So does this mean that Patrick has IMPROVED on Pawel's design and the "true" implementation within DM780 is not as effective, or is DM780 slower but better at decoding ?
Andy On Sat, Nov 22, 2008 at 4:34 PM, Patrick Lindecker <[EMAIL PROTECTED]> wrote: > Hello Votjech, > > >I believe the difference between Patrick's MultiPSK and Pawel's > >original Olivia code is in the way how the sync time is adjusted after > >the initial sync is reached. Partick's code locks in time and only > Yes it is as you described (you are perspicacious!). The symbol > synchronization is done as in MFSK16, or other mode with a non-linearity and > a PLL to follow slight variations. > > However, I use the complete Pawel strategy for RS ID. > > > synchronization and for decoding very weak signal, additionaly > > introduced 1 second lag in case of Olivia1000/32 is annoying. > I don't think there is some issue for weak signal. > > I tried here comparing Mixw, Multipsk and OliviaAid with a very noisy > transmission: the decodings are more or less equivalent. > > The results are the following (with a signal at -13 dB of S/N Gaussian > which is the limit for Olivia 32-1000 decoding): > * OliviaAid: 120 characters decoded, > * Mixw: 164 characters decoded, > * Multipsk: 208 characters decoded. > > However, I tested on Gaussian noise, when real conditions could be very > different from a Gaussian noise (QSB was not simulated for example) and so > the results could be different... > > 73 > > Patrick > > ----- Original Message ----- > From: "Vojtech Bubnik" <[EMAIL PROTECTED]> > To: <digitalradio@yahoogroups.com> > Sent: Saturday, November 22, 2008 4:14 PM > Subject: [digitalradio] Re: Olivia mode comparisons, testers needed. > > > Hi Andy. > > > > Let's say one works with Olivia 1000/32. Olivia sends/receives 7bit > > ASCII letters. Each 7 bit letter is coded by Walch-Hadamard > > transformation into 2^(7-1)=64 bits. One of 32 tones modulation codes > > 32=2^5 combinations, which equals to 5 binary bits. Olivia is > > spreading 5 7bit letters over 64 MFSK32 tones. It takes 64/31.25=2.048 > > seconds to transmit one block of 5 letters. I hope this explains why > > the received letters appear in groups of five and why there is a > > considerable lag, which cannot be lower than 2 seconds for any decoder. > > > > Olivia receiver searches for the Walch-Hadamard coded blocks in time > > and space. Pawel Jalocha's code is running matrix of decoders spaced > > by one half of Olivia tone spacing in frequency and one half of tone > > spacing in time. He is calculating signal level (or quality, > > correlation or whatever one wants to name it) of each of the decoder > > in the matrix to check, whether and/or where a valid Olivia block was > > received. > > > > I believe the difference between Patrick's MultiPSK and Pawel's > > original Olivia code is in the way how the sync time is adjusted after > > the initial sync is reached. Partick's code locks in time and only > > slightly adjusts the sync time to cope with differences in RX/TX sound > > card clock callibration the same way his or any other MFSK16 decoder > > works. Pawel's code is always looking up one half of block time after > > the expected sync time. While Pawel's strategy is good for initial > > synchronization and for decoding very weak signal, additionaly > > introduced 1 second lag in case of Olivia1000/32 is annoying. > > > > I believe Pawel's code may be improved to decrease time lag in case > > the decoder is already locked to a strong signal. Also if a strong > > correlation is detected, one does not need to wait another 1 second > > for even stronger signal, because this is highly improbable. I believe > > Patrick's MFSK is doing both. > > > > Also if the signal is very strong, then one may break into a middle of > > a block and the block will be detected correctly with the prerequisity > > that the decoder will be flushed at the time one changes frequency > > either on waterfall or by tuning knob. I don't think any Olivia > > decoder is flushed at tuning change. > > > > It sounds like a challenge for my PocketDigi code, but don't tell my > > wife I have a new project :-) > > > > 73, Vojtech OK1IAK > > > > > > --- In digitalradio@yahoogroups.com, "Andrew O'Brien" > > <[EMAIL PROTECTED]> wrote: > >> > >> Folks, when Simon was first adding Olivia to DM780 he studied Pawel > >> Jalocha's coding and consulted with him about the correct > > implementation. > >> The lag noticed in DM780 is reportedly as the Pawel Jalocha > > intended. What > >> I am looking for is people to get on the air with Olivia and see if the > >> applications that may have less lag , have any noticeable decoding > >> degradation. Since I know Olivia in MixW and Multipsk work well, I am > >> wondering if the "proper" implimentation of Olivia in DM780 is worth the > >> delay and issues this causes during a QSO (those not knowing about > > the lag > >> think we are not coming back to them and start a transmission again ) > >> > >> Andy > >> > >> On Thu, Nov 20, 2008 at 3:18 AM, Simon Brown (KNS) > > <[EMAIL PROTECTED]>wrote <[EMAIL PROTECTED]>: > >> > >> > The lag is in the software - it's part of the design for the error > >> > correction. Where error correction is part of the design then *in > > general* > >> > with Ham modes you have to wait a while before text is decoding is the > >> > error > >> > correction is applied. The lag is not caused by CPU load. > >> > > >> > To really understand this it's best to analyse the Olivia design > > although > >> > this can be rough for the brain :-) > >> > > >> > > >> > Simon Brown, HB9DRV > >> > www.ham-radio-deluxe.com > >> > > >> > ----- Original Message ----- > >> > From: "captcurt2000" <[EMAIL PROTECTED] <captcurt%40flash.net>> > >> > > >> > > Sooo. a 500Mhhz machine running at 20% is going to perform the > >> > > integrations and decoding same delay as a 2 Ghz machine running > > at 20%?? > >> > > > >> > > That seems counter intuitive to me.. > >> > > > >> > > I'm sure you're right but I don't understand how that can be. > >> > > > >> > > I thought the load information talked about resources not speed of > >> > > execution. > >> > > > >> > > Help me understand.. > >> > > >> > > >> > > >> > >> > >> > >> -- > >> Andy K3UK > >> > > > > > > > > ------------------------------------ > > > > Announce your digital presence via our Interactive Sked Page at > > > http://www.obriensweb.com/sked > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > -- Andy K3UK
