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EEE:464 Wireless

CommunicationInstructor: Shahwaiz Iqbal

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L ets know each other !My Introduction ± Email: [email protected] ± Phone:051 9049160 ± Office: 314 Academic block I

± Office hours: Tuesday: 2:30-4:00Friday: 2:30-4:00Or by appointment (taken either by email or at the end of everylecture)

Course Introduction, Objectives and My wishesIntroduce your self Suggestions are always welcome and some times would be required.

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R ecommended BackgroundIn the design of this course, it is assumed that the participants have general(but not advanced) background knowledge in the courses listed below. Dueto time constraints, I would not be able to teach the topics related to theseareas during this course.

Please do not expect from me to teach the below mentioned courses.Data Communication and Computer networks. (EEE 314)Digital Communication Systems (EEE 463)Probability theory and random variables (MTH 263)

Note: If you think you are weak in these courses, I would recommend youto either revise these courses in the starting weeks, or to drop the course .

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R ecommended BooksIn this course, we would not have a specific text book.Information about a lot of topics can be found in the following text books.

Wireless Communications , Andrea Goldsmith ,

C ambridge University

Press , 2005

Wireless Communications:Principles and Practice ,

Theodore S. Rappaport ,

2nd ed. , Prentice Hall , 2002

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Cheating & PlagiarismMy apologies if you are one of the vast majority of students who don¶tresort to academic dishonestyWhat is cheating & plagiarism?

Acting dishonestly, practicing fraudStealing or using (without my permission) other people¶s writings or ideas

± E.g. from other students, other sources such as web sites, solutionsfrom previous offerings of this course etc.

± Note that it doesn¶t have to be literal copying ± stealing ideas but presenting in a different style is still cheating and plagiarism.

You are also guilty if you aid in cheating & plagiarismMy policy: zero tolerance

HWs, paper presentation: zero score + one level reduction in course grade

Exam, project: ³F´ grade for the course + report to HODMore than 1 incident: : ³F´ grade for the course + report to HOD

Moreover, please remember that you may have to face me in other examsand professionally!

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Tentative OutlineTopics Covered

Week1 Introduction to Wireless Communication SystemsWeek 2 Propagation

Week 3 Wireless Link Design: Statistical Multipath Channel Models

Week4 Diversity Systems

Week 5 The Cellular Concept.

Week 6 Multiple Access Methods

Week 7 Equalization.

Week 7-8 Multicarrier modulation and Orthogonal Frequency Division Multiplexing (OFDM)

Week 9 Mobile Systems and Standards GSM.

Week 9 Existing Wireless Systems ± IS-95.

Week 10 Existing Wireless Systems ± UMTS

Week 10 IEEE and ESTI Wireless standards

Week 11 WLANS and Operations

Week 11 WCDMA and HSPA

Week 12 RFID, Sensor Networks

Week 12 Beyond 3G, Cellular Multihop network, Wimax, LTE

Week13 MIMO Wireless Communications.

Week 13 Seminar ± Latest Trends in Cellular Radio and Personal Communications.

Week 14 Seminar ± Special Topics in Wireless Communications.

Week 14 Course Review.

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Course Material Access

All the lecture slides and helping material, and course information would be available in the following yahoo group.

EEE464WirelessCom_SP11

On-line material ± lecture viewgraphs in PDF & PPT

check before class, and print them ± copies of handouts, home works, exams etc.

± important announcements

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What is Communication?

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Components of a Communication

System

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SystemThe source originates a message, which could be a human voice, atelevision picture or data. The source is converted by an input transducer into an electrical waveform referred to as the baseband signal or messagesignal.

The transmitter modifies the baseband signal for efficient transmission.The transmitter generally consists of one or more of the followingsubsystems: a pre-emphasizer, a sampler, a quantizer, a coder and amodulator.

The channel is a medium through which the transmitter output is sent,which could be a wire, a coaxial cable, an optical fiber, or a radio link, etc.Based on the channel type, modern communication systems are dividedinto two categories: wireline communication systems and wirelesscommunication systems.

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SystemThe receiver reprocessed the signal received from the channel by undoingthe signal modifications made at the transmitter and the channel. The task of the receiver is to extract the message from the distorted and noisy signalat the channel output. The receiver may consist of a demodulator, a

decoder, a filter, and a de-emphasizer.

The receiver output is fed to the output transducer , which converts theelectrical signal to its original form.

Transmitters and receivers are carefully designed to overcome the

distortion and noise. The G oal of Physical layer Communication System isto transmit information accurately and efficiently (power and spectrum).

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Digital vs. Analog Communications

Analog and Digital Signals

Messages are digital or analog.

Digital messages are constructed with a finite number of symbols. For example, a text file is a digital message constructed from 50 symbols,consists of 26 letters, 10 numbers, a space and several punctuation marks.Similarly, a Morse-coded telegraph is a binary message, implying only twosymbols ±mark and space.

Analog messages are characterized by data whose values vary over acontinuous range. For example, a speech waveform has amplitudes thatvary over a continuous range. A picture is also an analog message.

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Noise immunity of digital signals

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Digital vs. Analog Communications

Noise immunity of digital signals ±digital data can be recovered without any error as long as the distortion and noise are within limits. On the other hand, for ananalog message, even a slight distortion or interference in the waveform will causean error in the received signal.

Regenerative repeaters ±±Based on this ³noise immunity´, when transporting a bitstream over a long distance, regenerative repeaters or repeater stations are placedalong the path of a digital system at distances short enough to ensure that noise anddistortion remain within limit. The viability of regenerative repeaters is the mainreason for the superiority of digital systems over analog ones.

Every possible communication can be carried on with a minimum oftwosymbols , i.e., by using a proper binary sequence. In the last 20 years,digitalcommunication gradually replace its analog competitors, and the revolution is nownearly complete.

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Interface of Analog and DigitalSystems--A/D and D/A Conversion

Sampling Theorem A meeting ground exists for analog and digitalsignals: conversion of analog signals to digital signals. The backbone thatsupports the interface is Shannon's Sampling Theorem, which states that if the highest frequency in the signal spectrum is B (in hertz), then the signal

can be recovered from its samples, taken at a rate not less than 2B samples per second.Quantization each sample is approximated, or round off to the nearestquantized level, the information is thus digitalized. The quantized signal isan approximation of the original one. We can improve the accuracy of thequantized signal to any desired degree by increasing the number of levels.Coding

Source coding Convert thequantized signal into binary sequences.Channel coding Introduce redundancy in a controlled manner toovercome the effects of noise and interferences.

Mapping Map binary sequence into symbols.Transmission Symbols are applied to a transmitter filter, which produces acontinuous signal for transmission over a continuous channel.

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What is Wireless and MobileCommunication?

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Wireless Communication

Transmitting voice and data using electromagnetic waves in open space³Wireless´ used to be the only (limited and unreliable) way tocommunicate in ancient times

Modern wireless communications are based on the electromagnetic fieldtheory (Maxwell¶s equations, Marconi¶s invention)Electromagnetic waves

Travel at speed of light (c = 3x10 8 m/s)Has a frequency (f) and wavelength (l)

» c = f x lHigher frequency means higher energy photons

The higher the energy photon the more penetrating is the radiation

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Is there a future for wireless?

Ancient Systems: Smoke Signals, Carrier Pigeons,

R adio invented in the 1880s by Marconi

Many sophisticated military radio systems were developed during and after

WW2Cellular has enjoyed exponential growth since 1988, with almost 1 billionusers worldwide today ± Ignited the recent wireless revolution ± G rowth rate tapering off ± 3G (voice+data) roll-out disappointingMany spectacular failures recently ± 1G Wireless L ANs/Iridium/Metricom

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G limmers of Hope

Internet and laptop use exploding

2G /3G wireless L ANs growing rapidly

L ow rate data demand is high

Military and security needs require wireless

Emerging interdisciplinary applications

WiMAx and L TE/A L TE

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Future Wireless Networks

Wireless Internet accessNth generation CellularWireless Ad Hoc Networks

Sensor NetworksWireless EntertainmentSmart Homes/SpacesAutomated HighwaysAll this and more«

Ubiquitous Communication Among People and Devices

Hard Delay Constraints

Hard Energy Constraints

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Design Challenges

Wireless channels are a difficult and capacity-limited broadcastcommunications medium

Traffic patterns, user locations, and network conditions are constantly

changingApplications are heterogeneous with hard constraints that must be met bythe network

Energy and delay constraints change design principles across all layers of the protocol stack

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Multimedia R equirements

Voice VideoData

Delay

Packet L oss

BE R

Data R ate

Traffic

<100ms - <100ms

<1% 0 <1%

10 -3 10 -6 10 -6

8-32 Kbps 1-100 Mbps 1-20 MbpsContinuous Bursty Continuous

One-size-fits-all protocols and design do not work well

Wired networks use this approach, with poor results

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Wireless Performance G ap

WIDE AREA CIRCUIT SWITCHING

User Bit-Rate(kbps)

14.4digital cellular

28.8 modem

ISDN

ATM

9.6 modem

2.4 modem2.4 cellular

32 kbpsPCS

9.6 cellular

wired- wirelessbit-rate "gap"

1970 200019901980 YEAR

LOCAL AREA PACKET SWITCHING

User Bit-Rate(kbps)

Ethernet FDDI

ATM 100 M Ethernet

Polling

Packet Radio

1st genWLAN

2nd genWLAN

wired- wirelessbit-rate "gap"

1970 200019901980.01

.1

1

10

100

1000

10,000

100,000

YEAR

.01

.1

1

10

100

1000

10,000

100,000

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Frequency Carries/Channels

± The information from sender to receiver is carrier over a well definedfrequency band.

This is called a channel ± Each channel has a fixed frequency bandwidth (in KHz) and Capacity

(bit-rate) ± Different frequency bands (channels) can be used to transmit

information in parallel and independently.

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Example

Assume a spectrum of 90KHz is allocated over a basefrequency b for communication between stations A and BAssume each channel occupies 30KHz.There are 3 channels

± Each channel is simplex (Transmission occurs in one way)

± For full duplex communication:» Use two different channels (front and reverse channels)» Use time division in a channel

Channel 1 (b - b+3 0) Channel 2 (b+3 0 - b+6 0)

Channel 3 (b+6 0 - b+ 90)

Station A Station B

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Simplex/Duplex Communication

Normally, on a channel, a station can transmit only in one way.This is called simplex transmision

To enable two-way communication (called full-duplex communication)We can use Frequency Division MultiplexingWe can use Time Division Multiplexing

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What is Mobility

Initially Internet and Telephone Networks is designed assuming the user terminals are static

No change of location during a call/connectionA user terminals accesses the network always from a fixed location

Mobility and portability ± Portability means changing point of attachment to the network offline ± Mobility means changing point of attachment to the network online

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The Need for Wireless/Mobile Networking

Demand for Ubiquitous Computing ± Anywhere, anytime computing and communication

You don¶t have to go to the lab to check your email ± Pushing the computers more into background

Focus on the task and life, not on the computer Use computers seamlessly to help you and to make your life moreeasier.

± Computers should be location awareAdapt to the current location, discover services

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Some Example Applications of Ubiquitous Computing

You walk into your office and your computer automatically authenticatesyou through your active badge and logs you into the Unix systemYou go to a foreign building and your PDA automatically discovers theclosest public printer where you can print your schedule and give to your friend

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More Examples

You walk into a Conference room or a shopping Mall with your PDA andyour PDA is smart enough to collect and filter the public profiles of other

people that are passing nearby ± Of course other people should also have smart PDAs.

The cows in a village are equipped with G PS and G PR S devices and theyare monitored from a central location on a digital map.

± No need for a person to guide and feed themYou can find countless examples

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How to realize Ubiquitous Computing

Small and different size computing and communication devices ± Tabs, pads, boards ± PDAs, Handhelds, L aptops, Cell-phonesA communication network to support this ± Anywhere, anytime access ± Seamless, wireless and mobile access ± Need for Personal Communication Services (PCS)Ubiquitous Applications

± New software

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What does this course cover?

This course will cover the problems/solutions in the telecommunicationdomain ± G SM, G PR S, CDMA (telecom)«..We will also cover some fundamental problems/solutions for wirelessaccess

Wireless channel characteristicsIncreasing capacity through diversityMIMOOFDM

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Telecom and Data Networking

-R adio Propagation-L ink Characteristics-Error Models-Wireless MediumAccess (MAC)- Error Control

-Data Transmission-Mobile IP (integratingmobile hosts to internet)-Ad-hoc Networks-TCP over Wireless-Service Discovery

- Voice Transmission- Frequency R euse- Handoff Management-L ocation Tracking-R oaming-QoS-G SM, CDMA,Cordless Phones,-G PR S, ED G E

Telecom Interest Data Networking Interest

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Very Basic Cellular/PCSArchitecture

Base Station(BS) Mobile Station

Base StationController

MobilityDatabase

MobileSwitching

Center (MSC)

R adio Network

Public SwitchedTelephone Network

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Wireless System Definitions

± Mobile Station ± A station in the cellular radio service intended for use while in

motion at unspecified locations. They can be either hand-held personal units (portables) or installed on vehicles (mobiles)

± Base station ± A fixed station in a mobile radio system used for radio

communication with the mobile stations. Base stations arelocated at the center or edge of a coverage region. Theyconsists of radio channels and transmitter and receiver

antennas mounted on top of a tower.

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± Mobile Switching Center ± Switching center which coordinates the routing of calls in a

large service area. In a cellular radio system, the MSCconnections the cellular base stations and the mobiles to the

PSTN (telephone network). It is also called Mobile TelephoneSwitching Office (MTSO) ± Subscriber

± A user who pays subscription charges for using a mobilecommunication system

± Transceiver ± A device capable of simultaneously transmitting and receiving

radio signals

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± Control Channel ± R adio channel used for transmission of call setup, call request,

call initiation and other beacon and control purposes. ± Forward Channel

± R adio channel used for transmission of information from the base station to the mobile

± R everse Channel ± R adio channel used for transmission of information from

mobile to base station

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± Simplex Systems ± Communication systems which provide only one-way

communication ± Half Duplex Systems

± Communication Systems which allow two-way communication by using the same radio channel for both transmission andreception. At any given time, the user can either transmit or receive information.

± Full Duplex Systems

± Communication systems which allow simultaneous two-waycommunication. Transmission and reception is typically ontwo different channels (FDD).

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± Handoff ± The process of transferring a mobile station from one channel

or base station to an other. ± R oamer

± A mobile station which operates in a service area (market)other than that from which service has been subscribed.

± Page ± A brief message which is broadcast over the entire service

area, usually in simulcast fashion by many base stations at the

same time.

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Standards

Interacting systems require standardization

Companies want their systems adopted as standard ± Alternatively try for de-facto standards

Standards determined by TIA ( Telecommunication Industry StandardAssociation )/CTIA(Cellular Telephone Industry Association) in US ± IEEE standards often adopted

Worldwide standards determined by ITU-T(The telecom Standardization

Sector ) ± In Europe, ETSI (European Telecom Standard Association) isequivalent of IEEE

Standards process fraught withinefficiencies and conflicts of interest

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Electromagnetic Spectrum

< 30 KHz V L F30-300KHz L F

300KHz ± 3MHz MF3 MHz ± 30MHz HF30MHz ± 300MHz VHF300 MHz ± 3 G Hz UHF3-30 G Hz SHF> 30 G Hz EHF

1 04 1 02 1 00 1 0 -2 1 0 -4 1 0 -6 1 0 -8 1 0 -1 0 1 0 -1 2 1 0 -1 4 1 0 -16

1 04 1 0 6 1 0 8 1 0 1 0 1 0 1 2 1 0 1 4 1 0 16 1 0 18 1 020 1 022 1 024

IR UV X-Rays CosmicRays

RadioSpectrum

1MHz ==100m100MHz ==1m10 G Hz ==1cm

Microwave

Visible light

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Wavelength of Some Technologies

G SM Phones : ± frequency ~= 900 Mhz ± wavelength ~= 33cmPCS Phones

± frequency ~= 1.8 G hz ± wavelength ~= 17.5 cmBluetooth: ± frequency ~= 2.4 G z ± wavelength ~= 12.5cm

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Evolution of Current Systems

Wireless systems today ± 2G Cellular: ~30-70 Kbps. ± WL ANs: ~10 Mbps.

Next G eneration ± 3G Cellular: ~300 Kbps. ± WL ANs: ~70 Mbps.

Technology Enhancements ± Hardware: Better batteries. Better circuits/processors. ± L ink: Antennas, modulation, coding, adaptivity, DSP, BW. ± Network: Dynamic resource allocation. Mobility support. ± Application: Soft and adaptive QoS.

³ Current Systems on Steroids´

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Future G enerations

Rate

Mobility

2G

3G

4G802.11b WLAN

2G Cellular

Other Tradeoffs:Rate vs. CoverageRate vs. DelayRate vs. CostRate vs. Energy

Fundamental Design Breakthroughs Needed

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Current Wireless Systems

Cellular Systems

Wireless L ANs

Satellite Systems

Paging Systems

Bluetooth

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Cellular Phone Networks

BSBS

MTSOPSTN

MTSO

BS

San Francisco

New YorkInternet

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WL ANs connect ³local´ computers (100m range)

Breaks data into packets

Channel access is shared (random access)

Backbone Internet provides best-effort service

Poor performance in some apps (e.g. video)

01011011

InternetAccessPoint

0101 1011

Wireless L ocal Area Networks

(WL

ANs)

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Wireless L AN Standards802.11b (Current G eneration) ± Standard for 2.4 G Hz ISM band (80 MHz) ± Frequency hopped spread spectrum ± 1.6-10 Mbps, 500 ft range

802.11a (Emerging G eneration) ± Standard for 5 G Hz NII band (300 MHz) ± OFDM with time division ± 20-70 Mbps, variable range ± Similar to Hiper L AN in Europe

802.11g (New Standard) ± Standard in 2.4 G Hz and 5 G Hz bands ± OFDM

± Speeds up to 54 Mbps802.11n(New Standard) ± Standard for 2.4 G Hz and 2.5 G Hz bands ± DSSSCCK(Direct sequence spread spectrum complement key coding) or

OFDM ± Speed up to 600Mbps

± MIMO

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Satellite Systems

Cover very large areas

Different orbit heights ± G EOs (39000 Km) versus L EOs (2000 Km)Optimized for one-way transmission ± R adio (XM, DAB) and movie (SatTV) broadcasting

Most two-way systems struggling or bankrupt ± Expensive alternative to terrestrial system ± A few ambitious systems on the horizon

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Paging Systems

Broad coverage for short messagingMessage broadcast from all base stations

Simple terminalsOptimized for 1-way transmission

Answer-back hard

Overtaken by cellular

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8 C3 281 0.61- C imini -7/98

Bluetooth

Cable replacement R F technology (low cost)

Short range (10m, extendable to 100m)

2.4 G Hz band (crowded)

1 Data (700 Kbps) and 3 voice channels

Widely supported by telecommunications, PC, and consumer electronicscompanies

Few applications beyond cable replacement

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Ad-Hoc Networks

Peer-to-peer communications.No backbone infrastructure.

R outing can be multihop.

Topology is dynamic.Fully connected with different link SIN R s

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Design Issues

Ad-hoc networks provide a flexible network infrastructure for manyemerging applications.

The capacity of such networks is generally unknown.

Transmission, access, and routing strategies for ad-hoc networks aregenerally ad-hoc.

Crosslayer design critical and very challenging.

Energy constraints impose interesting design tradeoffs for communicationand networking.

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Energy-Constrained Nodes

Each node can only send a finite number of bits. ± Transmit energy minimized by maximizing bit time ± Circuit energy consumption increases with bit time ± Introduces a delay versus energy tradeoff for each bit

Short-range networks must consider transmit, circuit, and processing energy. ± Sophisticated techniques not necessarily energy-efficient. ± Sleep modes save energy but complicate networking.

Changes everything about the network design: ± Bit allocation must be optimized across all protocols. ± Delay vs. throughput vs. node/network lifetime tradeoffs. ± Optimization of node cooperation.

Di ib d C l Wi l

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Distributed Control over WirelessL inks

Packet loss and/or delays impacts controller performance.

Controller design should be robust to network faults.Joint application and communication network design.

Automated Vehicles- Cars- UAVs

- Insect flyers

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Joint Design Challenges

There is no methodology to incorporate random delays or packet losses intocontrol system designs.

The best rate/delay tradeoff for a communication system in distributed controlcannot be determined.

Current autonomous vehicle platoon controllers are not string stable with anycommunication delay

Can we make distributed control robust to the network?Yes, by a radical redesign of the controller and the network.

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Main Points

The wireless vision encompasses many exciting systems andapplications

Technical challenges transcend across all layers of the system design

Wireless systems today have limited performance and interoperability

Standards and spectral allocation heavily impact the evolution of wireless technology

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Homework

R ead and digest the following papers.Write a 500 words summary on both the papers and submit it by Next

Monday ± Fumiyuki Adachi, ³ Wireless Past and future Evolving Mobile

Communication Systems ´, IEIEC Trans, Fundamental, 2001

± D. Cox, Wireless Personal Communications: What is It? , IEEE

Perso nal Commu nicati o n s M agazin e , (April 1995), pp. 20-35.

These papers are on the course group

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Future Wireless Networks

Ubiquitous Communication Among People and Devices

Wireless Internet accessNth generation Cellular Wireless Ad Hoc

NetworksSensor NetworksWireless EntertainmentSmart Homes/SpacesAutomated HighwaysAll this and more«

Hard Delay Constraints

Hard Energy Constraints

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End

48731865-Lecture-1

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