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digital-communication-report.pptx
1.
2. Digital Communication
• Is an electronic transmission of information that has been
encoded digitally.
• Digital communications allows information to be
communicated over copper wire, fiber-optic cable, and the
air.
3. Standards
• An object of procedure considered by an authority or by
general consent as a basis of comparison.
• Authoritative principles or rules that imply a model or
pattern for guidance by comparison.
4. Digital Communication Standards
• Digital Communication systems and devices operate
using defined industry standards to exchange digital
messages. These standards define the syntax, semantics,
and synchronization of all digital communications and can
be implemented as hardware, software or both.
6. International Standards Organization (ISO)
ISO was started in 1946. The members of ISO are
selected from various governments throughout the world.
The ISO creates the sets of rules and standards for
graphics and document exchange and provides models for
equipment and system compatibility, quality and reduced
costs. The ISO is responsible for coordinating the work of
the other standards organizations. The member body of the
ISO from the United States is the American National
Standards Institute (ANSI).
7. International Telecommunications Union-
Telecommunications Sector(ITU-T)
It was formerly called as CCITT (Committe Consultant for International
Telephony and Telegraphy). It is situated in Geneva, Switzerland.
Membership in the ITU-T consists of government authorities and
representatives from many countires.
It develops the recommended sets of rules and standards for telephone
and data communications. It has developed three sets of specifications:(1).
The V series for modem interfacing and data transmission over telephone
lines (2). The X series for data transmission over public digital
networks,Email and directory serivces (3). The I and Q series for Integrated
Services Digital Network (ISDN) and its extension is Broadband ISDN. The
ITU-T is separated into 14 study groups
8. Institute of Electrical and Electronics Engineering
(IEEE)
• The IEEE is an international professional organization
founded in united states and is comprised of electronics,
computer and communications engineers.
• The IEEE works along with ANSI to develop
communications and information processing standards
with the aim of advancing theory, creativity and product
quality in any field associated with electrical engineering.
9. American National Standards Institute(ANSI)
• It is an official standards agency for the united states and
is the U.S voting representative for the ISO
• ANSI is a completely private, nonprofit organization
comprised of euipment manufacturers and users of data
processing equipment and services.
• ANSI membership is comprised of people from
professional societies, industry associations,
governmental and regulatory bodies and consumer
groups.
11. DIGITAL HIERACHY TRANSMISSION STANDARDS
• T-carrier(North america, Japan)
• E-carrier(Europe, South america)
• ISDN BRI / ISDN PRI
• Sonet/SDH(Worldwide new standards)
12. T-carrier
• T-carrier is a member of the series of carrier system that
developed by AT&T Bell Laboratories for digital
transmission of multiplexed telephone calls.
• The first version, the Transmission System 1(Tt1) was
introduced in 1962.
• T-1 is the method that is conventionally used by the
telephone companies for transporting digitized telephone
communincation among central offices
13. North American Standard Data Rates
8 bits/sample x 24 channels + framing bit = 193 bits/frame
The sampling rate of each channel is 8000 per second;
thus, in ordere to accommodate the entire group, 8000
frames must be submitted each second. The data rate for
this operation is:
193 bits/frame x 8000 frames/sec = 1,544,000 bits/sec
=1.544 Mb/s
15. T-1 Carrier
• T1 and up is the terminology for digital, two-way transmission of
voice, data, or video over a single highspeed circuit. The
transmission rate is based on the bandwidth for one voice channel
in digital form. This channel is called DS-0 and consists of 64 kbps
of bandwidth.
• By Time Division Multiplexing 24 DS-0 channels, T1 is formed. But
there is more. To separate the different channels a framing bit is
used. For framing 8000 bps are used.
• T1 gives you 24 analog voice channels plus the framing rate.
16.
17. T-1 carrier
• T-carrier technology is still being used today by Internet service
providers (ISPs), specifically the T-1. Owners of small businesses,
apartment buildings, and hotels once relied on T1 lines as their
primary method of internet access before business-class DSL
became prevalent. (T1) transmission are common in the US
(North America), Canada, and Japan.
• A T-1 physically includes two twisted pairs of copper wire. The
pairs use a full-duplex configuration in which one pair sends
information while the other receives information.
18. • T-2 are used in Japan, but not offered to the public in
the United States.
• T-4 is now obsolete, and used only in a few rare
instances.
19. European Standards Data Rates
• A hierarchy established for European
telecommunications, as defined by the Conference
Europeene des Postes et Telecommunications (CEPT)
standards
20. CEPT DATA RATES:
• Based on a group of 32 timeslots per frame, and two
channels transmit signaling and synchronization
information.
• (8 bits/sample) x (32 channels) x (8,000 frames/sec)
= 2,048,000 bits/sec = 2.048 Mb/s
21. EUROPEAN STANDARD DATA RATES:
• CEPT 0 (E0): 64Kb/s (1 standard PCM ch.)
• CEPT 1 (E1): 2.048 Mb/s (32 PCM ch.)
• CEPT 2 (E2): 8.448 Mb/s (4xCEPT 1, or 128 PCM ch.)
• CEPT 3 (E3): 34.368 Mb/s (4xCEPT 2, or 512 PCM ch.)
• CEPT 4 (E4): 139.264 Mb/s (4xCEPT 3, or 2,048 PCM
ch.
22.
23. E-carrier
• The E-carrier is a member of the series of carrier systems
developed for digital transmission of many simultaneous
telephone calls by time-division multiplexing. The European
Conference of Postal and Telecommunications
Administrations (CEPT) originally standardized the E-carrier
system, which revised and improved the earlier American T-
carrier technology, and this has now been adopted by the
International Telecommunication Union Telecommunication
Standardization Sector (ITU-T). It was widely adopted in
almost all countries outside the US, Canada, and Japan. E-
carrier deployments have steadily been replaced by Ethernet
as telecommunication networks transitions towards all IP.
24. E carrier
• E1 (or E-1) is a European digital transmission format
devised by the ITU-TS and given the name by the
Conference of European Postal and Telecommunication
Administration (CEPT). It's the equivalent of the North
American T-carrier system format. E2 through E5 are
carriers in increasing multiples of the E1 format. The E-1
is a member of the series of carrier systems developed for
digital transmission of many simultaneous telephone calls
by time-division multiplexing.
25. E carrier
• An E1 link operates over two separate sets of wires, usually
unshielded twisted pair (balanced cable) or using coaxial
(unbalanced cable). A nominal 3 volt peak signal is encoded
with pulses using a method avoiding long periods without
polarity changes.
• The E1 signal format carries data at a rate of 2.048 million bits
per second and can carry 32 channels of 64 Kbps each. E1
carries at a somewhat higher data rate than T-1 (which carries
1.544 million bits per second) because, unlike T-1, it does not
do bit-robbing and all eight bits per channel are used to code
the signal. E1 and T-1 can be interconnected for international
use.
26.
27. SYNCHRONOUS OPTICAL NETWORK(sonet)
• Acts as a carrier of multiple higher level application protocol.
• Like Ethernet, SONET provides layer 1 or interface layer technology
or physical layer.
• It was developed by AMERICAN NATIONAL STANDARDS
INSTITUTE (ANSI) Synchronous Digital Hierarchy (SDH) was
developed by Consultative Committee for International Telephony
and Telegraphy (CCITT). Now International Telecommunications
Union – Telecommunications Service Sector (ITU-T).
• It also contains recommendation for the standardization of Fiber
Optic Transmission System (FOTS) equipment by different
manufacturers.
28.
29. STS DATA RATES:
• SONET defines a hierarchy of signaling levels called
Synchronous Transport Signals (STSs). Each STS level
supports a certain data rate.
• OC or the Optical Carriers are physical links defined to
carry each level of STS. OC levels describe the
conceptual and physical specifications of the links
required to support each level of signaling.
30.
31. • A SONET STS-n - signal is transmitted at 8000 frames per
second.
STS -1 Signal Data Rate w/ Overheads:
• STS-1, like other STS signals, sends 8000 frames per
second. Each STS-1 frame is made of 9 by (1 × 90) bytes.
Each byte is made of 8 bits.
32. STS -1 Signal Data Rate w/o Overheads:
• The user data part in an STS-1 frame is made of 9
rows and 86 columns.
35. The SONET Network
• Point-to-Point – In this configuration the SONET path and
the service path are identical and this synchronous island
can exist within an asynchronous network world.
36. The SONET Network
• Point-to-Multipoint – A point-to-multipoint architecture
includes adding and dropping circuits along the way. The
ADM (add/drop multiplexer) is typically placed along a
SONET link to facilitate adding and dropping tributary
channels at intermediate points in the network.
37. The SONET Network
• Hub Network - The hub network architecture
accommodates unexpected growth and change more
easily than simple point-to-point networks. A hub
concentrates traffic at a central site and allows easy re-
provisioning of the circuits.
38. The SONET Network
• Ring Architecture – The SONET building block for a ring
architecture is the ADM. The main advantage of the ring
topology is its survivability… if a fiber cable is cut, the
multiplexers have the intelligence to send the services
affected via an alternate path through the ring without
interruption.
40. ISDN history
• ISDN (Integrated Services Digital Network) is a digital telephone
standard designed to replace analogue connections by utilizing
ordinary copper wires that are used in standard analogue
telephone systems.
• It started as a recommendation within the International
Telecommunication Union (ITU)'s Red Book in 1984, although
prior to 1992, the ITU was known as the International Telegraph
and Telephone Consultative Committee (CCITT).
• The ITU is responsible for developing recommendations on
international standards within the industry.
41. ISDN
• ISDN - is a set of
communication standards developed to provide
digital transmission of both voice and data,
resulting in better quality and speeds above those
traditional circuits of Public Switched Telephone
Network (PSTN) systems.
• ISDN – Used for voice, image and data
54. ISDN channels
Hybrid Channel (H-Channel)
• Used at high BW requirements
• 384/1536/1920 kbps
• Used for video, video-conferencing, high speed data/audio
etc,.
• Can be sub divided as per channel
• Can be used as B channel for high BW needs.
58. BRI (Basic Rate Interface)
• BRI can also be known as BA
(Basic Access). This operates a
single 16 Kbps D channel and two
64 Kbps B channels. Although it isn't
usually pointed out, the BRI total
speed is 192 Kbps; this is because
you have an additional 48 Kbps
overhead for framing and
synchronization on the D channel
(64 * 2) + (16 + 48) = (128 + 64) =
192 Kbps.
59. PRI (Primary Rate Interface)
• PRI can also be known as PA (Primary Access). This can operate in two different
modes, depending on geographic location.
• For European locations, PRI is made up of 30 x 64 Kbps B channels and a single 64
Kbps D channel, giving a total of 2.048 Mbps, which is also known as an E1 line (or
DS1).
• For American and Japanese locations, PRI is made up of 23 x 64 Kbps B channels
and a single 64 Kbps D channel, giving a total of 1.544 Mbps, which is also known
as a T1 line (or DS1).
• Framing and Synchronization is at 8 Kbps for T1 or 64 Kbps
for E1. T
I
E
I
T1 PRI is commonly referred to as
"23B+D"
E1 PRI is commonly referred to as
"30B+D"
65. ISDN Layer 1
• ISDN physical layer (Layer 1) frame formats differ depending on whether the frame
is outbound (from terminal to network) or inbound (from network to terminal).
• The frames are 48 bits long, of which 36 bits represent data.
• The bits of an ISDN physical layer frame are used as follows:
– F: Provides synchronization
– L: Adjusts the average bit value
– E: Ensures contention resolution when several terminals on a passive bus contend
for a channel
– A: Activates devices
– S: Is unassigned
– B1, B2, and D: Handle user data
66.
67. ISDN SPECIFICATIONS: Layer 1
• Multiple ISDN user devices can be physically attached to one
circuit.
• In this configuration, collisions can result if two terminals transmit
simultaneously.
• Therefore, ISDN provides features to determine link contention.
• When an NT receives a D bit from the TE, it echoes back the bit in
the next E-bit position.
68. ISDN SPECIFICATIONS: Layer 1
• Terminals cannot transmit into the D channel unless they first detect
a specific number of ones (indicating “no signal”) corresponding to
a pre-established priority.
• If the TE detects a bit in the echo (E) channel that is different from
its D bits, it must stop transmitting immediately.
• This simple technique ensures that only one terminal can transmit its
D message at one time.
69. ISDN SPECIFICATIONS: Layer 2
• Layer 2 of the ISDN signaling protocol is Link Access Procedure, D channel
(LAPD).
• As the expansion of the LAPD acronym indicates, this layer is used across the
D channel to ensure that control and signaling information flows and is
received properly.
• The LAPD protocol is formally specified in ITU-T Q.920 and ITU-T Q.921
70.
71. ISDN SPECIFICATIONS: Layer 3
• Two Layer 3 specifications are used for ISDN signaling: ITU-T (formerly
CCITT) I.450 (also known as ITU-T Q.930) and ITU-T I.451 (also known as
ITU-T Q.931).
• Together, these protocols support user-to-user, circuit-switched, and packet-
switched connections.
• A variety of call-establishment, call-termination, information, and
miscellaneous messages are specified, including SETUP, CONNECT,
RELEASE, USER INFORMATION, CANCEL, STATUS, and
DISCONNECT.
