White-space broadcasting advocate M2Z Networks fired yet another salvo in the public relations fusillade, trying to convince politicians to establish open access to the otherwise unused spectrum for wireless services.

M2Z was not merely advocating for white space schemes, however. The company sought to address specific concerns raised by T-Mobile and AT&T Wireless, which along with other cellular companies and broadcasters have been warning about potential interference problems.

White space is the unused spectrum in between terrestrial broadcast TV channels. Google, Microsoft, Intel and Motorola are the most prominent companies hoping to use the spectrum for new wireless services.

The FCC conducted tests earlier in the summer to determine if white-space systems will interfere with existing TV channels, and initial indications are that there is minimal, if any, interference.

That hasn’t stopped white space proponents from campaigning while the FCC prepares its report, which could be published at any time, but isn’t expected for several more weeks.

M2Z provided slightly more detail than other advocates. It said the test results confirmed the following:

  • The testing validated previous testing performed by ERA Technology, which provided the basis for the decision by Ofcom (the United Kingdom's independent telecommunications regulator) to permit TDD and FDD coexistence using an out-of-band emission limit of 49 + 10 log (P), which is far less stringent than the 60+10 log (P) proposed by the FCC.
  • The testing also demonstrated that AWS-3 handsets could operate safely at the Commission's standard power limit of +33 dBm.
  • Providing protection down to the level T-Mobile is asking to protect would mean that Bluetooth, WiFi, home and small business wireless cell sites, and even microwave ovens would cause interference.

The September test, M2Z claims, calls into question the validity of T-Mobile's July 25 adjacent channel tests. The FCC-observed test showed that the AWS-1 handsets experienced adjacent channel interference from a transmitting device in the unlicensed band at 2415 MHz (nearly 300 MHz away), M2Z said.

“Before the FCC issued its report, AT&T, T-Mobile and others attempted to distract attention from the actual results by making the unsupported conclusions in the press that the tests proved that the Commission's lifeline broadband rules would not work. Nothing could be further from the truth as discussed in our filing today,” said John Muleta, M2Z Networks’ CEO.

Muleta charged the cellular companies with trying to muddle the technology, rewrite rules and change policy.

The potential for white-space interference is a legitimate concern for anyone already using terrestrial spectrum. Since channel assignments are different in every market, white-space systems are supposed to detect where broadcast channels are and automatically move to unused spectrum.

Earlier tests of initial prototype equipment failed.

Initial indications from the recent round of testing are that there was minimal, if any, interference – with one exception.

White space transmitters were found to interfere with wireless microphones, of the type frequently used in sporting venues. The FCC fixed that problem by saying that if white-space transmission systems are approved, then wireless mikes will be subsequently barred from using that spectrum.

That the FCC made that determination is seen as a signal that it is inclined to approve the white spaces scheme.

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