TLMN 625 Wide Area Networking Systems

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TLMN 625 Wide Area Networking Systems

• Spring 03
• Class 1

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Types of Wired Telecom Networks

• Local Area Networks (LAN) TLMN 620
• Metropolitan Area Networks (MAN)
• Wide Area Networks (WAN) TLMN 625

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Example Leased Line WAN
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PSTN Network
Source IEC SS 7 Tutorial
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Level 3 first international communications
network to use IP (Internet
Protocol) technology end-to-end
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Level 3 ALL IP
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MAN
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Examples of WANs

• 1.
• 2.
• 3.
• 4.
• 5.
• 6.
• 7.

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Remote Access Definition

• Remote Access refers to any technology that
  enables you to connect users in geographically
  dispersed locations. This access is typically
  over some kind of dial-up connection, although it
  can include WAN connections.

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Remote Access Networking
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Peer to Peer Networking(No Server)
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Transmitter
Receiver
Communication channel
Figure 3.5
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d meters
communication channel
0110101...
0110101...
Figure 3.10
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Network
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Infrastructure
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Telecommunication Topologies

• One to One (point to point)
• One to Many (point to multipoint)
• Many to Many (multipoint to multipoint)
• Broadcast

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Fundamentals

• Network Infrastructure, Hardware
• Analog vs. Digital
• Frequency, Bandwith
• Modulation
• Multiplexing
• Coding

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DIGITAL TECHNOLOGY ADVANTAGES

• FLEXIBLE USE
• Digital Encoding permits a variety
• of information sources
• Voice, Video, Data
• COMPRESSION
• Lossless (Data)
• Lossy (Voice, Image, Video)

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Advantages of Digital Transmission

• repeaters (vs. amplifiers)
• compression of information ( compression modems)
• much information now digital (i.e. bits)
• processing easier (e.g. storing at store and
  hold- routers)

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What is the difference?

• Analog information and signalling?
• Digital information and digital signalling?

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Carrier Wave
ffrequency
wavelength
speedc 3 X108
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Bandwidth
B
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Modulation

• A signal processing technique in which one signal
  (the modulating signal) modifies a property of
  another signal (the carrier wave) so that a
  composite wave (the modulated wave) is formed.
• Examples amplitude, frequency, phase
• Thought question Explain spread spectrum
  modulation via the concepts above?

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The conversion of a BASEBAND signal to occupy a
channel elsewhere in the spectrum is called
MODULATION the BASEBAND Signal is used to MODIFY
some parameter of a high frequency carrier signal
fc
Baseband
f
f2
f1
0
fc
Carrier
Figure 3.27
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Modulate cos(2?fct) and sin (2?fct) by
multiplying them by Ak and Bk respectively for
(k-1)T lt t ltkT
Figure 3.31
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Information
1
(a)
Amplitude Shift Keying
t
-1
1
Frequency Shift Keying
(b)
t
-1
1
Phase Shift Keying
(c)
t
-1
Figure 3.28
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Amplitude Modulation
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Phase Modulation
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NOISE
signal noise
signal
noise
High SNR
t
t
t
noise
signal noise
signal
Low SNR
t
t
t
Average Signal Power
SNR
Average Noise Power
SNR (dB) 10 log10 SNR
Figure 3.12
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MULTIPLEXING Frequency and Time
(a)
(b)
A
A
A
A
Trunk group
B
B
B
MUX
MUX
B
C
C
C
C
Figure 4.1
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FREQUENCY MULTIPLEXING
(a) Individual signals occupy W Hz
(b) Combined signal fits into channel bandwidth
Figure 4.2
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MultiplexingData/ Time
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Statistical Multiplexing
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Conversion of digital information to analog
information
Source Comer (2000)
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Conversion of analog information to digital
information

• Waveform coding
• Sample
• Quantize
• Code to bits (64 kb/s for voice)
• Example voice (4 kHz bandwidth)
• Source coding (compression)
• Source coders operate using a model of how the
  source was generated
• vocoders ( e.g. 160 octets every 20 ms)

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Analog to Digital Conversion(CODEC)
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Example Calculation 4 kHz voice
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SPEECH ENCODING-LPCVocoders
A source(voice) is passed through a filter (the
vocal tract response) to produce the speech. The
simplest implementation of this is known as a
LPC synthesiser At every frame the speech is
analysed to compute the filter coefficients,
the energy of the excitation, a voicing
decision, and a pitch value if voiced. This is a
very efficient system and typically produces
speech coded at 1200-2400bps.
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Source Coding
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Parameters for Source coding
For ever frame, need to code A
representation of the LP filter Power
Degree of voicing Pitch (if
voiced) Most bits go into the LP
parameters Vocoders( e.g. 160 octets for 20 ms)
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Data Sources

• 2 page memo (text only) 8 kilobits
• PC program 3 Megabits
• 500 X 500 pixel 6 Megabits
• (24 bits/pixel)
• 500 X 500 pixel .06 Megabits
• (24 bits/pixel Compressed)

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STREAMING SOURCES (includes compression)

• CD quality stereo 256 kb/s
• Broadcast audio 56-64 kb/s
• POTS 64 kb/s
• Low Rate POTS 5-6 kb/s
• HDTV 20 Mb/s
• Video (MPEG 2) 4-6 Mb/s
• Low rate Video lt28.8 kb/s

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Math Homework

• Problem 16 p. 41 text (Garcia)v
• Problem 2 p. 180 in text.