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Switching and Transmission
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Packet Switching Types: ATM, Frame Relay, TCP/IP, X.25
Transmission: SONET T-Carrier
Services: [3G] [4G] [Bluetooth] [I-Mode] [WAP] [Wireless and packet switching]
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- Some of the first smart radios were built for the military. In Operation Desert Storm, the cacophony of allied combat radios-some 15 of them using a variety of frequencies, modulation techniques, encryption codes, and waveform standards, such as AM or FM or PCM (pulse code modulation)-created a virtual Babel in the sand. Units needed a separate radio system for every radio (or radar) standard. As a result, the Pentagon launched the Speakeasy project-one smart radio that could process all the different standards in software. Made by Hazeltine and TRW, the first prototypes were demonstrated successfully in 1994. Because standards change over time and hardware improves at the pace of Moore's law, a software programmable radio also saves money. Rather than upgrading the system in hardware every time the technology changes, software radios can be upgraded merely by downloading a new software module.
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- Speakeasy engineers have spread the word through the cellular industry. Stephen Blust, now at BellSouth Wireless, is leading an international effort to create smart radio standards-the MMITS project. Today, with the advance of an array of new digital technologies, including CDMA, TDMA, GSM, DECT 1900, SMR, PHS, and a spate of others, every urban area is becoming a Desert Storm of incompatible radios. Not only are these systems unable to communicate with one another, but they also require separate spectrum and base station equipment. All this redundant processing has raised the costs and reduced the universality of wireless and prevented cell phones from displacing wireline telephony.
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- The solution to complexity, however, is Moore's law: Put it on a chip. Reducing this Babel of complexity to silicon microchips, with hundreds of millions of transistors on centimeter slivers of sand that ultimately cost less than $2 to manufacture, smart radios can radically simplify the cellular landscape. Freed of most wires, poles, backhoes, trucks, workers, engineers, and rights of way, cellular should be far cheaper than wireline.
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- For example, the conventional analog base station that receives your cellular calls and connects them to the telephone network requires a million-dollar facility of 1,000 square feet. This structure may contain a central- office-style switch to link calls to the public switched telephone network, huge backup power supplies and batteries to handle utility breakdowns, and racks of radios covering every communications channel and modulation scheme used in the cell. This can add up to 416 radios, together with all the maintenance and expertise that multiple standards entail.
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- In the near future, one wideband radio will suffice. Digital signal processors ultimately costing a few dollars apiece and draining milliwatts of power will sort out all the channels, codes, modulation schemes, multipath signals, and filtering needs. Gone will be the large buildings, the racks of radios, the arrays of antennas, the specialized hardware processors. Gone will be the virtual honeycombs towering in the air in time and space with exclusive spectrum assignments and time slots, and possibly gone will even be the battalions of lawyers in the communications bar.
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- All this apparatus can be replaced by a programmable silicon base station in a briefcase, installed on any lamppost, elevator shaft, office closet, shopping mall ceiling, rooftop, or even a house. The result, estimated Don Cox of Stanford, the father of American PCS at Bellcore, could be a reduction of the capital costs of a wireless customer from an average of some $5,555 in 1994 to perhaps $14 after the turn of the century. That is a paradigm cliff of costs.
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- As smart radios (internal link) are delivered in the first years of the new century, they will allow escape from the zoo of conflicting protocols. Base stations will be programmable in software, able to handle any popular protocols, including the new technologies that will be emerging. The world of wireless will escape the bondage of air standards, where if you live in a GSM (global services mobile) area, you are forced to use GSM, and if you live in a CDMA (code division multiple access) area, your communications-poor cousins visiting from Europe will have to give up their GSM phone and demand to borrow yours (will they ever give it back?). Under the new regime, different standards mean different software loaded into RAM (random access memory) in real time. Any cell can accommodate a variety of access standards, channel assignments, and modulation schemes, and the best ones will win.
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- FROM MICROWAVES COME TORRENTIAL BITS
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- To get there from here, however, will require heroic achievements in the technology of radios. Every radio must combine four key components: an antenna, a tuner, a mixer, and a modem. Easiest is the antenna. Even though antennas too are converging with computer technology and becoming smart, for many purposes a shirt hanger will do the trick. It is the other components that deliver the message to the human ear.
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- Tuners usually employ the science of resonant circuits to select a specific carrier frequency or frequency band. The cellular band, for example, comprises 25 megahertz at around 850 megahertz. The PCS band comprises some 30 megahertz at around 1,950 megahertz. A mixer converts these relatively high microwave frequencies into an intermediate frequency (IF) or to a baseband frequency, which can be converted to a digital bitstream.
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- Familiar in the PC world, a modem is a modulator-demodulator. In transmitting, it applies an informative wiggle (AM or FM, say) to the carrier frequency. In receiving, it strips away the carrier, leaving the information. In the old world of dumb radios, transceivers join all these components into one analog hardware system. In the new world of smart radios, only the antenna and the front- end mixer are analog and hardwired. Channels, frequency bands, modulation schemes, and protocols all can be defined in software in real time. The radio becomes a programmable microwave eye-a device that can see whatever colors of RF you want to send it.
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- The key to digital radio is the analog-to-digital converter. It takes a radio or intermediate frequency and samples it at least at a rate double the frequency to translate it into a series of numbers. Imagine a strobe light illuminating a dancer. The light will have to strobe at least twice as fast as the dancer moves or you will not be able to detect the dance. Indeed, in a phenomenon called aliasing, you may see a different, slower dance, as you see a tire rotating slowly in the wrong direction on a film. In a similar way, an ADC strobes (samples) the dance of inflected frequencies on the carrier wave. The resolution of the ADC is measured in bits, setting how high the number can be that defines the waveform and, in samples per second, determining how high a frequency the ADC can capture without aliasing.
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- Ultimately, early in the next century, the advance of analog-to-digital converters will dispense even with the mixer. Then the all-software radio will be here. Analog-to-digital converters (ADCs) will be able to translate microwave frequencies directly from the antenna into a digital bitstream. Alcatel has already accomplished this feat in the GSM cellular band at its labs in Marcoussis, France. But so far this almost totally digital radio is a stunt rather than a product. That will change.
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- Most of today's ADCs cannot function reliably in real time at microwave frequencies (above 300 megahertz). Therefore, mixers are vital. Whether digital or analog, a mixer is essentially a multiplier. As invented by E. H. Armstrong, the father of FM, mixers are superheterodyne. They use local oscillators (LOs) to multiply the carrier frequency with a lower frequency. The key result is a frequency that represents the difference between the LO frequency and the carrier. This frequency is an intermediate frequency that holds all the information borne by the carrier but at a level that can be processed by existing ADCs.
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- By far the most effective mixer is the paramixer invented by Steinbrecher Corporation of Burlington, Massachusetts, now owned by Tellabs and renamed Tellabs Wireless. This device can range gigahertz of frequencies with a spur-free dynamic range (a range of volumes without spurious crackles or harmonics) that could capture the sound of a pin dropping at a heavy metal rock concert. For a fully digital superbroadband radio, a cascade of these still- costly devices is still the best bet. The pioneer of this technology since it was conceived a decade ago by MIT professor Donald Steinbrecher, Tellabs's Burlington operation introduced the Steinbrecher MiniCell in May for wireless local loop and interior cellular applications.
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- Tellabs has had trouble selling its wideband radios for cellular applications, for which they may be overdesigned. With the increasing spread of CDMA, which ordinarily uses only one to three channels, the initial gains from a broadband radio are small. But for a wireless local loop, with many thousands of customers in the Third World using all available channels, a broadband base station could offer large efficiencies. Replacing a large number of costly custom radios with one programmable device, the MiniCell may find its niche.
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- As ADC technology continues to advance, however, it will relieve pressure on the mixer, opening the way to still cheaper and lower power solutions. With the expiration of Steinbrecher's patent on the paramixer, the business is opening up. Watkins-Johnson has created a tiny mixer device in gallium arsenide the size of your smallest fingernail. So has Mini-Circuits of Brooklyn, New York. "It has 50% less performance than Steinbrecher's, but it costs only 10% as much. Many customers say, 'It's a deal,'" observes former Steinbrecher CEO and president R. Douglas Shute, now contemplating a startup.
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- AD converters are now edging toward microwave frequencies. Both Analog Devices and Comlinear, a National Semiconductor company, have introduced 40-megasample-per- second products at a resolution of 12 bits. This allows more of the mixing to move into digital multipliers. The first of the digital downconvertor chips came from Harris Corporation of Melbourne, Florida. Harris now has parlayed its expertise in RF and mixers into the creation of a sophisticated programmable machine that demonstrates the management of multiple modulation schemes in one cellular radio. Introduced on the floor of the Fifth Annual Wireless Symposium Exhibition in late February in Santa Clara, California, the Harris smart radio showcases its programmable HSP50214 digital downconvertor chip and is run from a PC. With an array of displays, the machine is designed to allow configuration and testing of smart transceivers from a Windows PC.
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- With high-powered digital signal processors and leading- edge ADCs, Analog Devices is a paragon of the digital radio paradigm. At the CTIA (Cellular Telecommunications Industry Association) meeting in San Francisco during the first week of March, Analog introduced a wideband smart radio tuned to the cellular band but applicable through the PCS band as well. A reference design to be used by infrastructure manufacturers, it displays an array of new chips from Analog comprising a specialized ADC called the 6600, tunable filters called the 6620 and the 6640 that function as a digital tuner, a SHARC DSP chip that performs the modem and channel-coding role (any advanced DSP will do), and a "sinfully cheap" Watkins-Johnson mixer chip the size of your fingernail. Incorporating an automatic gain control and a received signal strength indicator, the ADC is customized for smart radio applications.
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- The antenna is from Radio Shack (most any will do). From a Windows PC using Visual Basic, Analog engineers can move from one cellular channel to another and from GSM to CDMA to DECT 1900 to IS-136 to the Japanese Personal Handyphone system (PHS). As manufacturers around the globe converge on a single intermediate frequency of 70 megahertz, the reference radio could adapt to any cellular band, from 850 megahertz on up. All you would have to do is change or retune the mixer. According to Tom Gratzek, Analog Devices's director of base station marketing at the Analog communications center in Greensboro, North Carolina, customers say, "Shazaam!"
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- THE RUSH TO CASH IN ... WHO WINS, WHO LOSES
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- Interest is acute at all major telecom equipment manufacturers, from Ericsson to Motorola, and champions include every telecom company that thinks it may have guessed wrong in the GSM, TDMA, CDMA wars. BellSouth, for example, is slipping into a GSM ghetto, but it dreams of deploying smart radios that can play any popular standard and allow it to filch (i.e., service) CDMA customers. Also a TDMA orphan, AT&T could buy cheap, all-purpose base stations that allow it to sell any favored brand of service. Ericsson is using the technology to create indoor GSM base stations that can fit in a closet, and if worst comes to worst (as it will), Ericsson will also offer CDMA, perhaps initially as an overlay for data.
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- By drastically enhancing efficiency in the use of spectrum, broadband digital radios will lend new force to the industry's move up the frequency ladder toward bandwidth abundance. They enable the seamless convergence of the cellular band not only with the PCS band but also with an array of other applications such as the low-powered ISM (industrial, scientific, and medical) bands at 900 megahertz used by Baran's Metricom startup, the 24-gigahertz band of Associated Communications, the 28-gigahertz band of Local Multipoint Distribution Service (LMDS) used by CellularVision for wireless cable, and the 38-gigahertz band of WinStar. This up-spectrum bias assures the continued success of companies pressing the frontiers of microwave integrated circuits, low-noise amplifiers, power amplifiers, and other devices that function in the gigahertz.
- Going over the cliff of costs, the industry can introduce radically new products. We have just undergone the epoch of the personal computer, climaxing in 1996 with PCs outselling TVs in units for the first time. We are now entering a new era when a new form of PC will be dominant. It may not do Windows, but it will do doors. Tetherlessly transcending most of the limitations of the current PC era, the most common PC will be a digital cellular phone.
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- It will be a dataphone, as faithful readers of these pages will know. It will be as portable as your watch and as personal as your wallet. It will recognize speech and convert it to text. It will plug into a slot in your car and help you navigate streets. It will consult electronic yellow pages and give directions to the nearest gas station, restaurant, police headquarters, or hotel. It will collect your news and your mail and, if you wish, it will read them to you. It will conduct transactions and load credit into a credit chip on a smart card, which can be used like cash. It can pay your taxes, or help you avoid them, or soothe you with soft music as you do your calculus homework. It will take digital pictures and project them onto a wall or screen, or dispatch them to any other dataphone or computer. It will have an Internet address and a Java run-time engine that allows it to execute any applet or program written in that increasingly universal language. Or it will dock in a more powerful machine to perform more demanding functions. It will link to any compatible display, monitor, keyboard, storage device, or other peripheral through infrared pulses or radio frequencies.
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- And, oh yes, it will unlock your front door or car door, open your garage door, or even play Jim Morrison songs, if you are old enough to care for those swinging Doors of the 1960s (amazingly enough, my teenage daughters do).
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- Sorry, though, Nokia, your model 9000, which comes closest today to this new machine, will not cut it, at least in the United States, because it is based on Europe's increasingly obsolescent GSM standard. Also offering the right form factor but the wrong access standard is the IBM- BellSouth Simon, which is based on the U.S. analog cellular system (AMPS) or CDPD (cellular digital packet data). The most common PC will not be a GSM or CDPD device, because it will soon need to provide bandwidth on demand while draining the lowest possible power, whenever it is not plugged in. Thus the first PC of the new paradigm will probably have to be CDMA, built from the bottom up to provide bandwidth on demand, according to TCP/IP Internet standards, at a handful of milliwatts of communications power.
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- Among the companies soon to supply such machines, resembling the popular U.S. Robotics Pilot, are Sony, Qualcomm, Lucky-Goldstar, and Samsung. In cooperation with Alcatel, the European giant, which has just announced a CDMA program, Qualcomm base stations will soon contain a GSM link that can allow such CDMA dataphones to tie seamlessly to GSM systems in Europe. This will permit European carriers to use CDMA to expand capacity without jeopardizing their GSM customers.
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- Inspiring the Baran vision of wireless is the spectronic paradigm, in which most of the industry, from personal computers to cellular phones, moves on into the microwaves and is discussed more in terms of megahertz and gigahertz than in the usual metrics of mips and bits. The spectronic paradigm tends to favor the manufacturers of gallium arsenide, indium phosphide, and silicon germanium devices. Even as Philips and other firms push silicon bipolar chips toward microwave frequencies, the industry will move to higher domains of spectrum where gallium arsenide and indium phosphide tend to prevail. For the power amplifiers needed in every cell phone, gallium arsenide is superior to all the silicon variants. Pushed by the advance of the spectronics paradigm, the current ride of Vitesse, Anadigics, TriQuint, and other gallium arsenide innovators is likely to continue.
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- The major long-term winner is silicon germanium. Pioneered by IBM fellow Bernard Meyerson and tested and sampled by Analog Devices, silicon germanium combines much of the manufacturability of silicon with the high-frequency operation of gallium arsenide. IBM has recently contracted with Hughes's communications division to develop silicon germanium microwave devices.
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- As the technology advances, the broadband radios will be ideal to offer video teleconferencing, World Wide Web, and other image-rich wireless content, including CDMA bandwidth on demand. Data, not voice, will be the critical application. As people brandish their dataphones around the globe, linking to convenient displays through IR connectors, users can break out into a tetherless telecosm where they can work or play, study or pray, anywhere they go.
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- A major supplier of wireless in Third World countries may be NextWave, the aggressive CDMA vendor for PCS, now preparing an IPO. As a "carrier's carrier" providing only infrastructure and network services and leaving the sales and marketing to the locals, NextWave will join its complementary sister company in space, Globalstar, at the heart of a CDMA fabric of culture-independent worldwide communications. Watch Motorola's obsolescent Iridium, with its exclusive spectrum requirements and its effort to bypass all local infrastructure, sink like a stone.
- The new paradigm of wireless joins Baran's two key inspirations-Internet and smart radio-to burst the chains of geography. People who want leading-edge computers and communications can get them wherever they may live. Using Globalstar, Teledesic, and other low-earth-orbit (LEO) satellite systems that will be available as the smart radios roll out, students in the Third World can study or work in the First World. Teachers and entrepreneurs in the First World can serve and employ people around the globe. Imagined gaps between the information rich and poor will collapse in an infoscape equally accessible to all.
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- Baran has not spent his life in speculation or prophecy. Living at the heart of Silicon Valley in a walled and radiantly flowered community a few minutes down Middlefield Road from Netscape, Baran sits at the epicenter of a series of entrepreneurial creations. His home-office PCs and Power Macs are linked to the Internet through the Palo Alto Cable Co-op by cable modems from Com21, which he founded and now chairs. To run multimedia programming down twisted-pair wires, the regional Bell operating companies now propose to use discrete multitone technology (DMT), the basic technology conceived by Baran for Telebit and now the leading digital subscriber loop (DSL) method, taken up and perfected by Amati Communications, just down the road in San Jose. StrataCom, recently purchased by Cisco for $4 billion, began as a leveraged buyout spinoff from Baran's Packet Technologies.
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- Metricom, a Baran company with investments from Bill Gates, among others, offers wireless Internet services through Baran's neighborhood and at campuses across the country. Baran's company, Equatorial Communications, introduced spread spectrum commercially as a way of delivering information from satellites below the noise floor required by the FCC. Spread spectrum is now, in the form of the CDMA of Qualcomm and Globalstar, the world's fastest- growing communications technology. And it is the basis for the flourishing, unlicensed wireless systems, such as Metricom, operating at less than one watt of transmit power in the ISM (industrial, scientific, medical) bands.
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- Collectively, the visionary concepts of this once-myopic and still-modest engineer offer the foundation of an effort to reinvent the Internet in an increasingly wireless form and reshape the communications policies of the nation and the world.
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- http://www.gildertech.com/public/telecosm_series/inventing.html link now dead)
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- The following article, INVENTING THE INTERNET AGAIN, was first published in Forbes, June 2, 1997. It is a portion of George Gilder's book, Telecosm, which waspublished in 1997 by Simon & Schuster, as a sequel to Microcosm, published in 1989 and Life After Television published by Norton in 1992. Reposted by permission.
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