Standards Convergence Dave Evans Philips Research Laboratories UK [email protected].
16 February 2003 [email protected] TU/e Computer Science, System Architecture and...
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16 February 2003 [email protected]/e Computer Science, System Architecture and Networking
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Communication media
Thanks to A. Tanenbaum
16 February 2003 [email protected]/e Computer Science, System Architecture and Networking
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Fourier Coefficients
11
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1)(
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16 February 2003 [email protected]/e Computer Science, System Architecture and Networking
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Bandwidth-Limited Signals
A binary signal and its root-mean-square Fourier amplitudes.
(b) – (c) Successive approximations to the original signal.
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Bandwidth-Limited Signals (2)
(d) – (e) Successive approximations to the original signal.
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Twisted Pair
(a) Category 3 UTP.(b) Category 5 UTP.
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Coaxial Cable
A coaxial cable.
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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.
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Fiber Optic Networks
A fiber optic ring with active repeaters.
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Fiber Optic Networks (2)
A passive star connection in a fiber optics network.
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The Electromagnetic Spectrum
The electromagnetic spectrum and its uses for communication.
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Politics of the Electromagnetic Spectrum
The ISM bands in the United States.
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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.
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Data transmission
Receiver needs to know about sender• duration of each bit• length of elements in bits• duration of a frame
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Modems
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
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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
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Bit encoding(2)
(a) Binary encoding, (b) Manchester encoding, (c) Differential Manchester encoding.
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Modems (2)
(a) QPSK.
(b) QAM-16.
(c) QAM-64.
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Frequency Division Multiplexing
(a) The original bandwidths. (c) The multiplexed channel.
(b) The bandwidths raised in frequency.
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Wavelength Division Multiplexing
Wavelength division multiplexing.
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Time Division Multiplexing
The T1 carrier (1.544 Mbps).
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Time Division Multiplexing (2)
Delta modulation.
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Time Division Multiplexing (3)
Multiplexing T1 streams into higher carriers.
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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
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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
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Wireless coding
Direct Sequence Spread Spectrum (DSSS) basis for CDMAFrequency Hopping Spread Spectrum (FHSS)
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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.
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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
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Dynamic Channel Allocation
a) Terminals
b) Single Channel
c) Collision
d) Continuous time vs slotted time
e) Carrier sense or not
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Pure ALOHA
In pure ALOHA, frames are transmitted at completely arbitrary times.
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Pure ALOHA (2)
Vulnerable period for the shaded frame.
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Pure ALOHA (3)
Throughput versus offered traffic for ALOHA systems.
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Persistent and Nonpersistent CSMA
Comparison of the channel utilization versus load for various random access protocols.
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Collision detection interval
Collision detection can take as long as 2 .
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CSMA with Collision Detection
CSMA/CD can be in one of three states: contention, transmission, or idle.
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Collision-Free Protocols
The basic bit-map protocol.
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Collision-Free Protocols (2)
The binary countdown protocol. A dash indicates silence.
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Limited-Contention Protocols
Acquisition probability for a symmetric contention channel.
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Adaptive Tree Walk Protocol
The tree for eight stations.
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Wireless LAN protocols
(a) The hidden station problem.(b) The exposed station problem.
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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.
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Wireless Lan Protocol: CSMA/CA
The use of virtual channel sensing using CSMA/CA.
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Wireless LAN Protocol: CSMA/CA (2)
A fragment burst.
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Ethernet MAC Sublayer Protocol
Frame formats. (a) DIX Ethernet, (b) IEEE 802.3.
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Ethernet Performance
Efficiency of Ethernet at 10 Mbps with 512-bit slot times.
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IEEE 802.2: Logical Link Control
(a) Position of LLC. (b) Protocol formats.
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The 802.11 Protocol Stack
Part of the 802.11 protocol stack.
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The 802.11 MAC Sublayer Protocol (4)
Interframe spacing in 802.11.
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The 802.11 Frame Structure
The 802.11 data frame.
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Bluetooth Architecture
Two piconets can be connected to form a scatternet.
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Bridges from 802.x to 802.y (2)
The IEEE 802 frame formats. The drawing is not to scale.