There's one thing you can bank on when discussing radio spectrum: No one's making any more of it. It's a lot like property. The earth isn't getting any bigger, so what exists today is what you have to work with. What you see is what you get.

As new wireless applications are introduced and adopted, radio spectrum usage continues to grow. Despite all that activity, there are only two ways to make room for more users:

1. Developing new ideas and equipment that can make use of frequencies not currently in use.
2. Refarming the existing frequencies to make better use of what we currently have.

Over the years, the spectrum has “grown” to accommodate an ever-increasing number of users and uses. Designs evolved to create better receivers and more stable transmitters, and mobile radio equipment offered increasingly better communications. As demand increased, so did advances in technology, allowing frequencies once thought unusable because of their wavelength to provide new resources for additional users.

In fact, it wasn't very long ago that the 800MHz spectrum was considered useless because of its short wavelength and relatively limited coverage area. Today we're using systems at 800MHz, 900MHz and 2GHz to provide excellent wireless communications, such as public safety radio systems in the 800MHZ spectrum and digital pcs telephones at 2GHz.

Unfortunately, the demand for usable frequencies always outpaces the technology needed to keep up with that demand. More and more wireless users are trying to crowd their way into saturated frequency bands, because moving to new spectrum isn't practical for them. Limitiations such as propagation characteristics and huge investments in existing equipment force them to remain in the bands they currently use.

Where are we today? There are many efforts under way to help fire service, EMS and other public safety users to communicate through new spectrum and new technology.

• The FCC has authorized the use of a band newly available for land mobile use at 700MHz.
• We're changing the way we use VHF (150-170MHz) and UHF (450-512MHz) frequencies through refarming.
• We're studying the possibility of sharing Department of Defense VHF frequencies at 138-144 MHz.
• We're exploring expansion possibilities at higher frequencies, such as 4.9GHz.

700MHz public safety band: Spectrum and channels

Purpose	Spectrum	Narrowband (6.25kHz)	Wideband (50kHz)
General use	12.5MHz	7.7MHz (1,232 channels)	4.8MHz (96 channels)
Interoperability	2.6MHz	0.8MHz (128 channels)	1.8MHz (36 channels)
State license	2.4MHZ	2.4MHZ (384 channels)
Low-power	0.3MHZ	0.3MHZ (48 channels)
Reserve	6.2MHZ	0.8MHZ (128 channels)	5.4MHZ (108 channels)

New spectrum: The 700MHz band

Twenty-four megahertz of spectrum has been allocated for public safety use in what's commonly known as the 700 MHZ band: 764-776 and 794-806 MHz. Although this spectrum is currently used by UHF television stations, the FCC has set a date of 2006 to convert those frequencies from commercial broadcasting to public safety communications.

The FCC established a federal advisory committee, the Public Safety National Coordination Council, to advise the FCC on the best way to use these frequencies. The NCC is made up of public safety users, manufacturers and associations. Working with the NCC, the FCC has adopted technical requirements that include an all-digital band plan, eligibility for licensing, protection from commercial users and low-power on-scene communications requirements.

The band plan, which will promote better assignment and operational possibilities for public safety, includes narrowband and wideband channel groups for general use, interoperability and reserved spectrum. Narrowband is defined as 6.25kHz and 12.5kHz channels used primarily for voice communications and low-speed data. Wideband channels are 50kHz and wider channels for the transmission of moderate-speed data, video and similar applications.

Although public safety entities will be able to apply for 700MHz licensing, the FCC has also adopted a proposal for state licensing. Each state and U.S. territory, district and possession is eligible to apply for a geographic license totalling 2.4MHz for its needs, with each state's governor having until Dec. 31 to apply. Whatever part of the 2.4MHz that a state hasn't applied for by the deadline will revert to general use and be available for traditional licensing.

The FCC has authorized 48 narrowband channels for low-power use at on-scene communications, and it has reserved 128 narrowband channels and 5.4MHz of the 700MHz band between narrowband and wideband segments for future developments in broadband technologies. As a result of these actions, the 24MHz of spectrum in the 700MHz band will be as shown in the table above.

Regional Planning Committees, which were first used in the 800MHz spectrum, will be used to develop regional plans for this new spectrum. There will be 55 of the 700MHz RPCs, in the same regions as the existing 800MHz committees. There are provisions for states to request changes in the geographic layout of the RPCs, but the deadline for opting out of the existing regions closes on July 2.

Refarming VHF and UHF

When it comes to increasing the uses of the finite amount of spectrum, refarming is the name of the game. The process allows two or more users to occupy the same bandwidth, which had previously been available to only one user.

Think of it as changing a two-lane highway into four lanes so that twice as many cars can travel down the same road. The difference is that while we can double the number of lanes by doubling the amount of land we use, we can't double the amount of spectrum. As a practical matter, neither the FCC nor Congress will “condemn” the adjacent bands used by others so they can be transferred to public safety use.

The alternative is for each user to use less spectrum. For example, if a radio signal occupies 25kHz of bandwidth around a designated frequency, then simple division implies that two wireless transmissions could take place in the same space if each were limited to 12.5kHz.

In highway terms, this downsizing sleight-of-hand would entail making each car and truck half its current size, allowing twice as many cars to fit on the two-lane road. This is accomplished by designing transmitters and receivers capable of carrying the same amount of information on less spectrum, or bandwidth.

To implement refarming, in 1995 the FCC created both a narrowband channel plan for the bands below 800MHz and a transition schedule based on the approval process for newly manufactured equipment. This was an interesting approach. Instead of mandating the use of narrowband technologies by certain dates, the FCC chose to require new radio equipment manufactured after designated dates to be capable of the new, smaller bandwidths.

The intent is to allow the user community the opportunity to license the new narrowband channels while allowing existing wideband channel use to continue. The rules adopted in the refarming proceeding are only applicable to the bands below 800MHZ. Specifically, the technical rules adopted affect the licensing and use of radios in the following bands:

• 150-174MHz (VHF).
• 421-430MHz (UHF, available only in Detroit; Buffalo, N.Y.; and Cleveland).
• 450-470MHz (UHF).
• 470-512MHz (shared with UHF-TV, available in only 11 cities).

Prior to refarming, the 150-174MHz channels were 30kHz wide and, in general, spaced every 15kHz. Refarming added a new channel between each existing channel. The new channel is restricted to equipment designed to operate on channel bandwidths of 12.5kHz or less.

The 450-470 MHz channels, which are known as primary channels, were 25kHz wide and spaced every 25kHz. Refarming modified this channel plan by adding three new channels every 6.25kHZ above each existing primary channel.

Operation on new channels 6.25kHz removed from a primary channel is restricted to equipment designed to operate on channel bandwidths of 6.25kHz or less, and operation on new channels 12.5kHz removed from a primary channel is restricted to equipment designed for channel bandwidths of 12.5kHz or less. This same plan applied to the 421-430 and 470-512MHz bands.

As mentioned earlier, the FCC didn't set mandatory dates for changing out equipment. In fact, existing equipment can be used forever, or as long as it still works. However, the FCC has required that new models of land mobile equipment must be capable of a 12.5kHz operating bandwidth or equivalent. The rules also provide for multi-mode equipment, which can operate in both 12.5kHz and 25kHz bandwidths.

Beginning Jan. 1, 2005, all newly designed equipment must be capable of a 6.25kHz operating bandwidth or equivalent. As with today's models, multi-mode equipment is authorized so that this future equipment can also operate in the 12.5kHz and/or 25kHz modes.

You may think that the FCC split the existing private land mobile channels in half so that, for example, two 12.5kHz channels are created from a 25kHz channel. In reality, the FCC adopted a channel plan that centers some of the new narrower channels on the same frequencies as the existing 25kHz channels. This was done to ease the transition so that all old channels would remain unchanged in frequency and bandwidth and newer narrowband equipment could co-channel with existing equipment as licensees changed out equipment.

Sharing the 138-144MHz band

About 70% of fire departments have their principal radio systems in the 150-170MHz portion of the radio spectrum, which is extremely congested throughout most of the nation. Fire departments, emergency medical services, police, forestry agencies, highway maintenance departments and other public safety agencies need access to additional spectrum in the VHF high band, which spans from 138-170MHz.

Public safety access to the 138-144MHz band would help alleviate the VHF spectrum shortage. This band, which is currently allocated to the federal government, is used primarily by the Department of Defense at domestic military installations. Congress included a provision in the National Defense Authorization Act for FY 2000 that allowed the dod to retain use of the 138-144MHz band.

However, the Conference Report to the Act states, “The conferees urge the Secretary of Defense to share such frequencies with state and local government public safety radio services, to the extent that such sharing will not result in harmful interference between the dod systems and the public safety systems proposed for operation on those frequencies.”

The National Public Safety Telecommunications Council, which is composed of public safety associations including the International Municipal Signal Association, the International Association of Fire Chiefs and others, is working to convince the dod that public safety would be a good neighbor in this band.

As a first step, public safety agencies need the cooperation of the dod to develop sharing procedures, after identifying where the 138-144MHz band can be shared. The close proximity of 138-144MHz to the public safety frequency band at 150-170MHz would permit relatively inexpensive equipment modifications to existing systems.

For more information about the process, visit the NPSTC Web site at <<a href="http://www.npstc.org" target="_blank">www.npstc.org>.

Broadband at 4.9GHz

Broadband wireless services encompass a number of new technologies for public safety agencies. Broadband is a term for channels much larger than those discussed previously. These wider channels could support high-speed data, full-motion video and a host of other innovations. Two technologies of the future are wireless personal area networks and wireless vehicular area networks.

Using high bandwidth transmissions, a PAN could link a portable radio worn by a firefighter to many useful accessories, such as a helmet video camera, video viewing device, health monitor, wireless SCBA microphone and speaker, or a handheld computer. VAN technology could link a vehicle's radio to laptop computers, printers, remote headsets, bar-code readers and cameras.

Bringing broadband technologies to the field will require new spectrum. The FCC is currently considering allocating spectrum at 4.9GHz for broadband use by public safety. The 50MHz between 4.94-4.99GHz is the likely candidate for this use, because there are no current federal users and commercial interest is light. Although the FCC has proposed this band for auction to commercial users, the NPSTC and other organizations are actively working toward public safety use of this spectrum.

Communications is an important tool for every fire service leader, but few become involved with the technical and regulatory issues that will shape our future communications.

I urge you, or a member of your department, to become involved. Participating in communications committees at the national or state level, attending the meetings of the 800MHz and 700MHZ regional planning committees in your area, and remaining up to date with these and future communications issues will help you to better plan for and use this tool.

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A 25-year veteran of the fire service, Douglas Aiken is the chief coordinator of Lakes Region Mutual Fire Aid, a 35-community fire, EMS and hazmat district in central New Hampshire that encompasses more than 1,400 square miles. A member of the NCC steering committee, he's chairman of the IMSA Radio Committee, vice-chair of the ICHIEFS Communications Committee and vice-chair of the NPSTC. Chief Aiken is also a member of the NFPA 1221, Public Emergency Service Communications, technical committee and serves on the advisory board of the Congressional Fire Services Institute. He can be reached at <<a href="mailto:daiken@imsasafety.org" target="_blank">daiken@imsasafety.org>.