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www.huawei.com
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved.
TDM Voice Introduction
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 1
Foreword
Traditional voice network uses TDM technology and narrow
band signaling to realize the voice transmission.
This chapter describes the traditional voice network and basic
voice transmission knowledge.
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 2
Objectives
Upon completion of this course, you will be able to:
Understand the traditional voice network;
Understand the components, interfaces and signaling in the
traditional voice network.
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 3
Phone Terminals
Digital phone (Digital line)
Advantages: more feature, easy to use, connect quickly
Disadvantages: non-standard, expensive.
Analog phone (Analog line)
Advantages : universal, cheap
Disadvantages: few feature, connect slowly
Fax machine (Analog line)
PSTN Phone:
Digital Phone
Analog Phone
Fax
PBX
Fax
Terminal
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 4
PBX
PBX: Private Branch Exchange
Trunk Card
Signaling
Processor
Trunk Card
Subscriber
Card
Control System
Subscriber
Card
Switched
Network
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 5
PBX
Switching
Matrix
Common
Control
Analog
Line Card
Digital
Line Card
Data
Line Card
ISDN BRI
Line Card
Analog
Trunk Card
Digital
Trunk Card
User Interface Analog Trunks
Digital Trunks
Analog phone
Digital phone
Digital terminal
ISDN terminal
PSTN or PBX
PSTN or PBX
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 6
Analog Line
Electric currents are used to send analog signals.
Each analog circuit is composed of a pair of wires.
Time
voltage
Analog Phone Central Office
Ground
Battery (ring)-48V
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 7
Digital Line
Digital signals use discrete values to represent levels of voice
instead of a combination of electrical signals.
0
1
0
Central office
Digital connection
1 1 1 0 1
Time slot #1
Time slot #0
Time slot #0
Time slot #1
Time slot #31
… …
PBX
…
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 8
Type of Circuit
PSTN
PBX
Circuit Type
Analog Circuit
Digital Circuit
Digital Circuit
A digital circuit support multiple sessions at the same time
Advantage: Digital signaling connect quickly, high port density, more calling information
Disadvantage: The rent is more expensive
Analog Circuit
An analog circuit support only one session at the same time
Advantage: Apply for the number of circuit as your need, the rent is more cheap
Disadvantage: Analog signaling connect slowly, low port density, less calling information
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 9
Analog Circuit
Analog Circuit FXS (Foreign eXchange Station): It is analog voice interface, also called subscriber
interface, and it is the port that you plug a telephone, fax, or modem to provide
telephony service. FXO (Foreign eXchange Office): It is the port on the device that connect to the CO or PBX,
the port maybe on a telephone, fax and router that connects to the FXS port.
Interface Call out Call in Opposite
interface
FXS Loop current variety Receive ringing current FXO
FXO Close loop circuit Receive ringing current FXS
PSTN
PBX Telephone
FXO FXS FXO FXS
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 10
Digital Circuit/Trunk
PBX
E1
Type Bandwidth Area Number Signaling
Channel
T1 1.544 Mbit/s North America, Japan,
Hong Kong, Taiwan 24 23rd
E1 2.048 Mbit/s Europe, Asia 32 16th
E1
PSTN
T1 T1
64kbps/channel
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 11
Signaling
Signaling is the exchange information between involved points
in the network that sets up, controls, and terminates each
telephone call.
Types of signaling
Line Signaling: Loop start signaling, Ground start signaling.
Inter-office signaling: CAS, CCS.
Inter-office signaling Line Signaling PBX
Phone PBX Phone
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 12
Loop Start Signaling
Loop start signaling is a typical signaling between a user and
the exchange.
Voice signaling can be classified into three general types:
Supervisory
Addressing (Dual-Tone Multi-Frequency (DTMF) and Pulse)
Informational-indicates call progress
Analog phone Central office
Ground
-48V
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 13
Signaling - CAS
CAS (Channel Associated Signaling): Signaling and audio are
encoded and transmitted in the same channel.
PSTN
T1/E1 T1/E1
Signaling and Audio
PBX
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 14
CAS - R2
R2 Signaling
Line Signaling
Inter-register Signaling
PSTN
E1 E1
Line Signaling
Audio+ Inter-register Signaling
PBX
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 15
Signaling - CCS
CCS (Common Channel Signaling) transmits the signaling
information (control information) on a separate channel from
the audio. Signaling channel controls multiple audio channels.
For example, PRA and SS7.
PSTN
T1/E1 T1/E1
Signaling Audio
PBX
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 16
CCS - SS7
Signaling System No. 7 (SS7) is a set of telephony signaling
protocols which are used to set up most of the PSTN calls.
The network can be made up of several link types and three
signaling nodes - Service Switching Point (SSPs), Signal Transfer
Point (STPs), and Service Control Point (SCPs).
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 17
CCS - PRA
PRA consists of B-channel and D-channel;
T1 PRA consists of “23B+D”, E1 PRA contain ”30B+D”.
PSTN
E1/T1 E1/T1
D-channel: 64kbps
23 or 30 B-channel: 64kbps
PBX
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 18
CCS - PRA
Q.931
I.431/I.430
Q.921(LAPD)
Point to
point user
signaling
PRA
1
2
3
4
5
6
7
OSI
Physical Layer
Provides an electrical, mechanical, and procedural
interface to the transmission medium.
Data Link Layer
Provides the functional and procedural means to
transfer data between network entities and might
provide the means to detect and possibly correct errors
that may occur in the physical layer.
Network Layer
Responsible for packet forwarding including routing
through intermediate routers, whereas the data link
layer is responsible for media access control, flow
control and error checking.
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 19
PRA Basic Call Flow
SETUP
network caller
SETUP ACKNOWLEDGE
ALERTING
CONNECT
CALL PROCEEDING
CONNECT ACKNOWLEDGE
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 20
Traditional Voice Application Network
…
PBX
Phone Phone
New York Beijing
…
PBX
Phone Phone
PSTN
SS7/PRA
1
2
Phone
3
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 21
Fax Application
Fax machine can transmit signal through the existing PSTN
telephone network.
Fax machine needs modulation and demodulation for fax
communication.
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 22
Modem
A modem (modulator-demodulator) is a device that modulates
an analog carrier signal to encode digital information, and also
demodulates such a carrier signal to decode the transmitted
information.
The goal is to produce a signal that can be transmitted easily
and decoded to reproduce the original digital data.
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved. Page 23
Summary
Traditional terminals and PBX structure.
The narrow bandwidth trunk protocols about traditional voice
network.
Thank you www.huawei.com
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