This document discusses digital T-carriers and multiplexing. It describes various multiplexing techniques including time division multiplexing, frequency division multiplexing, and wavelength division multiplexing. It also discusses T1 digital carriers which carry 24 channels of digital data at 1.544 Mbps using time division multiplexing. Channel banks are used to convert analog signals to digital signals to be carried on T-carrier lines. Fractional T-carriers allow customers to purchase less than the full 24 channels of a T1. The document also covers digital signal hierarchy and uses of digital terminals for voice, data, pictures and video.

1. Digital T-Carriers and
Multiplexing
Group Reporters:
Bugayong, laurens Luis L.
Ramos, Romel R.
Costiniano, Mariela
Garcia, Gerald
Alarcon, Mariel Klaudine V.

2. Introduction

3. Multiplexing.
• Sometimes contracted to MUXING.
• is a method by which multiple analog message
signals or digital data streams are combined
into one signal over a shared medium.
• DEVICES THAT ARE USE FOR MULTIPLEXING:
– Multiplexer (MUX), a device that perform a
multiplexing
– Demultiplexer (DEMUX), A device that perform
the reverse function of the Multiplier.

4. Types of Multiplexing.
• Space Division Multiplexing
• Phase Division Multiplexing
• Time Division Multiplexing
• Frequency Division Multiplexing
• Wavelength Division Multiplexing
• Others..
– Polarization Division Multiplexing
– Orbital Angular Momentum Multiplexing
– Code Division Multiplexing

5. Space Division Multiplexing.
• It implies different point-to-point wires for
different channels.
Examples:

6. Phase Division Multiplexing
• It is a technique which allows two DSBSC
(Double Sideband Suppressed carriers)
channels sharing a common suppressed
carrier to occupy the same spectrum space.

7. Frequency Division Multiplexing
• Frequency-division multiplexing (FDM) is
inherently an analog technology. FDM
achieves the combining of several signals into
one medium by sending signals in several
distinct frequency ranges over a single
medium.

9. Wavelength Division Multiplexing
• Is a technology which multiplexes a number of
optical carrier signals onto a single optical
fiber by using different wavelengths (i.e.,
colors) of laser light. This technique enables
bidirectional communications over one strand
of fiber, as well as multiplication of capacity.

11. Time Division Multiplexing
• technology which uses time, instead of space
or frequency, to separate the different data
streams.

14. T1 Digital Carrier

15. T1 Digital Carrier
• 24 channels
• Sampled 800 times/second
• 1/24 total frame time
• 64 KBps
• 192 Bits per frame
• 1.536 Mbps
• Then later when an additional bits called the
FRAMING BIT added to each frame now it
became 1.544 Mbps

17. Channel Banks.
• A channel bank is a device that converts analog
signals into digital signals to be carried over
higher-speed lines between the central office and
other exchanges. The analog signal is converted
into a digital signal that transmits at a rate of 64
thousand bits per second ( Kbps ). This 64 Kbps
signal is a standard known as a DS0 signal. The
signal is multiplexed with other DS0 signals on
the same line using time-division multiplexing (
TDM ) . Usually, the digital information is put on
each DS0 signal using pulse code modulation (
PCM ).

18. Formats:
• Superframe TDM formats
• Extended Superframe Formats

19. Extended Superframes
• It not only provide frame synchronization but also error detection and a data
channel, all using the framing bit.
• The value in every 193 bits (in bits 193, 386 & so on) are used for three purpose:
1. Every 4th bit of this 24 bit cycle (i.e. the framing bits for frames 4,8,12,16,20 and
24) goes through the pattern 001011.This provide frame synchronization.
2. The framing bits for frames 2,6,10,……22 are used to send a 6 bit CRC,
generated from the data in previous 24 frames. This provide “Error
detection”.
3. The Channel Service Units (CSU) can then track the error rate and generate an
alarm if it gets too high. This error checking is done constantly while the links is
in service and for any type of data.
4. The remaining framing bits(for frames 1,3,5,7,….,23) provide a 4 kbps
supervisory data channel that is used for other functions such as remote
configuration and monitoring of CSU.
5. The 8th bit in every channel of frames 6,12,18 & 24 is used for signaling
between central offices.

21. Fractional T-Carrier Series.
• A Fractional T-carrier is one or more channels bundled
together and sold to a customer as a set. However less than
the full set of 24 channels is available to the customer.
• This allows a customer to purchase less than a full T1’s BW
at lower cost.
• The individual channels can be voice or data and a
CSU/DSU is used to split the channels.
• The fractional T-carrier emerged because standard T1
carriers provide a higher capacity (higher bit rate) than
most users require.
• It distributes the channels (i.e bits) in a standard T1 system
among more than one user, allowing several subscribers to
share one T1 line.

22. • Bit rates offered with fractional T1-carrier
system are 64 kbps(1-channel), 128 kbps(2-
channels), 256 kbps(4-channels), 384 kbps(6-
channels),512kbps(8-channels) and 768
kbps(12-channels) with 384 kbps(1/4T1) and
(1/2T1) being the most common.
• The minimum required data rate required to
propagate video information is 384 kbps.

24. Digital Signal Service
• Telephone companies implement TDM through a hierarchy of digital
signal, known as Digital Signal (DS) service.
DS Line Rate(Mbps) Voice
Channels
Services
DS-0 (Single Digital
Channel)
T-1
64Kbps 1 Voice & Data
DS-1 T-1 1.544 24 DS-0 Voice & Data
DS-2 T-2 6.312 4 DS-1
96 DS-0
Voice or Data, Picture
Phone
DS-3 T-3 44.736 7 DS-2 or 28
DS-1 or
672DS-0
Voice or Data, Picture
Phone, Broadcast
DS-4 T-4 274.176 4032 DS-0 Voice or Data, Picture
Phone, Broadcast
DS-5 T-5 560.160 8064 Voice or Data, Picture
Phone, Broadcast

25. TDM Hierarchy
4.25

26. MASTER GROUP &
COMMERCIAL TELEVISION
• The master group terminal receives voice band
channels which are multiplexed using FDM.
• The signal processor, shifts the master group signals
frequencies, from a 564 KHz to 3084 KHz bandwidth
to a 0 KHz to 2520 KHz BW.
• DC restoration is also provided to TV signals.
• The master group band is sampled at 5.1 MHz rate
& for commercial TV signal sampling rate is 10.2
MHz, i.e twice of master group rate.
4.26

27. T3 Signal
o/p
(46 Mbps)
Channel
for TV
(46 Mbps)
Recove 1
red
Master
Group
Block Diagram of Master group & Commercial
TV Digital Terminal
4.27
Signal
Process
or
Encoder
(9-bit)
Sampl
er
Signal
Process
or
&
Sampler
Digital
Process
or
TV
Cahnnel
Mast
er
Grou
p
or
TV
Signa
l
Digital
Process
or
Framer
PAM
Signa
l
12
9
T-3
Signal
Decode
r
(9-bit)
2
9
Or
TV
Signal

28. • A 9-bit PCM code is used to digitize each sample of the master
group or television signal.
• The output of digital processor is approx 46 Mbps for master
group and 92 Mbps for TV signal.
As there is no 92 Mbps line speed in the digital hierarchy, the
92 Mbps digital output must be split into two 46 Mbps signals
for TV terminal.
The digital terminal has three main functions:
1. Conversion of the parallel data from the output of the
encoder to the serial data.
2. Frame synchronizing bits are inserted.
3. It converts the serial binary signal to form more suitable for
transmission.
4.28

29. Picture Phone Terminal
1. Used to transmit the low quality video signals for the
use of non dedicated subscribers.
2. This picture phone signal is encoded into T2 capacity
of 6.312 Mbps, which is less than that for commercial
network broadcast signals.
3. Thus, reduced cost and affordability are achieved.
4. It allows adequate details and contrast resolution to
satisfy the average picture phone subscriber.
5. Picture phone service is ideally suited to a DPCM.
4.29

30. DATA TERMINAL
• These are designed to transmit the signals other than voice.
• In most of the cases, the data rate generated by each individual
subscriber are substantially less than the data rate capacities of
digital lines.
• Therefore, it seems only logical that terminals be designed that
transmit data signal from several sources over the same digital
line.
• Data coding method is more efficient & it codes the
transition time . The coding format is as follows:
1. It uses 3 bit code to indentify when transition occurs on the
data and whether the transition is from ‘1’ to ‘0’ or vice versa.
 First bit is referred as “Address bit”.
 Second bit indicate “Transition bit”
 Third bit indicate “Direction of transition or sign bit”
4.30