NAB: Cognitive Radio is Effective Enough to Allow Sharing of Critical Government Frequencies - But Not Good Enough to Protect Broadcast TV
So you can see how surprised and excited I was to get the e-mail shown at left from Dennis Wharton, Executive Vice President of Communications at NAB, with the subject line “The spectrum crisis is completely avoidable”. We certainly want to avoid this crisis and I was delighted to read what NAB’s new solution was. The message begins with “I thought you might find of interest this article from The New York Times about technological solutions to increase the efficiency of wireless mobile broadband networks.” The Times article was mainly about the PCAST spectrum report that SpectrumTalk readers read about here on May 28th. In the article Mr. Wharton was kind enough to recommend was a discussion of how effective cognitive radio technology now is and the statement “For example, if the government has reserved some spectrum for use at an Air Force bombing range, but no bombing is happening on a particular day, cognitive radio could allow a phone to sense the open channel and switch to it.”
Mr. Wharton, let me explain why it is much easier for a cognitive radio to sense in TV white space whether there are usable TV signals than the case of sensing the presence of military signals:
- TV signals are generally on 24/7, they do not turn on and off at random times as military signals do.
- TV transmitters are firmly bolted to the ground in well defined locations.
- TV signals have a very precisely defined (in a public documentation) 6 MHz wide waveform with very precise frequency stability and timing. It is almost as if they were designed to be detected at much greater sensitivity than a consumer receiver. Indeed, FCC testing showed that they could be detected at a power level 35 dB less than the sensitivity of a TV receiver and better detectors are possible. In general military signals do not have waveforms that are known to the public. Thus the U-NII cognitive radio rules in 47 CFR 15.407(h)(2) require a “Radar Detection Function of Dynamic Frequency Selection” that knows nothing about the radar signal it is trying to detect since the military would no divulge the specific technical details of the radars in the band - a far cry from the well known ATSC signal in the TV band!
- If interference is caused to TV reception, it may be unfortunate but there are no permanent negative consequences - like death or injury. If there is interference to a military system the consequences could me more severe.
Based on the above, cognitive radios in the TV band raise far fewer issues than cognitive radios that try to detect the presence of military signals.
Since Mr. Wharton has concluded that cognitive radio technology has now advanced to the point that it can reliably detect the presence of military signals to allow broadband use of military bands when and where they are not in use, I assume that NAB must now endorse the technically simpler case of using of cognitive radios in the TV bands under similar terms.
I hope Mr. Wharton comes to the DySPAN 2012 Conference in Bellevue WA in October and explains NAB’s new view on cognitive radio. I’m sure he’ll get a standing ovation!
Today, the Federal Communications Commission issued a Public Notice announcing that the Office of Engineering and Technology (OET) has approved Spectrum Bridge Inc.’s television white spaces database system, which may provide service to devices beginning January 26, 2012. OET has also approved a device by Koos Technical Services, Inc. (KTS) as the first product allowed to operate on an unlicensed basis on unused frequencies in the TV bands. The KTS device will operate in conjunction with the Spectrum Bridge TV band database.
The database announcement says the database approval is effective January 26, 2012. NAB reported some problems during testing and asked for both more testing and another round of comments. FCC rejected the need for more comments but required that the problems identified to date be fixed. However, the initial implementation of the database will be limited to “ to the Wilmington, NC market, specifically to the city of Wilmington and New Hanover County, NC” due to problems with the FCC registration system for nonbroadcaster high density wireless microphone usage sites such as concerts. Your blogger has serious doubts whether the FCC provision for registering these wireless miss will be practical. Time will tell.
Above is the first equipment authorization approval granted to Florida’s Koos Technical Services, a firm that seems to have some partnership with Spectrum Bridge. While the Commission’s Rules do not forbid this type of relationship, one wonders if anyone ever thought about it from the policy viewpoint.
The FCC grant is surprising in that the approved spectrum is not UHF, but rather 177-213 MHz in the upper VHF band. This is the middle of channel 7 to the middle of channel 13. The device’s manual states that “it is designed to provide a reliable wireless connection for digital communication in selected TV bands in the 174 – 216 MHz (VHF) or 470 - 698 MHz (UHF) frequency ranges.” The manual also states the power amplifier “provides up to 1 Watt (30 dBm) of RF output power” - but the approved power limit is 0.1 Watt. The manual states the data rate is “1.5 or 3.1 Mb/s” with a 6 MHz channel bandwidth. Indeed the test reports KTS submitted to FCC repeatedly mention “Transmit power 25 dBm” or 0.316 W, yet the authorized power is 0.1 W. So it is clear that the parameters that were approved are not the ones in the original submittal to FCC.
Perhaps KTS had to back off its intended performance to meet FCC emission limits. Previously, several mainstream manufacturers complained to FCC that they could not meet the out-of-band emission requirements in this band with off-the-shelf equipment designs. However, MSS client Adaptrum demonstrated to FCC in a March 2011 filing that it could comply with the OOBE limits.
Congratulations to Spectrum Bridge and KTS on these first approvals. We hope there will be many more soon.
Andrew Mancone, Director of Sales and Marketing at KTS Wireless posted this clarification to Linkedin’s Spectrum Experts group:
Unfortunately, that paragraph in the December 22nd FCC notice caused a bit of confusion. The project in Wilmington has approval to move forward but our certification is finalized and valid starting January 26th, 2012.
Rumor has it that there are some wireless microphone channel optimization efforts underway and the administrative cleanup will take until the 26th of January. Therefore, the staggered start.
Fear not, certified devices are now here and implementation plans can move forward.