White spaces: Technology overview

The radio frequency band used to broadcast TV in the United States has evolved over time, primarily due to the Federal Communication Commission's desire to make more bandwidth available for wireless two-way communications. When the TV industry transitioned from analog to digital signals it freed up radio frequency spectrum, some of which the FCC auctioned off to wireless carriers. The rest, having been designated for unlicensed use, is known as TV white spaces.

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TV white spaces have several important properties:

* Excellent propagation

* Ability to penetrate buildings and foliage

* Non-line of sight connectivity

* Broadband payload capacity

These are among the primary capabilities that make TV white spaces highly sought after for wireless communications and commonly referred to as "beachfront frequencies."

Consequently, the application potential for TV white spaces is essentially limitless. Just as other unlicensed wireless frequencies are used for a wide variety of services and technologies, TV white spaces can also be applied to an extensive range of uses and applications, including:

* Wide-area wireless Internet: There are unserved and underserved areas of the country, particularly in rural communities, that have limited or no broadband communications options. TV white spaces can provide a cost-effective and rapidly deployable solution to bring wireless broadband to these communities.

Wireless carriers are also experiencing an exponential increase in traffic volume, especially in urban areas due to the proliferation of smartphones. Wi-Fi technology has helped to alleviate some of this congestion, however, as demand for bandwidth continues to grow, white space technologies can provide an alternative for offloading traffic from traditional networks.

* Video: The broadband capacity and robust signal characteristics of TV white spaces make them ideal for video applications. TV white spaces can provide one-way and two-way video communications for security, monitoring, entertainment and other video applications in places where other frequencies, cable or fiber are not as cost-effective.

* Home and enterprise wireless networking: TV white spaces provide significantly better coverage and wall penetration inside buildings and other structures than the 2.4GHz and 5GHz Wi-Fi frequencies currently in use. In addition to wireless computer network applications, TV white spaces are being discussed as a solution for whole house media distribution and networking between home entertainment, as well as computer–based media storage and distribution.

* Smart city networks: Smart cities give a city government and citizens the digital tools to measure, monitor and alter the way they use valuable resources and services. The wireless applications extend over most services including healthcare, industry, education, buildings, infrastructure, environment, public safety, retail business, water, electricity (notably, expanding the country's smart grid), traffic and more. TV white spaces can be a valuable resource for the wireless ecosystem supporting these applications.

In addition to the applications above, the FCC has proposed that TV white spaces channels can also be used by a wide range of devices on an unlicensed basis. The FCC's TV white spaces Report and Order provides guidelines as to what devices may be used in which channels; however, not all devices are allowed to operate on all TV white spaces channels.

For example, a TV white spaces channel's proximity to a channel occupied by a protected user determines which devices may operate in which TV white spaces channels. These new unlicensed devices must also share the spectrum with existing incumbents like wireless microphones and low-power TV translators. There are still some open issues related to which of these devices should be protected from interference by the new unlicensed devices and how they should be protected, by sensing the database or both.

The basic device types as defined by the FCC are fixed devices that are stationary, and personal/portable devices that are allowed to be mobile.

The current FCC rules require that most TV white spaces devices access a list of allowable channels (based on device's specification and location) from an Internet-based TV white spaces database. This database would maintain a current view of all protected TV band users (i.e. occupied channels) and the white space devices could only transmit on the channels issued to them by the databases. The rules are very flexible on how these new devices will operate. The industry is hoping to leverage existing standards-based radios such as 802.11 Wi-Fi and 802.16 WiMAX resulting in white spaces devices being available more quickly.

Determining the availability of TV white spaces in different locations varies based on device types and typical applications. For example, TV white spaces bandwidth that would typically be used for rural Internet distribution or other wide-area broadband networks using fixed high-power devices would vary significantly across rural and urban markets.

The next phase towards making TV white space frequencies commercially available starts with the FCC finalizing the TV white space rules and appointing the TV white space database service providers. The FCC stated in the broadband plan that this should happen before the end of 2010.

Once that happens, the wireless industry can certify devices for use in TV white spaces, making TV white space commercial networks a reality. As TV white spaces continue to evolve as a potential source for additional bandwidth, it will be exciting to see the emergence of innovative equipment to help maximize the utilization of this robust new resource.

Spectrum Bridge Inc. (SBI) delivers software and services to wireless service providers and equipment manufacturers. SBI enables wireless networks to access and use all types of spectrum at any place or time via a database driven cognitive network architecture. The company's products are embedded in subscriber devices and network equipment to more efficiently allocate bandwidth throughout the entire wireless network. SBI's technology provides customers greater capacity, coverage and utilization of scarce spectrum resources.

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This story, "White spaces: Technology overview" was originally published by Network World.

Copyright © 2010 IDG Communications, Inc.

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