Is there a reason that the amateur radio community doesn't use iterative
coding schemes for FEC and instead relies on Golay or Reed-Solomon error
correction? Is it that LDPC codes are (usually) non systematic, somewhat
more complex to implement, or something else entirely that I'm missing?
Thanks,
Matthias Granberry - KD5PFT
On Jul 14, 2012 5:23 PM, "Kristoff Bonne" <[email protected]> wrote:
> Hi,
>
>
> We are two weeks since the last software-update of the gmskmodem; so ... I
> just pushed a new version onto github:
>
>
> Changes:
> - some additional error-checking for ALSA
>
> - There is now an option "-id" which enables the modem to play out a
> wav-file after every "n" transmissions. The reason is that all
> transmissions of hams have to be "in the clear" and hams have to give their
> callsign every "x" overs.
> As we are dealing with developing a new protocol -which cannot be
> understood by other hams- it might be usefull to add a small audio-fragment
> with your callsign in plain audio or CW after a transmission so that people
> are able to identify the source of "this strange broadcast".
>
> - I've also changed the Makefile so that the code can be compiled with
> floating-points instead of integer operations.
> This may sound a bit strange; but this is the result of helping out some
> people to port the "WSPR" application to the raspbery pie.
> It turns out that -on some devices, like the RasPi- calculating a filter
> in DSP is faster when using floating-point operations. The ARM1176 in the
> Pie seams needs more CPU cycles to do a 32 bit * 32 bit integer operations;
> then doing the calculation using the onboard VFP unit.
>
> By modifying a flag in the Makefile, one can now select if the code is
> compiled using integer or floating-point math.
>
> As usual, the code can be found at github:
> https://github.com/on1arf/gmsk/tree/master/gmskmodem_codec2
>
>
> Planned for the next releases:
> - implement the header. (who knows where I can find code for implementing
> golay FEC encoding)?
>
> - do some further experimenting with optimizing the integer math.
> After doing some research on the assembler-code generated by gcc when
> doing code-optimalisation of the integer math; it turns out that on a ARM9
> and a ARM11, every 32 * 16 multiplication in C is actually translated into
> three multiplications on assembler level: two "MUL" (multiply) and one
> "MLA" (Multiply-and-add) instructions.
>
> As some devices (like almost all D-STAR gmskmodems out there) actually
> operate with audio using only 10 bits (instead of 16), I want to experiment
> if it not possible to reduce the resolution of the audio and of the filter
> FIR coefficients; so that this 16*32 bit multiplication will be limited to
> an instruction that fits in 32 bit; hopefully reducing the CPU-power needed
> on certain devices without a FPU.
>
>
>
> 73
> Kristoff - ON1ARF
>
>
>
> ------------------------------------------------------------------------------
> Live Security Virtual Conference
> Exclusive live event will cover all the ways today's security and
> threat landscape has changed and how IT managers can respond. Discussions
> will include endpoint security, mobile security and the latest in malware
> threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
> _______________________________________________
> Freetel-codec2 mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/freetel-codec2
>
>
------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and
threat landscape has changed and how IT managers can respond. Discussions
will include endpoint security, mobile security and the latest in malware
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
Freetel-codec2 mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/freetel-codec2
