Google founder Larry Page calls White Space as ‘WiFi on steroids’ and Microsoft calls it ‘White fi’. Policy makers are excited because White Space remains the best option for providing broadband connectivity to rural areas including services like remote healthcare. In a nutshell, White Space networks take advantage of the empty fragments of spectrum interspaced between frequencies in use. White Spaces are significant because regulators in UK and USA have opened up portions of spectrum originally used by analogue TV for use by White Space applications. This has the potential to bring new innovation to the market and provide new services to customers. This article explores the opportunities and challenges for White Space spectrum applications.
White Space frequencies occupy the ranges traditionally used by Analogue TV in the UHF range. In the United States, this is 698 – 806 Mhz and in the UK it is 470 – 790 Mhz. Many other European and North American countries are expected to follow suit. There is considerable momentum behind White Space technologies currently. Through the White Spaces Coalition companies like Microsoft, Google, Dell, HP, Intel, Philips, Earthlink, and Samsung Electro-Mechanics are involved in developing the White Space ecosystem.
White Space devices are expected to have a range of miles instead of feet (in comparison to WiFi). They are expected to travel through physical obstacles like walls, trees etc just like conventional broadcast signals. Also, they are expected to deliver network speeds comparable to current 3G and 4G technology.
Despite these advantages, White Space spectrum has some unique limitations. These limitations arise primarily from the need to avoid interference with existing services like broadcast. Avoiding interference is a complex and dynamic process. The challenge is not only to find empty frequencies but also to refer back to an online database to see if things have changed. Thus, some White Space radios have a GPS inbuilt in it in addition to the radio functionality. A project from Microsoft called Networking Over White Spaces (KNOWS) is a pioneer in this domain. The project enhanced the basic ‘detect and avoid’ sensing technology by using the database approach. According to the KNOWS project, the White Space spectrum is fundamentally different from the ISM bands where Wi-Fi operates along three main axes: First, it exhibits spatial variation since a channel available at one node might be occupied by a primary user (TV, microphone) at another node in the network. Second, the spectrum is not contiguous. Some channels might be occupied by primary users hence causing the spectrum to be fragmented. Finally, there is temporal variation since an available spectrum might be occupied at a later time by a primary user, e.g. wireless microphone.
The success of the initial tests in Redmond in overcoming these technical challenges has led to more trials and research especially in Cambridge and Wilmington (North Carolina). The FCC has mandated that all White Space devices should be able to refer back to the online database, so these techniques are now an integral part of White Space technology. Of course, White Space applications have wider implications than rural broadband. Google has a clear business motivation in expanding the uptake of the Web and vendors like Dell and Microsoft could see PCs enabled by White Space technology (just like almost all PCs and laptops include WiFi today).
Any device that intends to use White Space channels for communication is deemed to be a White Space device. White Space devices will be cognitive radio devices. In wireless communication, cognitive radio is a transceiver that can intelligently detect what communication channels are in use and what are not. It can then instantly move into vacant channels and avoid occupied ones. This optimises the use of available radio frequency spectrum while minimising interference to other users. All mobile devices are cognitive to some extent for example a cellular handset will select one of many frequency bands and standards or use Wi-Fi depending on the networks it finds. Cognitive technologies have been used in DECT phones and other devices to a smaller extent, but with White Space radios, cognitive technologies are an integral part of the operation due to the need to dynamically sense and select the frequency.
In the UK, Ofcom have issued a test/experimental licence around Cambridge. This allows companies in the UK to demonstrate White Space technology and its applications.
On June 29, 2011, one of the largest commercial tests of White Space Wi-Fi was conducted in Cambridge, England by a consortium comprising Microsoft, Adaptrum, Nokia, BSkyB, the BBC, BT and Neul. In the demonstration, a client-side Microsoft Xbox was able to stream live HD videos from the Internet and also a live Xbox/Kinect video chat was established between two Xbox/Kinect units connected through the same TV White Space connection. These applications were demonstrated under a highly challenging radio propagation environment including buildings, foliage, walls, furniture, people etc.. The objective is to test if White Space radios can coexist with each other, and with the existing broadcast transmissions.
In another trial conducted in the city of Wilmington, N.C, White Space wireless connectivity was used in surveillance cameras and environmental sensors in a smart city deployment. The network was used for three main applications: traffic cameras at intersections to provide real-time traffic monitoring, to wirelessly connect cameras in city parks to police for surveillance and to remotely monitor and manage wetland areas.
In another UK trial conducted by Cambridge consultants, social media tools like Twitter, Skype and YouTube were used over a White Space network. Similarly, Google and the Hocking Valley Community Hospital used White Space technology for various medical uses like First responder and its outdoor video surveillance system.
White Space networks ‘democratise’ wireless networks. Anyone can deploy a network without the need of a nationwide contract. This makes a big impact in the deployment of innovative applications especially where traditional networks do not extend easily. This includes pop-up (ad-hoc) networks for concerts. It also could include network applications in specific scenarios for instant connectivity for example ability to stream video from a fire fighter’s helmet to the fire engine outside.
Companies like Neul are deploying a ‘White Space network in a box’ through NeulNET. NeulNET enables customers to operate your own White Space network that delivers up to 16Mb/s over 10Km range with excellent in building penetration. NeulNET uses frequency-hopping, by using different vacant 8MHz channel for each frame of data.
White Space devices have some unique characteristics. They need to transmit small amounts of data in ‘data gathering’ applications while operating in a chaotic/hostile environment. They need to have low power requirements and the ability to operate more than a decade. Neul has proposed the weightless protocol to cater for these requirements. Similar to the Bluetooth SIG, Neul will launch a SIG to standardise the weightless protocol. According to Neul, a Weightless network which can cover the entire country would cost only £50 million, and the spectrum to use it is free.
The IEEE 802.22 standard is designed for TV White Space frequencies also applies to White Space networks.
Based on the above, here is my analysis about White Space networks:
- The industry has now moved beyond the political arguments of Broadcast networks/White Space networks and we are now moving to an era of actually building real networks and solving customer issues. This is a good development.
- White Space networks have potential to unleash innovation by creating a new class of applications based on deploying networks in areas where traditional networks cannot be easily deployed(rural deployments, M2M etc)
- The early impact of White Space networks will be in rural areas benefitting the consumer.
- An ecosystem is emerging around white space applications with considerable support from traditional and new wireless entrants.
- Many questions still remain – both technical and business model related. For example, should the database be bi-directional? Who will maintain such a database?
- Finally, could the principles of cognitive radio be adopted into the wider telecoms spectrum management? Chunks of spectrum are claimed by Operators but remain unused. Will White Space technology and Cognitive radios cause a change in better management of Spectrum?
About Ajit Jaokar
- Ajit Jaokar is an analyst and researcher. He blogs at www.opengardensblog.futuretext.com. His PhD research involves White Space applications for healthcare and privacy. He can be contacted at: ajit.jaokar at futuretext.com or via twitter @AjitJaokar