Nov 1, 2008 12:00 PM, By Doug Mohney

Consensus on 6.25 kHz frequency coordination procedures comes easy.

Can new frequency coordination procedures established by an independent council of 19 disparate associations be so painless and uncontroversial that the Federal Communications Commission can't even muster a Public Notice over the results?

Apparently so.

Two years ago, the Land Mobile Communications Council (LMCC) began work on frequency coordination procedures for 6.25 kHz bandwidth equipment and equivalent systems. The LMCC, made up of the FCC's certified frequency advisory committees (FAC) along with government users and equipment manufacturers, started the process at the behest of the manufacturing community. Participating members range from private associations such as the American Automobile Association, public safety — represented in part by the Association of Public-Safety Communications Officials and the International Association of Fire Chiefs — and the manufacturing community, which is represented in part by the Telecommunications Industry Association (TIA) and the Enterprise Wireless Alliance (EWA).

“As 6.25 technology and equivalents are being introduced into the marketplace, the LMCC wants to ensure coordination efforts to protect existing 25 kHz users, as well as 12.5 kHz users,” said Al Ittner, president of the LMCC. “They can all play in the same arena.”

Ittner pointed out that 6.25 kHz bandwidth usage is more than just a simple use of a 6.25 kHz slot. “A number of technologies have 6.25 or 6.25 equivalents,” he said. “You can be operating in 12.5 kHz with two slots, two voice paths, or at 25 kHz, but with four slots. The technologies are being introduced in the VHF and UHF bands.”

The LMCC worked with all parties on proposed rules, as well as guidelines and best practices, to protect both existing services and new technologies.

“As technologies are being introduced into the marketplace, one of the things we wanted to ensure, speaking for the [land mobile radio] community, is to lay out guidelines that coordinators can agree to keep interference at a minimum for those technologies,” Ittner said. “It's a two-way street, obviously. We don't want to introduce new technologies and have old systems interfere with new systems going in.”

The LMCC arrived at a “frequency coordination consensus,” a set of procedures for 6.25 kHz equipment or equivalent systems that it sent along to the FCC on Aug. 8. The procedures contain the following:

1. VHF systems will use a 13 dB de-rating of the interference contour for systems spaced at 7.5 kHz. The service contour is 37 dBu f(50,50), while the interference contour is 32 dBu f(50,10).

2. UHF systems will use an 8 dB de-rating of the interference contour for systems spaced at 6.25 kHz. The service contour is 9 dBu f(50,50), while the interference contour is the 29 dBu f(50,10).

3. The criteria will be used in both directions. The interference contour of the proposed system may not overlap the service contour of the incumbent system; similarly, the interference contour of the incumbent system may not overlap the service contour of the proposed system.

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