Various proposals, including those from the White Spaces Coalition, have advocated using white spaces left by the termination of analog TV to provide wireless broadband Internet access. However, these efforts may impact wireless microphones, medical telemetry, and other technologies that have historically relied on these open frequencies.
A device intended to use these available channels is a white-space device (WSD). These are designed to detect the presence of existing signals, such as TV stations and other wireless users, and to then avoid the use of these channels. Early ideas proposed including GPS receivers and programming each WSD with a database of all TV stations in an area, however this would not have avoided other non-stationary or unlicensed users in the area, or any stations licensed or altered after the device was made.
United States
The FCC called for prototype white-space devices, and received one of the first from Microsoft. While one device performed flawlessly, another identical one failed, and opponents harped on this incessantly in trying to stop WSD approval.
Broadway theater producers and sports franchises hoped to derail or delay the decision, arguing that their own transmissions — whether from television signals or from wireless microphones used in live music performances — could face interference from new devices that use the white spaces. However, the FCC rejected their arguments, saying enough testing has been done, and through new regulations, possible interference will be minimized.
The White Spaces Coalition consists of eight large technology companies that plan to deliver high speed broadband internet access beginning in February 2009 to United States consumers via existing 'white space' in unused television frequencies between 54-698 MHz (TV Channels 2-51). The coalition expects speeds of 10 Mbyte/s and above, and 50 to 100 Mbyte/s for white space short-range networking. The group includes Microsoft, Google, Dell, HP, Intel, Philips, Earthlink, and Samsung Electro-Mechanics.
Senate Decision and 2008 Developments
Full power analog television broadcasts, which operate between the 54 MHz and 806 MHz television frequencies (Channels 2-69), are slated to cease operating in February 2009 per a United States digital switchover mandate. At that time, full power TV stations will be required to switch to digital transmission and operate only between 54-698 MHz. This is also the timetable that the white space coalition has set to begin offering wireless broadband services to consumers. The delay allows time for the United States Federal Communications Commission (FCC) to test the technology and make sure that it does not interfere with existing television broadcasts. Similar technologies could be used worldwide as much of the core technology is already in place.
The White Spaces Coalition formed in late 2006,soon after the Senate set the date to cease analog broadcasts. It doesn't appear to have a website, but many of the companies involved in the White Spaces Coalition are also involved in the Wireless Innovation Alliance.
TV broadcasters and other incumbent users of this spectrum (both licensed and unlicensed, including makers of wireless audio systems) feared that their systems would no longer function properly if unlicensed devices were to operate in the same spectrum. However, the Federal Communications Commission's Office of Engineering and Technology released a report dated October 15, 2008, which evaluated prototype TV-band white space devices submitted by Adaptrum, The Institute for Infocomm Research, Motorola and Philips. The report concluded that these devices had met the burden of "proof of concept" in their ability to detect and avoid legacy transmissions,although none of the tested devices adequately detected wireless microphone signals in the presence of a digital TV transmitter on an adjacent channel.
On November 4, 2008, the FCC voted 5-0 to approve the unlicensed use of white space, thereby silencing opposition from broadcasters. The actual Second Report and Order was released ten days later and contains some serious obstacles for the development and use of TV Band Devices as they are called by FCC. Devices must both consult an FCC-mandated database to determine which channels are available for use at a given location, and must also monitor the spectrum locally once every minute to confirm that no legacy wireless microphones, video assist devices or other emitters are present. If a single transmission is detected, the device may not transmit anywhere within the entire 6 MHz channel in which the transmission was received. It is hoped that, within a year, this new access will lead to more reliable WiFi and other technologies.
Preliminary test
The Federal Communications Commission's Office of Engineering and Technology released a report dated July 31, 2007 with results from its investigation of two preliminary devices submitted. The report concluded that the devices did not reliably sense the presence of television transmissions or other incumbent users, hence are not acceptable for use in their current state and no further testing was deemed necessary.
However, on August 13, 2007 Microsoft filed a document with the FCC in which it described a meeting that its engineers had with FCC engineers from the Office of Engineering and Technology on August 9 and 10. At this meeting the Microsoft engineers showed results from their testing done with identical prototype devices and using identical testing methods that "detected DTV signals at a threshold of -114 dBm in laboratory bench testing with 100 percent accuracy, performing exactly as expected." In the presence of FCC engineers, the Microsoft engineers took apart the device that the FCC had tested to find the cause of the poor performance. They found that "the scanner in the device had been damaged and operated at a severely degraded level" which explained the FCC unit's inability to detect when channels were occupied. It was also pointed out that the FCC was in possession of an identical backup prototype that was in perfect operating condition that they had not tested.
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