Frequency plan

Lore & Background

For each radio band, the ITU has a band plan which dictates how it is to be used and shared, to avoid interference and to set protocol for the compatibility of transmitters and receivers. Each frequency plan defines the frequency range to be included, how channels are to be defined, and what will be carried on those channels. Typical definitions set forth in a frequency plan include a numbering scheme, center frequencies, bandwidth and/or deviation, spectral mask, modulation, content, and licensing procedures. The actual authorized frequency bands are defined by the ITU and local regulating agencies like the US Federal Communications Commission (FCC), and voluntary best practices help avoid interference. The ITU divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten metres, with corresponding frequency of 3×10^(8-n) hertz, and each covering a decade of frequency or wavelength. These ITU radio bands are defined in the ITU Radio Regulations, Article 2, provision No. 2.1, which states that 'the radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table.' The table originated with a recommendation of the fourth CCIR meeting, held in Bucharest in 1937, and was approved by the International Radio Conference held at Atlantic City, NJ in 1947.

Reader's Guide

The significance of a frequency plan lies in its role as the regulatory and technical blueprint for using the radio spectrum. Because the radio spectrum is a fixed resource that has become increasingly congested in recent decades, frequency plans are essential for preventing interference between different users and services. They define how channels are numbered, their center frequencies, bandwidth, modulation types, and permissible content, as well as licensing procedures. The ITU coordinates these plans internationally, while local agencies like the FCC enforce them nationally. The legacy of frequency planning is that it enables the coexistence of some 40 radiocommunication services defined in the ITU's Radio Regulations, from broadcasting to mobile radio to navigation devices. Without such plans, the growing demand for spectrum would lead to chaos. The need to utilize the spectrum more effectively is driving modern telecommunications innovations such as trunked radio systems, spread spectrum, ultra-wideband, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio.

Did You Know?

• The band plan table originated with a recommendation of the fourth CCIR meeting in Bucharest in 1937 and was approved at the International Radio Conference in Atlantic City, NJ in 1947.
• Typical definitions in a frequency plan include numbering scheme, center frequencies, bandwidth, spectral mask, modulation, content, and licensing.
• The idea to give each band a number based on the logarithm of the approximate geometric mean of the band limits in Hz originated with B. C. Fleming-Williams in 1942.