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Modulation/Signaling scheme for transfering information over an acoustic channel

Started by John McDermick November 9, 2011
Which modulation scheme is most suitable for transmitting information
(a bitstream) over an acoustic channel? i.e. a loudspeaker outputs the
modulated signal and a cell phone microphone picks up the acoustic
signal and extracts the information from the modulated signal. I'm
looking  for a modulation/signaling scheme which is robust with
respect to ambient noise in the acoustic channel.

On 9 Nov, 15:49, John McDermick <johnthedsp...@gmail.com> wrote:
> Which modulation scheme is most suitable for transmitting information > (a bitstream) over an acoustic channel? i.e. a loudspeaker outputs the > modulated signal and a cell phone microphone picks up the acoustic > signal and extracts the information from the modulated signal. I'm > looking =A0for a modulation/signaling scheme which is robust with > respect to ambient noise in the acoustic channel.
No you are not. No relevant acoustic comm channel exist where ambient noise is at all interesting. The problems are 1) Reverberation 2) Quickly changing transfer functions, either because source and reciever moves, because the channel geometry / properties change, or all the above. Rune

John McDermick wrote:
> Which modulation scheme is most suitable for transmitting information > (a bitstream) over an acoustic channel? i.e. a loudspeaker outputs the > modulated signal and a cell phone microphone picks up the acoustic > signal and extracts the information from the modulated signal.
And there is a vocoder in the path, too ?
> I'm > looking for a modulation/signaling scheme which is robust with > respect to ambient noise in the acoustic channel.
Aborigenes use tomtoms. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
These papers talks about transmitting information over an acoustic
channel:

http://www.cmlab.csie.ntu.edu.tw/~ipr/mmsec2007/data/homework/hw2/Introduction%20to%20Audio%20Watermarking%20Schemes.pdf

http://www.apl.utoronto.ca/publication/i/nevena_tmm06.pdf

On 9 Nov, 17:48, John McDermick <johnthedsp...@gmail.com> wrote:
> These papers talks about transmitting information over an acoustic > channel: > > http://www.cmlab.csie.ntu.edu.tw/~ipr/mmsec2007/data/homework/hw2/Int... > > http://www.apl.utoronto.ca/publication/i/nevena_tmm06.pdf
People have been *talking* and *writing* about such stuff for decades. You would be hard pressed to come up with examples of systems that actually *work*. Rune
On Wed, 9 Nov 2011 06:49:41 -0800 (PST), John McDermick
<johnthedspguy@gmail.com> wrote:

>Which modulation scheme is most suitable for transmitting information >(a bitstream) over an acoustic channel? i.e. a loudspeaker outputs the >modulated signal and a cell phone microphone picks up the acoustic >signal and extracts the information from the modulated signal. I'm >looking for a modulation/signaling scheme which is robust with >respect to ambient noise in the acoustic channel. >
A friend used BPSK transmitted from a little speaker and picked up by the mic on a laptop. It actually worked pretty well, considering. BPSK is pretty fundamental and robust. That being said, the range will be expected to be short and there will be susceptibility to interference from ambient noise. Eric Jacobsen Anchor Hill Communications www.anchorhill.com
On 11/9/2011 9:03 AM, Rune Allnor wrote:
> On 9 Nov, 17:48, John McDermick<johnthedsp...@gmail.com> wrote: >> These papers talks about transmitting information over an acoustic >> channel: >> >> http://www.cmlab.csie.ntu.edu.tw/~ipr/mmsec2007/data/homework/hw2/Int... >> >> http://www.apl.utoronto.ca/publication/i/nevena_tmm06.pdf > > People have been *talking* and *writing* about such > stuff for decades. You would be hard pressed to > come up with examples of systems that actually *work*. > > Rune
The oil well guys do acoustic channel transmission, they call it pressure pulses or something of that nature. Data rates in the 5 baud (that's not a typo) sort of region. -- Rob Gaddi, Highland Technology -- www.highlandtechnology.com Email address domain is currently out of order. See above to fix.
On 9 Nov, 18:13, Rob Gaddi <rga...@technologyhighland.invalid> wrote:
> On 11/9/2011 9:03 AM, Rune Allnor wrote: > > > On 9 Nov, 17:48, John McDermick<johnthedsp...@gmail.com> =A0wrote: > >> These papers talks about transmitting information over an acoustic > >> channel: > > >>http://www.cmlab.csie.ntu.edu.tw/~ipr/mmsec2007/data/homework/hw2/Int..=
.
> > >>http://www.apl.utoronto.ca/publication/i/nevena_tmm06.pdf > > > People have been *talking* and *writing* about such > > stuff for decades. You would be hard pressed to > > come up with examples of systems that actually *work*. > > > Rune > > The oil well guys do acoustic channel transmission, they call it > pressure pulses or something of that nature. =A0Data rates in the 5 baud > (that's not a typo)
I know. Investigating the reasons why one can't get more, is really enlightening.
> sort of region.
I didn't say this is *impossible*; just that there are very good reasons that very few such systems exist. I know acoustic comm systems is used in certain marine between-submersibles comms, so that's two applications of acoustic comms. I would be very surprised if one cane come up with as many as five. Rune
On Wed, 09 Nov 2011 09:03:05 -0800, Rune Allnor wrote:

> On 9 Nov, 17:48, John McDermick <johnthedsp...@gmail.com> wrote: >> These papers talks about transmitting information over an acoustic >> channel: >> >> http://www.cmlab.csie.ntu.edu.tw/~ipr/mmsec2007/data/homework/hw2/
Int...
>> >> http://www.apl.utoronto.ca/publication/i/nevena_tmm06.pdf > > People have been *talking* and *writing* about such stuff for decades. > You would be hard pressed to come up with examples of systems that > actually *work*.
Hah! Hand-held DTMF generators, from back when rotary dial phones were still commonplace, but voice-response systems were starting to take over the WORLD!!! Hold gizmo up to mouthpiece, punch buttons -- joy ensues (well, as much joy as can ensue when you're in Voice Mail Hell). Hah!! Old-style modems, with the handset holder thingie. Put handset in holder, joy ensues (well, as much -- oh, never mind). (I'm trying to get up to four examples so I can say 'Hah!V', but I'm not getting there, unless you count shouting). -- www.wescottdesign.com

Rune Allnor wrote:

> On 9 Nov, 18:13, Rob Gaddi <rga...@technologyhighland.invalid> wrote: > >>On 11/9/2011 9:03 AM, Rune Allnor wrote: >> >>>People have been *talking* and *writing* about such >>>stuff for decades. You would be hard pressed to >>>come up with examples of systems that actually *work*.
Well, I did such demo once. It is trivial to accomplish trivial data rate; it is non-trivial to get beyond that.
>>The oil well guys do acoustic channel transmission, they call it >>pressure pulses or something of that nature. Data rates in the 5 baud >>(that's not a typo) > > I know. Investigating the reasons why one can't get more, is > really enlightening.
The downhole telemetry has different set of problems; slow data rate is not only because of accoustics.
> I didn't say this is *impossible*; just that there are > very good reasons that very few such systems exist.
Why spending lots of effort with knowingly small outcome when better solutions exist?
> I know acoustic comm systems is used in certain marine > between-submersibles comms, so that's two applications > of acoustic comms. > > I would be very surprised if one cane come up with as > many as five. > > Rune
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com