Computing Now Exclusive Content — March 2010

News Archive

July 2012

Gig.U Project Aims for an Ultrafast US Internet

June 2012

Bringing Location and Navigation Technology Indoors

May 2012

Plans Under Way for Roaming between Cellular and Wi-Fi Networks

Encryption System Flaw Threatens Internet Security

April 2012

For Business Intelligence, the Trend Is Location, Location, Location

Corpus Linguistics Keep Up-to-Date with Language

March 2012

Are Tomorrow's Firewalls Finally Here Today?

February 2012

Spatial Humanities Brings History to Life

December 2011

Could Hackers Take Your Car for a Ride?

November 2011

What to Do about Supercookies?

October 2011

Lights, Camera, Virtual Moviemaking

September 2011

Revolutionizing Wall Street with News Analytics

August 2011

Growing Network-Encryption Use Puts Systems at Risk

New Project Could Promote Semantic Web

July 2011

FBI Employs New Botnet Eradication Tactics

Google and Twitter "Like" Social Indexing

June 2011

Computing Commodities Market in the Cloud

May 2011

Intel Chips Step up to 3D

Apple Programming Error Raises Privacy Concerns

Thunderbolt Promises Lightning Speed

April 2011

Industrial Control Systems Face More Security Challenges

Microsoft Effort Takes Down Massive Botnet

March 2011

IP Addresses Getting Security Upgrade

February 2011

Studios Agree on DRM Infrastructure

January 2011

New Web Protocol Promises to Reduce Browser Latency

To Be or NAT to Be?

December 2010

Intel Gets inside the Helmet

Tuning Body-to-Body Networks with RF Modeling

November 2010

New Wi-Fi Spec Simplifies Connectivity

Expanded Top-Level Domains Could Spur Internet Real Estate Boom

October 2010

New Weapon in War on Botnets

September 2010

Content-Centered Internet Architecture Gets a Boost

Gesturing Going Mainstream

August 2010

Is Context-Aware Computing Ready for the Limelight?

Flexible Routing in the Cloud

Signal Congestion Rejuvenates Interest in Cell Paging-Channel Protocol

July 2010

New Protocol Improves Interaction among Networked Devices and Applications

Security for Domain Name System Takes a Big Step Forward

The ROADM to Smarter Optical Networking

Distributed Cache Goes Mainstream

June 2010

New Application Protects Mobile-Phone Passwords

WiGig Alliance Reveals Ultrafast Wireless Specification

Cognitive Radio Adds Intelligence to Wireless Technology

May 2010

New Product Uses Light Connections in Blade Server

April 2010

Browser Fingerprints Threaten Privacy

New Animation Technique Uses Motion Frequencies to Shake Trees

March 2010

Researchers Take Promising Approach to Chemical Computing

Screen-Capture Programming: What You See is What You Script

Research Project Sends Data Wirelessly at High Speeds via Light

February 2010

Faster Testing for Complex Software Systems

IEEE 802.1Qbg/h to Simplify Data Center Virtual LAN Management

Distributed Data-Analysis Approach Gains Popularity

Twitter Tweak Helps Haiti Relief Effort

January 2010

2010 Rings in Some Y2K-like Problems

Infrastructure Sensors Improve Home Monitoring

Internet Search Takes a Semantic Turn

December 2009

Phase-Change Memory Technology Moves toward Mass Production

IBM Crowdsources Translation Software

Digital Ants Promise New Security Paradigm

November 2009

Program Uses Mobile Technology to Help with Crises

More Cores Keep Power Down

White-Space Networking Goes Live

Mobile Web 2.0 Experiences Growing Pains

October 2009

More Spectrum Sought for Body Sensor Networks

Optics for Universal I/O and Speed

High-Performance Computing Adds Virtualization to the Mix

ICANN Accountability Goes Multinational

RFID Tags Chat Their Way to Energy Efficiency

September 2009

Delay-Tolerant Networks in Your Pocket

Flash Cookies Stir Privacy Concerns

Addressing the Challenge of Cloud-Computing Interoperability

Ephemeralizing the Web

August 2009

Bluetooth Speeds Up

Grids Get Closer

DCN Gets Ready for Production

The Sims Meet Science

Sexy Space Threat Comes to Mobile Phones

July 2009

WiGig Alliance Makes Push for HD Specification

New Dilemnas, Same Principles:
Changing Landscape Requires IT Ethics to Go Mainstream

Synthetic DNS Stirs Controversy:
Why Breaking Is a Good Thing

New Approach Fights Microchip Piracy

Technique Makes Strong Encryption Easier to Use

New Adobe Flash Streams Internet Directly to TVs

June 2009

Aging Satellites Spark GPS Concerns

The Changing World of Outsourcing

North American CS Enrollment Rises for First Time in Seven Years

Materials Breakthrough Could Eliminate Bootups

April 2009

Trusted Computing Shapes Self-Encrypting Drives

March 2009

Google, Publishers to Try New Advertising Methods

Siftables Offer New Interaction Model for Serious Games

Hulu Boxed In by Media Conglomerates

February 2009

Chips on Verge of Reaching 32 nm Nodes

Hathaway to Lead Cybersecurity Review

A Match Made in Heaven: Gaming Enters the Cloud

January 2009

Government Support Could Spell Big Year for Open Source

25 Reasons For Better Programming

Web Guide Turns Playstation 3 Consoles into Supercomputing Cluster

Flagbearers for Technology: Contemporary Techniques Showcase US Artifact and European Treasures

December 2008

.Tel TLD Debuts As New Way to Network

Science Exchange

November 2008

The Future is Reconfigurable

Research Project Sends Data Wirelessly at High Speeds via Light

by George Lawton

Siemens scientists are working with the Heinrich Hertz Institute the Visible Light Communication (VLC) project. VLC uses white-light-emitting diode (LED) technology to transmit data at 500 Mbits per second over 5 meters. "This is much faster than other VLC work using this type of LED by a long shot," said Dominic O'Brien, an engineering science researcher at the University of Oxford. This beats the previous record of 200 Mbps set by the same group and is much faster than current Wi-Fi technologies, which operate at speeds up to 150 Mbps with 802.11n.

The researchers used Ostar white-LEDs designed for room lighting from Siemens' subsidiary, OSRAM Opto Semiconductors. This technology could allow ceiling lights to double as high-speed data broadcasting equipment, said Sebastian Randel, research scientist at Siemens. "Today's LEDs are slowly starting to replace conventional light bulbs," he said. "The idea is to upgrade the existing driver electronics systems to provide communications features on the transmitter side. Improvements are also needed for the receivers."

The VLC research started four years ago and was incorporated into the EU-funded Omega project that launched in 2008. Omega aims to increase wireless bandwidth for homes and offices to 1 Gbps, using VLC and radio frequency technologies. "The goal for VLC is to demonstrate 100 Mbps by modulation of ceiling lighting, and the work is going according to plan," said Jelena Vucic research scientist at the Heinrich Hertz Institute in Germany. VLC partners successfully demonstrated an VLC implementation earlier this year at the Omega Open Event 2010, operating at 84 Mbps and transmitting three parallel HD video signals.

Transmitting light indoors causes challenges from reflections and multipath interference as the light rays bounce off the walls and cause the signals to interfere with each other. The high data rates are only possible with a direct line of sight between the light and the receiver. Data can also be transmitted with the diffuse light that reflects off the walls for uses outside a line of sight, but the data rates are much lower.

Improved Modulation Techniques

Current white LEDs are built using blue LEDs that energize a layer of phosphorous material, causing it to glow white. The blue LED itself can be rapidly turned on and off, making it easy to modulate with a digital signal. However, the phosphor has a much slower response time, so the researchers use a filter on the receiver to isolate the blue light, which improves the data rate.

Efficient modulation of the LED also requires a special driver-amplifier design, which has been a major challenge for the project. "The main hindrance to achieving high data rates is the limited system bandwidth due to the LED itself or its driver," said Vucic, "even with blue filtering."

The simplest modulation scheme uses on-off keying, which turns the light rapidly on and off, but this only allows a data rate of 1 bit/second/Hz. To achieve higher data rates, the researchers have been investigating two separate modulation schemes: discrete multitone modulation (DMT) and multilevel pulsed-amplitude modulation (M-PAM). DMT systems have achieved link spectral efficiencies of up to 4 bits/second/Hz.

DMT lets the system modulate different subcarriers within the transmission band separately, which supports adaptation based on transmission band noise and interference. Through a process called bit-loading, DMT can carry more information on frequency slices with low-noise and throttle down the data rate on noisier parts of the spectrum. This isolates the impact of noise across the entire system.

M-PAM is spectrally efficient as well, but it's usually regarded as a baseband technique, which doesn't support bit-loading. Consequently, noise on one spectral slice impacts the entire transmission band.

VLC's Prospects

VLC offers several potential advantages over RF communications. It can provide more secure communications over a shorter range because walls and curtains can easily block light signals, whereas potential eavesdroppers can easily detect RF signals from outside buildings. The technology could be useful in factories and hospitals, in which radio transmissions are either impossible or limited owing to concerns about RF interference with critical equipment.

The new technology's main limitation is that it is primarily envisioned as a one-way broadcast technology. Bidirectional communications would have to occur over a different technology such as Wi-Fi.

Several efforts are under way to develop VLC standards. The IEEE 802.15 task group 7 is working on one standard. Meanwhile, the VLC Consortium in Japan is working to harmonize VLC technology with the existing IrDA standard for infrared-based communications so that? VLC transmitters and receivers could use existing IrDA optoelectronic modules with only slight modification.

Other VLC projects in Japan are focused on increasing VLC communication distances to hundreds of meters rather than the data rate. VLC could then support signaling between special stop lights and trains or beam digital information from special bill boards. The Japanese are also exploring the possible use of VLC to send position-tracking information to specially equipped shopping carts.

For more information on VLC, visit the following Web sites: the Visible Light Communication Consortium at, the 802.15 Task Group 7 at, and the Omega Home Gigabit Access project:

George Lawton is a freelance technology writer based in Guerneville, California. Contact him at