A radio technique that continuously alters its transmission pattern either by constantly changing carrier frequencies or by constantly changing the data pattern.
Direct Sequence Spread Spectrum (DSSS)
DSSS multiplies the data bits by a very fast pseudo-random bit pattern (PN sequence) that "spreads" the data into a large coded stream that takes the full bandwidth of the channel. DSSS is the basis for CDMA cellphones and 802.11 Wi-Fi wireless transmission. For a technical example of DSSS technology, see CDMA.
Frequency Hopping Spread Spectrum (FHSS)
FHSS continuously changes the center frequency of a conventional carrier several times per second according to a pseudo-random set of channels, while chirp spread spectrum changes the carrier frequency. Because a fixed frequency is not used, illegal monitoring of spread spectrum signals is extremely difficult, if not downright impossible depending on the particular method. FHSS is the transmission technology in Bluetooth. See 802.11, Wi-Fi and Bluetooth.
Invented in Hollywood
In 1940, Austrian-born Hedy Lamarr, considered one of the sexiest actresses of her time, was also a co-inventor of frequency hopping. She, along with George Antheil, an American composer, invented the concept of switching frequencies in order to develop torpedo radio signals that could not be jammed. In 1942, Lamarr and Antheil were awarded a patent on the concept, but the patent later expired, and they never made any money from the idea. It would be many years later before the technology was actually deployed. What made a famous actress take an interest in radio? Lamarr was previously married to an Austrian munitions tycoon and had carefully listened to his business discussions. She conceived the idea of hopping from frequency to frequency just like a pianist can play the same notes, but in different octaves.
A Dazzling Inventor
Hardly the typical geek, Hedy Lamarr was a famous actress and brilliant inventor. (Image courtesy of T.C. Candler, www.tccandler.com)
Direct Sequence Spread Spectrum (DSSS)
DSSS multiplies the data bits by a very fast pseudo-random bit pattern (PN sequence) that "spreads" the data into a large coded stream that takes the full bandwidth of the channel. DSSS is the basis for CDMA cellphones and 802.11 Wi-Fi wireless transmission. For a technical example of DSSS technology, see CDMA.
Frequency Hopping Spread Spectrum (FHSS)
FHSS continuously changes the center frequency of a conventional carrier several times per second according to a pseudo-random set of channels, while chirp spread spectrum changes the carrier frequency. Because a fixed frequency is not used, illegal monitoring of spread spectrum signals is extremely difficult, if not downright impossible depending on the particular method. FHSS is the transmission technology in Bluetooth. See 802.11, Wi-Fi and Bluetooth.
Invented in Hollywood
In 1940, Austrian-born Hedy Lamarr, considered one of the sexiest actresses of her time, was also a co-inventor of frequency hopping. She, along with George Antheil, an American composer, invented the concept of switching frequencies in order to develop torpedo radio signals that could not be jammed. In 1942, Lamarr and Antheil were awarded a patent on the concept, but the patent later expired, and they never made any money from the idea. It would be many years later before the technology was actually deployed. What made a famous actress take an interest in radio? Lamarr was previously married to an Austrian munitions tycoon and had carefully listened to his business discussions. She conceived the idea of hopping from frequency to frequency just like a pianist can play the same notes, but in different octaves.
A Dazzling Inventor
Hardly the typical geek, Hedy Lamarr was a famous actress and brilliant inventor. (Image courtesy of T.C. Candler, www.tccandler.com)
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2009 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- How Verizon might ruin Android
- Okay Dana - how might Verizon ruin Android?By not actually writing an answer to the posited headline, it sure appears to me that you are trying to get comments from people like me to write your article for you. It might work a little better if you actually posited an...
- Discussion threads 2009-10-06
- Palm tattles on Apple, finds itself in the hot seat instead
- Why?Apple has been proven to be far worse then Palm(read: Google Voice App), so what goes around, should come around.Untill Aplle confesses, and discontinue their shenanigans when it comes to apps on their devices, then they have no reason to voice any indignation against those that do the same thing...
- Discussion threads 2009-09-23
- Analyst: Apple to offer iPhone on U.S. carriers within a year; replace cable with iTunes subscriptions
- THANK GOD!!!!Ditch AT&T PLEASE!!!"Should never have been Allowed"AT&T Definitely needs competition. They are only gouging because they can. Exclusive deals are never good for the consumer. As it is, there are only two major cell phone providers which grab 70% of the market. AT&T and Verizon both overcharge for their...
- Discussion threads 2009-08-31
- Google, Microsoft demand place at medical stimulus table
- No, of course notNo, Obama doesn't want to kill your grandma. But he DOES want her to wait in the back of the line for that hip transplant while other, younger, patients get higher priority. If she dies while waiting, well, that's a shame, but there's limits to...
- Discussion threads 2009-08-08
- LEDs get royal treatment, will they save the planet?
- LEDs get royal treatment, will they save the planet?We have mostly CFLs in our house.They are very bright for the wattage the use. They also have different spectrum values. But the mercury is a nasty drawback. I hope the LEDs will have a similar selection of the...
- Discussion threads 2009-05-31
- Social PR Survey II: Continued disconnect between clients, agencies
- Back in February I published the results of a social public relations survey that attempted to gauge client satisfaction levels with their current PR agencies. What showed up was dismal - and really showed that client trust in their agencies was low. Given that data, and several...
- Blog posts 2009-05-11
- Report: US air-traffic control systems hacked
- Report: US air-traffic control systems hacked Why does....The FAA need to have these systems linked to a public facing system? Couldn't they use private networks and segment this stuff from the internet? I just don't understand why there needs to be a connection. I would just like someone...
- Discussion threads 2009-05-08
- News to know: Windows 7; Swine flu; Facebook; SOA
- Here are today’s notable headlines. You can get News To Know via email alert and RSS daily. For continuous updates see BNET’s around-the-Web tech coverage. Zack Whittaker: Tech-take on the spread of swine flu. Techmeme Ed Bott: What you need to know about the Windows 7 Release Candidate ...
- Blog posts 2009-04-27
- Washington state rejects open source
- Washington state rejects open sourcePerfect example...Of what loibiest have the power to do. MS gets the big guys in their pocket. And then those big guys could care less if they lose half their workforce so long as they get whatever MS promised them.Just what problem is he trying to...
- Discussion threads 2009-04-17
- White House hates Martin's free Net plan
- Bad week for FCC chairman Kevin Martin. First he has to suffer through a 110-page litany of his management failures and now, the Wall Street Journal reports, the White House is hard-set against his plan for free Internet. Commerce Secretary Carlos Gutierrez sent this letter to Martin...
- Blog posts 2008-12-11
- FCC agrees to free white-space spectrum
- America wins. Large broadcasting companies and makers of devices like wireless microphones are squirming today after the FCC announced that it has voted in favor of Google -- freeing the frequencies between television channels to create a wireless broadband service. What does that really...
- Blog posts 2008-11-05
- FCC opens up wireless 'white spaces;' Assessing winners, losers and wild-cards
- The Federal Communications Commission has opened up so-called wireless white spaces--unused spectrum between broadcast channels--in a move the agency hopes paves the way for 'Wi-Fi on Steroids'. In a statement following the FCC's 5-0 approval Techmeme, Chairman Kevin Martin said: Opening the white spaces will allow...
- Blog posts 2008-11-05
- BIOS settings demystified
- BIOS settings demystifiedVery good info - thanks!One thing I found which maybe everyone else already knew, and I don't know if it is common to all BIOS versions or just the ASUS KV8 that I have, but under the Advanced tab, there's a Legacy USB support option - having it...
- Discussion threads 2008-09-30
- ROFLthing 2008
- Have you ever been to an internet culture conference? Earlier this year, Harvard senior Tim Hwang threw one in Cambridge, Mass., and it was a massive success. This time, Hwang wanted to have a smaller get together in San Francisco to chat about memes. Welcome to ROFLthing...
- Blog posts 2008-08-29
- UK CS graduates more likely to be unemployed
- UK CS graduates more likely to be unemployedIf you're any good, I wouldn't worry about itMy first question is whether that study takes into account whether people were employed in their actual field of study?Ie, does a job at McDonalds classify as being 'employed' or does every psychology major actually...
- Discussion threads 2008-08-20
- Wordcamp 2008
- In the quiet flats of University of California San Francisco Mission Bay campus, bloggers, thinkers, journalists, developers, and inventors melt together for a full day of lectures and learning. The goal of Wordcamp 2008 is to figure out the future of publishing on the web. ...
- Blog posts 2008-08-16
- Understanding Spectrum Intelligence
- While many bands of the Radio Frequency RF spectrum have a dedicated purpose, Wi-Fi operates in an unlicensed band of RF spectrum carved out by the Federal Communications Commission FCC, with few rules other than limiting the amount of transmit power, and encouraging the use of spread-spectrum technology. On the...
- White papers 2008-06-01
- Narrow-Band Interference Suppression in CDMA Spread-Spectrum Communication Systems Using Pre-Processing Based Techniques in Transform-Domain
- This paper presents two pre-processing based techniques in unitary transform-domain for narrow-band interference rejection in CDMA communication systems. In the techniques, by using Karhaunen-Loeve Transform KLT and Discrete Fourier Transform DFT, at the transmitter, eigenvectors occupied by NBI are determined; then the energy of the transmitted signal is set to...
- White papers 2008-03-19
- A geek's trip to Capitol Hill on Network Management
- I appeared before congressional and government staffers on Capitol Hill for a panel on Network Management sponsored by iGrowthGlobal. This was my first time in Washington DC and while it was a little cold for my Californian bones, it was a beautiful city and seeing the capitol of the nation...
- Blog posts 2008-03-03
- Wi-Fi crushes Bluetooth mouse for RF airspace
- Wi-Fi crushes Bluetooth mouse for RF airspaceMessage has been deleted.And your pavilion is an All-in-one?Not even sure why you need to resort to name calling. The computer has nothing to do with the network or bluetooth adapter anyways. Again, having them 1mm apart may have a lot to...
- Discussion threads 2007-11-28
Neighboring Terms
Premier Vendor Content Whitepapers, webcasts & resources from our Power Center Sponsors
- The best support in the Linux business
-
If Linux is going to power your mission-critical applications, you'd better have the best support known to business. Novell was rated the top provider of Linux technical support.
- Learn more >>
- Keep Up With The Latest In Document Management with The DocuMentor.
-
Doc delivers the scoop on today's enterprise content management, printer maintenance, and all other issues related to document management. It's the DocuMentor Blog.
- Learn more >>
- The best support in the Linux business
-
If Linux is going to power your mission-critical applications, you'd better have the best support known to business. Novell was rated the top provider of Linux technical support.
- Learn more >>
- The more you simplify, the more you save
-
When you transition from your existing Red Hat environment to SUSE Linux Enterprise from Novell, you can recognize dramatic cost savings, perhaps as much 50%
- Learn more >>
- New Online Dashboard for IT Leaders
-
Read about top issues IT decision-makers face every day, plus get cost-effective solutions to real-life IT problems.
- Learn more >>
- Microsoft Dynamics CRM Online - Free Six-Month Trial for Eligible Organizations
-
Microsoft Dynamics CRM Online provides fast online access, simple contact management and better sales performance for a low monthly cost - the best value on the market today.
- Learn more about the free, six-month trial offer>>
SmartPlanet
- Thought-provoking progressive ideas on diverse topics that intersect with technology, business, and life, and matter to the world at large. Visit SmartPlanet
- More from IBM
-
- How to Drive Better Business Outcomes with Exceptional Web Experiences Download the eBook
- Driving Business Agility through SOA Connectivity & Integration Read the White Paper from IBM
- Linking Decisions and Information for Organizational Performance Read the Tom Davenport study
