1 Research in Wireless Communications Anders Høst-Madsen Department of EE University of Hawaii

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

ALOHA net l University Hawaii pioneer in wireless networking l World’s first wireless “internet” l Part of DARPA net project n Military project developing internet l Developed by Norm Abramson in 1970s l Interisland wireless connections l ALOHA protocol n Still widely used

The Three Wireless Revolutions l The Wireless n Marconi 1899 l Wireless Everywhere – The past n Radio in every home n 1930s l Wireless Everyone – The present n Mobile phones n 1990s l Wireless Everything – The future n Devices n 2000s, 2010s

Mobile Communication World Wide l Europe n Largest mobile phone market n Driving innovation n Rather low internet penetration l North America n High internet penetration n Low mobile phone penetration l Japan & Korea n High penetration –50% in Japan –70% in Korea! n Mobile phones are small! n First with IMT2000 (2000!) n Japan behind with (fixed) internet n Japan: 6 mill wireless internet subscribers (I-mode) Even babies in Korea have mobile phones!

Wireless Everywhere Broadcast Radio Systems

Wireless Everyone Cellular Systems

Wireless Everything l Every device can have built in wireless transceiver n TV, HiFi, speakers –Home entertainment center n Watches –Microsoft watch n Refrigerators n Plants n Pacemakers and other internal sensors n Clothes: environment, sunshine n Microwaves l RFID technology

Wireless Sensor Networks l Sensors n Temperature, humidity n Movement n Chemical, biological detectors n Cameras, microphones –X10 l Actuators n Acts on sensed data n Robots n Computers l Applications n Home environment, cleaning, n Environment monitoring n 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 Everything Ad-hoc networks

Communication System … Bit errors … … Errors at random positions Bit error rate (BER)=percentage of wrong bits

Error Correcting Coding Repetition coding Parity check Hamming code

Information Theory l n repetitions n Error decreases to zero with increasing n n Rate decreases to zero with increasing n l Shannon n It is possible to communicate with zero BER with a finite rate! n Channel capacity

Research in Communications l Coding n Shannon(1948): proved theoretically that communication near channel capacity possible n 45 years of efforts to practically approach Shannon limit n 1993: turbo codes, close to Shannon limit n 1995: LDPC codes rediscovered, invented in 1962 n Currently: improvement of turbo, LDPC codes l Information Theory n Channel capacity of more advanced networks

Ad-Hoc Networks Existing Technologies l IEEE n Not real ad-hoc standard l Bluetooth n Primitive n For small networks

Wireless Everything Ad-hoc networks

Other Systems Research l Signal Processing l Control Theory l Networking l Image Processing

Volumetric Data Compression using the Derivative of Gaussian Transform Professor Todd R. Reed Data courtesy of: The original volume. After 30:1 compression. Original volume Compressed volume A 1-D DGT basis. A 3-D basis function.