Specifications

Timing
Network Planning
A-2 68P81095E55-E August 08, 2000
Pleisiochronous Timing
To reduce the cost and complexity network timing the iDEN system uses locally
recovered timing. Locally recovered timing uses clock signals from the Global
Positioning System (GPS). GPS receivers (Stratum 1 clocks) at major network
elements receive a highly accurate clock pulse from the GPS system. This single
source (plesiochronous) timing is used for bit-rate and frame synchronization
throughout the network. The Building Integrated Timing System (BITS) performs
the recovery and distribution timing across the network. This provides highly
accurate timing to each network element and highly accurate synchronization. The
synchronized payloads improve throughput (Figure A-2).
Figure A-2 GPS Derived Plesiochronous Clock
The accuracy of these sources is not less than 1x10
-11
and is defined as Stratum 1, a
highly accurate clock. Figure A-3 shows the recommended configuration and
implementation of BITS for an installation.
Figure A-3 Typical BITS Configuration
Switch A
Switch B
Frame 1 Frame 2 Frame 3 Frame 4 Frame 5
Frame 1 Frame 2 Frame 3 Frame 4 Frame 5
Time A = Time B
Single Source
Time signal
GPS
( or Loran-C )
T. N. French
BITS
T. N .
French
MPS
DAC
APD
DAP
ETBS
circuit
breakers
HLR
BSC
XCDR
MSC
T1/E1
iSC
ACG
iMU
STP
Pair
Channel
Bank
PSTN
(if used)
OR
CC1
CC2
T1/E1
2048
Square
2048
Square
ADC
RS-422
RS-422
T1/E1
BSC
CP
RS-422
GPS
GPS
CEPT
or
DS1
Input
DSX
Bridging Monitoring Ports
T1/E1
SMS
Voice
Mail
IWF
T. N. French