pradesh, IIT Bombay has conducted trials in Palghar district, near Mumbai.

“We purposely took up a remote village and an area which has humidity, a lot of environmental disturbances so that we could test out the project in different conditions because all the IITs were taking up the project in dry villages. We wanted to test the behaviour in humidity and wind,” explained ERNET director general Neena Pahuja in an interaction with Governance Now.

Elaborating on the trial conducted at Srikakulam, Pahuja says, “We had taken a backbone from BSNL at one of the schools and had connected all the other four schools to that school. The connectivity is good. We have been doing Skype.”

The experiment proved to be a success for ERNET. The first connection was achieved in two hours. According to Pahuja, “There was no need to get right of way. We were able to set up the first connection within two hours in an aerial distance of six plus kilometres (the road distance was even more). Within two or three days, my team had connected all the five schools.”

ERNET has also conducted another experiment in Varanasi where BHEL has adopted a village as part of their corporate social responsibility initiative. “They wanted to carry out some experiments including white space. They have aligned a backhaul to their factory. From the backhaul they have used white space through an antenna and now they have connectivity to the village school also.”

According to Karandikar, whose team at IIT Bombay has been exploring the use of white space around Maharashtra villages, explained further that the idea was to use the TV white space for alternative connectivity. “We have developed a base station radio which works in this band. Since it has good propagation, we want to test whether it can be used to address the needs of rural broadband.”

His team has developed a technology prototype in the lab and has done some trials in villages around Palghar district of Maharashtra. “We believe that end client device could be Wi-Fi and it can be connected to a Wi-Fi point. But Wi-Fi needs an optical fibre ultimately to get connected to a network. What we are saying is that the Wi-Fi access point may be backhauled using the TV and be expanded to radio frequency to a cyber point.”

Karandikar explains that buildings like that of gram panchayat can be used as access points. Within clusters of house around that gram panchayat, hotspots can be set up. Then these Wi-Fi hotspots get connected to the fibre network in the gram panchayats through this TV band radio.

The success of the trial has been central to the discussion around white space. The professor goes on to say, “We have set up a network in seven villages there (Palghar district) in collaboration with Tata Tele Services and Tata Communications. We are now in the process of submitting the results, conclusions and recommendations to department of telecommunications (DoT) and telecom regulatory authority of India (TRAI) to take some policy decisions.”

IIT Hyderabad too has its success story to share. According to Dr Mohd Zafar, associate professor and head of department of electrical engineering at IIT Hyderabad, his team has been able to provide internet access to two remote villages – Terpoia and Fougurpuni. “The pilot project was started in December 2015 after we got three licenses. We are trying to provide internet through TV white space because broadband is very costly. Using the technology we have been able to provide internet at 2 Mbps speed,” he said.

“As of now the villages have no infrastructure. We will be providing computers to the schools so that they can access the internet. We are also in the process of installing Wi-Fi router so that the other villagers can also get connectivity,” Zafar added. The pilot project by Zafar and his team has been conducted in collaboration with IIT Delhi, which is exploring the possibilities of the technology in the city space.
Why white space?

It is a spectrum that is now being vacated and has no other use. And India is not the only unique user to explore the possibilities. The TV white space spectrum in the US and Europe are being regulated to operate under unlicensed or lightly licensed manner to provide platform for innovation in wireless industry. “This innovation will create methods to provide future broadband wireless services and applications to people at a lower cost,” Karandikar said.

From the regulation perspective, as per the Indian National Frequency Allocation Plan (NFAP), 2011, the spectrum in the frequency band 470-890 MHz is earmarked for fixed, mobile, and broadcasting services. “After the completion of digitisation, Doordarshan will operate within the frequency band 585-698 MHz, which has been exclusively earmarked for digital TV broadcasting in India. It is important to note that 470-585 MHz band can be considered for providing fixed services as primary service (and not secondary service) in India. This is permitted under NFAP also,” he explained further.

According to a white space factsheet prepared by Karandikar, “One of the major impediments to providing broadband connectivity in semi-urban and rural India is the lack of robust cost-effective backhaul. Even in urban areas, one of the major impediments for widespread deployment of Wi-Fi hotspots is the lack of connectivity to Wi-Fi access points.”

He further explained that the fibre connectivity in terms of backhaul that is being planned by the BharatNet would reach only till the gram panchayats in the country. “In such a scenario, the problem of connecting the backhaul link to the access network can be addressed using a mesh based last-mile or middle-mile network. A middle-mile backhaul network is a multi-hop wireless mesh network that is capable of providing coverage within a radius of one to five kilometres to enable seamless connectivity from the access network such as Wi-Fi zones, access points and clusters to a backhaul point such as the BharatNet node.”

Experts point out that the sub-GHz spectrum that white space offers provides excellent propagation characteristics to connect these last mile points. Besides, the technology does not require expensive infrastructure such as high towers and strict line-of-sight.

To make sure that this technological experiment percolates from lab to field, companies like Bengaluru-based Saankhya Labs and biggies like Microsoft, Facebook and Google have also got into the space. While Saankhya has designed a postal stamp-sized chip – Pruthvi – that can power system that can use television white space to provide internet, Microsoft is already working with the Andhra Pradesh government to implement its white space technology on a pilot basis in the Srikakulam district.

Saankhya has also developed a system called Meghdoot that can utilise the white space bandwidth in India to provide wireless broadband to remote areas. The system is powered by its own Pruthvi chip. According to the company, its Meghdoot product family consists of a base station and end user modem that can be used to provide wireless broadband connectivity using the 400 to 800MHz white space spectrum.
Experts like Karandikar and Zafar point out that the technology does not require line-of-sight and the possibility of low cost licensing model for the 470 –685 MHz frequency since it is a spectrum band that has no other commercial use. Besides, the technology provides an ample opportunity to Indian academia and industry to create intellectual property in devising methods used for TV white space spectrum usage, something that various IIT teams and companies like Saankhya have already demonstrated.

All you wanted to know about white space

What is the worldwide scenario in the TV band?

In the US, terrestrial TV broadcasting has been (and is being) operated by many private service providers in the VHF and the UHF bands. When analog TV channels switched to digital or when some broadcasters stopped their transmission, spectrum bands became available in various channels at different geographic locations. These spectrum holes are called white spaces. The situation is similar in the UK and Japan as well. 

What are the white spaces regulations in the US, UK and other countries?

In the US and the UK, regulators – FCC and Ofcom, respectively – have permitted devices to make use of white spaces as a ‘secondary user’ without causing interference to the ‘primary user’, which is the TV broadcasting on a ‘license-exempt’ basis.
Low power license exempt operation on a ‘secondary basis’ was followed by FCC where the regulators would like to optimally utilise the spectrum which was earlier being utilised fully for analog transmission, but now is part of white spaces due to the digital dividend.

How is the TV band utilisation in India?

Unlike in the US and the UK, there is only one terrestrial TV broadcaster in India – Doordarshan – which occupies either a bandwidth of 7MHz in the VHF band or a bandwidth of 8MHz in the UHF band. Doordarshan has 1,415 TV transmitters operating in India, of which eight transmitters operate in the VHF Band I , 1,034 transmitters operate in the VHF Band III and the remaining 373 transmitters operate in the UHF Band IV. 

Thus, a majority of the TV transmitters in India operate in the VHF band. A detailed quantitative assessment of spectrum in 470-585MHz has revealed that, unlike in the developed countries, major portion of the UHF TV band in India is unutilised. Also, since digitisation of broadcasting services in India is under progress, it will operate within the frequency band 585-698 MHz that has been exclusively earmarked for digital TV broadcasting in the country. This will free up the full spectrum of 470-585 MHz for other applications.

Is the Indian situation different?

In 470-585MHz, white spaces (or spectrum holes) have not been created in India in a manner similar to the way it has been dynamically created in the US, UK, and other countries by digital TV switchover of terrestrial broadcasting. In India, practically about 100MHz spectrum is available in the 470-585MHz band, which has been lying unutilised even by analog transmission. Also, the country does not require the ‘spectrum sensing’ based approach because: (a) there is a single broadcaster – Doordarshan – which is using the spectrum; (b) the usage of spectrum by Doordarshan is (nearly) static and has not  changed for decades; (c) at any given location, minimum 96MHz is available as against unutilised frequency band in 470-585MHz; and (d) information about free channels at any given location is also known and a geo-location database can be created to ascertain these free channels (IIT Bombay has already created such a database). 

What technologies and services are deployed in the US and the UK in the white spaces?

In these countries, only low power secondary operation is permitted. Technologies based on standards such as IEEE 802.22 and IEEE 802.11af has been deployed. These technologies also support wide area network including multi-cell architecture and mobility. Since India is highly cost sensitive market, it is unlikely to see the deployment of IEEE 802.22 as the end consumer device. For end consumers, 802.11 based Wi-Fi devices still form cost effective way of accessing broadband.

What kind of regulatory approach should be adopted by India?

India should explore the possibility of reallocation of spectrum. However, it is different from the traditional reallocation as it provides access to spectrum for fixed services based on Doordarshan voluntarily relinquishing spectrum by geographic areas through an incentive method of dynamic allocation. Thus, parts of the spectrum and geographic areas could be used for broadcasting services and parts of the spectrum and geographic areas could be used for fixed services. The broadcasting services could share the same frequencies with the new fixed services based on the band plan that may also be established on geographic separation.

The sharing conditions can be defined as was done to permit sharing during the transition of the 700MHz (698-806 MHz) band from broadcasting to fixed and mobile services, and to permit sharing in other parts of the spectrum allocated to TV broadcasting.
Once Doordarshan voluntarily relinquishes spectrum in a particular geographical area, fixed services could enter this spectrum based on geographical separation between services and specified technical criteria including coexistence with adjacent bands. The above approach is consistent with ITU Region 3 Frequency Allocation and our own NFAP 2011.

So what should India do?

Essentially India needs to unlock about 100MHz in 470-585MHz band for last mile and middle mile connectivity, particularly since the country is facing spectrum scarcity and the vast amount of white space spectrum is lying unutilised and being wasted.
The unutilised UHF band can be used for affordable backhaul. This fixed service backhaul can be used for connecting Wi-Fi clusters. It can eventually terminate into urban, sub-urban or village gram panchayat node. At other places, it can even provide alternative to fibre connectivity (for example, in remote locations, difficult terrain, and scenarios where right of way for fibre is not possible). This can accelerate the deployment of broadband services thus making Digital India goals to be achieved faster. Thus, middle-mile and last-mile network using UHF band system can be developed along with BharatNet (NOFN).

Excerpted from ‘UHF TV band spectrum in India and roadmap for unlocking its potential’ by Abhay Karandikar.


(The article appears in the February 16-29, 2016 issue)



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