Microsoft looks to white space for spectrum

Microsoft says that it has the fix to the world's spectrum crisis: unused broadcast TV spectrum called "white space." But consumers shouldn't get too excited; it could take years before technology supporting white space spectrum finds its way into popular mobile products.
Written by Marguerite Reardon, Contributor

Microsoft says that it has the fix to the world's spectrum crisis: unused broadcast TV spectrum called "white space." But consumers shouldn't get too excited; it could take years before technology supporting white space spectrum finds its way into popular mobile products.

Microsoft announced yesterday that it has joined forces with broadcasters and technology companies in the United Kingdom to launch the most wide-scale test network to date of the technology. This is designed to show how this spectrum can be used to offload wireless data traffic in urban areas, as well as provide wireless broadband service in rural communities.

The new group, called The Cambridge TV White Spaces Consortium, includes British broadcasters the BBC and British Sky Broadcasting, as well as telecommunications provider BT, and technology companies Microsoft, Nokia, Samsung Electronics, Neul and Spectrum Bridge, among others.

The so-called "white space" spectrum is unused wireless spectrum that sits between analog TV channels to protect those channels from interference. Now that TV broadcasters have moved to digital technology, broadcasts use spectrum more efficiently, and those white spaces are no longer needed. Technology companies, such as Microsoft, believe that with the help of smart radios that can sniff out unused radio frequencies, unlicensed white space spectrum could be used to augment wireless broadband services that use licensed spectrum.

The 300MHz to 400MHz of unused white space spectrum is considered as being prime spectrum for offering wireless broadband services, because it can travel long distances and penetrate through walls. The Federal Communications Commission (FCC) in the US unanimously agreed in November 2008 to open up this spectrum for unlicensed use.

The spectrum crunch

As more people use smartphones and other portable wireless devices, such as tablets, to surf the web and stream video, more capacity is needed to support demand on wireless networks. All around the world, the wireless industry and regulators have said that more wireless spectrum is needed to increase capacity for wireless operators. In the US, the FCC is looking to free up 500MHz of additional wireless spectrum within the next decade. In Australia, the Australian Communications and Media Authority (ACMA) predicts that there will be a shortfall of 300MHz of spectrum by 2020.

Dan Reed, corporate vice president of technology policy at Microsoft, likens the situation to a five-lane freeway at rush hour. Four of the five lanes are assigned to specific uses, and all of the traffic is funnelled to one lane of the freeway. The result is a huge traffic jam. In the case of the internet, packets get lost and dropped, which causes dropped calls and slow internet connections on smartphones and tablets.

White space spectrum represents these other unused lanes of traffic — and through the use of technology that can detect when these lanes are free, service providers can use these lanes to ease congestion on the one lane of internet traffic.

Wireless operators around the world have already begun using Wi-Fi, which also uses unlicensed spectrum at frequencies higher than the white space TV frequencies, to offload some network traffic.

Microsoft and other technology companies developing products for the white space market believe that the unused broadcast spectrum could be used in much the same way. But because white space spectrum operates at much lower frequencies, it can travel further distances and penetrate through walls more easily than Wi-Fi, which operates at much higher frequencies.

"A new generation of radio technologies may hold the key to unlocking large, often unused chunks of spectrum with the help of online databases and devices that enable wireless traffic to flow in the most efficient manner, and avoid interfering with licensed broadcasts and other primary uses," Reed wrote in a blog for Microsoft on Monday.

The US FCC was the first regulator to give the green light for the use of the unused white space spectrum. Other countries around the world are still developing their policies for the use of this spectrum in their own countries. This trial in the UK is designed to provide more information for Ofcom, the UK regulator, and the European Commission, which regulates spectrum among European countries.

Ofcom has granted a multi-site test licence for the UK test network that will allow the project to get off the ground. The group has set up white space hotspots throughout the city of Cambridge, and has extended the network into two adjacent villages.

"This is a much bigger test network in terms of the diversity of devices and the scope of the trial," said Paul Garnett, director of interoperability and standards for Microsoft. "The goal is to really show regulators in the UK and around the world what is possible with this technology both in rural areas as well as in urban settings."

Challenges ahead

While Microsoft and others involved in this trial see great potential in using this new spectrum, it could still take years before white spaces could be used in commercial services. For one, chip manufacturers have not developed small enough processors for handheld devices, like smartphones. During the trial, technology companies Neul, Adaptrum and KTS have built router-like devices that act as bridges so that the white space signals can be translated into Wi-Fi, so that people can use their existing smartphones and other Wi-Fi-enabled devices to test the white space network.

But Microsoft's Garnett points out that this is a temporary solution, and that chips will eventually be developed so that they can be embedded into smaller devices.

Still, even after the technology is ready, smartphone makers, tablet developers and others must embed the processors into their devices. The proliferation of the technology into the mass market could take years.

This is why broadband providers aren't even thinking of white spaces as a solution yet. During a panel discussion at the National Cable and Telecommunications Cable Show recently, a group of cable operators, who were all exploring ways to use wireless technology to extend their broadband services, said that they weren't even considering white space technology.

"From a technical standpoint, I think it probably has potential," said Kevin Curran, senior vice president of wireless product development of Cablevision Systems. "But I don't think any of us will take a virgin technology that doesn't yet have scale or a developed ecosystem."

Microsoft's Garnett said that it's to be expected, since it is still early days for the technology. To help fuel the ecosystem for white space technology, the IEEE's 802.11 working group that defines standards for Wi-Fi is including white space frequencies and technology into its standards process.

What this means for consumers is that future Wi-Fi products may include radios and technology that not only support the current range of 2.4GHz to 2.5GHz spectrum for Wi-Fi, but would also include spectrum in the 700MHz band for white space. The IEEE schedule calls for the standard to be completed at the end of 2012 or in early 2013. But there could be some pre-standard products in the market before then.

Garnett said that Microsoft envisions a scenario in which wireless subscribers may have a smartphone that supports the traditional Wi-Fi spectrum bands as well as Wi-Fi that supports the white space spectrum bands. Since white space spectrum can travel further distances, it may be useful in extending the reach of Wi-Fi networks. So when white space service is available, the device may connect to that network. And when it is not, it may connect to the traditional Wi-Fi network, instead.

"Until standards are finalised for white spaces, it will be difficult to develop mass market devices," Garnett admitted. "So, initially, we won't see this. But once those standards are complete, it will have a much better chance of wide-scale adoption."


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