Don't error correction codes tend to "mix" the bits and give you more
independent errors even for the case of narrowband interference?
Jean-Marc
On 17/02/12 03:36 PM, David Rowe wrote:
> Hi Bruce,
>
> Your point re a narrowband interferer, like a "birdie" at HF, is a good
> one. It would be good to "instrument" our modem code to record the bit
> error patterns off real channels so we can tune the whole system to deal
> with these sorts of effects.
>
> Cheers,
>
> David
>
> On Thu, 2012-02-16 at 17:11 -0800, Bruce Perens wrote:
>> David,
>>
>> Really clever. So, the effect of an error is that you potentially lose
>> bits rather than the whole frame, and you stay synched for the next
>> frame.
>>
>> The downside, I guess, is that in the case of narrowband noise, you
>> lose the same bits from one frame to the next. But you could
>> 1. Send two frames per symbol, and only one per pair would be subject
>> to the noise.
>> 2. Alternate the bit distribution pattern, but then you'd have to sync
>> to that.
>>
>> Thanks
>>
>> Bruce
>>
>> On 02/16/2012 04:39 PM, David Rowe wrote:
>>> Peter Martinez suggested making the frame period the same as the PSK symbol
>>> period. For example the 1500 bit/s mode would have 60 carriers at 25 bit/s
>>> (40 ms symbol period). The advantage of this mode is no frame sync
>>> overhead is reqd.
>>>
>>
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>
>
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