Monday, August 1, 2011

Steve Perlman’s white paper explains “impossible” wireless tech | VentureBeat

With the caveat that when a talented engineer says something is "impossible," it means the speaker honestly believes something cannot be done, because "we cannot, with our known technology, do so." That might not be the same thing as saying "nobody else can do this." That might be the case for a new mobile bandwidth grooming approach championed by
Steve Perlman, who believes a different approach to bandwidth management could exceed "Shannon's Law" by about an order of magnitude.

Shannon’s Law is a rule of thumb about the theoretical capacity of any communications channel. But some might quip that "Shannon was wrong."

Perlman’s “distributed input distributed output” technology allows each wireless user on a network to use the full data capacity of shared spectrum, simultaneously with a bunch of other users. It claims to do so by eliminating interference between users sharing the same spectrum.

Critics will say it violates the laws of physics. But some of us have heard the best engineers in a field say such things in the past, only to be proven wrong. I was once at a meeting of top engineers from the broadcast and cable TV industry hear a proposal from Telecommunications Inc. (TCI) that would allow delivery of high-definition television in 6 megahertz of bandwidth. The room essentially exploded into disbelief, as the current proposals then in circulation suggested it would take 20 MHz to deliver HDTV.

As it turned out, TCI was right, and HDTV now is delivered in 6 MHz.

On another occasion, I was quietly informed by some very senior Bell Laboratories engineers that an analog fiber optic access network "could not" deliver 40 cable TV signals, as cable industry engineers were saying was a minimum requirement for cable network fiber optic access systems. The reason for the belief was that lasers capable of doing so could not be produced.

As it turns out, it was entirely possible to produce lasers with characteristics that would allow delivery of 40 channels of analog TV on a single laser, at reasonable distances. When those engineers said "it could not be done," what they meant was that "we cannot do so."

That doesn't mean that all such "impossible feats" actually result in commercially-significant deployments. But one has to translate. When somebody says "something cannot be done," that sometimes only means "we cannot do that." There's a big difference. Sometimes, the smart guys just aren't aware that somebody else might be able to do something formerly regarded as "impossible" or a violation of the laws of physics.

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