Stephanie Alvelda and Madelyn Homick
Microdisplay technology has advanced rapidly over the past five years from purely speculative research to the inception of manufacturing. The US Defense Advanced Research Projects Agency (DARPA; Arlington, VA) has contributed significantly to this advancement by funding development of liquid-crystal-on-silicon display technology in the USA.1
DARPA's latest investment in the technology comes in the form of a nearly $5 million contract, managed by the US Army Soldier Center (Natick, MA), given to the Massachusetts Institute of Technology (MIT; Cambridge, MA) to support the technology research and product-development costs for a hand-held hardware platform that would ultimately access the World Wide Web. The MicroDisplay Corporation (San Pablo, CA) was awarded a $3 million subcontract by MIT to provide the high-performance miniature displays necessary for the Internet-access portable handset to be developed under the contract.
Central to the success of the program is MIT's development of a natural language-recognition system.2 "Jupiter" is a conversational system that allows users to access weather information through interactive conversationthe computer remembers and builds conversation abilities based upon previous exchanges. The military application for this program would allow soldiers to access information through voice queries to a computer, without requiring further human interaction. DARPA's interest is to provide a novel and effective means of communication for the US Marine Corps and eventually for the other uniformed services.
A miniature information display and graphics driver system for high-content visual displays in ultraportable consumer electronics and projection devices integrates a tiny, high-resolution, active-matrix liquid-crystal display with on-chip driver and decoding circuitry that exploits the liquid-crystal-on-semiconductor technology and operates in reflective mode. The miniature displays provide VGA, SVGA, and XGA resolutions, all of which are 0.63 in. in diagonal or smaller. Pixel sizes vary between 10 and 12.5 m to vary the resolution within roughly the same form factor.
The DARPA/MIT requirements call for distributing the drive electronics between the display itself and discrete components. Initially, this allows compatibility with legacy analog video formats, such as those provided by most laptop PCs. Ultimately, it enables low-cost application-specific integrated circuits to process emerging digital video formats, such as those in the latest consumer products. Addressing the drive electronics will require determining the optimal level of very-large-scale integration to maintain an aggressive power budget, while allowing for future system flexibility.
The silicon backplane allows additional functionality such as driver circuitry, video decoders, and signal-conditioning electronics to be integrated into the display itself. This technology is ideal for portable electronics, such as mobile phone handsets, in which small size and low power consumption are very important.
Consumer market
One more step is needed before such a device is ready for consumer usean upgrade to the wireless network that will enable enough bandwidth for visual images. Mobile communications providers currently are exploring the integration of the Internet with wireless devices by designing products that operate with the current wireless infrastructure, using low-resolution monochrome displays. The Wireless Access Protocol (WAP) standard targets fast delivery of Internet information to mobile users along with advanced value-added services.
The WAP is a communications protocol and application environment that can be used in hand-held digital wireless devices such as cellular telephones and pagers. It has been designed to work with most wireless networks, such as cellular digital packet data (CDPD), code division multiple access (CDMA), and global system for mobile communications (GSM). This open global standard has the support of a high percentage of the communications industry, as evidenced by communications giants such as Motorola (Schaumburg, IL), Ericsson (Stockholm, Sweden), and Nokia (Keilalahdentie, Finland), who are providing infrastructures to support the WAP standard. Cellular phones are emerging to equip consumers with access to the Internet in the palm of their hands. By implementing wireless mark-up language (WML), a simplified version of hypertext markup language (HTML), the WAP enables an Internet page to fit the display of a mobile communication device.
Making the wireless applications ready for the Internet forces designers to address the specific constraints of several portable electronics products. Wireless terminals are by definition feature phones, smart phones, and communicators. A feature phone will offer Internet browsing and text messaging. Smart phones have similar capabilities with a larger display, and the communicator is an advanced terminal about the size of a palmtop computer with a large display. The specifications define a microbrowser that can fit in a limited amount of memory in any of these mobile devices. Proxy technology and compression in the network interface minimizes process load enabling use of an inexpensive central processing unit in the handset.
Products using this technology consume less power, thereby extending battery life. The WAP intends to offer interactive services such as weather, banking, and news to users regardless of the wireless network or the small-screen wireless terminal that they are using.
The continued advance of mobile communications will allow concurrent voice, image, and data transfer, facilitating transfer of larger amounts of data, allowing the use of high-resolution displays. Many future communications and information services will be developed in the Internet Protocol environment. Cellular data-transfer capabilities will provide far more bandwidth, enabling wireless services with higher graphic content. There are close to 500 million mobile subscribers today, and the number is expected to grow to 1 billion during the beginning of this century.
Third-generation wireless
The device developed under MicroDisplay's DARPA subcontract could be commercialized to take advantage of third-generation (3-G) wireless networks scheduled to begin operation in this year. The emerging communications architecture for 3-G wireless networks will provide interconnectivity with global telecommunications networks. The fundamental technology for these networks already exists, combining high-speed mobile access with Internet Protocol-based services. When the marketplace is ready and wide-bandwidth radio interfaces are standardized, 3-G wireless networks and technology will be in sync with one another.
High-speed data capabilities in the form of general packet radio service and enhanced data rates for global evolution (EDGE) are emerging. General packet radio service is critical to launching current GSM networks to the third generation and delivers mobile Internet functionality. Data-throughput rates will jump from 9.6 to 115 kbit/s.
EDGE, the next step toward the third generation, will offer services at speeds up to 384 kbit/s, while still using the same infrastructure for the most part. This is a great advantage to operators, who will be able to offer more wireless data applications without making changes to their network structure.
Wideband code division multiple access (WCDMA) is the radio access technology chosen by the European Telecommunications Standards Institute (ETSI) to support third-generation multimedia via wide-bandwidth radio access. To process the higher data rates necessary to communicate voice and Internet access, WCDMA was selected due to its 5-MHz carrier compared to the 200-kHz carrier for narrow-bandwith GSM. The Universal Mobile Telecommunications System is the standard for delivering 3-G services in development under the power of the ETSI. It builds upon GSM technology and offers new potential for wireless multimedia.
REFERENCES
- See the Web: www.darpa.mil.
- See the Web: www.sls.lcs.mit.edu/sls/whatwedo/applications/Jupiter.html.
STEPHANIE ALVELDA is a marketing communications specialist and MADELYN HOMICK is a project coordinator for engineering at The MicroDisplay Corp., 3055 Research Dr., San Pablo, CA 94806; e-mail: [email protected].