Since the 1920s, Private Land Mobile Radio Services (PLMRS) have been meeting the internal communication needs of private companies, state and local governments, and other organizations. These services provide voice and data communications that allow users to control their business operations and production processes, protect worker and public safety, and respond quickly in times of natural disaster or other emergencies.
In 1934, shortly after its establishment, the Federal Communications Commission (FCC) identified four private land mobile services—Emergency Service, Geophysical Service; Mobile Press Service, and Temporary Service, which applied to frequencies used by the motion picture industry. Over the years, the FCC refined these categories.
Until 1997, PLMRS consisted of 20 services spread among six service categories: Public Safety, Special Emergency, Industrial, Land Transportation, Radiolocation, and Transportation Infrastructure. In that year, the FCC did away with 20 discrete radio services and the six service categories and replaced them with two frequency pools: the Public Safety Pool and the Industrial/Business Pool.
Public Safety Radio Pool
The Public Safety Radio Pool was created in 1997. It covers the licensing of the radio communications of state and local governmental entities and the following categories of activities: medical services, rescue organizations, veterinarians, persons with disabilities, disaster-relief organizations, school buses, beach patrols, establishments in isolated places, communications standby facilities, and emergency repair of public communications facilities.
The FCC has established an 800-MHz National Plan that specifies special policies and procedures governing the Public Safety Pool. The principal spectrum resource for the National Plan is the 821- to 824-MHz and the 866- to 869- MHz bands. The National Plan establishes planning regions covering all parts of the United States, Puerto Rico, and the U.S. Virgin Islands. The license application to provide service must be approved by the appropriate regional planning committee before frequency assignments will be made in these bands.
The Industrial/Business Pool consists of a number of frequencies that were previously allotted to the Industrial or Land Transportation Radio Services, including the Business Radio Service. Anyone eligible in one of these radio services is eligible in the new Industrial/Business Pool for any frequency in that pool.
In this regard, the FCC has adopted the eligibility criteria from the old Business Radio Service. The Industrial/Business Radio Pool covers the licensing of the radio communications of entities engaged in commercial activities; engaged in clergy activities; operating educational, philanthropic, or ecclesiastical institutions; or operating hospitals, clinics, or medical associations.
General Access Pool
Prior to 1977, channels in the 470- to 512-MHz band were allocated to seven frequency pools based on category of eligibility. The FCC eliminated the separate allocation to these pools and created a General Access Pool to permit greater flexibility and foster more effective and efficient use of the 470- to 512-MHz band. Frequencies in the 470- to 512-MHz band are shared with UHF TV Channels 14 to 20 and are available in only 11 cities.
All unassigned channels, including those which subsequently become unassigned, are considered to be in the General Access Pool and available to all eligible parties on a first-come, first-served basis. If a channel is assigned in an area, however, subsequent authorizations on that channel will only be granted to users from the same category.
Applications for PLMRS
PLMRS are used by organizations that are engaged in a wide variety of activities. Police, fire, ambulance, and emergency relief organizations such as the Red Cross use private wireless systems to dispatch help when emergency calls come in or disaster strikes.
Utility companies, railroad and other transportation providers, and other infrastructurerelated companies use their systems to provide vital day-today control of their systems (including monitoring and control and routine maintenance and repair), as well as to respond to emergencies and disasters—often working with public safety agencies.
A wide variety of businesses, including package delivery companies, plumbers, airlines, taxis, manufacturers, and even the American Automobile Association (AAA), rely on private wireless systems to monitor, control, and coordinate their production processes, personnel, and vehicles.
Although commercial services can serve some of the needs of these organizations, private users generally believe that their own systems provide them with capabilities, features, and efficiencies that commercial services cannot. Some of the requirements and features that PLMRS users believe make their systems unique include:
- Immediate access to a radio channel (no dialing required)
- Coverage in areas where commercial systems cannot provide service.
- Peak usage patterns that could overwhelm commercial systems.
- High reliability.
- Priority access, especially in emergencies.
- Specialized equipment required by the job.
In a conventional radio system, a radio can access only one channel at a time. If that channel is in use, the user must either wait for the channel to become idle or manually search for a free channel. Atrunked radio system differs from a conventional system by having the ability to automatically search all available channels for one that is clear. The FCC has recognized two types of trunking: centralized and decentralized.
A centralized trunked system uses one or more control channels to transmit channel-assignment information to the mobile radios. In a decentralized trunked system, the mobile radios scan the available channels and find one that is clear. The rules require that licensees take reasonable precautions to avoid causing harmful interference, including monitoring the transmitting frequency for communications in progress.
This requirement is met in decentralized trunked systems because each mobile unit monitors each channel and finds a clear one on which to transmit. In a centralized trunked radio system, radios typically monitor the control channel(s), not the specific transmit frequencies. Therefore, this form of trunking generally has not been allowed in the shared bands below 800 MHz.
Under certain conditions, however, the FCC allows some licensees to implement centralized trunked radio systems in the shared bands below 800 MHz. Centralized trunking may be authorized if the licensee has an exclusive service area and uses the 470- to 512-MHz band only. If the licensee does not have an exclusive service area, it must obtain consent from all licensees who have cochannel and/or adjacent channel stations.
Private radio systems serve a great variety of communication needs that common carriers and other commercial service providers traditionally have not been able or willing to fulfill. Companies large and small use their private systems to support their business operations, safety, and emergency needs.
The one characteristic that all these uses share—and that differentiates private wireless use from commercial use—is that private wireless licensees use radio as a tool to accomplish their missions in the most effective and efficient ways possible. Private radio users employ wireless communications as they would any other tool or machine—radio contributes to their production of some other good or service.
For commercial wireless service providers, by contrast, the services offered over the radio system are the end products. Cellular, PCS, and Specialized Mobile Radio (SMR) providers sell service or capacity on wireless systems, permitting a wide range of mobile and portable communications that extend the national communications infrastructure. This difference in purpose is significant because it determines how the services are regulated.