If you have any radio systems operating in the 150-174 MHz or 421-512 MHz private land mobile radio bands, you should begin to plan now for the mandatory conversion to "narrowband" technologies. On March 22, 2007, the U.S. Federal Communications Commission (FCC) confirmed the timetable to govern the transition, thus removing a few uncertainties as to when licensees must stop using wider bandwidth technologies.

Although the mandatory conversion date is a few years away, licensees should begin planning now. They should review their current frequency assignments, longer term communications requirements and equipment capabilities in order to develop a viable migration plan.

Background

The narrowbanding mandate has its origins in the land mobile "refarming" proceeding dating back to 1989. In addition to making certain structural changes in the rules governing the private land mobile radio services, the FCC initiated steps to introduce use of more spectrum-efficient radio equipment in these bands. Ultimately, the FCC decided on a push-pull type approach, in which it would gradually force radio equipment manufacturers to start producing more efficient equipment, while imposing deadlines for licensees to start deploying this equipment. For example, since February 14, 1997, the FCC has certified new radio equipment in these bands only if it is capable of operating on 12.5 kHz or narrower channels or with equivalent efficiency (e.g., two TDMA voice channels in a 25 kHz bandwidth, or 4800 bits per second per 6.25 kHz bandwidth). The FCC also clarified in earlier orders that narrowbanding does not apply to part 90 channels that are specifically allocated for paging. However, paging systems operating on other mobile channels are not exempt from the narrowbanding rules.

Timetable for Conversion

In its March 2007 decision, the FCC deferred setting any deadlines for converting to "very narrowband" technologies (i.e., 6.25 kHz per voice channel or equivalent), but emphasized that it ultimately intends to require such a conversion, with 12.5 kHz narrowbanding only an interim step. As it now stands, the following timetable will govern the transition to 12.5 kHz or equivalent-efficiency technologies:

  • January 1, 2011: Applications for new licenses or for license modifications that will increase an existing station’s coverage must propose to use equipment with an efficiency of at least one voice channel per 12.5 kHz of bandwidth. Also, as of this date the FCC will approve radio equipment for manufacture or importation only if it meets this efficiency standard. Moreover, equipment must have a capability of using 6.25 kHz or equivalent efficiency per voice channel.
  • January 1, 2013: Licensees in the 150 to 174 and 421 to 512 MHz private land mobile bands must operate with a maximum bandwidth of 12.5 kHz per voice channel or equivalent efficiency.

While it was suggested at one time that stations operating at wider bandwidth should become "secondary" to stations operating in compliance with the bandwidth limitations, the FCC has not provided for continued operations on a secondary basis. For example, continuing to operate a 25 kHz land mobile station with only one voice channel after January 1, 2013, would be a rule violation and subject the licensee to monetary forfeiture and, most likely, an order to cease and desist further operation.