SIGNALS and SYSTEMS
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Transcript SIGNALS and SYSTEMS
CMPE 150 – Winter 2009
Lecture 3
January 13, 2009
P.E. Mantey
CMPE 150 -- Introduction to
Computer Networks
Instructor: Patrick Mantey
[email protected]
http://www.soe.ucsc.edu/~mantey/
Office: Engr. 2 Room 595J
Office hours: Tuesday 3-5 PM
TA: Anselm Kia [email protected]
Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/
Text: Tannenbaum: Computer Networks
(4th edition – available in bookstore, etc. )
Syllabus
Today’s Agenda
Standards
Layered Network Architecture - review
Networks and History
Physical Layer
Signals and Systems
Fourier Analysis
Communication Theory
Standards
Required to allow for interoperability between
equipment
Advantages
Ensures a large market for equipment and
software
Allows products from different vendors to
communicate
Disadvantages
Freeze technology
May be multiple standards for the same thing
Standards Organizations
IEEE
ANSI
Internet Society
ISO
ITU-T (formally CCITT)
ATM forum
Network Standardization
Who’s Who in the Telecommunications
World
Who’s Who in the International
Standards World
Who’s Who in the Internet Standards
World
ITU
Main sectors
•
•
•
Radiocommunications
Telecommunications Standardization
Development
Classes of Members
•
•
•
•
National governments
Sector members
Associate members
Regulatory agencies
IEEE 802 Standards
The 802 working groups. The important ones are
marked with *. The ones marked with are
hibernating. The one marked with † gave up.
Metric Units
The principal metric prefixes.
Reference Models
The TCP/IP reference model.
Reference Models
Protocols and networks in the TCP/IP model initially.
Comparing OSI and TCP/IP
Models
Concepts central to the
OSI model
Services
Interfaces
Protocols
A Critique of the OSI Model and
Protocols
Why OSI did not take over
the world
Bad timing
Bad technology
Bad implementations
Bad politics
Bad Timing
“The apocalypse of the two elephants.”
A Critique of the TCP/IP
Reference Model
Problems:
Service, interface, and protocol not
distinguished
Not a general model
Host-to-network “layer” not really a layer
No mention of physical and data link
layers
Minor protocols deeply entrenched, hard
to replace
Hybrid Model
The hybrid reference model used by Tannenbaum
Internet Layering
Level 4
-- Application Layer
(rlogin, ftp, SMTP, POP3, IMAP, HTTP..)
-- Transport Layer(a.k.a Host-to-Host)
Level 3
Level 2
(TCP, UDP, ARP, ICMP, etc.)
-- Network Layer (a.k.a. Internet) (IP)
-- (Data) Link Layer / MAC sub-layer
Level 1
(a.k.a. Network Interface or
Network Access Layer)
-- Physical Layer
Level 5
Example Networks
The Internet
Connection-Oriented Networks:
X.25, Frame Relay, and ATM
Ethernet
Wireless LANs: 802:11
Architecture of the Internet
TCP/IP Reference Model
Protocols and networks in the TCP/IP model initially.
Characteristics
Internet Layer
Connectionless
Internet Protocol (IP)
Task is to deliver packets to destination
Transport Layer
Transmission Control Protocol (TCP)
Connection-oriented
Reliable
User Datagram Protocol (UDP)
Connectionless
Unreliable
TELCO Networks
Connection-Oriented Networks
X.25
Frame Relay
ATM
Fixed Route (set up at start of call)
Quality of Service
Billing – for connection time
T’s and D’s
http://www.netstreamsol.com.au/networking/notes/general/t1_e1_t3_e3_ds0_ds1_ds3.html
T1
• Time-division multiplexed stream of 24
telephone channels
• The basic technology upon which all T-carrier
facilities are based
• Uses a full-duplex digital signal over two wire
pairs.
• Bandwidth of 1.544 Mbps through telephoneswitching network
• Uses AMI or B8ZS coding.
O’s
SONET
•
•
•
•
•
•
Synchronous Optical NETwork
Synchronous Digital Hierarchy (SDH) Europe
Internet for CARRIERS
Worldwide standard
Multiplex multiple digital channels
Management support for
– Operations
– Administration
– Maintenance
X.25 and Frame Relay
• X.25 -- First Public Data Network – 1970s
– Call and connect “Data Terminal Equipment”
– Simple packet structure
– Implemented “virtual circuit” connections
– Flow control, hop-by-hop error control
– Multiplexing – up to 4095 circuits at a time
• Frame Relay – 1980s (up to 2Mbps)
– Limited error control, flow control
– VC based packet switching --“wide area LAN”
Asynchronous Transfer Mode
•
•
•
•
Vintage mid -1980s
Goal to unify voice networks and data networks
Packet Switching with virtual circuits (“channels”)
Fixed-length packets (“cells”) - @ 53 bytes
– 5 byte header, 48 byte “payload”
– Virtual channel header (VCI)
– No retransmission link-by-link
Error correction codes only
• Envisioned to reach the end user
• Used widely today for backbones
ATM Virtual Circuits
A virtual circuit.
ATM Virtual Circuits (2)
An ATM cell.
The ATM Reference Model
The ATM reference model.
The ATM Reference Model (2)
The ATM layers and sublayers and their functions
Ethernet
Architecture of the original Ethernet.
Wireless LANs
(a) Wireless networking with a base
station.
(b) Ad hoc networking.
Wireless LANs (2)
The range of a single radio may not cover
the entire system.
Wireless LANs (3)
A multicell 802.11 network.
The ARPANET
(a) Structure of the telephone system.
(b) Baran’s proposed distributed switching
system.
The ARPANET (2)
The original ARPANET design.
IMP = Interface Message Processor (Honeywell
DDP-316)
The ARPANET (3)
Growth of the ARPANET (a) December 1969.
(b) July 1970.(c) March 1971. (d) April 1972.
(e) September 1972.
NSFNET
The NSFNET backbone in 1988.
http://www.internet2.edu/pubs/networkmap.pdf
UC CENIC January 2009
http://doc.cenic.org/tools/topology_map.pl?network=uc
SIGNALS and SYSTEMS
SIGNALS and SYSTEMS
What is a signal?
SIGNALS and SYSTEMS
What is a signal?
What is a system?
SIGNALS and SYSTEMS
What is a signal?
What is a system?
SIGNALS and SYSTEMS
What is a signal?
What is a system?
Signal: time varying function
produced by physical device
(voltage, current, etc.)
SIGNALS and SYSTEMS
What is a signal?
What is a system?
Signal: time varying function
produced by physical device
(voltage, current, etc.)
System: device or process (algorithm)
having signals as input and output
Input x(t) output y(t)
SIGNALS and SYSTEMS
ax(t)
ay(t)
a1 x1(t) + a2 x2(t)
a1 y1(t) + a2 y2(t)
Superposition
SIGNALS and SYSTEMS
Periodic signals --
f(t+T) = f(t)
Period = T (seconds)
Frequency = 1/ Period
(“cycles” / sec. = Hertz (Hz)
f 0 1/ T0
SIGNALS and SYSTEMS
Periodic signals --
f(t+T) = f(t)
Period = T (seconds)
Frequency = 1/ Period
(“cycles” / sec. = Hertz (Hz)
Radian frequency:
2 f
(radians/sec.)
SIGNALS and SYSTEMS
Reference: Signals, Systems and Tranforms
Leland B. Jackson
Addison Wesley
SIGNALS and SYSTEMS
SIGNALS and SYSTEMS
100MHz square wave
What bandwidth required for transmission?
SIGNALS and SYSTEMS
Periodic Signal --- Composed of sinusoids
MATLAB Demo
SIGNALS and SYSTEMS
Periodic Signal --- Composed of sinusoids
Fourier Series
N
1
x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt )
2
n 1
an
bn
1
1
2
x(t ) cos(2 nf t )d ( t )
0
0
0
2
x(t ) sin(2 nf t )d ( t )
0
0
0
1
f0
T0
is the “fundamental frequency”
0t 2 f 0 t
1
2
d (0t ) 2 f 0 dt 2
dt
dt
T0
T0
Fourier Series
N
1
x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt )
2
n 1
Integration limits: when 0t 2
2
2
1
t
0 2 / T0 T0
,
then
so we get:
2
an
T0
2
bn
T0
T0
x(t ) cos(2 nf t )dt
0
0
T0
x(t ) sin(2 nf t )dt
0
0
Fourier Series
N
1
x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt )
2
n 1
x(t )
ce
n
jn 2 f 0t
n
x(t )
Euler:
e
j 2 f i t
ce
n
jn 2 f 0t
i
cos(2 fi t ) j sin(2 fit )
Fourier Series
x(t )
ce
n
1
cn
T0
jn 2 f 0t
n
T0
2
x(t )e
jn0t
dt
T0
2
We can show
cn a b
2
n
2
n
;
tan (bn / an )
1
recall that
b
a cos( ) b sin( ) a b cos( tan ( ))
a
2
2
1
Phasors:
a
b
a b
2
Phasors
2
References
Stallings, W. Data and Computer Communications
(7th edition), Prentice Hall 2004 chapter 1
Web site for Stallings book
http://williamstallings.com/DCC/DCC7e.html
Web sites for IETF, IEEE, ITU-T, ISO
Internet Requests for Comment (RFCs)
Usenet News groups
comp.dcom.*
comp.protocols.tcp-ip