The Longley–Rice model (LR) is a radio propagation model: a method for predicting the attenuation of radio signals for a telecommunication link in the frequency range of 20 MHz to 20 GHz.[1]
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 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.
Contents |
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.
Several applications use the Longley-Rice Model. Three examples are
Further information on Longley-Rice model, including a full description of the algorithm 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.com[1] or http://radioamador.files.wordpress.com/2011/07/longley_rice.pdf[2]
An on-line model operated by the Communications Research Centre Canada is available at [3].