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Research inWireless Communications

Anders Høst-MadsenAnders Høst-Madsen

Department of EEDepartment of EE

University of HawaiiUniversity of Hawaii

Overview

The wireless revolution(s) Wireless systems Wireless principles Error correcting codes Information theory

ALOHA net

University Hawaii pioneer in wireless networking World’s first wireless “internet” Part of DARPA net project

Military project developing internet Developed by Norm Abramson in 1970s Interisland wireless connections ALOHA protocol

Still widely used

The Three Wireless Revolutions

The Wireless Marconi 1899

Wireless Everywhere – The past Radio in every home 1930s

Wireless Everyone – The present Mobile phones 1990s

Wireless Everything – The future Devices 2000s, 2010s

Mobile CommunicationWorld Wide

Europe Largest mobile phone market Driving innovation Rather low internet penetration

North America High internet penetration Low mobile phone penetration

Japan & Korea High penetration

– 50% in Japan– 70% in Korea!

Mobile phones are small! First with IMT2000 (2000!) Japan behind with (fixed) internet Japan: 6 mill wireless internet subscribers (I-mode)

Even babies in Korea have mobile phones!

Wireless Everywhere Broadcast Radio Systems

Wireless EveryoneCellular Systems

Wireless Everything

Every device can have built in wireless transceiver TV, HiFi, speakers

– Home entertainment center Watches

– Microsoft watch Refrigerators Plants Pacemakers and other internal sensors Clothes: environment, sunshine Microwaves

RFID technology

Wireless Sensor Networks

Sensors Temperature, humidity Movement Chemical, biological detectors Cameras, microphones

– X10 Actuators

Acts on sensed data Robots Computers

Applications Home environment, cleaning, Environment monitoring Battlefield, homeland security

Protecting Endangered Plants

Hard to do without knowing plants' needs, so

Study the environment

See how the plants are doing

Use sensors and hi-res cameras

Wireless EverythingAd-hoc networks

Communication System

0110100011100110…0110100011100110…

Bit errors

0110100011100110…0110000011101110…

Errors at random positionsBit error rate (BER)=percentage of wrong bits

Error Correcting Coding

01101 000 111 111 000 111

100 101 111 110 111

0 1 1 1 1

Repetition coding

Parity check

Hamming code

01101 011011 00101 011010

Information Theory

n repetitions Error decreases to zero with increasing n Rate decreases to zero with increasing n

Shannon It is possible to communicate with zero BER with a finite rate! Channel capacity

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53.0)1.0(

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Research in Communications

Coding Shannon(1948): proved theoretically that communication near channel

capacity possible 45 years of efforts to practically approach Shannon limit 1993: turbo codes, close to Shannon limit 1995: LDPC codes rediscovered, invented in 1962 Currently: improvement of turbo, LDPC codes

Information Theory Channel capacity of more advanced networks

Ad-Hoc NetworksExisting Technologies

IEEE 802.11 Not real ad-hoc standard

Bluetooth Primitive For small networks

Wireless EverythingAd-hoc networks

Wireless EverythingAd-hoc networks

Other Systems Research

Signal Processing Control Theory Networking Image Processing

Volumetric Data Compression using the Derivative of Gaussian Transform

n = 0 n = 3 n = 10 n = 21

n = 36 n = 53 n = 74 n = 99

0 5 10 15 20 25 30 35 40 45 500

0.1

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1

Frequency in cycles/degree

Con

tras

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nsiti

vity

CSFBasis function sensitivity

Professor Todd R. Reed

Data courtesy of:

The original volume. After 30:1 compression.

3-D DGT QuantizationLosslessCoding

Original volume

Compressedvolume

A 1-D DGT basis.A 3-D basis function.