Codan Radio P25 Training Guide - Manual (Page 13)

P25 RADIO SYSTEMS | TRAINING GUIDE
Chapter 1: Introduction To P25 Page 5
P25 secure transmissions may be enabled by digital encryption. The P25 standards specify the use of
the Advanced Encryption Standard (AES) algorithm, Data Encryption Standard (DES-OFB) algorithm,
and other encryption algorithms. There are additional standards and specifi cations for over-the-air
rekeying (OTAR) features. OTAR allows subscriber encryption key management through a radio
network.
Phase 1 P25 channels that carry voice or data operate at 9600 bits per second (bps). These voice or
data channels are protected by forward error correction, which compensates for poor RF conditions
and improves useable range. Phase 1 P25 supports data transmission, either piggybacked with voice
(low speed data), or in several other modes up to the full traffi c channel rate of 9600 bps.
P25 RADIO SYSTEM ARCHITECTURE
Figure 1-2: P25 Radio System Architecture
Figure 1-2 represents a basic digital transceiver.
A to D
Speech
Coder
Channel
Coder Modulator Tx Amplifier
D to A Speech
Decoder
Channel
Decoder Demod--
ulator
Rx
Amplifier
Filters &
Equalizer
Baseband
filters
Duplexer
V.C.O.
IMBE™
Vocoder
IMBE™
Vocoder
IDs &
FEP
C4FM
C4FM
IDs &
EC
Micro-
phone
Speaker
Repeat Path