Wireless Wireless Communication:Communication:Foundations and Foundations and
FrontiersFrontiers
Dr. Dennis MartinezDr. Dennis Martinez
Vice President, TechnologyVice President, Technology
M/A-COM Wireless SystemsM/A-COM Wireless Systems
How many of these wireless How many of these wireless devices will you use today?devices will you use today?
Cell phoneCell phone Cordless phoneCordless phone Wireless LANWireless LAN AM/FM radioAM/FM radio TelevisionTelevision Garage door openerGarage door opener Remote control deviceRemote control device Automobile remote key entryAutomobile remote key entry
How We Experience the World How We Experience the World Around UsAround Us
The 5 Senses – Taste, Smell, Feel, Hearing, The 5 Senses – Taste, Smell, Feel, Hearing, SightSight
We have learned how to remotely We have learned how to remotely experience only 2 of them – why?experience only 2 of them – why?
Wireless communication is now one of our Wireless communication is now one of our primary means of delivering this remote primary means of delivering this remote experienceexperience
Started with broadcast radio and television Started with broadcast radio and television – one-way experience– one-way experience
Today cell phones and wireless LAN Today cell phones and wireless LAN provide for feature-rich two-way provide for feature-rich two-way communicationcommunication
Our Remote ExperienceOur Remote Experience
Remote experience involves Remote experience involves communicationcommunication
Communication involvesCommunication involves– A A sourcesource that provides the content that provides the content– A A mediummedium over which the content is over which the content is
delivereddelivered– A A destinationdestination that receives the content that receives the content
Wireless Communication Key Wireless Communication Key EventsEvents
18641864 Maxwell unifies electromagnetic theoryMaxwell unifies electromagnetic theory 18951895 Marconi sends wireless messages over 1 mileMarconi sends wireless messages over 1 mile 19071907 First wireless voice transmissionsFirst wireless voice transmissions 19271927 First wireless television transmission First wireless television transmission
demonstrateddemonstrated 19391939 FM radio broadcasts beginFM radio broadcasts begin 19471947 Shockley et. al. invent the transistorShockley et. al. invent the transistor 19481948 Shannon formalizes digital communication Shannon formalizes digital communication
theorytheory 19591959 Invention of the Integrated CircuitInvention of the Integrated Circuit 19761976 First satellite-to-the-home television service First satellite-to-the-home television service 19781978 First trial cellular telephone system operates in First trial cellular telephone system operates in
ChicagoChicago 19971997 802.11 Wireless LAN standard is created802.11 Wireless LAN standard is created 19981998 Satellite radio services beganSatellite radio services began
Electromagnetic TheoryElectromagnetic Theory Maxwell’s Equations – (1864)Maxwell’s Equations – (1864)
– Faraday’s law of induction:Faraday’s law of induction: Electric fields are induced by time Electric fields are induced by time
varying magnetic fieldsvarying magnetic fields
– Ampere’s law:Ampere’s law: Magnetic fields are induced by time Magnetic fields are induced by time
varying electric fieldsvarying electric fields
– Like a perpetual motion machine, Like a perpetual motion machine, Electric and magnetic fields Electric and magnetic fields perpetuate each other as an perpetuate each other as an electromagnetic waveelectromagnetic wave These waves These waves travel at the speed of lighttravel at the speed of light
and and carry energycarry energy from one point to from one point to anotheranother
James Clerk MaxwellScottish physicist and
mathematician
1831-1879
N S
Faraday’s LawFaraday’s Law
Time varying magnetic fields induce electric Time varying magnetic fields induce electric fieldsfields– Today this is our primary means of generating Today this is our primary means of generating
electricityelectricity The electric field is measured by the meterThe electric field is measured by the meter
Ampere’s LawAmpere’s Law Static currents induce magnetic fieldsStatic currents induce magnetic fields
– This is how electromagnets workThis is how electromagnets work Time varying electric fields also induce magnetic Time varying electric fields also induce magnetic
fieldsfields
~~~~
+ + + +
- - - -
Electric Field
Magnetic FieldCurrent
Magnetic Field
~~~~
Electromagnetic WavesElectromagnetic Waves Generated by accelerating electrons on the Generated by accelerating electrons on the
surface of an antennasurface of an antenna Electric and Magnetic fields are perpendicular to Electric and Magnetic fields are perpendicular to
each other and to the direction of motioneach other and to the direction of motion
Electromagnetic Electromagnetic PropagationPropagation Radio waves propagate outwards from the sourceRadio waves propagate outwards from the source
Since they transmit energy, they obey the conservation of Since they transmit energy, they obey the conservation of energy principleenergy principle
When radio waves encounter matter, energy can be When radio waves encounter matter, energy can be absorbed, reflected and scatteredabsorbed, reflected and scattered
r
Surface area = 4r2
In free space energy density (energy per unit area) decays as 1/r2
In the real environment energy densitydecays much faster than 1/r2
Antenna’s have apertures that capture this energy
At the turn of the 20At the turn of the 20thth centurycentury
Devices existed that could generate and Devices existed that could generate and receive radio wavesreceive radio waves
These radio waves could be modulated by These radio waves could be modulated by keying transmitters on and off – Morse keying transmitters on and off – Morse CodeCode
Shortly after, Amplitude and Frequency Shortly after, Amplitude and Frequency Modulation was possible to transmit sound Modulation was possible to transmit sound and picturesand pictures
By 1950 Analog radio and television was By 1950 Analog radio and television was widely availablewidely available
This laid the ground work for the advent of This laid the ground work for the advent of digital communicationdigital communication
Information TheoryInformation Theory Mathematical Theory of Communication (1948)Mathematical Theory of Communication (1948)
– Forms the basis for modern digital communicationForms the basis for modern digital communication– Information = RandomnessInformation = Randomness
Entropy is a measure of randomnessEntropy is a measure of randomness– Information Sources & Source CodingInformation Sources & Source Coding
Information sources are characterized by their EntropyInformation sources are characterized by their Entropy Source Coding removes the redundancy of an information Source Coding removes the redundancy of an information
sourcesource– Channel CapacityChannel Capacity
Bandwidth and noise only limit the rate that we can Bandwidth and noise only limit the rate that we can communicate, not the accuracycommunicate, not the accuracy
– Rate DistortionRate Distortion Coding with a fidelity criterionCoding with a fidelity criterion
Claude ShannonResearch Mathematician
1916-2001
SourceCoder
WaveformCoder
ReceiverSource
DecoderInformation
Source
Symbols
Channel Introduces Noise
Waveforms Symbols
Source Coding ExampleSource Coding Example Lossless codingLossless coding
– Doesn’t depend on information source or Doesn’t depend on information source or contentcontent
– Achieve limited compressionAchieve limited compression Coding with a fidelity critieronCoding with a fidelity critieron
– Achieve much greater compressionAchieve much greater compression– Requires a lot of domain knowledge about Requires a lot of domain knowledge about
source and the perception of distortionsource and the perception of distortion
352 K .bmp File24 Bit Color, 300 x 400 Resolution
32 K .jpg File
11 to 1Coding with loss
213 K .zip File
1.6 to 1Lossless Coding
Compare
Waveform CodingWaveform Coding
How we turn bits into radio wavesHow we turn bits into radio waves– ModulatorsModulators take groups of bits and select take groups of bits and select
an appropriate waveform to transmitan appropriate waveform to transmit– DemodulatorsDemodulators compare the received compare the received
waveform and decide which waveform was waveform and decide which waveform was transmitted and hence the bits that were transmitted and hence the bits that were sentsent
10 00 11 01 0100
01
10
11
01
Transmitted Waveform
2-bitSymbols T
Baud Rate2 bits/T
Distance and Data RateDistance and Data Rate
A radio link has a useable rangeA radio link has a useable range Towers have a usable coverage Towers have a usable coverage
areaarea Handoff occurs as radios leave one Handoff occurs as radios leave one
coverage area and enter anothercoverage area and enter another
Distance
Rece
ived S
ignal Pow
er
Noise limit
Usable Range
Cell Boundaries
Handoff
Coverage Area
Types of NoiseThermalMan-MadeAtmosphericSolarCosmicQuantum
Computers & Computers & SemiconductorsSemiconductors
1948 William Shockley leads team that 1948 William Shockley leads team that invents the transistorinvents the transistor
1958-1959 Jack Kilby and Robert Noyce 1958-1959 Jack Kilby and Robert Noyce independently invent the Integrated independently invent the Integrated CircuitCircuit
Enabling wireless communicationEnabling wireless communication– General purpose processorsGeneral purpose processors– Digital signal processorsDigital signal processors– MicrocontrollersMicrocontrollers– Application Specific IC’sApplication Specific IC’s– Radio Frequency IC’sRadio Frequency IC’s– Many othersMany others
William ShockleyPhysicist
1910 - 1989
Jack KilbyEngineer
1923 - 2005
Robert NoycePhysicist
1927 - 1990
Semiconductor AdvancesSemiconductor Advances
1970 1975 1980 1985 1990 20000.01
0.1
1
10
100
1000
Processor Speed (MIPS)
1970 1975 1980 1985 1990 20001
10
100
1000
10,000
100,000
1,000,000
10,000,000
100,000,000
Chip Density Transistors per die)
Processor SpeedProcessor Speed– More complex coding More complex coding
and waveform and waveform schemes = more schemes = more bits/sec/Hzbits/sec/Hz
– Larger bandwidthsLarger bandwidths Chip DensityChip Density
– Reduces the sizeReduces the size– Increases battery lifeIncreases battery life– Reduces the costReduces the cost
Technology FrontiersTechnology Frontiers Wireless TechnologyWireless Technology
– Cognitive RadioCognitive Radio Radios that sense & adapt to the RF environmentRadios that sense & adapt to the RF environment
– Software defined radioSoftware defined radio Replacing analog & RF with digital processorsReplacing analog & RF with digital processors
– BroadbandBroadband Moving all multi-media services to packet switchingMoving all multi-media services to packet switching Ubiquitous networksUbiquitous networks
– Cordless Phones Cordless Phones Cell Phones Cell Phones– WiFi Wireless LAN WiFi Wireless LAN WiMax Wireless Wide Area WiMax Wireless Wide Area
NetworksNetworks Enabling TechnologiesEnabling Technologies
– Information & SoftwareInformation & Software Networks & protocolsNetworks & protocols
– Semiconductors & ComputingSemiconductors & Computing Materials, circuits, architectures, & systemsMaterials, circuits, architectures, & systems Quantum computing, bio-computing, DNA computersQuantum computing, bio-computing, DNA computers
– Energy Sources (Batteries)Energy Sources (Batteries)
Emerging Technologies for Emerging Technologies for Wide Area BroadbandWide Area Broadband
Network ProcessingNetwork Processing– 900 MHz 32 Bit RISC Processor900 MHz 32 Bit RISC Processor– (4) 900 MHz Micro-engines(4) 900 MHz Micro-engines– (2) 200 MHz Network Processors(2) 200 MHz Network Processors
Digital Signal ProcessingDigital Signal Processing– (308) 160 MHz RISC Processors(308) 160 MHz RISC Processors– (14) 160 MHz Function (14) 160 MHz Function
AcceleratorsAccelerators– 197 GIPS197 GIPS
RF ProcessingRF Processing– 4.9 GHz Transceiver4.9 GHz Transceiver– 5 MHz channels5 MHz channels– 256 subcarriers256 subcarriers– 13 Mbps data rate13 Mbps data rate
Challenges - SpectrumChallenges - Spectrum
Spectrum – A scarce natural resourceSpectrum – A scarce natural resource
The band from 100 MHz to 10 GHz is the most important for wireless communication today
Application FrontiersApplication Frontiers
Applications – Increasing our Applications – Increasing our experience of the world around usexperience of the world around us– Increasing the Increasing the intensityintensity of our of our
experienceexperience From Hi-FI to High DefinitionFrom Hi-FI to High Definition
– Increasing the Increasing the interactivityinteractivity of our of our experienceexperience From broadcast to n-wayFrom broadcast to n-way
– Increasing the Increasing the mobilitymobility of our of our experienceexperience The ubiquitous networkThe ubiquitous network
Which picture do you prefer?Why?
AM Radio – 10 kHzFM Radio – 200 kHzTelevision – 6 MHz
Thank you!Thank you!
Questions?Questions?
