The Evolution of Microwave Communications


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A brief history of microwave communications by Richard Laine, Principal Engineer, Aviat Networks.

Published in: Technology, Business

The Evolution of Microwave Communications

  2. 2. Agenda • Historical Perspective, not without controversy • “Wireless” in its Infancy—the Intertwining of Edison, Marconi, and Tesla • Propagation—the Intertwining of Huygens, Newton, Fresnel, and Einstein • Microwave Radios—The Early Days: PPM “digital,” Analog FM-FDM • Evolution of the U.S. Microwave Communications Industry • Evolution to Aviat Networks • Upgrade from Analog to Digital Microwave Hops • Digital Microwave Attributes—A Media Comparison2 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  3. 3. Wireless Communications – The Early Days Excerpt from the Scientific American July 1892 In the specification to one of his recent patents, Thomas A. Edison says: “I have discovered that if sufficient elevation be obtained to overcome the curvature of the earth’s surface and to reduce to the minimum the earth’s absorption, electric signaling between distant points can be carried on by induction without the use of wires.” MICROWAVE PATH ENGINEERING 117 YEARS AGO! Thomas A. Edison (1847-1931)Ohio3 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  4. 4. The First Wireless Communications Age The radio is one hundred years old, but it doesn’t look it! ... it is interesting to note that Samuel F. B. Morse’s telegraph was followed only 40 years later by the increasingly remarkable invention of radio frequency transmission. Thomas Edison experimented with signals that could be generated and detected at a distance in 1883, but did not appreciate the importance of “the Edison Effect.” Edison received a patent for wireless telegraphy in 1885, but was preoccupied with other projects. Edison sold the patent “for a song” to Marconi, who put extensive effort into the technology. By 1901, he sent Morse Code from Massachusetts to Cornwall, England. Roger Rusch Applied Microwave & Wireless Fall 1995 Samuel F. B. Morse (1791 – 1872) Scotland4 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  5. 5. Wireless – Marconi Inventor of the Radio? January 1897 An invention which promises to be of the greatest practical value in the world of telegraphy has received its first public announcement at the hands of Mr. William H. Preece, the telegraphic expert of the London post office. During a lecture on "Telegraphy Without Wires" recently delivered in London, Mr. Preece introduced a young Italian, a Mr. Marconi, who, he said, had recently come to him with such a system. Telegraphing without wires was, of course, no new idea. In 1893, telegrams were transmitted a distance of three miles across the Bristol Channel by induction. Young Marconi solved the problem on different principles, and post office officials had made a successful test on Salisbury Plain at a distance of three-quarters of a mile. Scientific American - January 1897 The roots of modern radio-links can be perceived in the first experiments carried out by Marconi, Guglielmo Marconi (1874-1937) Italy as he used very high frequencies—practically in the field of microwaves—and had recourse to 1909 Nobel Prize for Wireless Telegraphy parabolic-cylinder reflectors. Here is the first invention which Marconi anticipated. Many scientists before Marconi had devoted their work to the electric and magnetic phenomena, taking advantage of the extraordinary synthesis which James Clerk Maxwell’s equations had given them. In 1894, when he was only twenty, the young man from Bologna set up his first laboratory at Villa Griffone, about fourteen kilometers from his native city. Marconi’s basic contribution, for which he deserves the name of “inventor of the radio”, was, first of all, that he modulated by a signal the electromagnetic waves that a spark produced in a Hertz oscillator sent in space. James Clerk Maxwell (1831-1879) Scotland Gian Carlo Corazza 1996 European Conference for Radio-Relay, Bologna5 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  6. 6. Wireless – Marconi Inventor of the Radio? Or Not!! On 11 June 1943, the U.S Supreme Court overturned most of Marconi’s wireless communications patents thus upholding Nikola Tesla’s earlier September 1897 patent for radio, that in 1904 was reversed by the U.S. Patent Office and awarded to Marconi, based upon Tesla’s wireless communication demonstrations in 1894. This Supreme Court decision—five months after he died impoverished, alone in a New York hotel room—in effect recognized Tesla (who, shortly after arriving in the U.S. in 1884, had worked for Thomas Edison for $18 per week) as the inventor of the radio. This added to Tesla’s remarkable credentials as the inventor and architect of alternating current machinery and long-distance electrical distribution, this rendering obsolete his adversary Edison’s direct current electrical powerhouses that had been built up and down the Atlantic seaboard. Nikola Tesla (1856-1943) Austrian Empire “The Man who Invented the 20th Century”6 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  7. 7. Propagation – Huygens’ Principle? Or Not!! Christiaan Huygens, a contemporary of Sir Isaac Newton, is said to have gained most of his insights into wave motion by observing waves in a canal. In 1678, this great Dutch physicist wrote the treatise Traite de la Lumiere on the wave theory of light, and in this work he stated that the wavefront of a propagating wave of light at any instant conforms to the envelope of spherical wavelets (Huygens’ “Combination Wavefront” of separate waves) emanating from every point on the wavefront at the prior instant, with the understanding that the wavelets have the same speed as the overall wave. Christiaan Huygens Sir Isaac Newton Augustin-Jean Fresnel Albert Einstein (1629-1695) - Netherlands (1643-1727) - England (1788-1827) - France (1879-1955) - Germany7 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  8. 8. Propagation – Huygens’ Principle? Or Not!! An illustration of this idea, now known as Huygens Principle, is shown. Disbelieving, Newton continued to push his “Corpuscular Theory” of particle propagation of light, so because of that it was not until some 100 years later when Augustin-Jean Fresnel of “Fresnel lens” and “Fresnel zone” fame Illustration of Huygens’ Principle. Einstein and others opine the duality revisited Huygens’ Principle in 1815 The pinholes in the mask act as that light functions as both a particle secondary point sources of radio (per Newton) and a wave (per that his term “diffraction” was Huygens) depending on how the energy. reintroduced.* experiment is conducted and when observations are made.8 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  9. 9. Microwave Radio Links - The Early Days 2 GHz PPM “Digital” Radios 6 Bays!! 24xVF or 24x300 baud data channel capacity!! General Electric’s 2 GHz “radar-like” pulse position modulated (PPM, used during WW2 then declassified) hot standby terminal. Many hundreds of similar GE and ITT PPM radio hops were deployed in long pipeline, power and turnpike systems in the 1940s-50s, some up to 75 hops in length with no end-to- end noise buildup (like modern digital systems), all over the U.S. and worldwide for the military.9 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  10. 10. Microwave Radio Links - The Early Days AT&T Long-Haul Analog Routes Deployed 35,000 TD2 Repeaters The San Francisco-New York transcontinental route of hundreds of 4 GHz TD2 analog FM-FDM hops completed in 1951 for all long distance VF and TV was upgraded with high-capacity L6 GHz TH1 radios in 1955 and improved TD3 radios in 1962. The performance of analog hops was far more affected than later generation digital radio hops to equipment nonlinearities, interference, thermal noise, multipath distortion, waveguide echoes and moding, and fading.10 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  11. 11. U.S. Microwave Industry Evolution Through 1991 The Early Days U.S. Microwave Communications EXTINCT 50 Manufacturers from 1931 (ITT) through 1991 Farinon/Harris MCD (1958) and DMC/Stratex Networks (1984) merged to form Harris Stratex Networks (2007), which changed names to EXTANT 20 Aviat Networks (2010) (growing rapidly)11 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  13. 13. How We Evolved into Aviat Networks Kurt Appert* Len Erickson 1944 San Francisco 1947 San Carlos, CA Bill Farinon Lenkurt Electric Company Feb 1958 Bill Gibson 1959 Merger San Carlos Jan 1984 1980 San Jose Merger ( ) 1963 1981 Jan 26, 2007 Merger 1982 GTE Network Systems 2002 1998 1983 Microwave Communications Division (MCD) Siemens 1984 Transmission Systems 2010 Boca Raton Siemens Information and Communications Networks * Bancroft Library Oral history: EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  14. 14. The Migration from Analog to Digital Microwave Links It’s Been a Challenge! • Canadian Marconi delivered the first PCM digital radios to private microwave users in North America in 1970, some hops remaining in service into the millennium, thus triggering the rapid development and deployment of higher capacity (first 1152 VF ch/78 Mbit/s, then 1344 VF ch/90 Mbit/s) digital radios for LOS (line-of-sight) radio-relay hops. • This culminated in 1980 with the realization that the alarm/network management systems and adaptive equalization in these trailblazing digital radios were often found totally inadequate to accommodate the fragile, bursty characteristics of many high capacity digital microwave radios and spectral distortion caused by dispersive fading in hops not before seen in FM-FDM analog radio systems.14 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  15. 15. The Migration from Analog to Digital Microwave Links It’s Been a Challenge! • The 1980s thus brought about dramatic improvements in digital microwave modulation efficiencies and, with new adaptive equalization and powerful error correction, robustness to the dispersive (spectrum- distorting) fade activity that so degraded digital radio hop performance in the 1970s. • The mid-1990s heralded DSP equalizers that replaced discrete devices in far more robust advanced asynchronous (PDH) and 2016/1890 ch SONET/SDH point-to-point TDM digital radios. The FCC’s relocation of analog microwave hops from 2 GHz in the late 1990s to accommodate cellular deployment sped this digital migration. • These new PDH and SDH digital technologies supported the explosive birth of new high-performance terrestrial Fixed Wireless Systems and Fixed Wireless Access networks in all of their forms, e.g. Point-to-Point and Point-to-Multipoint, in synergism with fiber optics and FSO (free- space optical) networks.15 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011
  16. 16. Digital Microwave Attributes - a Media Comparison • Superior availability (“uptime”) —route security (no fiber optics cable cuts) Long Favors Fiber • Rapidly expandable and upgradeable, in-service if protected • High quality—no multihop “noise” addition as in analog microwave hops Turn-Up Time Microwave or Fiber • Rapid deployment over difficult terrain and into urban areas, unlike cable • Economical and secure—no copper or fiber optic cable deployment with right-of-way and security issues, and very high costs Favors Microwave • Robust to fading and interference compared to analog microwave hops Transport Choices Short • Much less sensitive to antenna feeder system and long-delayed ,on-path Low Required Transport Capacity High echoes compared to analog microwave hops Radio Fiber • Highly efficient data and broadband transport Availability/security  • Exacting in-service visibility of radio hop performance with NMS, PCR Payload (transport)  • Seamless interconnectivity to an ever-expanding digital transport (fiber Cost effectiveness  optics and other), PABX/MSC switch, and LAN/IP world Implementation time  Terrain considerations 16 EVOLUTION OF MICROWAVE COMMUNICATIONS: A BRIEF HISTORY JULY 2011