Transcript Wireless Communication: Foundations and Frontiers

Wireless Communication:
Foundations and Frontiers
Dr. Dennis Martinez
Vice President, Technology
M/A-COM Wireless Systems
How many of these wireless
devices will you use today?
Cell phone
 Cordless phone
 Wireless LAN
 AM/FM radio
 Television
 Garage door opener
 Remote control device
 Automobile remote key entry
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How We Experience the World
Around Us
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The 5 Senses – Taste, Smell, Feel, Hearing, Sight
We have learned how to remotely experience
only 2 of them – why?
Wireless communication is now one of our
primary means of delivering this remote
experience
Started with broadcast radio and television –
one-way experience
Today cell phones and wireless LAN provide for
feature-rich two-way communication
Our Remote Experience
Remote experience involves communication
 Communication involves
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– A source that provides the content
– A medium over which the content is delivered
– A destination that receives the content
Wireless Communication Key Events
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1864
1895
1907
1927
1939
1947
1948
1959
1976
1978
1997
1998
Maxwell unifies electromagnetic theory
Marconi sends wireless messages over 1 mile
First wireless voice transmissions
First wireless television transmission demonstrated
FM radio broadcasts begin
Shockley et. al. invent the transistor
Shannon formalizes digital communication theory
Invention of the Integrated Circuit
First satellite-to-the-home television service
First trial cellular telephone system operates in Chicago
802.11 Wireless LAN standard is created
Satellite radio services began
Electromagnetic Theory
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Maxwell’s Equations – (1864)
– Faraday’s law of induction:
 Electric fields are induced by time varying
magnetic fields
– Ampere’s law:
 Magnetic fields are induced by time varying
electric fields
– Like a perpetual motion machine,
Electric and magnetic fields perpetuate
each other as an electromagnetic wave
 These waves travel at the speed of light and
carry energy from one point to another
James Clerk Maxwell
Scottish physicist and
mathematician
1831-1879
Faraday’s Law
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Time varying magnetic fields induce electric fields
– Today this is our primary means of generating
electricity
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The electric field is measured by the meter
N
S
Ampere’s Law
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Static currents induce magnetic fields
– This is how electromagnets work
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Time varying electric fields also induce magnetic fields
Current
Magnetic Field
+ + + +
~
~
- - - Electric Field
Magnetic Field
Electromagnetic Waves
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Generated by accelerating electrons on the surface of an
antenna
Electric and Magnetic fields are perpendicular to each
other and to the direction of motion
Electromagnetic Propagation
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Radio waves propagate outwards from the source
Since they transmit energy, they obey the conservation of energy
principle
In free space energy density (energy per unit area) decays as 1/r2
r
Antenna’s have apertures
that capture this energy
Surface area = 4r2
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When radio waves encounter matter, energy can be absorbed,
reflected and scattered
In the real environment energy density
decays much faster than 1/r2
At the turn of the
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th
20
century
Devices existed that could generate and receive
radio waves
These radio waves could be modulated by
keying transmitters on and off – Morse Code
Shortly after, Amplitude and Frequency
Modulation was possible to transmit sound and
pictures
By 1950 Analog radio and television was widely
available
This laid the ground work for the advent of
digital communication
Information Theory
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Mathematical Theory of Communication (1948)
– Forms the basis for modern digital communication
– Information = Randomness
 Entropy is a measure of randomness
– Information Sources & Source Coding
 Information sources are characterized by their Entropy
 Source Coding removes the redundancy of an information source
Claude Shannon
Research Mathematician
– Channel Capacity
1916-2001
 Bandwidth and noise only limit the rate that we can communicate,
not the accuracy
– Rate Distortion
 Coding with a fidelity criterion
Channel Introduces Noise
Information
Source
Source
Coder
Waveform
Coder
Symbols
Receiver
Waveforms
Source
Decoder
Symbols
Source Coding Example
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Lossless coding
– Doesn’t depend on information source or content
– Achieve limited compression
213 K .zip File
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1.6 to 1
Lossless Coding
Coding with a fidelity critieron
– Achieve much greater compression
– Requires a lot of domain knowledge about source
and the perception of distortion
11 to 1
Coding with loss
352 K .bmp File
24 Bit Color, 300 x 400 Resolution
32 K .jpg File
Waveform Coding
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How we turn bits into radio waves
– Modulators take groups of bits and select an
appropriate waveform to transmit
– Demodulators compare the received
waveform and decide which waveform was
transmitted and hence the bits that were sent
10 00 11 01 01 00
Transmitted Waveform
01
2-bit
Symbols
10
11
Compare
01
T
Baud Rate
2 bits/T
Distance and Data Rate
A radio link has a useable range
 Towers have a usable coverage area
 Handoff occurs as radios leave one
coverage area and enter another
Cell Boundaries
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Coverage Area
Received Signal Power
Usable Range
Noise limit
Distance
Types of Noise
Thermal
Man-Made
Atmospheric
Solar
Cosmic
Quantum
Handoff
Computers & Semiconductors
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1948 William Shockley leads team that
invents the transistor
1958-1959 Jack Kilby and Robert Noyce
independently invent the Integrated Circuit
Enabling wireless communication
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General purpose processors
Digital signal processors
Microcontrollers
Application Specific IC’s
Radio Frequency IC’s
Many others
Robert Noyce
Physicist
1927 - 1990
William Shockley
Physicist
1910 - 1989
Jack Kilby
Engineer
1923 - 2005
Semiconductor Advances
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Processor Speed
– More complex coding
and waveform schemes
= more bits/sec/Hz
– Larger bandwidths
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Chip Density
– Reduces the size
– Increases battery life
– Reduces the cost
Processor Speed (MIPS)
1000
100
10
1
0.1
0.01
1970
1975
1980
1985
1990
2000
Chip Density Transistors per die)
100,000,000
10,000,000
1,000,000
100,000
10,000
1000
100
10
1
1970
1975
1980
1985
1990
2000
Technology Frontiers
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Wireless Technology
– Cognitive Radio
 Radios that sense & adapt to the RF environment
– Software defined radio
 Replacing analog & RF with digital processors
– Broadband
 Moving all multi-media services to packet switching
 Ubiquitous networks
– Cordless Phones  Cell Phones
– WiFi Wireless LAN  WiMax Wireless Wide Area Networks
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Enabling Technologies
– Information & Software
 Networks & protocols
– Semiconductors & Computing
 Materials, circuits, architectures, & systems
 Quantum computing, bio-computing, DNA computers
– Energy Sources (Batteries)
Emerging Technologies for Wide
Area Broadband
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Network Processing
– 900 MHz 32 Bit RISC Processor
– (4) 900 MHz Micro-engines
– (2) 200 MHz Network Processors
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Digital Signal Processing
– (308) 160 MHz RISC Processors
– (14) 160 MHz Function Accelerators
– 197 GIPS
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RF Processing
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4.9 GHz Transceiver
5 MHz channels
256 subcarriers
13 Mbps data rate
Challenges - Spectrum
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Spectrum – A scarce natural resource
The band from 100 MHz to 10 GHz is the most important for wireless communication today
Application Frontiers
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Applications – Increasing our
experience of the world around us
– Increasing the intensity of our
AM Radio – 10 kHz
experience
FM Radio – 200 kHz
 From Hi-FI to High Definition
Television – 6 MHz
– Increasing the interactivity of our
experience
 From broadcast to n-way
– Increasing the mobility of our
experience
 The ubiquitous network
Which picture do you prefer?
Why?
Thank you!
Questions?