Clearing the air
The land mobile radio industry is well-known for regulatory confusion. Currently, the most confusing regulatory matter concerns narrowbanding at 150 and 450 MHz. I have heard a variety of misinformation about narrowbanding, anywhere from narrowbanding being a mandate at 800 MHz (it isn’t) to a requirement that all new narrowband systems must be digital and P25-compliant (again, not true).
One area of narrowbanding that is rightfully confusing is how narrowband systems, particularly those that are digital, will be coordinated in a shared-radio environment. The Land Mobile Communications Council (LMCC), after consultation with its member equipment manufacturers, has taken up this issue. LMCC is an umbrella association consisting of all of the various public-safety and non-public-safety frequency coordinators, as well as the Telecommunications Industry Association (TIA).
In a letter sent to the FCC on June 12, LMCC took a stab at rewriting Section 90.187 of the commission’s rules. The purpose of the rewrite is to establish rules for when and where new technology systems can be integrated into the landscape.
The proposed changes include determining whether an incumbent licensee is an Affected Licensee (one that has to be considered for interference purposes). This process would be governed by the proposed table at left. At that point, the coordinator would perform a contour analysis. Presently, in the 150-174 MHz band, there must not be an overlap of the incumbent’s 37 dBu service contour with the applicant’s 19 dBu interference contour. In the 421-470 MHz band, that overlap is 39/21 dBu.
When the stations are offset and have various bandwidths, LMCC has developed a series of “de-rating” values that consider a variety of factors. These values will not be codified in the rules, but rather will be regarded as consensus criteria, with the understanding that experience in the field may lead to the need for adjustments.
A mobile-only license without center city coordinates on its authorization will not be considered an affected licensee with regard to where an exclusive trunked system can be coordinated. For mobile-only systems, those systems’ interference and service contours will be calculated from those coordinates.
By reaching a consensus on these issues, the LMCC has taken significant steps toward achieving consistent coordination results among the various coordinators. This reduces “coordinator shopping” and ultimately reduces the number of arguments before the FCC.
Now that we have an agreement on coordination standards, narrowband applications should be able to flow through coordinators and the FCC more quickly, while at the same time providing the spectrum opportunities that narrowbanding was designed to yield.
Alan Tilles is counsel to numerous entities in the private radio and Internet industries. He is a partner in the law firm of Shulman Rogers Gandal Pordy & Ecker and can be reached at [email protected].
FREQUENCY RANGE ABOVE AND BELOW PROPOSED CHANNEL CENTER
|Incumbent 25 kHz||Incumbent 12.5 kHz||Incumbent 6.25 kHz|
|Proposed trunked station 25 kHz||15||15||15|
|Proposed trunked station 12.5 kHz||15||7.5||7.5|
|Proposed trunked station 6.25 kHz||15||7.5||0|
Source: LMCC filing