What is White Fi/Space?
The IEEE 802.11af or White-Fi proposal for Wi-Fi using the TV White spaces using cognitive radio technology.
What is Cognitive Radio?
With pressure on radio spectrum increasing all the time, it is necessary to utilise the available spectrum as efficently as possible. One method of helping to achieve this is utlise radio technology that is able to sense the environment and configure itself accordingly – Cognitive Radio. The technology is heavily dependent upon Software Defined Radio technology as the radio needs to be configurable according to the prevailing radio environment.
Unfortunately, even in the most developed economies there are gaps in wireless coverage, access points and base stations become overloaded in busy areas, and pricing presents an affordability barrier for many. In addition, hundreds of millions of wirelessly-connected devices are coming online, all requiring wireless connectivity and bandwidth, further increasing demand for spectrum resources.
At the same time that available spectrum resources are being constrained in many markets, broadband access remains unavailable and/or unaffordable for several billion people around the world. Fixed broadband access is unaffordable for 3.9 billion people spread across every country in the world. Mobile broadband is unaffordable for over 2.6 billion people. Availability and affordability gaps are disproportionately impacting people in Africa, Asia, and Latin America.
Wireless technologies and management techniques exist today that can replace artificial spectrum scarcity with naturally occurring spectrum abundance. One example is Dynamic Spectrum Access (DSA), a term used to describe a set of technologies enabling radio communications devices to opportunistically transmit on available radio spectrum. These technologies ensure that consumers and their devices have wireless bandwidth when and where they need it.
The first globally-harmonized opportunity to use DSA technologies will be in the TV band white spaces – unused VHF and UHF TV channels that can be used to deliver broadband access over wider areas than possible using today’s Wi-Fi spectrum. These excellent range and obstacle penetration characteristics explain why people increasingly refer to TV white spaces as “Super Wi-Fi.”
Although the first globally-harmonized opportunity to showcase DSA is occurring through license-exempt (unlicensed) access to the TV band white spaces, DSA technologies will be used in a variety of spectrum bands. Underpinned by a regulatory framework that maximizes spectral efficiency and minimizes barriers to market entry, application of these new technologies will help networks and markets scale to inexpensively deliver the services demanded by consumers.
The basic concept behind White-Fi technology, IEEE 802.11af is that broadcast television coverage has to be organised so that space is left between the coverage area of different transmitters using the same channels so that interference does not occur.
Sufficient space has to be left so that even when tropospheric propagation conditions increase the distances over which signals can be received, interference does not normally occur.
This means that there are significant areas where these channels are unused and this leads to very poor spectrum use efficiency.
With Wi-Fi applications only requiring low power, it is possible to use this unused spectrum between the coverage areas without the fear of interference being caused within the television transmitter coverage area.
How it Works?
The most common implementation of Super Wi-Fi networks will be accessed using smart, radio-enabled devices that report their location to an Internet database. The database will tell the device which TV white spaces channels, and at what power level, it is permitted to operate on in its current location. The database has a list of all protected TV stations and frequencies across the country, so the devices can avoid causing interference to TV broadcasts and wireless microphone signals. This technology is truly dynamic – as different TV channels become available, Super Wi-Fi devices that can opportunistically switch from one group of channels to another. This win-win translates to greater network capacity, allowing a greater number of users in a given area while, at the same time, protecting television reception from interference. All of this engineering will be invisible to the consumer, who will simply experience more ubiquitous broadband connectivity.
Benefits of IEEE 802.11af, White-Fi ….
There are many benefits for a system such as IEEE 802.11af from using TV white space. While the exact nature of the IEEE 802.11af system has not been fully defined, it is still possible to see many of the benefits that can be gained from White-Fi technology:
- Propagation characteristics: In view of the fact that the 802.11af white-fi system operating the TV white spaces would use frequencies below 1 GHz, this would allow for greater distances to be achieved. Current Wi-Fi systems use frequencies in the ISM bands – the lowest band is 2.4 GHz and here signals are easily absorbed.
- Additional bandwidth: One of the advantages of using TV white space is that additional otherwise unused frequencies can be accessed. However, it will be necessary to aggregate several TV channels to provide the bandwidths that Wi-Fi uses on 2.4 and 5.6 GHz, to achieve the required data throughput rates. It is possible that vacant channels in any given area will vary widely in frequency and this presents some challenges in managing the data sharing across the different channels, although this has been successfully achieved in technologies such as LTE.
- Geographic sensing: Another method that is favoured by many is geographic sensing. Although details are not fully defined, having a geographic database and a knowledge of what channels are available there is another way of allowing the system to avoid used channels.
- Range: Current wireless routers are lucky if they can cover a football field. A range of a couple hundred feet is considered acceptable. White space wireless devices will have a range of miles instead of feet.
- Obstacles:One of the primary factors limiting the range of current wireless technology is that it is easily obstructed. While the signal can theoretically travel hundreds of feet, place a couple walls between the wireless router and the mobile device trying to connect and the signal quality could be questionable at best. White space wireless networks can travel seamlessly through walls, trees, and other obstructions just as broadcast TV signals have done for decades.
- Speed:802.11n wireless networks can transmit data between 160 and 300 megabits per second. That is significantly faster than the previous 802.11b or 802.11g networks, but less than half of the 400 to 800 megabits per second expected from white space wireless devices. Even at long range, white space wireless networks can deliver network speeds much greater than current 3G or even 4G mobile broadband technologies.
- Longer Distance– The 200-300 MHz spectrum in the white space can reach up to 10 km as compared to current Wi-Fi technology that allows you a range of about 100 metres. The 200-300 MHz spectrum currently belongs to Doordarshan TV channel and isn’t used at all.
- Solar Power Operated:- It can be run on solar power and thus overcome a key hindrance that currently impedes internet service providers, namely the high cost of installation equipment.
As white space wireless devices hit the mainstream, businesses will be able to replace the current wireless infrastructure with a fraction of the hardware. Microsoft is already experimenting with white space Wi-Fi at its Redmond campus and can replace thousands of current wireless access points with just two white space Wi-Fi routers.
Salient features …
The table below gives a summary of the salient features of 802.11af technology.
|Operating frequency range||470 – 710MHz|
The proposal for the implementation of White-Fi is sill in its draft or development stages. However it provides an effective way of accessing more radio spectrum in an area where available bandwidth is at a premium, and utilising the resource more effectively.
What is delaying adoption of White-Fi at a larger scale?
We are waiting for the government to come back. They wanted us to show them the technical viability, which we have done. Now, they want to get feedback from multiple different sources and then they have to take a decision.So you (the government) can either sit on the so-called unused spectrum or you can decide to give it to the citizens of India and improve their lives.
Where its implemented as for smart village?
So far we’ve implemented the White-Fi technology only in schools in Varanasi and Srikakulam. At Harisal, the idea is to put internet at the village panchayat level and then look actually look at what are the potential applications that can have an impact.
We’ve been working on it for some time and the fact of the matter is that any of this kind of technologies have to have an impact on the lives of the villagers. And that is not very apparent how to do it. Because you have to raise the incomes so that people can afford to pay for this kind of technology.
Each village has a different ecosystem. So, we’ve finally found that it is not a technology problem. The problem is anthropological in terms of what is it that you’re trying to solve.What we are doing at Harisal is conglomeration of multiple different companies with one goal, which is to uplift Harisal because if it works there it can basically work anywhere.
At Srikakulam, it is only about Skype and education and getting access to the internet. But at Harisal we’ve actually have specific projects identified, applications and services identified. We’re trying to bring about change transformation which is also required for people to accept this.
We’ll put a project manager there who will live there for two years and will coordinate all these different projects.
Progress to Date
Microsoft has been working with industry consortium and regulators around the world to demonstrate the viability and potential of Super Wi-Fi. With over a dozen successful trials and demonstrations, it is clear the approach works and most of the technical questions have been addressed. Demonstrations have been successfully implemented in Belgium, Kenya, Switzerland, Singapore, the United Kingdom, the United States, Uruguay, and other countries. The U.S. FCC has already adopted regulations allowing non-exclusive license-exempt access to the TV White Spaces. A recent full scale deployment trial in Cambridge, UK was completed with results that exceeded expectations and the UK regulator, Ofcom, is using these results to inform regulatory proceedings. Other regulators, in addition to the FCC in the US and Ofcom in the UK, have begun to implement the changes necessary to enable.
Commercialization of this approach and it is only a matter of time before both the heavy bandwidth users in developed markets and those yet to even be connected in the furthest corners of the world to benefit from the innovative use of Super Wi-Fi.