Speech coding for security and defense apps, Why do we need very low bitrate? |
Speech coding for security and defense apps, Why do we need very low bitrate? |
  Jan 18 2006, 03:13
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#1
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 Group: Developer Posts: 1245 Joined: 16-December 02 From: Australia Member No.: 4097  |
Hi everyone,
I've heard that ultra low bitrate speech coding (< 800 bps) that use simple modifications to the LPC vocoder (such as segmented LPC vocoders), are of interest mainly for security and defense applications. At such low bitrates, I assume that intelligibility is the only criteria here. My question is why do we need to go to such low bitrates for defense and security? Is it because we want to reserve bandwidth for error-correcting redundancy? Or perhaps encryption? The only thing that I've read which sort of remotely justifies the low bitrate is a lesser chance of being intercepted.  If anyone can enlighten me as to why we need such low bitrates (< 800 bps) for security and defense, that would be splendid.  Thanks, QK |
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Aug 9 2006, 14:58
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#2
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 Group: Members Posts: 2 Joined: 30-March 04 Member No.: 13117 |
QUOTE (QuantumKnot @ Jan 18 2006, 04:13)  If anyone can enlighten me as to why we need such low bitrates (< 800 bps) for security and defense, that would be splendid. When using low bitrates you can use spread-spectrum algorithms to distribute the signal power over a very wide range - even to a degree where the signal power will be lower than the background noise - and thus "hide" the signal in the background noise and make it practically impossible for any other party to even detect that you are transmitting something. |
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Aug 13 2006, 08:26
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#3
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Group: Members Posts: 113 Joined: 28-December 05 Member No.: 26686 |
QUOTE (maxonen @ Aug 9 2006, 08:58) QUOTE (QuantumKnot @ Jan 18 2006, 04:13) If anyone can enlighten me as to why we need such low bitrates (< 800 bps) for security and defense, that would be splendid. When using low bitrates you can use spread-spectrum algorithms to distribute the signal power over a very wide range - even to a degree where the signal power will be lower than the background noise - and thus "hide" the signal in the background noise and make it practically impossible for any other party to even detect that you are transmitting something. Can you enlightened me further in this area? How about some detail equations presentations? 
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Aug 13 2006, 10:49
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#4
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 Server Admin Group: Admin Posts: 4808 Joined: 24-September 01 Member No.: 13 |
QUOTE (kwwong @ Aug 13 2006, 09:26) QUOTE (maxonen @ Aug 9 2006, 08:58) QUOTE (QuantumKnot @ Jan 18 2006, 04:13) If anyone can enlighten me as to why we need such low bitrates (< 800 bps) for security and defense, that would be splendid. When using low bitrates you can use spread-spectrum algorithms to distribute the signal power over a very wide range - even to a degree where the signal power will be lower than the background noise - and thus "hide" the signal in the background noise and make it practically impossible for any other party to even detect that you are transmitting something. Can you enlightened me further in this area? How about some detail equations presentations? http://en.wikipedia.org/wiki/Spread_Spectr...ecommunications |
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QuantumKnot Speech coding for security and defense apps Jan 18 2006, 03:13
clintb Possibly because they (the men in black) can store... Jan 18 2006, 04:12 boojum I would ask the people who tell me this stuff. If... Jan 18 2006, 04:32
Shade[ST] Why not steganography? At such a low bitrate, you... Jan 18 2006, 04:48 Mike Giacomelli Bandwidth is a good thing to save whenever you are... Jan 18 2006, 05:42 QuantumKnot QUOTE (Mike Giacomelli @ Jan 18 2006, 02:42 P... Jan 18 2006, 06:24 Shade[ST] QUOTE (QuantumKnot @ Jan 17 2006, 11:24 PM)QU... Jan 18 2006, 06:30 HotshotGG QUOTE Why not steganography? At such a low bitrate... Jan 18 2006, 05:46 audio_geek Do you need lossless eompression for speech commun... Jan 23 2006, 06:49 HbG The less bandwidth the easier to transmit and thus... Jan 23 2006, 16:44 pepoluan QUOTE (HbG @ Jan 23 2006, 10:44 PM)The less b... Jan 23 2006, 20:10 HbG Actually the global submarine communications trans... Jan 24 2006, 01:11 QuantumKnot Thanks for the replies everyone.
Another reason ... Feb 9 2006, 23:55 Garf I would say another advantage is that low bitrate ... Feb 10 2006, 00:20 pepoluan QUOTE (Garf @ Feb 10 2006, 06:20) I would... Jun 28 2006, 19:00 Garf QUOTE (pepoluan @ Jun 28 2006, 20:00) QUO... Jun 28 2006, 19:07 HbG QUOTE (pepoluan @ Jun 28 2006, 10:00) QUO... Jun 28 2006, 19:40 jmvalin QUOTE (QuantumKnot @ Jan 18 2006, 12:13 P... Apr 10 2006, 16:24 HbG 802.11 based wireless networks extend range by swi... Jun 28 2006, 01:49 kwwong QUOTE (Garf @ Aug 13 2006, 04:49) QUOTE (... Aug 14 2006, 11:55 Woodinville Because the channels they use for communications a... Aug 9 2006, 19:01 HbG I recall bluetooth is a good example of spread spe... Aug 13 2006, 11:30 Woodinville QUOTE (HbG @ Aug 13 2006, 03:30) How you ... Aug 14 2006, 20:15 kwwong QUOTE (Woodinville @ Aug 14 2006, 14:15) ... Sep 3 2006, 09:30 beto It's against common sense but it works.
See CD... Aug 13 2006, 15:07 cabbagerat I think Garf's theory that it is to avoid dire... Sep 3 2006, 13:09 DonP Another consideration, and I really don't know... Nov 9 2010, 14:20 |
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