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IEEE Communications Society - 17th floor , 3 Park Avenue, New York, NY 10016
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Showing posts with label telecom. Show all posts
Showing posts with label telecom. Show all posts
Wednesday, January 16, 2013
IEEE GLOBECOM'13, Atlanta, Call for Papers
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Tuesday, September 11, 2012
The Foundations of Mobile and Cellular Telephony, IEEE Today's Engineer
The Foundations of Mobile and Cellular Telephony
A Southwestern Bell foreman testing mobile telephone service, St. Louis, 1946
(Courtesy AT&T Archives and History Center.)
Dave Meilhan, the first cellular telephone customer in Chicago, makes a call from his car phone, 1983. (Courtesy AT&T Archives and History Center.)
The Foundations of Mobile and Cellular Telephony
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BY SHELDON HOCHHEISER, PH.D., ARCHIVIST AND INSTITUTIONAL HISTORIAN, IEEE HISTORY CENTER
On 17 June 1946, a driver in St. Louis pulled out a handset from under his car’s dashboard, placed a phone call and made history. It was the first mobile telephone call, placed on a system inaugurated by Southwestern Bell, one of AT&T’s local operating companies.
A team including Alton Dickieson and D. Mitchell from AT&T’s research unit, Bell Labs, and H. I. Romnes from AT&T’s manufacturing subsidiary, Western Electric, had worked more than a decade to achieve this feat. By 1948, wireless telephone service was available in almost one hundred cities and highway corridors. Customers included utilities, truck fleet operators and reporters. But with only 5,000 customers making 30,000 weekly calls, it was far from commonplace.
This wireless network could handle only a small volume of calls. A single transmitter on a central tower provided a handful of channels for an entire metropolitan area. Between one and eight receiver towers handled the call return signals. At most, three subscribers could make calls at one time in any city using the single transmitter and the tiny amount of spectrum allocated by the Federal Communications Commission to this service. It was in effect a massive party line, where a tightly controlled number of subscribers had to listen first for someone else on the line, and, if finding the line free, signal an operator, who would place the call. During the call, the user depressed a button on the handset to talk and released it to listen. The equipment, of course employing vacuum tubes, weighed eighty pounds, filled much of a vehicle’s trunk and drew so much power that it would cause the headlights to dim. Service cost $15 per month, plus thirty to forty cents per local call, equivalent to $175 2012 dollars, plus $3.50 to $4.65 per call.
A Southwestern Bell foreman testing mobile telephone service, St. Louis, 1946
(Courtesy AT&T Archives and History Center.)
In 1965 an improved system, known as IMPS (for Improved Mobile Telephone Service), combined with a small increase in available spectrum, brought a few more channels and customer dialing, and eliminated the push-to-talk button in favor of full duplex capabilities. But capacity remained limited to the point that Bell System officials rationed the service to 40,000 subscribers, selected according to agreements with state regulatory agencies. For example, 2,000 subscribers in New York City shared just twelve channels, and typically waited thirty minutes to place a call. There was a long waiting list for would-be subscribers attesting to the demand for the service; a demand that could likely only be met by better technology.
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Something better — cellular telephone service — had been conceived in 1947 by Donald H. Ring at Bell Labs, but the idea could not be put into practice. His concept included multiple low power transmitters and receivers spread throughout a region or highway in series of cells, with different frequencies used in adjacent cells but reused within a city (or along a highway), and a way to switch the calls to adjacent cells as a vehicle moved down the road. The technology to implement such a scheme did not yet exist and the spectrum needed was not available. AT&T had applied to the FCC for more spectrum as early as 1946 and again in 1958, but none was forthcoming until 1968, when the FCC asked AT&T for a proposal for using a significant swath of spectrum that had been allocated to UHF TV channels 70-83, but was underused. A team of young research engineers at Bell Labs, including future IEEE fellows Joel Engel and Richard Frenkiel, had begun working on advanced mobile telephony two years earlier, rediscovering Ring’s concept, and developing it as a network of hexagonal cells. With the availability of solid-state electronics and computers they were able to propose a working system. Bell Labs switching expert (and IEEE Fellow) Amos Joel contributed another other crucial piece — a system to automatically switch the call from one cell to another. In 1971 AT&T submitted its report to the FCC for an analog cellular telephone system to be operated by AT&T on spectrum to be allocated by the FCC.
AT&T considered the system as a better way to provide telephone service to moving vehicles. Since all the vehicle equipment for the existing system was made for AT&T by Motorola, AT&T shared its work on the new system with the other company. Motorola, however, had another larger and more profitable business providing point-to-point private vehicle systems for Radio Common Carrier (RCC) uses like taxi dispatching. Motorola was afraid that a cellular system under AT&T control would mean the end of this business. So, Motorola did two things — it convinced their RCC customers to work with Motorola to argue before the FCC that the new spectrum and technology should not be the exclusive province of the telephone company, and it put a team to work on developing a hand-held cell phone, under the direction of company Vice President Marty Cooper. Cooper’s team succeeded, demonstrating a working prototype in April 1973. It weighed 45 ounces (1.28 kg) and its rechargeable battery was good for only around 30 minutes of calling, but it worked. His first call, made from a New York City street minutes before the scheduled public demonstration, went to his counterpart Engel at Bell Labs. The demonstration got the media’s and, more importantly, the FCC’s attention. Nonetheless, the FCC took eight years to decide what to do. While the FCC commissioners were deliberating, they authorized AT&T to demonstrate a working prototype commercial system in Chicago in 1978 and Motorola a system in Washington the following year.
Finally, in October 1981, the FCC announced that it would allocate two swaths of frequencies in the 800MHz range to cellular telephony, and would award two licenses in each market — one reserved for an incumbent wireline (i.e. telephone) company, and one for a non-wireline competitor. AT&T and its subsidiary Illinois Bell opened the first modern cellular system in Chicago in October 1983. A Motorola-designed system opened in Washington and Baltimore soon thereafter.The phones were expensive — a car phone cost $2500 and a portable phone $4000, not including airtime. With the breakup of the Bell System on 1 January 1984, all of the Bell System licenses passed to the newly divested regional telephone companies.
Dave Meilhan, the first cellular telephone customer in Chicago, makes a call from his car phone, 1983. (Courtesy AT&T Archives and History Center.)
Cell phone service availability quickly spread throughout the country as the FCC awarded more and more local licenses in what proved to be an increasingly complicated process. Cell phone sales and subscriptions far exceeded all expectations; apparently almost no one anticipated that mobile telephony would become more than a niche service. One well known, but not unique study, done by the consulting firm McKinsey and Company for AT&T in 1983, predicted that there would be 900,000 subscribers in the U.S. by 2000; that number was reached in 1987. (The actual total in 2000 was 109,000,000.) With this rapid growth, the available spectrum quickly became crowded. This led to pressure for the FCC to authorize additional spectrum (a pressure that has never ended), which it did. It also led to research by several companies into more efficient spectrum use. This resulted in two distinct digital transmission systems, TDMA, introduced in 1989 and CDMA, introduced in 1995.
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Sheldon Hochheiser, Ph.D., is archivist and institutional historian at the IEEE History Center at Rutgers University in New Brunswick, N.J.
Visit the IEEE History Center's Web page at:www.ieee.org/organizations/history_center.
The Foundations of Mobile and Cellular Telephony
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Saturday, June 23, 2012
Your Engineering Heritage: Pulse Code Modulation: It all Started 75 Years Ago with Alec Reeves
Your Engineering Heritage: Pulse Code Modulation: It all Started 75 Years Ago with Alec Reeves:
Pulse Code Modulation: It all Started 75 Years Ago with Alec Reeves
The First Disclosure of PCM: Paul M. Rainey, "Facsimile Telegraph System," U.S. Patent 1,608,527. Filed 20 July 1921.Issued 30 November 1926.
In 1969, the U.K. issued a 1 shilling stamp to commemorate PCM.
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Pulse Code Modulation: It all Started 75 Years Ago with Alec Reeves
BY JOHN VARDALAS, PH.D., OUTREACH HISTORIAN, IEEE HISTORY CENTER
In 1937, Alec Reeves came up with the idea of Pulse Code Modulation (PCM). At the time, few, if any, took notice of Reeve’s development. Even Reeves was forced to abandon his invention unable to see how it could be implemented with the technology of the day. In 1965, some 28 years later, the Franklin Institute awarded Alec Reeves the Stuart Ballantine Medal for his pioneering work on PCM. Labeling it a “major communications invention”, the Franklin institute’s press release reminded the public that PCM had made it possible for the Mariner IV spacecraft to transmit its wonderful images of Mars back to Earth. But in 1965, the true potential of PCM was still untapped. Today, on the seventy-fifth anniversary of Reeves idea, PCM has become an indispensable element in our modern communications infrastructure and a fundamental enabler of modern popular culture. For example, PCM has very dramatically transformed the way we record, distribute, and listen to music.
Long Distance Telephony and Noise
Alec Reeves, like other engineers working in telephony, grappled with the problem of the additive nature of noise when a signal underwent multiple amplifications along a long distance line. The development of telephony was a remarkable advance over telegraphy but it also introduced a new challenge. How was one to transmit an analog signal over long distances? Lee De Forest’s invention of the triode vacuum tube in 1906, which he called the Audion, not only heralded the birth of electronics and the rise of the radio broadcast technology, it also provided telephony with an important tool to expand the range of long distance calls: an amplification device. But each time the telephone signal was amplified, more noise would be introduced. Because of the dot-dash encoding, telegraphy did not suffer from the same problem. A telegraph repeater could easily replicate a weak dot or dash into a fresh one without introducing any noise. In 1937, Reeve’s had concluded that the best way to overcome the noise issue in long distance telephony was to transmit a digitized version of the analog voice signal.
Alec Reeves was born on 10 March 1902, in Redhill, Surrey, U.K. Reeves’s father, Edward Ayearst Reeves, had a distinguished career as a geographer. He was noted author on cartography and the Royal Geographical Society’s Surveyor. In 1918, Alec Reeves went to Imperial College, London, to study engineering. After graduating in 1921, he did postgraduate study at Imperial College. In 1923, Reeves joined the London Laboratory of International Western Electric, a leading manufacturer of radio and telecommunications equipment. In 1925, after his firm had been taken over by International Telephone and Telegraph (IT&T), Reeves went to work at IT&T's laboratory in Paris. It was there that Reeves came up, in 1937, with the idea of using a binary representation of sound to overcome the noise issue in long distance analog telephone transmissions. It a sense it was a return to the robustness of telegraphy.
Nearly seventeen years earlier, in 1921, Paul M. Rainey, from Western Electric, had filed a patent for a machine that would send faxes via telegraphy using a PCM-like technique to encode the optical scans of the pages.” An object of this invention,” claimed Rainey in his patent, “is to provide means whereby facsimile pictures, drawings or the like may be transmitted by means of code combinations or permutations of electrical impulses.” It took five years for the patent to be granted. Perhaps the patent office had difficulty wrapping its mind around the idea. Little is known as to whether Western Electric took the idea seriously and tried to produce a working prototype. Reeve’s knew nothing of Rainey’s PCM technique, which used an opto-mechanical implementation. Besides, Reeves was interested in an entirely different problem: noise in long distance telephony, using purely electronic digital techniques.
The First Disclosure of PCM: Paul M. Rainey, "Facsimile Telegraph System," U.S. Patent 1,608,527. Filed 20 July 1921.Issued 30 November 1926.
In 1938, after obtaining a French patent for his idea, he filed for a U.S. patent in 1939, which was then granted in 1942. His patent’s characterless title, “Electric Signaling System,” stood in sharp contrast to the great import of the patent’s contents. Many years later, Reeves recalled that, from the beginning, he “realized that it could be the most powerful tool so far against the effects of interference on speech — especially on long routes with many regenerative repeaters, since these devices could easily be designed and spaced so as to make the noise nearly noncumulative.” And yet Reeves walked away from this work. He realized that the PCM was an idea ahead of its time. The state of electronics at the outbreak of WW II was not up to the task of making PCM a viable commercial solution for telephony. Time would be needed for digital electronic hardware to catch up to the demands required by PCM. Finally, with the outbreak of war, Reeves’s focus shifted to the war effort and radar. He became be the Chief Scientist at Britain’s the Air Ministry Research Establishment, which had been founded by Watson Watt. During this time he also invented “Oboe” a system to for accurate bombing through overcast skies. “Oboe” was used in the large bombing raids over Germany and in the Pacific. Paradoxically, a wartime imperative brought a new impetus to the development of PCM, but this time from a very different need, one that had little to do with long distance telephony and noise.
Making Telephone Calls Secret: Bell Labs and SIGSALY
At the start of WW II, the only available technology for secure voice communication was the A-3 Scrambler system. U.S. military authorities did not know that the Germans had broken the A-3 Scrambler. Nevertheless top military officers like General George Marshal did not trust A-3 to securely transmit the most sensitive of information. Very early on in the war, the U.S. Army asked Bell Labs to come up with a new way of securing voice communications. It soon became apparent that digitizing the analog voice signal would allow one to apply cyphering techniques to the message. With cross-licensing agreements with IT&T, the Bell Labs people turned to Reeves work on PCM. The resulting speech enciphering system, called SYGSALY, became the first working example of PCM technology. Under the cloak of secrecy, Bell Labs made great strides in advancing the state-of-the-art in PCM techniques. By the war's end, several groups at Bell Labs had worked on PCM.
During the 1947-48 period, in numerous articles, the Bell Labs work on PCM finally became public. H.S. Black and J.O. Edson, who had been key people in Bell’s speech encryption efforts, published their account in the AIEE Transactions. They announced to the world that a “radically new modulation technique for multichannel telephony has been developed which involves the conversion of speech into coded pulses.” They also recognized the importance of Reeves patent. They concluded this important paper with “PCM appears to have exceptional possibilities from the standpoint of freedom from interference especially when applied to systems having many repeaters in tandem, but its full significance in connection with future radio and wire transmission may take some time to reveal.” It is interesting that Black and Edson chose an AIEE and not IRE journal in which to reveal this work to the world. In 1957, Black went on to win AIEE’s Lamme Medal. In 1948, which, in part, was due to his work in PCM. In 1948, Oliver, Pierce and Shannon published their landmark “The Philosophy of PCM” in the Proceedings of the IRE. Their paper, a rigorous analysis of PCM, confirmed the merits of Reeves original conception.
“PCM offers a greater improvement in signal-to-noise than other systems. By using binary (on-off) PCM, a high-quality signal can be obtained under conditions of noise and interference so bad that it is just possible to recognize the presence of each pulse. Further, by using regenerative repeaters which detect the presence or absence of pulses and then emit reshaped, respaced pulses, the initial signal-to-noise ratio can be maintained through a long chain of repeaters.”
Although they saw equipment for PCM as more complex than other forms of modulation, Oliver, Pierce, and Shannon concluded that “in all, PCM seems ideally suited for multiplex message circuits, where a standard quality and high reliability are required.”
What is striking about these papers, and all the others published by the Bells Labs group during the late 1940s, is the absence of any reference to speech encryption, which had been the driving force for Bell’s entry into PCM. The transition to civilian applications appears to have been seamless. When it came to it R&D investment in PCM, Bell Labs never took its eye off the company’s central mission, the telephone communications business. Although PCM for civilian uses had gotten off to a good start, progress remained slow.
Reeves observed that PCM had been a child with a long infancy, and that, even in 1965, this technology was still in the adolescent stage. Adequate miniaturization was still holding back its development. But two decades after the invention of the transistor at Bell Labs, semiconductor technology was finally diffusing rapidly through the economy. This accelerated progress was finally providing the hardware needed to make PCM economically viable for the wider civilian market. Reeves believed that PCM was going to be essential enabler for the information society that was appearing on the horizon. ARPANET, timesharing services, and the rise of cable television pointed to a demand for technology that could move large volumes of information across national and international networks. In 1965, Reeves argued that, by the year 2000, transmitting “moving pictures” would also be an essential part of data networks. He also felt that the pressures on the transportation infrastructure would further increase the importance of PCM. In the year 2000 “commuters will refuse to accept the delays and inconveniences that even a moderate journey to and from their place of work would entail. We shall have to transport the brains, the skills of the staff, not their bodies, to their daily jobs, again involving not merely ordinary data !inks but a great many private television channels as well.” Reeves concluded his crystal ball gazing by suggesting that PCM would form the very backbone of the communications systems. He was on the mark with this prediction, but his suggestion of a revolution in commuting patterns may need a few more decades before it comes to pass.
Although PCM had advanced considerably during Reeves’s life time, he never lived to see it outgrow adolescence. Reeves died in 1971.
In 1969, the U.K. issued a 1 shilling stamp to commemorate PCM.
Additional Readings and References
Alec Reeves, “Electric Signaling System”, U.S. Patent 2,272,070, 3 February 1942.
H.S. Black and J.O. Edson, “Pulse Code Modulation”, AIEE Transactions, Vol. 66 (1947), 895-9
B.M. Oliver, J.R Pierce, and C.E. Shannon, “The Philosophy of PCM”, Proceedings of the I.R.E., November 1948, 1324 – 31.
Alec H. Reeves, “The Past, Present, and Future of PCM”, IEEE Spectrum, May 1965, 58-63.
F. Maurice Deloraine, “The 25th Anniversary of pulse code modulation: Historical Background”, IEEE Spectrum, May 1965, 56-57.
For a Alec Reeves’s professional CV go to http://www.quantium.plus.com/ahr/
James E. Brittain, “Electrical Engineering Hall of Fame: Harold S. Black”,Proceedings of the IEEE, Vol. 99, No. 2 (Feb. 2011), 351-3.
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John Vardalas, Ph.D., is outreach historian at the IEEE History Center at Rutgers University in New Brunswick, N.J. Visit the IEEE History Center's Web page at:www.ieee.org/organizations/history_center.
Visit the IEEE History Center's Web page at:www.ieee.org/organizations/history_center.
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