Post on 22-Dec-2015
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
1
Communication media
Thanks to A. Tanenbaum
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
2
Fourier Coefficients
11
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16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
3
Bandwidth-Limited Signals
A binary signal and its root-mean-square Fourier amplitudes.
(b) – (c) Successive approximations to the original signal.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
4
Bandwidth-Limited Signals (2)
(d) – (e) Successive approximations to the original signal.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
5
Twisted Pair
(a) Category 3 UTP.(b) Category 5 UTP.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
6
Coaxial Cable
A coaxial cable.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Fiber Optics
(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.
(b) Light trapped by total internal reflection.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
8
Fiber Optic Networks
A fiber optic ring with active repeaters.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Fiber Optic Networks (2)
A passive star connection in a fiber optics network.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
10
The Electromagnetic Spectrum
The electromagnetic spectrum and its uses for communication.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
11
Politics of the Electromagnetic Spectrum
The ISM bands in the United States.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
12
The Local Loop: Modems, ADSL, and Wireless
The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
13
Data transmission
Receiver needs to know about sender• duration of each bit• length of elements in bits• duration of a frame
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Modems
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Bit encoding(1)
Asynchronous data transmission
Used for• character oriented devices• large indeterminate intervals between characters
receiver resynchronizes with sender on start and stop bits
polarity of stop bit different from polarity of start bit
1 0 0 1 0 0 1 0Stopbit(s)
Startbit
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
16
Bit encoding(2)
(a) Binary encoding, (b) Manchester encoding, (c) Differential Manchester encoding.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
17
Modems (2)
(a) QPSK.
(b) QAM-16.
(c) QAM-64.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Frequency Division Multiplexing
(a) The original bandwidths. (c) The multiplexed channel.
(b) The bandwidths raised in frequency.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
19
Wavelength Division Multiplexing
Wavelength division multiplexing.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Time Division Multiplexing
The T1 carrier (1.544 Mbps).
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Time Division Multiplexing (2)
Delta modulation.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Time Division Multiplexing (3)
Multiplexing T1 streams into higher carriers.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
23
Code Division Multiple Access (CDMA)
Every single bit Xor with individual Walsh code1 bit is extended to 64 or 128 chipsConsequence 64 (128) more bits transmitted
Walsh codes are orthogonalSo assume two codes A and B then A.B = 0
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
24
Code Division Multiple Access (CDMA) (2)
Example, two stations with Walsh codes A and BA: -1 -1 -1 1 1 -1 1 1B: -1 -1 1 -1 1 1 1 -1
A and B both transmit 1, Xor with Walsh codeAddition of signals then gives S = -2 -2 0 0 2 0 2 0 S.A = (2+2+0+0+2+0+2+0)/8 = 1 S.B = (2+2+0+0+2+0+2+0)/8 = 1
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
25
Wireless coding
Direct Sequence Spread Spectrum (DSSS) basis for CDMAFrequency Hopping Spread Spectrum (FHSS)
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Advanced Mobile Phone System
(a) Frequencies are not reused in adjacent cells.
(b) To add more users, smaller cells can be used.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Multiple Access Protocols
a) ALOHA
b) Carrier Sense Multiple Access Protocols
c) Collision-Free Protocols
d) Limited-Contention Protocols
e) Wavelength Division Multiple Access Protocols
f) Wireless LAN Protocols
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
28
Dynamic Channel Allocation
a) Terminals
b) Single Channel
c) Collision
d) Continuous time vs slotted time
e) Carrier sense or not
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Pure ALOHA
In pure ALOHA, frames are transmitted at completely arbitrary times.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
30
Pure ALOHA (2)
Vulnerable period for the shaded frame.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
31
Pure ALOHA (3)
Throughput versus offered traffic for ALOHA systems.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
32
Persistent and Nonpersistent CSMA
Comparison of the channel utilization versus load for various random access protocols.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Collision detection interval
Collision detection can take as long as 2 .
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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CSMA with Collision Detection
CSMA/CD can be in one of three states: contention, transmission, or idle.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
35
Collision-Free Protocols
The basic bit-map protocol.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Collision-Free Protocols (2)
The binary countdown protocol. A dash indicates silence.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
37
Limited-Contention Protocols
Acquisition probability for a symmetric contention channel.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Adaptive Tree Walk Protocol
The tree for eight stations.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Wireless LAN protocols
(a) The hidden station problem.(b) The exposed station problem.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Wireless LAN Protocols (2)
The MACA protocol. (a) A sending an RTS to B.
(b) B responding with a CTS to A.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
41
Wireless Lan Protocol: CSMA/CA
The use of virtual channel sensing using CSMA/CA.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
42
Wireless LAN Protocol: CSMA/CA (2)
A fragment burst.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
43
Ethernet MAC Sublayer Protocol
Frame formats. (a) DIX Ethernet, (b) IEEE 802.3.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Ethernet Performance
Efficiency of Ethernet at 10 Mbps with 512-bit slot times.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
45
IEEE 802.2: Logical Link Control
(a) Position of LLC. (b) Protocol formats.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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The 802.11 Protocol Stack
Part of the 802.11 protocol stack.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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The 802.11 MAC Sublayer Protocol (4)
Interframe spacing in 802.11.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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The 802.11 Frame Structure
The 802.11 data frame.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Bluetooth Architecture
Two piconets can be connected to form a scatternet.
16 February 2003 Peter.van.der.stok@philips.comTU/e Computer Science, System Architecture and Networking
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Bridges from 802.x to 802.y (2)
The IEEE 802 frame formats. The drawing is not to scale.