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Telecommunication Network Course Details Semester 1, 2006 Prof. Madya Dr Mahamod Ismail Lecturer in UKM since 1987. Diploma - UTM (Electrical Communication), 1981 BSc. – Univ of Strathclyde (Electronics & Electrical) ,UK, 1985

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telecommunication network

TelecommunicationNetwork

Course Details

Semester 1, 2006

prof madya dr mahamod ismail
Prof. Madya Dr Mahamod Ismail
  • Lecturer in UKM since 1987.
  • Diploma - UTM (Electrical Communication), 1981
  • BSc. – Univ of Strathclyde (Electronics & Electrical) ,UK, 1985
  • MSc – UMIST, Manchester (Communication Eng. & Digital Electronics), 1987
  • PhD – Univ of Bradford, Mobile Communication, 1996
  • Research Area – Mobile Communication & Wireless Networking
  • Team Engineer, Tiungsat, 1997-98, Uni. of Surrey, U.K.
  • Guest Professor, University Duisburg Essen, Germany , 2002
  • Currently: Coordinator UKM Mercator Office, Fac. of Eng. UKM
  • Email: mahamod@eng.ukm.my, dr_mbi@yahoo.com
  • Telephone: 019-3275425, 03-89216191/6322

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syllabus program booklet
Syllabus – Program Booklet

KT6123 – TELECOMMUNICATION NETWORK

Switching system engineering: Types of public switched network. Switching system: circuit, store and forward, packet. Numbering, routing system and charging. Subscriber function. Telephone system basic requirement. Telephone equipment characteristics. Local circuit and hybrid transformation. Dialing system: decadic and DTMF. Subscriber and group switching. Analog and digital switching. Switching: Strowger, cross-bar and time and space. Digital analysis. Controlling sections. Stored Programmable Controlled exchange. Signaling: subscriber, line and register. Transmission system: FDM and PCM 30/32 channel. CCITT, CCIR function in switching planning. Digital Network: ISDN, SDH. Teletraffic Engineering: telephone traffic performance. Teletraffic and queuing theory. Delay and loss system, Grade of service. Erlang and Bernoulli distribution. Broadband network: ATM and B-ISDN. Intelligent network.

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course outline
Course Outline
  • Introduction
  • Transmission
  • Multiplexing and Hierarchy
  • Switching
  • Telecommunication Traffics
  • Switching Network
  • Signaling
  • Services

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references
References

1. J.E.Flood, Telecommunications Switching, Traffic and Networks, Prentice Hall, 1994

2. E.H. Jolley, Introduction to Telephony and Teleplay, Pittman Publication.

3. Schwartz, M., Telecommunication Networks Protocols, Modelling & Analysis, Addison-Wesley

4. Clarke, M.P., Network & Telecommunications: Design & Operation, Wiley

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evaluation
Evaluation
  • 2 Assignments 30%
  • Midterm exam 20%
  • Quiz 10%
  • Final exam 40%

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assignment 1
Assignment 1
  • Report
    • Format 1
    • Content 5
    • Discussion/Conclusion 2
    • References 2
  • Presentation 5

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telecommunication network8

TelecommunicationNetwork

Introduction

Semester 1, 2006

introduction
Introduction
  • Tele/communications
    • The process of transmitting a message between two remote locations.
    • Message - could be Voice, Music, Textual, Pictorial (graph, diagram, image, etc.) or moving image (video).
  • Recently we have a better proportion of data communications links and speech is being converted into digital forms as well as “data” will eventually be conveyed more naturally in these digital forms.
  • The purpose of telecommunications is to convey information from one location to another.
    • Data : Precise communication
    • Voice : More convenient to convey information, that’s why voice communication has predominated for over a century
  • The telephone network, until the last decade, was almost entirely analog

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slide10

Communication

Telecommunication

Introduction

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introduction11
Introduction
  • Broadband :
    • is a technique where the data to be transmitted is sent using a carrier signal, such as a sinusoidal wave. Many different frequency carrier signal can be transmitted simultaneously, more than one signal can be sent on the same wire.
  • Baseband :
    • a single data signal is transmitted directly on a wire. The data is transmitted directly on the wire using positive and negative voltages. RS-232 interface is an example of baseband transmission.
  • A baseband signal
    • is an information signal that has not undergone the modulation process.
    • represents voice, data, or video information signal.
    • must be band-limited before being used to modulate a carrier signal.

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introduction12
Introduction
  • When data (or any other signal) is to be conveyed outside one’s place, this involves the modulation of the broadband signal onto a carrier frequency, either by
    • Amplitude Shift Keying (ASK)
    • Frequency Shift Keying (FSK)
    • Phase Shift Keying (PSK)
    • or Combination of the ASK and PSK (QPSK, /4-PSK, DQPSK)
  • In baseband signal recently, speech is being conveyed by Pulse Code Modulation (PCM)
  • The standard digital voice channel that available in today has a capacity of 64 Kbps, or a multiplexed of 1.544Mbps [T1], 2.048Mbps [E1]

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telecommunication system

Transmitter

Receiver

Transmission Channel

Telecommunication System

Input Transducer

Encoder

Modulator

Amplifier

Air, Free Space

Copper Cable

Optical Fiber

Output Transducer

Decoder

Demodulator

Amplifier

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telecommunication system14
Telecommunication System

Information signal output

Information signal input

Encoder

Modulator/

Transmitter

Transmission Channel

Demodulator/

Receiver

Decoder

Free-space loss

Reflection

Refraction

scattering

Multipath

Diffraction

Shadowing

Noise

Interference

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telecommunication system15
Telecommunication System
  • Transducer : transform one form of Energy into another
    • eg. Sound Electrical
  • Transmitter : amplifies and processes the electrical replica of message for transmission
  • Receiver : amplifies and processes the received elctrical signal in reverse manner to recover the original message
  • Transmission Channel : a path connecting Transmitter [Tx] to Receiver [Rx], which is characterized by attenuation
  • Factors involve in a communication system:
    • Type of information (data, text, graphic, voice, music, multimedia, etc.)
    • Information format (analog, discrete, digital, random, deterministic, periodic etc.)
    • Transmission speed (low, medium, high, etc.)
    • Transmission medium (wired, wireless)
    • Transmission distance (short, medium, long)
    • Modulation techniques (AM, PM, ASK, PSK, GMSK, PCM, OFDM, etc.)
    • Error control (BCD, Gray, Morse, ASCII, FEC, cyclic, etc.)

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transmission mode
Transmission Mode
  • Simplex transmission
    • Only one way communication
  • Half duplex transmission
    • Two ways communication, but one at a time; not simultaneously
  • Full duplex transmission
    • Simultaneously in both directions
  • Unicast, Multicast, Anycast, Broadcast

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modes of transmission
Modes of transmission
  • Asynchronous
    • Each character is considered a unit of information
    • All timing and error checking is included within it
  • Synchronous
    • Information is sent as a block of data
    • Control and error checking information is added to each block

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asynchronous versus synchronous

Asynchronous transmission

1

0

0

0

0

1

1

1

0

1

0

1

0

1

1

0

1

0

0

1

0

1

0

1

0

1

0

0

modem

modem

Stop bit

Start bit

Characteristics:

Efficiency (1000 character transmission)

Data is sent one character at a time

Control / overhead bits: 1 start and stop bits per

Each character has a start and 1, 1.5, or 2 stop bits

character

Synchronization is reestablished for each character

2 control bits per character x 1000 characters = 2000

Time between character is unsynchronized and of

control bits

random length

7000 data bits / 9000 total bits = 77.7% efficient

Synchronous transmission

1

0

0

0

0

1

1

1

0

1

0

1

0

1

1

0

1

0

0

1

0

1

0

1

0

1

0

0

modem

modem

Synchronization character

Characteristics:

Efficiency (1000 character transmission)

Data is sent as a block of uninterrupted characters

Control / overhead bits: 48 total control bits per block

Synchronization characters precede and follow the

using HDLC

data block

48 control bits per block x 1 block = 48 control bits

The data block may be 1000 uninterrupted characters

7000 data bits / 7048 total bits = 99.3% efficient

Synchronization is maintained whether data is

actually being sent and detected or not

Modems remain synchronized during idle time

Asynchronous versus Synchronous

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asynchronous transmission
Asynchronous Transmission
  • Each character is sent independent of the next (or previous character sent)
  • Before each character is a START bit
  • Time between each character is not constant
  • Requires control bits for each character sent (for error checking)
  • At the end of each character is a STOP bit
  • At least 3 of 9 bits (for a 7 bit code) sent are not information but overhead. Hence this is inefficient

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synchronous transmission
Synchronous Transmission
  • Information is transmitted in a block of bits
  • Each block is preceded by a sequence of bits called a preamble
  • Each block ends with a sequence of bits called a postamble
  • Control bits are added to allow error checking
  • The data plus preamble plus postamble plus control information is called a Frame.
  • Much more efficient as compared to Asynchronous transmission
  • More complex and expensive to implement than Asynchronous

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serial versus parallel transmission

Receiver

|0|1|0|1|1|0|1|1|

|0|1|0|1|1|0|1|1|

Sender

Receiver

Sender

Serial versus Parallel Transmission
  • Serial mode
    • Message is sent one bit at a time
  • Parallel mode
    • Each character is sent over

a different wire, simultaneously

    • The size of messages depends on its context
      • Credit card authorization = 1000 bits
      • One page typed memo = 15000 bits
      • One second of digital voice = 56000 bits
      • One second of Full motion video = 100 million bits

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transmission topology26
Transmission Topology

As the area covered by a star network and the number of stations served by it grow, line costs increase and it then economic to divide the network into several smaller network served by its own exchange

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slide28
PSTN
  • Transmission links/nodes
    • Customer nodes
    • Switching nodes
    • Transmission nodes
    • Service nodes
  • Subsystem
    • Transmission systems
    • Switching systems
    • Signalling system

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slide30

Telecommunication Network

  • Bearer Service

provides a "transport system" for exchanging information

  • Tele-services

complete…

includes functions for connection, and a uniform "language" for communication and for shaping the messages conveyed

Example: two telephones talk to each

other via telephone network

Also, Voice/Data/Text/Image etc

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typical network services
Typical Network Services
  • PSTN(Public Switched Telephone Network)
  • PLMN(Public Land Mobile Network)
  • PSPDN(Packet Switched Public Data Network)
  • ISDN(Integrated Services Digital Network)
  • Frame Relay
  • Signaling Network(CAS/CCS)
  • Internet
  • IN(Intelligence Network)

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network services
Network Services

Teleservices – depend on particular terminal apparatus e.g. telephone, teleprinter

Bearer Services – transmission capacity that can be used for any desired function e.g. private circuit

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more about wans
More About WANs
  • Virtual private networks (VPNs):
    • A private network configured within a public network
    • Can be built on top of the Internet
    • Service offered by the telephone companies and ISPs

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slide35
Value added networks (VANs):
    • Public data networks that “add value” by transmitting data and by providing access to commercial databases and software
    • Use packet switching
    • Subscription based
    • Often used in electronic data interchange (EDI) systems

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slide36
Public switched data network technologies (PSDN)
    • Data flows through a public network managed by a telecommunications carrier
    • Most common technologies:
      • ISDN (integrated service digital network)
      • X.25
      • Frame relay
      • Asynchronous transfer mode (ATM)

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sending multiple bits simultaneously
Sending Multiple Bits Simultaneously

Each of the three modulation techniques can be refined to send more than one bit at a time. It is possible to send two bits on one wave by defining four different amplitudes.

This technique could be further refined to send three bits at the same time by defining 8 different amplitude levels or four bits by defining 16, etc. The same approach can be used for frequency and phase modulation.

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hybrid amplitude and phase modulation
Hybrid Amplitude and Phase modulation
  • QAM : Quadrature Amplitude Modulation
    • represents 4 bits per baud (I.e. V = 16)

90o

8 phase changes

2 different amplitude

levels

Therefore V = 16

135o

45o

0o

180o

315o

225o

Used in ITU V.32 modems

270o

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digital encoding of analog signals pcm
Digital Encoding of Analog Signals (PCM)
  • Concept:
    • Take samples of analog signal. To each sample - assign a code. Then transmit that code (digital signal).
    • If we sample at the rate of twice the bandwidth of the channel then the resulting digital signal contains all the information in the original analog signal - Nyquist’s theorem (1924)

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pcm pulse code modulation
PCM - Pulse Code Modulation

Samples

time

Each is assigned a

n bit binary code

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slide44
PCM
  • Transmitting an analog signal over a digital network (eg. Voice on telephone n/w)
    • Each signal is sampled 8000 times per second
    • Each sample is converted to a 7 bit code
    • 1 bit is added for control information
    • there are 128 different such codes (27)
    • The digital signal is then transmitted at 64,000 = 64 Kbps = 8*8000

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differential pcm
Differential PCM
  • Voice signals do not change extremely rapidly
  • Changes of more than +/- 16 levels between samples is very rare
  • Hence use just 5 bits instead of 7 to represent each sample
  • If signal jumps very widely then several samples are needed to “catch up”

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delta modulation
Delta Modulation
  • Voice signals do not change very rapidly
  • Transmit only one bit at each sample (indicating a +1 or -1) to indicate whether the signal is increasing or decreasing.
  • Amplitude of next sample differs from previous one by 1 unit (either +1 or -1).
  • If very rapid changes take place then the coding takes a while to “catch up”

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problems delta modulation
Problems (Delta Modulation)

Samples cannot keep up with rapidly

changing signal

time

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predictive encoding
Predictive Encoding
  • Both sender and receiver extrapolate from the last few values received to predict what the next value would be.
  • The transmitter sends a value only if it were different from what is predicted

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data transfer in the presence of noise
Data transfer in the presence of noise
  • Shannons Law:

C = B * log2 (1 + S/N) where:

      • C = achievable channel capacity
      • B= Bandwidth of line (in Hz)
      • S = Average signal power
      • N = Average Noise power
      • S/N = Signal to Noise Ratio
        • this is usually measured in decibels (dB)
        • where dB = 10 * log10 (S/N)

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telephone channel capacity
Telephone Channel Capacity

Voice Channel

0-4,000 Hz

Voice Bandwidth 300-3,300 Hz

Voltage

Guard

Band

Guard

Band

0

300

3,300

4,000

Frequency (Hertz)

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slide51
Example: Channel capacity of a telephone line (voice grade):
      • typical signal to noise ratio of a voice grade line

= 30 decibels

      • i.e. 30 = 10* log10(S/N) => S/N = 1000
      • Bandwidth = 3000 Hz
      • Thus C = 3000 * log2 (1+1000)
      • C = 30, 894 bits per second = 30 Kbps (approx)
      • This is the extreme limit though, hardly ever reached since ideal conditions are not present.

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converting voice analog to digital
Converting Voice (analog) to digital :
  • Use PCM
  • Sample 8000 times in each second
  • Time between each sample = 1/8000 = 125 micro seconds (not perceptible to the human ear)
  • Voice signals lie between 300 - 3300 Hz hence we are sampling at twice the frequency
  • What does Nyquist’s theorem imply ?

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data encoding
Data Encoding
  • Data needs to be encoded in a format that computers can understand :
    • ASCII (8 bits), 128 characters, 1 bit used for error detection
    • EBCDIC (8 bits), 256 characters
    • Baudot (5 bits)

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transmitting data
Transmitting Data
  • In order for data to be transmitted and received in a legible form
    • The receiver must know where
      • a character starts
      • a character ends
    • in the stream of bits that is received from a transmitter

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slide56
Flow Control
    • Hardware flow control RTS/CTS
    • Software flow control XON/XOFF

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flow control
Flow Control
  • Necessary when data is being sent faster than it can be processed by receiver
  • Computer to printer is typical setting
  • Can also be from computer to computer, when a processing program is limited in capacity

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stop and wait flow control
Stop-and-Wait Flow Control
  • Simplest form
  • Source may not send new frame until receiver acknowledges the frame already sent
  • Very inefficient, especially when a single message is broken into separate frames

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basic data communications h w

CODEC’s

Local PC

Remote PC

1000001

1000001

PSTN

Phone network

modem

modem

Input

Processing

Output - Input

Processing

Output

Digital data

Transform digital data input

Analog

Transform analog data input

Digital data

to analog data output

to digital data output

(modulation)

(demodulation)

Basic data communications H/W
  • Modem - MOdulator/DEModulator
    • used to convert digital signals from a computer to analog signals via modulation so as to transmit over telephone networks

Old modem (voice-graded telephone line) - ASK Modern modem – FSKSophisticated modem - PSK

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modem standards
Modem Standards
  • V.22bis
    • transmission rate 2400 bps
    • baud rate 600 bauds
    • data compression V.42bis
    • Error correction V.42
    • Modulation method 4QAM and TCM

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modem standards62
Modem Standards
  • V.32
      • transmission rate 9.6 Kbps
      • Baud rate 2400 bauds
      • Data compression/error correction same
      • Modulation method 4QAM and TCM
  • V.32bis
    • same as above except uses 6QAM and TCM

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