Codan Radio P25 Training Guide - Manual (Page 21)

P25 RADIO SYSTEMS | TRAINING GUIDE
Chapter 1: Introduction To P25 Page 13
TETRA
A number of European countries submitted TETRA to ITU-R Working Party 8A on behalf of ETSI (the
European Telecommunication Standards Institute). TETRA’s primary mode uses ›/4DQPSK modulation
that requires a linear or linearized amplifi er and fi ts four-slot TDMA within a 25 kHz channel mask.
DIMRS
Canada submitted DIMRS to ITU-R Working Party 8A. It is a six-slot TDMA system using 16QAM
modulation that fi ts within a 25 kHz channel mask. It is designed primarily for public systems and is
in use in a number of countries around the world. Motorola Inc. is the principal manufacturer of this
equipment, under the name IDEN™.
IDRA
Japan submitted IDRA to ITU-R Working Party 8A. It also is a six-slot TDMA system using 16QAM (16
point Quadrature Amplitude Modulation) that fi t within a 25 kHz channel mask. A major difference from
DIMRS is the use of a different vocoder.
FHMA
Israel submitted FHMA to ITU-R Working Party 8A. The system primarily makes use of frequency
hopping and sectorized base station antennas to gain spectrum effi ciency. The signals are error
protected and when a radio is at a sector boundary, due to different frequency hop patterns between
sectors, interference to and from nearby radios in the other sector is minimized.
Although the other digital standards seem to work well for their original intentions, APCO felt that these
standards would not meet all of the requirements for a public safety agency within North America. P25
standards were designed primarily for the public safety user, with range and performance given very
high priority. Also, unique fl exibility has been designed into the standards to enhance interoperability,
privacy, gradual phase-in of new technologies, and the reliable transmission of voice and data.