What you should know about refarming
What do the refarming orders really mean, and how do they affect your decision to use centralized or decentralized UHF trunking?
“Refarming” is subject to misunderstanding and misinformation. Refarming is the FCC’s procedure to increase the capacity of the FCC land mobile radio spectrum below 512MHz. Refarming has been an ongoing process for almost 10 years, but many people are still uncertain what refarming actually requires and doesn’t require.
Many people incorrectly believe that refarming requires licensees to discard perfectly good wideband equipment – equipment that uses a 25kHz operating bandwidth – and replace it with narrowband equipment – equipment that uses a 12.5kHz operating bandwidth or less. Refarming does not require any licensee to discard any equipment at any time.
Others talk about 800/900MHz refarming. There is no such thing. This refarming proceeding only applied to the FCC LMR spectrum below 800MHz, which is, in reality, only the LMR spectrum below 512MHz.
So refarming does not require mandatory narrowbanding or changes at 800/900MHz.
Refarming did change the channel spacing in the 150MHz-174MHz VHF band and in the 450MHz-512MHz UHF band. Before refarming, channels in the VHF band were spaced 15kHz apart. As part of the refarming effort, the FCC added a channel midway between the original channel centers, making post-refarming VHF channel spacing 7.5kHz and, in effect, doubling the number of VHF channels. At UHF before refarming, channels were spaced 25kHz apart. The FCC wanted to quadruple the number of channels, so three channels were added between the original channel centers, thus making post-refarming UHF channel spacing 6.25kHz. Post-refarming VHF and UHF channel spacing is diagrammed at the left and on page 34.
The FCC realized that allowing wideband operations on all of the new channels in the VHF and UHF bands could cause some confusion. So, in addition to adding channels in both bands, the FCC imposed operating bandwidth limitations for the newly added channels. In both the VHF and UHF bands, however, the FCC decided to allow a maximum operating bandwidth limitation of 25kHz on all of the original channels that existed before refarming. On the new VHF channels – those displaced 67.5kHz from the original channel centers – a maximum operating bandwidth limitation of 12.5kHz was adopted. Because more channels were added in UHF, a number of operating bandwidth limitations were adopted. For those new UHF channels that are located 612.5kHz from the original channel centers (midway between the original UHF channels), the operating bandwidth limitation is 12.5kHz, maximum. New UHF channels located 66.25kHz from the original UHF channel centers have an operating bandwidth limitation of 6.25kHz maximum. The operating bandwidth limitations for the various VHF and UHF post-refarming channels are also depicted in the diagrams.
As these diagrams show, even though operating bandwidth limitations have been imposed on the new channels, there will be an increase of interference between systems because of the overlap.
Do the rules adopted require one licensee or another to take steps to reduce this sort of interference? For example, is the licensee using a wideband-operating bandwidth subservient to those using narrower operating bandwidths? The answer is no. As long as a licensee and the licensee’s equipment are operating within the technical constraints of the license granted, there is no obligation to do anything to reduce the overlapping interference phenomena.
Having chosen to add new channels, some with operating bandwidth limitations, the FCC realized that it needed to foster the use of equipment meeting these improved spectrum efficiency benchmarks. However, the FCC did not want to be accused of subjecting licensees to another “unfunded mandate from Washington”, by requiring them to migrate to narrowband equipment by some specific date. Therefore, the requirement for new spectrally efficient equipment was placed on the manufacturers through the type-acceptance process. As of Feb. 14, 1997, any equipment submitted for type acceptance was to have the capability of providing at least one voice path per 12.5kHz of occupied bandwidth for voice communications and/or 4.8kbps per 6.25kHz of occupied bandwidth for data communications. Beginning on Jan. 1, 2005, newly developed equipment must provide at least one voice path per 6.25kHz of occupied bandwidth for voice communications to be type-accepted. Interestingly, the Jan. 1, 2005, requirement for data communications did not change.
It is important that the FCC rules concerning efficiency specifically allow for multiple-mode equipment. As long as the equipment meets the efficiency requirements in one of the modes, it is acceptable for a manufacturer to include modes that may or may not satisfy the requirements. Likely, the net result is that 25kHz operating bandwidth equipment will continue to be available as long as it is just one of the modes in otherwise compliant multimode equipment.
Refarming adopted many other rules and standards. The FCC consolidated the 20 LMR radio services into two pools, providing licensees within a pool a greater choice of frequencies and creating some measure of competition between frequency coordinators. Antenna-height and transmit-power limitations were also adopted to limit service areas for new systems as a means of packing more licensees into a given geographic area.
However, possibly the most radical and easily misunderstood item that comes under the refarming banner is the rule adopted to provide the possibility, although maybe not the probability, of using centralized trunking systems in the VHF and UHF bands where exclusive channel assignments are not common. Centralized trunked systems do not monitor the system frequencies to determine it is being used by some licensee outside of the trunked system, before the trunked system assigns that frequency to a user within the system.
The FCC has long recognized that centralized trunked systems are effective for efficient use of limited spectrum resources, but failure to monitor would likely result in interference for other users in a shared frequency environment. While the FCC continues to investigate the concept of exclusive channel assignments for the currently shared VHF and UHF bands, it has adopted concurrence rules that may provide pseudo-exclusivity to those wanting to use centralized trunking at VHF and UHF. The rules consider the closeness of the outside users’ frequencies to the frequencies within the trunking system and the closeness of the outside users’ service areas to the area where the trunked system is likely to cause interference.
The diagram at the lower left depicts the analysis necessary to identify what frequency range is included for determining concurrence. If the proposed trunked system uses a 25kHz operating bandwidth, then the window for co-channel and adjacent-channel licensees that must be considered is 615kHz from each frequency in the trunked system. If the trunked system uses 12.5kHz operating bandwidth, then the window is 67.5kHz. If 6.25kHz operating bandwidth will be used in the trunked system, then the window is 63.75kHz. The diagrams on page 35 show the two alternative means to evaluate the likelihood of interference to the co-channel and adjacent-channel licensees’ service areas. A potential user of the trunked system can use either method to identify who must agree to the trunked system. The top diagram shows the method of comparing a 70-mile circle around the proposed trunked base stations and the service areas of the relevant co-channel and adjacent channel licensees.
The lower diagram shows the comparison between the interference contour of the proposed trunked system base stations and the same service areas. In either analysis, if the service area of the co-channel or adjacent-channel licensee is touched by the 70-mile circle or by the interference contour, as appropriate, then that co-channel or adjacent-channel licensee must agree, in writing, with the centralized trunking proposal.
The final result of making the comparisons of frequencies and areas may be a long list of licensees, and each must consent to the use of centralized trunking. A person proposing to use centralized trunking is well-advised to select frequencies, operating bandwidths and comparison methods to pare a potentially long list to the absolute minimum.
Another question may be, “We know what the rules say, but does refarming really accomplish anything?” That is a question with as many reasonable answers as there are people who have asked the question. Refarming is still not officially accomplished. Changes may occur in the future as part of refarming or as part of other FCC proceedings.
If you have any questions about refarming, please seek assistance from competent, unbiased sources. Refer to the refarming FAQ on the FCC Web site www.fcc.gov/wtb/plmrs/refarmfq.html or to the “Refarming-Truths & Myths” booklet prepared by Ralph Haller and myself. The booklet is available for free in hard copy or electronic copy by calling me at (804) 385-2465 or email me at [email protected].
