Franz,
the PSKmail server calculates the necessity for a mode change based on
several
parameters, the most important ones are S/N (or rather signal
quality), and
ARQ success based on the number of repeats.
For different modes, different strategies are necessary, there is also
a need
to base the strategy on different channel conditions, like multipath,
frequency jitter,
QRM etc.
To achieve this the server mangles the S/N value in different ways for
each mode
to achieve efficient use of the channel. It contains a LinkQuality
counter which
tracks overall link performance. E.g. when 2 blocks within a received
frame
are damaged, the counter will be decreased, and when 2 consecutive
frames are received without error, the counter is increased.
When the counter reaches 0, first the block size is reduced by a
factor of 2.
When the minimum block size is reached, the mode is changed to a more
robust one,
and the counter put mid-range.
The reverse happens when the counter reaches 6.
This means there are several tries before a mode change can occur.
Normal frames have 8 blocks, PSK500 frames have 16. Which makes for
a really fast link with 3000 characters per minute.
But PSK500 is very QRM sensitive, so it can only be used on a clear
channel,
and with an everage signal quality of 85%...
The server software calculates all this. The algorithms used have been
fixed
experimentally, based on >10.000 hours of testing under adverse
conditions,
which does not mean they cannot be improved. The software is open
source, so
in case somebody has a lot of spare time...... :-)
Hope this sheds some light on the matter.
Rein PA0R
Rein,
is there an error in the routine calculating 'Server's s2n averaged'?
In the example below Server's rx s2n is always 100 (client and server
had been connected by audio-cables), but 'averaged' changes each 3rd
time to 66.6....
Should'nt it grow up to values > 90?
73 de
franz, oe5rtl
See a copy of server's output:
12:03 UTC Nov-6-2013: <SOH> 2s&CC2AB5<EOT>
12:03 UTC Nov-6-2013: > Status : last=6 good=35 end=35 missing=
Server's rx s2n: 100 , averaged: 77.7777777777778
Client's rx s2n: 100 , averaged: 99.6146326685371
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&SS26B9<EOT>
12:03 UTC Nov-6-2013: <SOH> 2s&SS26B9<EOT>
12:03 UTC Nov-6-2013: > Status : last=6 good=51 end=51 missing=
Server's rx s2n: 100 , averaged: 85.1851851851852
Upgrading RX speed
Client's rx s2n: 100 , averaged: 99.7430884456914
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&##029D<EOT>
12:04 UTC Nov-6-2013: <SOH> 2s&##029D<EOT>
12:04 UTC Nov-6-2013: > Status : last=6 good=3 end=3 missing=
Server's rx s2n: 100 , averaged: 66.6666666666667
Client's rx s2n: 100 , averaged: 99.828725630461
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&330E91<EOT>
12:04 UTC Nov-6-2013: <SOH> 2s&330E91<EOT>
12:04 UTC Nov-6-2013: > Status : last=6 good=19 end=19 missing=
Server's rx s2n: 100 , averaged: 77.7777777777778
Client's rx s2n: 100 , averaged: 99.885817086974
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&CC2AB5<EOT>
12:05 UTC Nov-6-2013: <SOH> 2s&CC2AB5<EOT>
12:05 UTC Nov-6-2013: > Status : last=6 good=35 end=35 missing=
Server's rx s2n: 100 , averaged: 85.1851851851852
Upgrading RX speed
Client's rx s2n: 100 , averaged: 99.9238780579827
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&SS26B9<EOT>
12:05 UTC Nov-6-2013: <SOH> 2s&SS26B9<EOT>
12:05 UTC Nov-6-2013: > Status : last=6 good=51 end=51 missing=
Server's rx s2n: 100 , averaged: 66.6666666666667
Client's rx s2n: 100 , averaged: 99.9492520386551
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&##029D<EOT>
12:06 UTC Nov-6-2013: <SOH> 2s&##029D<EOT>
12:06 UTC Nov-6-2013: > Status : last=6 good=3 end=3 missing=
Server's rx s2n: 100 , averaged: 77.7777777777778
Client's rx s2n: 100 , averaged: 99.9661680257701
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&330E91<EOT>
12:07 UTC Nov-6-2013: <SOH> 2s&330E91<EOT>
12:07 UTC Nov-6-2013: > Status : last=6 good=19 end=19 missing=
Server's rx s2n: 100 , averaged: 85.1851851851852
Upgrading RX speed
Client's rx s2n: 100 , averaged: 99.9774453505134
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s&CC2AB5<EOT>
12:07 UTC Nov-6-2013: <SOH> 2s&CC2AB5<EOT>
12:07 UTC Nov-6-2013: > Status : last=6 good=35 end=35 missing=
Server's rx s2n: 100 , averaged: 66.6666666666667
Client's rx s2n: 100 , averaged: 99.9849635670089
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'SSE6E8<EOT>
12:08 UTC Nov-6-2013: <SOH>02'~FA:m68Gox
175F<SOH>
12:08 UTC Nov-6-2013: > Data: 7
~FA:m68Gox
12:08 UTC Nov-6-2013: <SOH> 2s'SSE6E8<EOT>
12:08 UTC Nov-6-2013: > Status : last=7 good=51 end=51 missing=
Server's rx s2n: 100 , averaged: 77.7777777777778
Client's rx s2n: 100 , averaged: 99.9899757113393
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
~FA:m68Gox
READLINE:~FA:m68Gox
Deleting transaction m68Gox
12:08 UTC Nov-6-2013:
Send>APRS-IS:OE5RTL>PSKAPR:@061208z4826.75NP01432.25E& 2.1.n test with
fldigi-3.21.76PSKMAIL/10148kHz/dipole/15Watts/mailto:oe5rtl(at)gmx.at
<SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: <SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: > Status : last=7 good=63 end=63 missing=
Server's rx s2n: 100 , averaged: 85.1851851851852
Upgrading RX speed
Client's rx s2n: 100 , averaged: 99.9933171408929
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: <SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: > Status : last=7 good=63 end=63 missing=
Server's rx s2n: 100 , averaged: 66.6666666666667
Client's rx s2n: 100 , averaged: 99.9955447605953
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: <SOH> 2s'__E3ED<EOT>
12:08 UTC Nov-6-2013: > Status : last=7 good=63 end=63 missing=
Server's rx s2n: 100 , averaged: 77.7777777777778
Client's rx s2n: 100 , averaged: 99.9970298403969
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'__E3ED<EOT>
12:09 UTC Nov-6-2013: <SOH> 2s'__E3ED<EOT>
12:09 UTC Nov-6-2013: > Status : last=7 good=63 end=63 missing=
Server's rx s2n: 100 , averaged: 85.1851851851852
Upgrading RX speed
Client's rx s2n: 100 , averaged: 99.9980198935979
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'__E3ED<EOT>
12:09 UTC Nov-6-2013: <SOH> 2s'__E3ED<EOT>
12:09 UTC Nov-6-2013: > Status : last=7 good=63 end=63 missing=
Server's rx s2n: 100 , averaged: 66.6666666666667
Client's rx s2n: 100 , averaged: 99.9986799290653
Try Turbo upgrade of TX mode
TX=PSK500 , RX=PSK500 , T=0 LQ=0 BL=6
<SOH> 2s'__E3ED<EOT>
Disconnected
12:09 UTC Nov-6-2013:
Listening to the radio
