What Is UHF Communication?

UHF communication is the use of radio frequencies in the ultra-high frequency band, from 300 MHz to 3 GHz, to transmit voice, data, and video between points separated by distances ranging from a few meters to several hundred kilometers. The UHF band is the most heavily used segment of the radio spectrum, supporting cellular telephony, terrestrial television broadcasting, land mobile radio, GPS navigation, RFID, and Wi-Fi, among other services. Its combination of relatively compact antenna sizes, good penetration of structures, and sufficient bandwidth for high-data-rate services has made it the preferred band for the majority of consumer and professional wireless systems developed since the mid-twentieth century.

The band's utility comes with competing demands. Because so many services share the UHF range, spectrum management by national and international regulatory authorities is an ongoing engineering and policy challenge. The International Telecommunication Union's Radio Regulations and the national frequency tables derived from them divide UHF spectrum into service categories and assign specific frequency blocks to specific uses. The United States frequency allocation is administered jointly by the FCC and the National Telecommunications and Information Administration.

Propagation and Link Characteristics

UHF signals travel primarily by line-of-sight and ground-reflected paths, with no significant ionospheric refraction at these frequencies. The practical consequence is that communication range is limited to the radio horizon, roughly 40 to 80 kilometers for elevated base stations and much less for ground-level installations. Multipath propagation caused by reflections from buildings, vehicles, and terrain produces fading and intersymbol interference, particularly in dense urban environments. Unlike the high-frequency (HF) band, UHF signals penetrate building walls and foliage reasonably well, which enables indoor coverage and portable operation. Atmospheric absorption becomes significant only near the top of the band, around 2 to 3 GHz, where molecular oxygen and water vapor begin to attenuate signals noticeably over long paths.

Spectrum and Frequency Allocation

The UHF band is divided among a large number of services. In the United States, the portion from 300 to 512 MHz is allocated to UHF television broadcasting, land mobile radio, and federal uses including radar. The cellular bands (700 MHz, 850 MHz, 1900 MHz, and others) were carved out over successive decades of licensing proceedings. The FCC's UHF/VHF band rules establish the licensing and technical standards, including bandwidth efficiency requirements, for public safety and commercial land mobile operations. The reallocation of broadcast television spectrum in the 600 MHz range through the FCC's broadcast incentive auction of 2017 is one example of how growing demand for mobile broadband has driven regulatory restructuring of UHF allocations.

System Architectures and Services

UHF communication systems range from simplex point-to-point links, such as a handheld radio talking to a repeater, to continent-spanning cellular networks with millions of simultaneously active connections. Cellular systems divide coverage areas into cells, each served by a base station, and reuse frequency blocks in geographically separated cells to increase spectral efficiency. Modern 4G LTE and 5G NR standards, both of which operate extensively in the UHF band, use orthogonal frequency-division multiple access (OFDMA) and multiple-input multiple-output (MIMO) antenna techniques to achieve high throughput in multipath environments. Trunked land mobile radio systems, used by public safety agencies and utilities, operate on shared channel pools managed dynamically by a controller, increasing efficiency over conventional single-frequency dispatch. Spectrum congestion in the UHF land-mobile bands, particularly around 450 to 470 MHz, is examined in the NTIA's land mobile spectrum planning analysis, which documents utilization patterns and options for improving capacity through technology transitions.

Applications

UHF communication has applications in a wide range of fields, including:

• Mobile handsets and cellular network infrastructure across 4G LTE and 5G NR bands
• Land mobile radio for public safety, emergency services, and transportation
• Terrestrial broadcast television distribution
• GPS and satellite navigation receivers
• RFID systems for supply-chain management, access control, and asset tracking