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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 How We Experience the World Around Us 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 – A source that provides the content – A medium over which the content is delivered – A destination that receives the content Wireless Communication Key Events 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 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 Time varying magnetic fields induce electric fields – Today this is our primary means of generating electricity The electric field is measured by the meter N S Ampere’s Law Static currents induce magnetic fields – This is how electromagnets work Time varying electric fields also induce magnetic fields Current Magnetic Field + + + + ~ ~ - - - Electric Field Magnetic Field Electromagnetic Waves 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 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 = 4r2 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 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 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 Lossless coding – Doesn’t depend on information source or content – Achieve limited compression 213 K .zip File 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 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 Coverage Area Received Signal Power Usable Range Noise limit Distance Types of Noise Thermal Man-Made Atmospheric Solar Cosmic Quantum Handoff Computers & Semiconductors 1948 William Shockley leads team that invents the transistor 1958-1959 Jack Kilby and Robert Noyce independently invent the Integrated Circuit Enabling wireless communication – – – – – – 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 Processor Speed – More complex coding and waveform schemes = more bits/sec/Hz – Larger bandwidths 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 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 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 Network Processing – 900 MHz 32 Bit RISC Processor – (4) 900 MHz Micro-engines – (2) 200 MHz Network Processors Digital Signal Processing – (308) 160 MHz RISC Processors – (14) 160 MHz Function Accelerators – 197 GIPS RF Processing – – – – 4.9 GHz Transceiver 5 MHz channels 256 subcarriers 13 Mbps data rate Challenges - Spectrum Spectrum – A scarce natural resource The band from 100 MHz to 10 GHz is the most important for wireless communication today Application Frontiers 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?