Transcript unit 4 PPT

UNIT-IV
Digital Subscriber Access
ISDN
• The telephone network has evolved into a
digital one with digital exchanges and links
• The signalling system has become a digital
message-oriented common channel signalling
system (SS#7)
• The term ‘Integrated Digital Network’ is used
to describe these developments
2
ISDN
• The Public Switched Telephone network is still
analogue from the subscriber to the local
exchange
• The need has arisen to extend the digital
network out to subscribers and to provide a
single standardised interface to all different
users of public networks
• ISDN fulfils that need
3
Integrated Services Digital Network
Packet
switched
network
Telephone
Circuit
switched
network
Data
terminal
PBX
Alarm
LAN
Customer
ISDN
Interface
ISDN
central
office
Databases
‘Digital
pipe’
Other
Networks
& services
4
ISDN
• In Practice there are multiple networks
providing the service nationally
• The user however, sees a single network
5
Benefits to Subscribers
• Single access line for all services
• Ability to tailor service purchased to suit
needs
• Competition among equipment vendors due
to standards
• Availability of competitive service providers
6
Architecture
Integrated Digital Network
Common
physical
interface
ISDN
central
office
Digital circuitswitched backbone
Packet-switched network
ISDN subscriber loop
Basic 2B+D
Primary 30B+D
Network-based
processing
services
7
ISDN Standards
•
•
•
•
•
•
•
•
•
Contained in the I-series recommendations
Issued by CCITT (now ITU-T)
Six main groupings I.100 to I.600 series
I.100 series - General Concepts
I.200 series - Service Capabilities
I.300 series - Network Aspects
I.400 series - User-Network Interfaces
I.500 series - Internetwork Interfaces
I.600 series - Maintenance Principles
8
ISDN Channels
• The Digital pipe is made up of channels - one
of three types
• B channel, D channel or H channel
• Channels are grouped and offered as a
package to users
9
B Channel
• B channel-64 kbps
• B is basic user channel
– can carry digital data or PCM-encoded voice
– or mixture of lower rate traffic.
10
B Channel
•
•
•
•
•
Four kinds of connection possible
Circuit-switched
Packet-switched - X.25
Frame mode - frame relay (LAPF)
Semipermanent - equivalent to a leased line
11
D Channel
• D Channel - 16 or 64 kbps
• Carries signalling information to control
circuit-switched calls on B channels
• Can also be used for packet switching or lowspeed telemetry
12
H Channel
• Carry user information at higher bit rates
384kbps or 1536kbps or 1920kbps
• Can be used as a high-speed trunk
• Can also be subdivided as per user’s own TDM
scheme
• Uses include high speed data, fast facsimile,
video, high-quality audio
13
ISDN Channels and their Applications
B Channel
(64 kbps)
Digital voice
High-speed data
(e.g. packet and
circuit switched
data)
Other (e.g. fax,
slow video)
D Channel
(16/64 kbps)
Signalling
(using SS#7)
Low- speed
data, (e.g.
packet, terminal,
videotex)
Other (e.g.
telemetry)
H Channel
(384/1536 kbps)
High-speed trunk
Very high speed
data
Other (e.g. fast
fax. Video)
14
ISDN Basic Access
• Intended for small business and residential
use
• A single physical interface is provided
• Data rate is 144kbps plus 48kbps overhead
bits totalling 192 kbps
• Most existing subscriber loops can support
basic access
15
ISDN Primary Access
• Intended for users with greater capacity
requirements
• Example would be a digital PBX
• Two standards exist
– 1.544 Mbps American
– 2.048 Mbps European
16
ISDN Primary Access
• Typically it is structured as 30 B channels plus
one 64kbps D channel (Europe)
• Can also be structured as H channels
– 5H0 +D for a 2.048 Mbps interface
– or 1H12 +D
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ISDN Frame Structure Basic Rate Access
48 bits in 250 usec
TE to NT
FL
B1
LDL
F
L
a
B2
LDL
B1
LDL
B2
LDL
FL
B1
F
EDA N
a
B2
E DM
B1
EDS
B2
EDL
8 bits
F= Framing bit
L = dc balancing bit
E = D-echo channel bit
A = Activation bit
NT to TE
Fa = Auxiliary Framing bit
N = opposite of Fa
M = multiframing bit
B1 = B channel bits
B2 = B channel bits
D = D channel bits
S = Spare bits
18
ISDN Contention Resolution
• Several TE’s can share a single line
• How is contention resolved?
• B-channel Traffic
– No contention as each channel dedicated to
particular TE
• D - Channel used for data and control so
requires a contention resolution mechanism
19
D Channel Contention
• Incoming Traffic
– LAPD protocol resolves contention
• Outgoing Traffic
– Multiple devices share D channel
– Contention resolution algorithm required
20
D Channel Contention
•
•
•
•
Idle TEs sends binary 1s on D channel
This means no signal (pseudoternery)
NT echos received binary value back as echo bit
When NT wishes to send on D channel, it listens
to echo bits
• If it hears a string of 1’s equal in length to a
threshold value Xi, it may transmit
• Otherwise it must wait
21
ISDN Primary Interface
• Multiple channels multiplexed on single
medium
• Only point to point configuration is allowed
• Typically supports a digital PBX and provides a
synchronous TDM facility
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ISDN Primary Access Frame Formats
125 micro-seconds 193 bits
timeslot 1
Timeslot 24
timeslot 2
F
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
……………….
1 2 3 4 5 6 7 8
Interface at 1.544 Mbps
125 micro-seconds 256 bits
timeslot 0
Framing Channel
1 2 3 4 5 6 7 8
Timeslot 31
timeslot 1
1 2 3 4 5 6 7 8
……………….
Interface at 2.048Mbps
1 2 3 4 5 6 7 8
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ISDN Protocol Architecture
Application
Presentation
Session
End-end
user
signalling
Transport
Network
I.451/Q.931
X.25
for further
call control packet level
study
Datalink
LAPD (Q921)
Physical
Physical
X.25
packet level
Frame
Relay
LAPB
I.430 basic interface + I.431 primary interface
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Broadband ISDN
• Recommendations to support video
services as well as normal ISDN services
• Provides user with additional data rates
– 155.52 Mbps full-duplex
– 155.52 Mbps / 622.08 Mbps
– 622.08 Mbps full-duplex
• Exploits optical fibre transmission
technology
• Very high performance switches
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B-ISDN Architecture
BISDN
TE
LFC
User to Network
Signalling
TE = Terminal equipment
LFC = Local function capabilities
Narrowband
Capabilities
Broadband
Capabilities
LFC
TE
Inter-exchange
Signalling
Capabilities
26
B-ISDN
• ATM is specified for Information transfer
across the user-network interface
• Fixed size 53 octet packet with a 5 octet
header
• Implies that internal switching will be packetbased
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BISDN Protocol Structure
Plane management function
Control Plane
User Plane
Higher Layers:
protocols and functions
Higher Layers:
protocols and functions
Adaptation Layer
ATM Layer
Physical medium dependent Layer
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Digital
Subscriber
Line BLOCK
DIAGRAM
Asymmetrical DSL (ADSL)
• ADSL divides up the available frequencies in a
line on the assumption that most Internet
users look at, or download, much more
information than they send, or upload.
– Under this assumption, if the connection speed
from the Internet to the user is three to four
times faster than the connection from the user
back to the Internet, then the user will see the
most benefit (most of the time).
Asymmetrical DSL (ADSL)
• ADSL is an adaptive technology.
• The system uses a data rate based on the
condition of the local loop line.
• Speed:
Most existing local loops can handle
bandwidths up to 1.1 MHz.
ADSL Modem
Two standards for ADSL
1. Discrete multitone (DMT)
2. Carrierless amplitude/phase (CAP)
CAP - three distinct bands:
1. Voice channel - 0 to 4 KHz
2. Upstream channel - 25 and 160 KHz
3. Downstream channel - 1.5 MHz
Carrierless amplitude/phase (CAP)
• Advantage:
Minimizes the possibility of interference
between the channels on one line, or
between the signals on different lines
Discrete multitone (DMT)
• Constantly shifts signals between different
channels, searching for the best channels for
transmission and reception
Discrete multitone (DMT)
Asymmetrical DSL (ADSL)
• ADSL is an asymmetric communication
technology designed for residential users; it is
not suitable for businesses.
Distance Limitations
• ADSL is a distance-sensitive technology
• The limit for ADSL service is 18,000 feet (5,460
meters)
• At the extremes of the distance limits, ADSL
customers may see speeds far below the promised
maximums
• customers nearer the central office have faster
connections and may see extremely high speeds
OTHER TYPES OF DSL:
• Symmetric DSL (SDSL)
• High-bit-rate DSL (HDSL)
• Very high bit-rate DSL (VDSL)
Symmetric DSL (SDSL)
• Used mainly by small businesses & residential
areas
• Bit rate of downstream is higher than
upstream
High-bit-rate DSL (HDSL)
• Used as alternative of T-1 line
• Uses 2B1Q encoding
• Less susceptible to attenuation at higher
frequencies
• Unlike T-1 line (AMI/1.544Mbps/1km), it can
reach 2Mbps @ 3.6Km
Very high bit-rate DSL (VDSL)
• Uses DMT modulation technique
• Effective only for short distances(300-1800m)
• Speed:
downstream : 50 - 55 Mbps
upstream
: 1.5-2.5 Mbps
PSTN
Review
Digital Loop Carrier
Pushes the digital PSTN closer to customer
AT&T SLC-40, SLC-96, Nortel DMS P-phone,
TR-08 Mode 1 pair-gain:
Replace 96 pairs with 5 T1s
Access Network
CLASS
5
“pair-gain”
(one spare for “span protection”)
UTP/coax/fiber Street
FTTB/FTTC cabinet
CPE
96 – 10 = 86
TR-08 Mode 2 pair-gain:
Replace 96 pairs with 2 T1s
pedestal
(without “span protection”)
UTP
96 – 4 = 92
TR-08 multiplex 96 lines on:
Mode 1: 4 T1s
Mode 2: 2 T1s (2:1 concentration)
GR303/V5.1/V5.2 multiplex up to 2048 lines
telephony
Slide 44
Fiber in the Loop
What is FTTP?

Fiber To The “x” (FTTx, with x being the “C” for the Curb,
or “P” for to the premises) is an important, emerging
technology that will provide customers with new featurerich services and improved quality of current services.
Why FTTP?
Consumers
will require additional bandwidth to
the home in the near future
Competition is beginning to offer a “triple-play”
(i.e., voice, video, and data) bundle
FTTP provides SPs with the ability to provide
“cutting edge” technology and “best-in-class”
services
Deploying a fiber optic cable to each premises
will provide an extraordinary amount of bandwidth
for future services
An FTTP based network will result in less
operational expenses
Why FTTP? (Cont’d)
100M
12 - 50M
Access
Bandwidth
Growth
12 – 25M
FTTP has the
necessary
bandwidth to
support near term
and long term
services
1.5M – 3M
256K – 1.5M
144K
2.4 – 56K
DDS
1970’s
ISDN
ADSL
Cable Modem
ADSL2(+)
VDSL
FTTP
2004
Today's applications are continuing to drive demand for increased bandwidth
Historically, unforeseen applications have quickly consumed available
bandwidth and driven the development of higher speed platforms
Why Now? (Cont’d)
 SPs
are losing access lines
– Bundling with the triple-play should reduce the churn
 Competition
with cable providers is forcing action
– Cable Modems currently have over 60% of the HSD market
share and the gap is expected to increase
– Cable companies are beginning to offer voice over cable
– A number of IP telephony trials are currently underway:



Time Warner in Portland, ME
Comcast in Coatesville, PA
Cablevision in LI / NJ
– Experience suggests that cable will be very successful, absent
an effective competitive response.
Matching Application and Network
Requirements
Data Application
Typical bandwidth (downstream)
High Speed Internet Access (browsing, IM,
Chat, FTP, VPN, access, etc)
E-Mail
Up to 3 Mb/s
Live TV on PC
300 to 750 kb/s
Internet Video on Demand
300 to 750 kb/s
Video Conferencing
300 to 750 kb/s
Voice telephony
5 to 128 kb/s
Interactive Games
10 to 750 kb/s
Broadcast TV – (e.g., MPEG2)
2 to 6 Mb/s
High definition TV – HDTV
12 to 19 Mb/s
Pay Per View and NVOD (e.g., MPEG2)
2 to 6 Mb/s
As above
Deployment of FTTH

Plan is to reach 1 Million Homes by end of 2004 in the
20Mb to 30Mb rate

Double that rate as we move into 2005

Reach 100Mb by 2007
Picture Messaging
Voice
Data
Video Conferencing
Common Protocol
Common Infrastructure
Video Service
Voice over IP
Gaming
Virtual Private Network
FTTP Basics
Full Service Access Network (FSAN) – Primary source of PON standards.
Created by service providers in order to facilitate suitable standards.
FSAN Standards – ITU-T G.983
Passive Optical Network (PON) – a point-to-multipoint local access Network.
Optical Line Terminal (OLT) – active component typically located in the central
office.
Passive Optical Splitter – distributes optical signal from a single fiber to multiple
fibers, merges signals from all fibers, & connects them to the OLT receiver.
Optical Network Terminal (ONT) – housed in a network interface device
enclosure.
FTTP Lingo
PON – Passive Optical Network
OLT – Optical Line Terminal
ONT – Optical Network Terminal
FTTP – Fiber to the Premises
APON – ATM PON
BPON – Broadband PON
GPON – Gigabit PON
FSAN PON Solution
How Does an APON/BPON Work?
CO, Feeder: OLT
(Optical Line Termination)
Outside Plant: Optical Distribution Network
Customer Premise: ONT
(Optical Network Termination)
Downstream: 622 Mbps @ 1490nm
ATM switch,
PSTN,
Internet
Passive Optical Splitter
Services to user:
POTS,
Internet Access
Upstream: 155 Mbps @ 1310nm
Downstream: Time Division Multiplex
ONT A
A B C + GRANT
Upstream: Time Division Multiple Access
ONT A A
A B C + GRANT
ONT B
ONT B
ONT C
ONT C
Current Standards

FCC 76.605 - Multichannel Video and Cable
Television Service Requirements, Technical
Standards. Code of Federal Regulations, Title
47, Volume 4, Part 76, Subpart K, Section
76.605 (47CFR76.605).

ITU-T Recommendation G.983.1 - Broadband
optical access systems based on Passive
Optical Networks (PON).
Overview



Satellite technology has progressed tremendously over
the last 50 years since Arthur C. Clarke first proposed its
idea in 1945 in his article in Wireless World.
Today, satellite systems can provide a variety of services
including broadband communications, audio/video
distribution networks, maritime navigation, worldwide
customer service and support as well as military
command and control.
Satellite systems are also expected to play an important
role in the emerging 4G global infrastructure providing
the wide area coverage necessary for the realization of
the “Optimally Connected Anywhere, Anytime” vision
that drives the growth of modern telecom industry.
Course Objectives
This course aims to:
 Provide a broad overview of the status of digital satellite
communications.
 Discuss main physical, architectural and networking
issues of satellite systems.
 Provide in-depth understanding of modern modulation,
coding and multiple access schemes.
 Review the state of the art in open research areas such
as speech and video coding, satellite networking, internet
over satellite and satellite personal communications.
 Highlight trends and future directions of satellite
communication
Section 1: The SATCOM
Industry – System Design
Issues

An Overview of Satellite Communications
– Examples of current military and commercial systems.
– Satellite orbits and transponder characteristics (LEO, MEO, GEO)
– Traffic Connectivity: Mesh, Hub-Spoke, Point-to-Point, Broadcast

Basic satellite transmission theory
– Impairments of the Satellite Channel: Weather and Doppler effects,
Channel models.
– Communications Link Calculations: Definition of EIRP, Noise
temperature and G/T ratio, Eb/No. Transponder gain and SFD. Link
Budget Calculations. Down-link requirements. Design of satellite links to
achieve a specified performance.
– Earth Station Antenna types: Pointing/Tracking. Small antennas at Ku
band. FCC-Intelsat-ITU antenna requirements and EIRP density
limitations.
– Brief introduction to implementation issues: LNA, Up/down converters,
oscillator phase noise.
Section 2: Elements of
Transponder Design – The
Baseband


Physical Layer of the Transponder – The Baseband
System
Introduction to the theory of Digital Communications:
Modulation, Equalization and FEC
– Digital Modulation Techniques: BPSK, QPSK, Nyquist signal
shaping.
– Overview of Bandwidth Efficient Modulation (BEM)
Techniques: M-ary PSK, Trellis Coded 8PSK, QAM.
– PSK Receiver Implementation issues: Carrier recovery,
phase slips, differential coding.

Overview of Forward Error Correction (FEC):
Standard FEC types (Block and Convolution Coding
schemes, Viterbi Decoding), Coding Gain,
Concatenated coding, Turbo coding.
Section 3: Multiple Access
Issues


Spread Spectrum Techniques: Military and
commercial use of spread-spectrum. DirectSequence PN, Frequency-Hop and CDMA systems.
Principles of Multiple Access Communications
– Multiplexing & Multiple Access FDD/TDD, FDMA, TDMA
– Concepts of Random Access: ALOHA, CSMA


Multiple Access Techniques: FDMA, TDMA, CDMA.
DAMA and Bandwidth-on-Demand (BoD).
TDMA Networks: Time Slots, Preambles, Suitability
for DAMA and BoD.
Section 4: SATCOM
Networks and Services

Satellite Communication Systems & Networks
– Characteristics of IP and TCP/UDP over satellite:
Unicast and Multicast. Need for Performance

Enhancing Proxy (PEP) techniques.
– VSAT Networks and their system characteristics.
– DVB standards and MF-TDMA

The Future of SATCOM
– SATCOM’s role in the emerging 4G Information
and Communications (ICT) infrastructure.
Intelsat

INTELSAT is the original "Inter-governmental Satellite
organization". It once owned and operated most of the World's
satellites used for international communications, and still
maintains a substantial fleet of satellites.
INTELSAT is moving towards "privatization", with increasing
competition from commercial operators (e.g. Panamsat, Loral
Skynet, etc.).
INTELSAT Timeline:
Interim organization formed in 1964 by 11 countries

Permanent structure formed in 1973

Commercial "spin-off", New Skies Satellites in 1998

Full "privatization" by April 2001
INTELSAT has 143 members and signatories listed here.




Intelsat Structure
Eutelsat

Permanent General Secretariat opened September 1978
Intergovernmental Conference adopted definitive statutes with 26 members on
14 May 1982
Definitive organization entered into force on 1 September 1985

General Secretariat -> Executive Organ

Executive Council -> EUTELSAT Board of Signatories

Secretary General -> Director General

Current DG is Giuliano Berretta
Currently almost 50 members
Moving towards "privatization"
Limited company owning and controlling of all assets and activities






Also a "residual" intergovernmental organization which will ensure that basic
principles of pan-European coverage, universal service, non-discrimination and
fair competition are observed by the company
Eutelsat Structure
Communication Satellite


A Communication Satellite can be looked upon as a large
microwave repeater
It contains several transponders which listens to some
portion of spectrum, amplifies the incoming signal and
broadcasts it in another frequency to avoid interference
with incoming signals.
Motivation to use Satellites
Satellite Missions
Source: Union of Concerned Scientists [www.ucsusa.org]
Satellite Uplink and Downlink

Downlink
– The link from a satellite down to one or more
ground stations or receivers

Uplink
– The link from a ground station up to a satellite.

Some companies sell uplink and downlink
services to
– television stations, corporations, and to other
telecommunication carriers.
– A company can specialize in providing uplinks,
downlinks, or both.
Satellite Uplink and Downlink