Well, at this point I'm still experimenting, and I'm really focused on
providing the best possible HF modem for FreeDV. Of course, if I come up
with something that can be used elsewhere, all the better. Most of the
OFDM stuff has really complex synchronization and a lot of bits per symbol.
I'm starting from the FDMDV philosophy where things are a lot simpler -
for example, a single, stationary carrier for easy and fast time and
frequency sync. I doubt my implementation will end up anywhere near as
complex as the DRM stuff, for example.
The questions I am trying to answer are:
1) Will the orthogonality of the OFDM carriers be degraded significantly by
the HF channel, compared to FDM?
2) If not, can we take advantage of that spectrum 'between the carriers'
that FDMDV is not using?
3) If we keep a symbol rate of 50Hz with a carrier spacing of 75Hz, this is
equivalent to a 6.67ms guard band. Will having this guard band in time
rather than spacing between carriers be more robust to multipath?
These questions are all very interesting to me, even if the FDMDV modem
turns out to be ideal.
-Frank
On Wed, Jun 5, 2013 at 10:52 AM, Karel Fassotte <[email protected]>wrote:
> hello Frank,
> I am not a programmer bur very interested in a windows application for the
> OFDM modem, not necesarly Codec2 integrated.
> Just a OFDM modem for SW with an easy Gui in windows for data
> transmissions. Idealy I want be capable to run ip traffic through the
> modem. Speed should be autobaud and 4800bs, 3600bs,2400bs,1200bs,600bs,
> 300bs. Do you have any material or perhaps something running?
> Thanks
> 73
> Karel
> HC1AKP
> PE2KFA
>
>
> 2013/6/5 Frank Palazzolo <[email protected]>
>
>>
>> So, I've done some experimenting with an OFDM modem implementation in
>> Octave. I still think the idea has a lot of promise, so and I've decided
>> it's time to try to build codec2 and FreeDV.
>>
>> Codec2-dev was no big deal, as it has no dependancies. I didn't have
>> trouble getting the mingw/MSYS toolchain going. For FreeDV, I spent a lot
>> of time bringing in each dependant package one at a time and trying to
>> build or integrate them. I ended up getting surprised and stuck with ctb,
>> since it seems to not want to build in the the mingw environment, due to
>> slash conventions in the makefile. (even if it is ok on Linux). Has anyone
>> made this work on mingw?
>>
>> Now I've come to realize that maybe I should have started with cmake.
>> Will that make it all easier? Does the cmake build work on mingw ok?
>>
>> This may be blasphemy, but when all is said and done, I am tempted to put
>> together a set of project files for devstudio 2010 and binaries for
>> everything but codec2 and freedv. I think this would make it a lot easier
>> for developers on windows to get their feet wet without going through a
>> long startup process. Nothing kills incentive like having to spend a bunch
>> of time building third party stuff...
>>
>> Thanks,
>> Frank
>> NQ8N
>>
>>
>>
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