So far, so good
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?
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:
- 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).
- 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).
- 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.
The de-rating factors will be reviewed in two years and increased by 3 dB unless harmful interference cases are documented. “If there are any problems, we want to review that two years from now to see if we cause any problems or if those [guidelines] can be loosened up further,” Ittner said.
Using a less rigid process to implement coordination procedures is a faster way to come to agreement than a more formalized one, according to Ittner
“In the FCC, the rules process is a lengthy one, so we’re not trying to define rules,” he said. “We’re trying to coordinate the community to come to a consensus. … We don’t want to overburden the issue.”
And what does the FCC think of the LMCC’s work? The agency wouldn’t comment on the record, but a spokesperson noted that the FCC has granted LMCC coordinators the opportunity to police themselves and that the proposed coordination procedures already are in accord with existing FCC rules.
“We wanted the FCC to get the word out to let users know what LMCC is doing,” Ittner said. “We requested a Public Notice, but they didn’t see a need for one at this time. … I think it’s largely because this effort is one that LMCC has been engaged in, not one specifically requested by FCC. We’re taking the initiative here.”
Though the transition to 6.25 kHz is still well in the future as the FCC has yet to set a hard date for the migration, manufacturers already are working with the end-user community to ensure they can sell commercial products today without interfering with — or receiving interference from — existing or future systems. Right now, the action is in the private sector, which is expected to establish precedents for the first-responder community when it eventually makes its move to greater spectrum efficiency.
“Initial systems going in are the mid- and lower-tier kinds of radios best-suited for private businesses,” Ittner said.
“[6.25 kHz] solutions are in the marketplace today,” agreed Donald Vasek, executive director EWA, which represents enterprise business users, dealers, service providers and technology vendors. (EWA also is an FAC that coordinates more than 6000 business and industrial/land transportation radio licenses annually.)
“We worked with a couple of manufacturers,” Vasek said. “They came to us, helped us to make sure the technologies that our customers are acquiring can be implemented and can be implemented such that they don’t cause interference with existing systems.”
It is expected that Project 25, the North American public-safety standard for interoperable digital radios, ultimately will implement a 6.25 kHz equivalent bandwidth scheme for better spectrum efficiency. Indeed, the APCO Project 25 Interface Committee, or APIC, in August sent the physical-layer proposal for the second phase of the standard — which includes a harmonized, industry-consensus, two-slot time division multiple access, or TDMA, common air interface standard for 12.5 kHz channels — to TIA for review. (Two-slot TDMA meets the FCC’s requirement for 6.25 kHz channel equivalency by creating two voice paths within a 12.5 kHz channel, which is achieved by using an enhanced half-rate IMBE vocoder in a 12 kb/s air link data stream.)
However, finalizing the second phase of the standard will take a while. In the meantime, the public-safety community is taking a cautious stance on the 6.25 kHz coordination procedures, said Farokh Latif, director of automated frequency coordination for APCO.
“It’s way too early to tell with the proposed rules from LMCC,” he said. “Is there any equipment deployed that supports [6.25 kHz]? The only manufacturer is ICOM, but there’s not much of a deployment thus far.”
Latif added that the LMCC may have to change the de-rating factor to a more conservative approach, depending on the number and type of interference cases reported over the next two years.
One event Latif doesn’t see happening is a pullback of channels from public safety when 6.25 kHz finally is implemented. “It’s a misnomer to say that you create channels with the technology — you’re only operating on tighter bandwidth,” he said. “You may create separate channels to pack more users on there, but reclaiming [spectrum]? Definitely not.”
Because public safety is constantly petitioning for more spectrum, Latif said it is unlikely that the FCC actually would be able to reclaim spectrum from public safety with the implementation of 6.25 kHz. Under a study conducted by the Public Safety Wireless Network program, a joint effort of the U.S. Justice and Treasury departments, public safety needs an additional 96 MHz of spectrum, he said. “It was allocated 24 MHz out of the 700 MHz [rebanding]. If you do the numbers, we’re still 70 MHz short.”
Land Mobile Communications Council Members
- APCO International
- Lakes Region Mutual Fire Aid
- International Association of Fire Chiefs
- International Municipal Signal Association
- American Association of State Highway and Transportation Officials
- Association of Fish and Wildlife Agencies
- Forestry Conversation Communications Association
- National Association of State Foresters
- American Automobile Association
- American Petroleum Institute
- Association of American Railroads
- Aviation Spectrum Resources Inc.
- Central Station Alarm Association
- Enterprise Wireless Alliance
- Forest Industries Telecommunications
- Intelligent Transportation Society of America
- MRFAC Inc.
- PCIA — The Wireless Infrastructure Association
- Telecommunications Industry Association
- Utilities Telecommunications Council