What with the buzz around the FCCs auction rules on the upcoming 700 MHz sale few noticed the Commissions geek squad also flew its Kitty Hawk into white spaces between TV broadcast spectrum bands that same July. The Streamyx Registration flight wasnt spectacular or anything but Windows Xp Antivirus the Wright brothers bird it quietly made history.
While the FCC commissioners were lining up to announce final edicts on managing the 700 MHz auction, their Office of Engineering and Technology made its own announcement on initial testing results for a couple of prototype devices that might be used in television white spaces. Looking beyond the Google ?Verizon squabble that took center stage in the auction related media coverage the second announcement was the more important one as it charts a course outside the box to decide where we go once these auctions have played out. The FCC hoped these tests would lead to white spaces (unused by TV broadcasters) being made available for unlicensed use by opportunistic (cognitive radio) devices that would sense when frequencies were in use by television or other signals. Two prototypes were tested one from Microsoft and the other by a consortium lead by Philips Electronics. Things didnt go too well and the FCC concluded the devices werent sensitive enough. But then the Kitty Hawk just flew 12 seconds on its first flight.
To understand the logic behind cognitive radio (CR) lets stay with the airplane analogy a bit. As things stand today we treat radio spectrum like real estate parceling bands off to licensees for their exclusive use as operators. Such allocation was fine in the good Pc Tech Support days but now wears thin in the face of an overwhelming demand for radio space by contending applications. However radios keep getting smarter and its time we began treating spectrum like the skies where theres no technical reason why an airplane cant fly amidst congested air traffic as long as navigational rules are followed.
The funny thing is that the perceived spectral congestion is more a function of our inefficient method of parsing bandwidth to licensees than due to any real irresolvable contention. Measurements carried out by the IEEE on frequency bands below 3 GHZ conducted from January 2004 to August 2005 showed that only about 5.2% of the spectrum was actually in use in the US in any given location and at any given time. Even more interesting was the revelation that heavy spectrum utilization often takes place in unlicensed bands while licensed bands often experience low (e.g. TV bands) or medium (e.g. some cellular bands) utilization. Its safe to say these American studies on spectrum utilization may also hold true in other countries. The results should resonate especially so in countries like India where the whole matter of allocating spectrum is increasingly fraught with a liberalizing Regulator, a truculent cellular lobby and nonplussed government officials drawing battle lines.
These alarming measurements suggesting spectrum under-utilization in the midst of a perceived scarcity coupled with recent advances in radio technology prompted the FCC to test CR and see whether base stations and Customer Equipment (CPEs) could competently connect and stay within unused white bands in spectrum allocated to TV broadcast.
There was some patronizing smugness at the cellular establishment with the sub-par performance but its a nascent technology and can only improve. Lets pray it does because selling off chunks of spectrum doesnt work anymore for anyone other than the cellular operators. Todays artificial scarcity impacts a more universal telecommunications service deployment, especially broadband. Education, health care, communications, public safety and leisure are all casualties.
For those not blinkered there appears little choice but to gradually do away with reserving spectrum and instead have service providers deploy equipment with radio characteristics Antivirus For Windows Vista to the real-time conditions of the environment, which is what cognitive or adaptive radio is all about.
When mastered, CR technology would utilize the large amount of spectrum lying unused in reserved lots while not interfering with other incumbent devices in these frequency bands already licensed for specific uses. Folks, this is huge. Globally. In its September 2007 recommendations on spectrum allocation & pricing the Indian regulator (TRAI) mentions eventually doing away with licensed spectrum management in favor of well defined rules of interaction once cognitive radio becomes real. The TRAI uses ocean lanes to make the point I made earlier with air traffic but I wont quibble because the message clearly comes across. CR is happening.
More so because IEEE, the folks who brought you WiFi and WiMax, has announced work on CR type air interface under the 802.22 group of standards. It beats cellular & WiMax on range because this specific air interface standard works in ?or rather in between - the VHF & UHF portions of the radio spectrum allotted to TV broadcast. This end of the spectrum has better propagation characteristics than the upper bands allotted to cellular, WiMax or WiFi and hence the impressive range.
The reason for focus at the lower end of the spectrum is primarily because the broadcasters are about to release these bands (the reason for the auction) as they go digital. The FCC can therefore play around here far easier than anywhere close to the cellular establishments spectral property. But unless you fervently believe in the tooth fairy, know that for CR technology to worm its way and eventually squat on unused cellular real estate is only a matter of time.
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