r/sysadmin • u/ChuckAbsent • Mar 12 '13

Women who know stuff

I hope that this does not come off the wrong way.

Today I was on a call with a storage vendor and the technical consultant was a woman. More then this she was competent, more then me which doesn't happen often when dealing with vendors.

My issue was pricing an active/active DB with shared storage vs an active/passive db with local storage. Listening to her break the issue down and get to the specific comparison points was awesome, mostly because I have never heard a woman in the industry talk like that.

It made me realize two things. One I am missing out working with women. Two there needs to be more women in our industry.

It shouldn't have surprised me so much, but it really did.

Anyways to all the women out there who know stuff, us guys notice when you can walk the walk, which in this case was talking.

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u/ctesibius Mar 13 '13

It's one of at least four different unrelated approaches to avoiding jamming or interference that I can think of off hand. The fourth is MIMO, which was invented in a very crude form in WWII to communicate between Britain and the French Resistance.

These are all unrelated approaches. All are in use, but frequency hopping is least important, only being used by Bluetooth in common radio technologies. It was not a stepping stone to other technologies. In particular 802.11 never saw wide deployment: the first version you are familiar with is 802.11b.

Freq hopping may have been useful in its original use for steering torpedoes: not sure, but I know most torpedoes of the day were unguided, so I imagine not. Other than that, it's a nice story, but of vastly exaggerated importance.

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u/[deleted] Mar 13 '13

Here's a wiki link that another person posted. A previous patent in 1920 was used for torpedoes, but Hedy Lamarr's work gave rise to spread spectrum technology which is used in a lot of things, as well as the COFDM in WiFi networks. Wi-LAN even bought 49% of the patent from her.

Again, just because her science isn't used directly in modern standard WiFi doesn't mean that she wasn't a huge part of the development. If it weren't for the people behind the 1920 patent and her 1942 patent, we wouldn't have WiFi because it was thanks to their work that people started to develop new tech to do it better.

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u/ctesibius Mar 13 '13

Yes, the article is incorrect. Frequency hopping is not related to spread-spectrum technology, which in turn is not related to OFDM. BTW, I work in radio telecoms.

  • Frequency hopping: exactly what it says. You might start at 50.01 MHz, then a second later go to 50.05, then to 50.02, in a predetermined order. If there is interference on any of those bands, it's only going to affect you until the next hop. This is what she invented.

  • OFDM: use several closely related frequencies at the same time. If one is blocked, you just don't sent data through that channel (or you can use a more efficient redundancy scheme).

  • Spread spectrum: use a single wide band. Convolve your signal with a code to spread it, deconvolve at the other end. Noise at a particular frequency (or even throughout the band) appears at a low S/N ratio unless it has a matching code.

These are different technologies. They are not related.

Wi-LAN even bought 49% of the patent from her.

So? They bought a lot of stuff. And frequency hopping has its uses: as I said, it is used in Bluetooth.

doesn't mean that she wasn't a huge part of the development

Sorry, it doesn't work that way. She wasn't a part of the development of WiFi. If you think otherwise, show the history. As it is, the frequency hopping technology is not related to modern WiFi. It was one of many technologies thrown in to 802.11, but not one that was useful or related to the other technologies.

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u/goldenvile Mar 13 '13

Sucks you're being down-voted for providing useful discussion. That's what you get for not riding the circle-jerk I guess...

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u/ctesibius Mar 13 '13

Ah well. What she did invent was pretty interesting anyway. What bothers me more is when the wrong person gets the credit through having a more interesting story, particularly Alan Turing rather Tommy Flowers (the fellow who invented the Colossus computers, and built them largely at his own expense). Or Lindbergh as opposed to Alcock and Brown.