NCJ Number
189616
Journal
Law Enforcement Technology Volume: 28 Issue: 7 Dated: July 2001 Pages: 36-38,40,41
Date Published
July 2001
Length
5 pages
Annotation
This article describes different time division multiplexing options.
Abstract
The Association of Public-Safety Communications Officials Project 25 (P25), originally named Frequency Division Multiple Access (FDMA), is a type of technology that divides frequencies into smaller, more efficient channels. P25 has embarked on several different Time Division Multiplexing options which divide channels up by fractions of a second and standards development is under way for these Time Division Multiple Access (TDMA) radios. There are two versions of FDMA, one where a voice is carried over a 12.5-kHz band, and one where a voice is carried over a 6.25-kHz band, making it twice as spectrally efficient. TDMA is capable of simultaneous transmission of voice data and monitoring while transmitting. Terrestrial Trunked Radio is currently in use in Europe but some of its features are not appropriate for use in the United States. P25 standards do not specify encryption standards, just that a common mode of encryption be employed throughout a transmission. Each country has its own standards for encryption.