Real-time speech communication on packet networks named an IEEE Milestone

MIT Lincoln Laboratory's role in this seminal R&D effort is honored


On 8 December at a ceremony held at MIT Lincoln Laboratory, the IEEE Signal Processing Society and the IEEE Boston Section presented the Laboratory with an engraved plaque honoring the inclusion of the "First Real-Time Speech Communication on Packet Networks" in the select list of IEEE Milestones in Electrical Engineering and Computing. The plaque that is now permanently installed at the Laboratory reads: "This work in real-time network protocols and speech coding laid the foundation for voice-over-Internet-protocol (VoIP) communications and related applications including Internet videoconferencing." IEEE leaders who joined in the presentations were Dr. Karen Panetta, chair of Boston Section IEEE, and Dr. Mostafa Kaveh, president of the IEEE Signal Processing Society. Dr. Peter Staecker, president-elect of the IEEE, presented the award plaque to Dr. Eric Evans, director of Lincoln Laboratory.

photo of plaque and attendees at IEEE Milestone ceremonyThe plaque honoring "First Real-Time Speech Communication on Packet Networks" as an IEEE Milestone in Electrical Engineering and Computing seen here is installed permanently at Lincoln Laboratory. From left to right are Dr. Clifford Weinstein, a contributor to the milestone achievement and leader of the Human Language Technology Group, Lincoln Laboratory; Dr. Peter Staecker, president-elect, IEEE; Dr. Karen Panetta, chair, Boston Section IEEE; Gilmore Cooke, IEEE Boston Section History and Milestone Committee; and Dr. Eric Evans, director, Lincoln Laboratory.

In the 1970s and early 1980s, the Laboratory, working on its own and in collaboration with other research laboratories, conducted pioneering research, development, and experiments in the use of packet networks for speech communications. In August 1974, the first real-time packet speech, between Lincoln Laboratory and the University of California's Information Sciences Institute in Marina del Rey, California, used 8 kbps continuously variable slope delta modulation to digitize the speech, and traversed at least eight hops on the ARPANET (for Advanced Research Projects Agency Network). The first real-time linear predictive coding (LPC) communication over the ARPANET, with speech coded at 3.5 kbps, took place between Culler Harrison, Inc. (CHI) in Goleta, California, and the Laboratory in December 1974. In 1976, CHI, SRI in Palo Alto, California, and Lincoln Laboratory participated in the first real-time LPC conferencing over the ARPANET. And, in June 1982, a major achievement was realized: packet-speech conferencing over a wideband satellite network was demonstrated by linking voice terminals on local-area cable networks at Lincoln Laboratory, a mobile packet radio net at SRI, and the Information Sciences Institute, where a special interface provided connection to the regular switched telephone network.

The ground-breaking work on speech in packet networks combined major developments in multiple areas, including the first real-time implementations of narrowband LPC for speech coding on digital signal processors, network protocols to enable real-time packet delivery, strategies for reconstituting speech, techniques for reconstitution of speech from packets arriving at nonuniform intervals, packet speech conferencing techniques, and interoperation over different types of packet networks (land-line, Ethernet, satellite, radio).

The development of a network voice protocol to address packet and reliability constraints of the then-available transmission-control protocol (TCP) implementation that made TCP unsuitable for real-time communication was critical to the subsequent development of technology enabling real-time Internet applications such as packet video, so that now systems like Skype provide real-time voice and video at home and in offices.

In his introductory remarks at the plaque presentation, Dr. Clifford Weinstein, leader of the Human Language Technology Group at Lincoln Laboratory and a contributor to the packet speech milestone work noted, "When I have Skype conversations with my grandchildren out in California, I think of all the innovators here who did groundwork that made those packet voice and video conversations possible."

Dedication Brings Internet Pioneers to Lincoln Laboratory
Many of the people who collaborated in the packet speech achievements attended the presentation event, including Dr. Duane Adams, the DARPA program manager for the work starting around 1977, and contributors from SRI International, BBN Technologies, and Lincoln Laboratory.

Photo of Governor Deval Patrick and other dignitaries at press conference at Lincoln LaboratoryContributors to the "First Real-Time Speech Communication on Packet Networks" are seen here with special guests at the presentation event. The permanent plaque for the Milestone resides at Lincoln Laboratory; contributors received commemorative versions.


Dr. Robert E. Kahn, the original program manager from the Defense Advanced Research Projects Agency (DARPA) who initiated the research and led it through its first several years, gave the keynote talk, "Perspectives on Packet Speech, ARPANET, and the Development of the Internet." Dr. Kahn, now chairman, chief operating officer, and president of the Corporation for National Research Initiatives, was a co-inventor of the TCP/IP protocols and an originator of DARPA's Internet program. Kahn emphasized the outstanding collaboration in the packet speech work: "The program was remarkable in that this was a really collegial group of folks, from multiple organizations and with expertise across multiple technical areas, working together to make it succeed and generous in sharing the credit."

Mr. Stephen Casner, a leader in packet speech and video and a major contributor to the milestone work when he was at the Information Sciences Institute, spoke on the "Development of Real-Time Speech and Video Applications on Packet Networks." Casner's talk included a video showing an early packet speech conferencing demonstration and featuring Dr. Danny Cohen, the principal architect of the network voice protocol.

Background of the IEEE Milestones
The IEEE Milestones recognize technologies for their excellence, innovativeness, and benefit to humanity. Established in 1983 in conjunction with the 1984 IEEE Centennial Celebration, the Milestones are a component of the IEEE's Global History Network (GHN), a wiki that is administered by the IEEE History Center and to which IEEE members and invited experts may contribute. The GHN’s mission is "to be the world's premier site for the documentation, analysis and explanation of the history of electrical, electronic, and computer technologies, the scientists, engineers and business people who made these technologies happen, and on the history of the organizations to which these men and women belonged." Milestones, which may be unique products, seminal papers, patents, or decisive accomplishments, are nominated by an IEEE section, society, or chapter and are approved by the IEEE Board of Directors after recommendation by the IEEE History Committee.

The "First Real-Time Speech Communication on Packet Networks, 1974–1982" joins a prestigious catalog of more than 120 revolutionary technical achievements, starting with the 1751 publication of Experiments and Observations on Electricity by Benjamin Franklin and including the construction of the U.S. transcontinental telegraph in 1861, Alexander Graham Bell's first intelligible voice transmission over electric wire in 1876, the development of electronic television by Japanese researchers from 1924 to 1941, the invention of the first transistor at Bell Telephone Laboratories in 1947, the demonstration of the first semiconductor integrated circuit in 1958, the first transatlantic transmission of a television signal via satellite in 1962, and the inception of the ARPANET (the forerunner of the Internet) in 1969. The packet speech milestone is the first IEEE milestone awarded to Lincoln Laboratory, and the second awarded to MIT. The first MIT IEEE milestone is for the operation of the MIT Radiation Laboratory from 1940 to 1945. Each Milestone is commemorated with a bronze plaque that is placed at an appropriately meaningful site during a dedication ceremony.

Posted February 2012


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