Computer
Communications
Hi! I am Prof.Doug Lyon
I Welcome you to this class
Computer Communications I:
System Analysis
Course Number :
CpE 471
Meets : Monday 5
-
7:30
Room :
Dana 123
Prof :
Doug Lyon
Office Hours :
1:30
–
2:30 MWF
and by appointment
Computer Communications I:
System Analysis
Text:
Data and Computer
communications by
William Stallings,
MacMillan Co. Fourth
Edition
Grading
•
Home work is optional
•
Attendance is optional
•
Final is optional
•
Grade is average quiz score
Grading
•
A 15 min. cumulative open
-
book/
open
-
notes calculators permitted
quiz every week (but not today!)
Next quiz 9/13/93 since no class
9/6/93
Grading
•
Lowest two quizzes dropped (or are
optional, i.e. sick days)
•
You MUST pick one of the
following:
•
Final = 4 quiz grades
PROJECT
•
Project = 4 quiz grades
•
You will be responsible for
obtaining software for your project.
STELLA should be at the book
store. STELLA is optional. Call
them at 603
-
643
-
9636 for a copy
PROJECT
•
Project examples: Symbolic
Computation, teaching aids,
functional simulation etc. See me
for projects.
•
Paper = 4 quiz grades.
•
Survey of approved journal articles
•
Topics include ,but are not limited
to,(by chapter)
TOPICS:
•
Week 1
-
History ,architectural
overview and design issues in
computer communications.CH1
Outline
Outline
•
Week2
-
Theoretical basis for data
communications,bandwidth
-
limits ,
data transmission,signal
parameters, media,attenuation
delay. Fourier analysis.Fiber optics.
CH 2.1,2.2
Outline
•
Week3
-
Data encoding,Modulation
Techniques .Information Theory.
FM,AM,PM,sampling Theorem,
coding,Modems,RS232
interfacing,serial standards,CH
-
2.3
•
Week4,5
-
Digital TransmissionPCM
encodingsystems,X.21,AX.21. CH2.4
Outline
•
Week6
-
Transmission and switching
FDM,TDM,STDM.Multiplexing
ISDN.
CH 2.5,2.6
•
Week 7
-
Coding and interface
standards,error detection and
interfacing.
Outline
•
Week 8,9
-
Data link
control,control of
retransmission,HDLC protocol
PROJECT
•
T
he project and paper are due on
11/29/93 (day after Thanksgiving
weekend). A late project has 10
points out of 100 removed from
the project grade per day late,
resulting in a 0 after 12/9/93
Outline
•
Week 10
-
Introduction to
Queueing Theory,M/M/ 1,
networks of M/M/1,
queues,simulating queueing
systems,applications of
queueing.CH: Appendix A
Outline
•
Week 11
-
Circuit
switching,virtual curcuits,
packet switching and datagram
packet switching.ATM,data kit.
Outline
•
Week 12
-
Circuit
switching,PBX,Networkcontrol,
routing algorithms for point
-
top
-
point networks.
•
Week 13
-
Packet
switching,virtual circuits and
datagrams.Routing Algorithms.
Hardware networks.
Outline
•
Week 14
-
Radio and satellite
networks:Explores design and
performance issues for antenna
-
based communication
nets.Wireless packet radio
systems
Outline
•
Week 15
-
LANs,examine CSMA/CD,
various topologies,alternative
mediums and access control
techniques.
A COMMUNICATION
MODEL
DATA COMMUNICATION
NETWORK
comm.net
comm net node
net station i.e
computer terminal or telephone
DATA COMMUNICATION
NETWORKS
Communication networks
switched
unswitched
Switched
Circuit Switched
Packet Switched
DATA COMMUNICATION
NETWORKS
Unswitched(broadcast nets)
DATA COMMUNICATION
NETWORKS
packet radio
satellite
local
Packet switched nets are store and forward nets.
ckt switched nets have dedicated communication
paths (i.e. telephone)
For example:
DATA COMMUNICATION
NETWORKS
A Broadcast Comm. Net can be WAN, the media is unshared
DATA COMMUNICATION
NETWORKS
Dish
LAN EXAMPLES:
DATA COMMUNICATION
NETWORKS
Ethernet with a bus topology:
DATA COMMUNICATION
NETWORKS
Ring topology net:
Note: No switching nodes ,media is shared in LAN
For packet radio,every station can hear every other,
the media is shared so this is a LAN technology
DATA COMMUNICATION
NETWORKS
Agent input device
transmitter
channel
channel receiver output device
This course addresses the communication systems
parts between the input and output devices.
Computer Communications
Architecture
The Three Layer Model
Application run on computer which use networks
•
network layer
-
xchange of data between computer
and network
•
transport layer
-
error detection and correction
•
application layer
-
file xfer etc.
Computer Communications
Architecture
File xfer modules
•
xmits passwords
•
file commands
•
file records
Computer Communications
Architecture
•
communications service module
–
error correction
–
encryption
–
keeps track of data to ensure delivery
•
Network Access Module
-
net specific stuff
Computer Communications
Architecture
Computer Communications
Architecture
•
The transport layer will break data into chunks
adds control information and this is called a
PDU or protocol data unit
•
Network access layer is told which computer but
not which SAP
(SAP)
service acess points 1 2 and 3 are used
to uniquely identify the application communicating
Computer Communications
Architecture
Protocol Data Units
•
TPDU1
= transport protocol data
unit := transport hdr, chunk1
•
TPDU2
= transport hdr, chunk2
•
NPDU
= network protocol data
unit network hdr, TPDU
Protocol Data Units
•
Application data = chunk1 +
chunk2 + ...
•
Destination SAP (service access
points)
•
TPDU has destination SAP so that
appropriate application obtains
data
Protocol Data Units
•
Sequence # TPDU’s may be sent in any
order,and by different routes and
may arrive at different times.
•
TPDU may have error detection or correction
codes built
-
in
•
NPDU
destination address (i.e. IP address)
facilities requires (i.e. priority)
Transmission Terminology
•
point
-
to
-
point :
-
guided
transmission is unshared
I.e. O(N**2) connectivity
(completely connected)
=
number of links
Transmission Terminology
Multipoint guided transmission allows shared medium
Transmission Terminology
ANSI Defs:
–
simplex
-
one direction only
–
half
-
duplex
-
two
-
way but not at the
same time.
–
full
-
duplex
-
simultaneous two way
transmission
Transmission Terminology
•
CCITT
–
CCITT vs ANSI
–
simplex = half
-
duplex
–
duplex = full
-
duplex
•
CCITT
= international telegraph and
telephone consultive committee
Analog and Digital Data
Transmission
•
data
-
entities which convey meaning
•
signals
-
encoding of data
•
signaling
-
act of sending a signal
•
transmission
-
communication of data by
propagation and processing
of signals
Analog and Digital Data
Transmission
•
digital data
-
takes on discrete values, i.e. text integers.
•
analog data
-
takes on continuously varying patterns of
intensity, i.e.. sound
But what is digital? What is Analog? How
do we defines these things?
Analog and Digital Data
Transmission
s(t) is continuous (i.e. analog) iff
for all a
Analog and Digital Data
Transmission
A signal, s(t) is discrete iff
for some
a
For example, the function s(t) has multiple values
or does not exist and there fore the limit does not
exist.
Analog and Digital Data
Transmission
•
Let the function f be defined on the set
S. f is continuous at a point P0 of S iff
whenever
Analog and Digital Data
Transmission
•
If f is defined on an interval [a, b]
and is continuous at then given an
DATA and SIGNALS
•
Modem (modulator/demodulator)
modulation involves two waveforms: The
modulating signal (the message) and the carrier
wave which is altered by the modulating signal
•
The complementary process is called
demodulation
Bits <
-
> modem <
-
> analog signal <
-
> modem <
-
> bits
DATA and SIGNALS
•
Codec := coder
-
decoder
•
analog <
-
> codec <
-
> bits
•
In General a digital waveform has
infinite bandwidth.
•
Band limited channels low
-
pass filter
square waves, this rounds their corners.
•
Rule of thumb: if a signal
is W bps, you may need 2W
Hz bandwidth.
Signal Strenth
•
attenuation := a loss of signal
strength
–
signal strength falls off
logarithmically so the decibel is used
to measure the loss
–
Decibel gains and losses are computed
via simple addition and subtraction.
Signal Strenth
Let
number of decibels
Signal Strenth
•
Example
loss=10log(5/10)=
-
3 dB
Signal Strenth
dBw=decibel watt
Signal Strenth
About Those Exponents...
The Laws of Exponents give us the laws of logarithms
Enter the password to open this PDF file:
File name:
-
File size:
-
Title:
-
Author:
-
Subject:
-
Keywords:
-
Creation Date:
-
Modification Date:
-
Creator:
-
PDF Producer:
-
PDF Version:
-
Page Count:
-
Preparing document for printing…
0%
Comments 0
Log in to post a comment