The Longley–Rice model is a radio propagation model

Radio propagation model

A radio propagation model, also known as the Radio Wave Propagation Model or the Radio Frequency Propagation Model, is an empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions...

: a method for predicting the attenuation of radio signals for a telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

 link in the frequency range of 20 MHz to 20 GHz

GHZ

GHZ or GHz may refer to:# Gigahertz .# Greenberger-Horne-Zeilinger state — a quantum entanglement of three particles.# Galactic Habitable Zone — the region of a galaxy that is favorable to the formation of life....

.

Longley-Rice is also known as the irregular terrain model (ITM). It was created for the needs of frequency planning in television broadcasting in [the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in the 1960s and was extensively used for preparing the tables of channel allocations for VHF/UHF broadcasting there. LR has two parts: a model for predictions over an area and a model for point-to-point link predictions.

Publications

A description of the method was published by the U.S. government under the title "Prediction of tropospheric radio transmission loss over irregular terrain. A computer method-1968", A. G. Longley and P. L. Rice, ESSA Tech. Rep. ERL 79-ITS 67, U.S. Government Printing Office, Washington, DC, July 1968. This document followed on an earlier publication titled "Transmission loss predictions for tropospheric communication circuits", P.L. Rice, Volume I & II, National Bureau of Standards, Tech. Note 101.

Software

Several applications use the Longley-Rice Model. Three examples are

• CRC-COVWEB
• SPLAT!
  SPLAT!
  SPLAT! is a free terrestrial Radio propagation model application initially written for Linux but has since been ported for Windows...
  
  
• Radio Mobile

External links

Further information on Longley-Rice model, including a full description of the algorithm

Algorithm

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

 and source-code examples can be found on the website of U.S. Department of Commerce NTIA/ITS, Institute for Telecommunication Sciences.

Radio Mobile information can be found at cplus.org

If you want to see another presentation (English/Portuguese] see in http://www.radioamador.wordpress.comhttp://www.radioamador.wordpress.com
or
http://radioamador.files.wordpress.com/2011/07/longley_rice.pdfhttp://radioamador.files.wordpress.com/2011/07/longley_rice.pdf

An on-line model operated by the Communications Research Centre

Communications Research Centre

The Communications Research Centre Canada is a Canadian government scientific laboratory for research and development in the field of advanced telecommunications. For over 40 years, it has made significant contributions to the information and communications technology sector in Canada and abroad...

Canada is available at http://lrcov.crc.ca/main/.