A primer for finding and securing radio spectrum
The 150-174 MHz band is experiencing somewhat of a resurgence, given its very favorable propagation characteristics that can reduce infrastructure costs substantially by reducing the number of transmitters needed. However, this band was established decades ago for single-channel simplex operations and never was a paired band. Consequently, system designers and frequency coordinators alike are challenged to successfully identify single frequencies to create decent duplex assignments that do not negatively affect incumbent operations that may use the transmit/receive channels in reverse.
Exclusive channels can be identified (see FCC Rule Section 90.187), but it is difficult to identify sufficient quantities of exclusive-use channels that are required for optimum trunked-system operations. For wide-area systems that utilize multiple sites, the propagation benefits of this band start to work against system planners, as more channels are needed to avoid intrasystem interference issues. For public-safety systems, it should be noted that all public-safety coordinators have adopted a rigid technical evaluation process that is designed to protect incumbent analog systems from proposed TDMA digital systems. In other words, advance planning in this band is an absolute necessity.
The 450-470 MHz band is a critical resource for both business/industrial and public-safety systems. The band already is paired, and while in urban areas it may be difficult to secure exclusive-use channels, shared channels always are available, but not all may be ideal for certain system applications. Knowing who your co-channel and adjacent-channel neighbors are — and whether they are operating analog or digital systems — is highly recommended to optimize channel-selection decisions. Public-safety coordinators normally seek letters of consent from incumbent licensees for channels in congested areas, which may significantly slow the channel-identification process.
The 470-512 MHz band (aka the T Band) has been a critical spectrum resource for public-safety, business/industrial and regional private-carrier operations for more than 40 years in 11 top markets. However, due to revised spectrum priorities within the federal government, this band has been identified for reallocation in 2021. Incumbents are not permitted to expand their current systems, and no new systems — even if spectrum capacity was available — will be licensed by the FCC. Industry organizations are trying to reverse the current dismal outlook for the band.
Meanwhile, critical spectrum capacity is available in the 700 MHz narrowband channels dedicated to public-safety organizations. The process to apply for this spectrum is not particularly complicated. The public-safety sector’s regional planning committees administer this spectrum. Upon review and approval of a request, the applicable RPC issues a letter of concurrence, which must be submitted formally to a public-safety frequency-advisory committee for formal certification and FCC application submission. There are no shortcuts to the 700 MHz spectrum-access process, but advance due diligence with the local RPC is recommended.
The 800 MHz band has been, and will remain, a critical spectrum resource for both business/industrial and public-safety entities. Rebanding has been completed in 11 public-safety RPC regions, and additional quantities of exclusive, Sprint-vacated spectrum will be made available for public-safety entities — and, eventually, for critical-infrastructure entities — in more locations in the coming months and years. This spectrum is understandably in high demand, given that its use is exclusive in virtually all cases. However, there remains spectrum-availability issues along the Canadian and Mexican borders that affect several major cities.
The seven coordinators that currently are authorized to assist public-safety entities in securing Sprint-vacated spectrum are developing revised processes to ensure that no mutually exclusive applications are submitted to the FCC. Meanwhile, the commission has before it a long-standing request to consider the licensing of 12.5 kHz interstitial channels to maximize spectrum efficiency in this band. Advance spectrum-availability analyses in this band should be performed in all instances to verify that channels can be used and to ensure the appropriate timing of applications. In other words, this band is complicated, but not to a frequency advisory committee that knows the rules of the road. Capacity is not available in all areas but is becoming increasingly available in many new areas.
The 900 MHz band is available only for business/industrial entities and was frozen many years ago by the FCC to accommodate Sprint Nextel green-space requirements — a requirement that is not needed today. If there is capacity available, incumbent 900 MHz licensees may modify existing licenses, but new-system applications will be considered only in public-safety regions where rebanding has been completed. It is anticipated that the FCC eventually will recognize that the application freeze no longer serves any beneficial purpose and will lift it entirely. This is optimum exclusive spectrum, and its availability may be determined readily for system-planning purposes.
In conclusion, it makes little business sense to delay spectrum-availability reviews for those planning to either expand or replace their private wireless communications systems, because securing approval for the necessary levels of spectrum capacity can prove to be a complicated effort. Some bands have more administrative processes and technical-evaluation hurdles than others. Quality spectrum capacity is available, but it’s best identified and secured as early as possible to maximize investments in private communications systems.
Mark E. Crosby is president and CEO of the Enterprise Wireless Alliance in Emmitsburg, Md. He can be reached at [email protected]