Codan Radio P25 Training Guide - Manual (Page 85)

P25 RADIO SYSTEMS | TRAINING GUIDE
Chapter 6: P25 Trunking Page 77
TRUNKING SYSTEM OPERATION
In order to understand how a P25 trunking system operates, it is important to understand the basic
sequence of events that occur in a P25 trunking system. Figure 6-3 shows the basics of a P25 trunking
system operation.
Figure 6-3: P25 Trunking System Operation
(1) Control Channel Hunt
Subscriber searches for the OSP
of the control channel
Subscriber Unit
OSP
Broadcast
continuously
every 37.5 ms
Control
Channel
Traffic
Channel
Traffic
Channel
Subscriber Unit
OSP
(2) Registration Request
Subscriber transmits ISP to
control channel on the basis of
Slotted ALOHA
(3) Registration Grant
Control channel validates subscriber
and transmits OSP to Subscriber
with registration and group
affiliation information
ISP
Slotted
ALOHA
Subscriber Unit
Subscriber Unit
(4) Idle
Subscriber Idles
(monitoring control channel)
until a traffic channel
is requested (PTT)
OSP
Subscriber Unit
ISP
(5) Traffic Channel Request
Subscriber requests a traffic channel
via an ISP (Slotted ALOHA)
Talk Group
(6) Traffic Channel Grant
All Subscribers in Talk Group
are granted a traffic channel
OSP
Talk Group
(7) Voice or Data Communications
All Subscribers in Talk Group
use assigned Traffic Channel
for communication
(8) Call Termination
All Subscribers in Talk Group
return to Idle (4) and
Traffic Channel is free
Talk Group
OSP