Hedy Lamarr

How to Talk to People Who Use the Word “Orthogonal”

by Leslie Ellis // September 04 2012

Here’s one that’s sauntering back into tech-speak: Orthogonal.

Orthogonal is an oldie-but-goodie tech term, sure to imbue the person who utters it with an unmistakable whiff of tech intelligence. (It has nothing to do with your feet or shoes.)

As an everyday term, though, “orthogonal” is still largely inscrutable: A (math) term, meaning “at right angles.” Generally speaking, when people say “orthogonal” and they’re not talking about OFDM (yes there are people who say “orthogonal” conversationally), they mostly mean “irrelevant.” One thing doesn’t affect or disaffect the other thing.

In cable tech-talk, listen for “orthogonal” in tech-talk from broadband-side technologists working on what comes next with the DOCSIS cable modem specification. One of the potential expansions: OFDM, or, Orthogonal Frequency Division Multiplexing.

Know going in that OFDM is an upstream modulation thing, just as is QAM (quadrature amplitude modulation), QPSK (quaterny phase shift key), and S-CDMA (synchronous code division multiple access.)

Refresher: Modulation is the process of imprinting information onto a communications carrier, itself an electro-magnetic wave, so as to move that information from one physical location to another.

So, people talk about OFDM in the context of getting more stuff upstream, or responding to faster upstream speeds. (OFDM could be used for downstream modulation, too, but that’s not the initial application.)

OFDM, with improved error correction, could kick up some serious capacity – half as much again as what’s already down there. Which is good, because the upstream path is a slender five percent of total available capacity on any cable system.

How to earn style points when talking to engineers about OFDM: Ask the person who utters “OFDM” what they think Hedy Lamarr would say, if asked how it compares to her invention of CDMA. (A variation of which – Synchronous CDMA, or S-CDMA — is still used in cable modems.)

Lamarr, a celebrated MGM actress in the ‘30s and ‘40s, was romantically involved with a ranking military official in Europe, and endured the tedium of being treated as a bubblehead long enough to collect the facts she needed to develop what is now CDMA. (It also goes by “spread spectrum.”)

CDMA works by compartmentalizing a signal into a series of packets, which are smeared across a chunk of spectrum for transmission. It was initially used by the Dept. of Defense to transmit coded information. It’s like OFDM in that it codes data to move over smaller spectral slices.

But in every other sense, OFDM is essentially orthogonal to your everyday life.

This column originally appeared in the Platforms section of Multichannel News.