VARA HF Modem Speeds
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Tony
All:
I observed an unusually fast file transfer while using VARA on 40 meters today (see below). It's not uncommon to see speeds of 15,000 to 20,000 bytes/minute when the band is stable, but today's observation shows that faster speeds are possible under the right conditions. I should mention that the 30K b/m speed was recorded while receiving a 30K image. Tony -K2MO *** Winlink Vara Connection to KC8YJJ @ 2021/01/17 20:09:59 USB Dial: 7101.000 *** Station Bearing: 268, Range: 393 miles RMS Trimode 1.3.36.0 K2MO has 120 minutes remaining with KC8YJJ {SFI = 078 On 2021-01-17 20:00 UTC} [WL2K-5.0-B2FWIHJM$] ;PQ: 44766187 CMS via KC8YJJ > ;FW: K2MO [RMS Express-1.5.34.0-B2FHM$] ;PR: 17655197 ; KC8YJJ DE K2MO (FN30JV) FF ;PM: K2MO 36Y27O2YLIPH 30887 73guddx@gmail.com --- FC EM 36Y27O2YLIPH 32990 30887 0 F> C5 FS Y *** Receiving 36Y27O2YLIPH *** 36Y27O2YLIPH - 33005/30899 bytes received *** Bytes: 31145, Time: 01:03, bytes/minute: 29618 FF FQ *** --- End of session at 2021/01/17 20:11:49 --- *** Messages sent: 0. Total bytes sent: 0, Time: 01:49, bytes/minute: 0 *** Messages Received: 1. Total bytes received: 31145, Total session time: 01:49, bytes/minute: 17035 *** Disconnected from Winlink RMS: KC8YJJ @ 2021/01/17 20:11:56 *** Session: 1.9 min; Avg Throughput: 15552 Bytes/min; 1 Min Peak Throughput: 15552 Bytes/min
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Andrew OBrien
By the way Tony, I have sent you a few emails via your Winlink address lately and each time winlink says nop such address. Andy K3UK
On Sun, Jan 17, 2021 at 5:45 PM Tony <73GUDDX@...> wrote: All:
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Tony
Andy:
Had to edit my whitelist to include
gmail addresses.
Please try again when you get the
chance.
Tony -K2MO
On 1/17/2021 6:36 PM, Andrew OBrien
wrote:
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Andrew O'Brien
OK , will try again. I have been using my Winlink address. Andy
On Sun, Jan 17, 2021 at 9:22 PM Tony <73GUDDX@...> wrote:
--
Andy
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Rick Muething
Tony/All,
toggle quoted messageShow quoted text
VARA is truly a very capable protocol and throughput on HF can exceed 20 K bytes/minute over some channels. Tom Whiteside N5TW of the Winlink development team recently completed an extensive comparison of several HF and VHF/UHF ARQ protocols over a wide range of S:N and Multipath propagation using a new low-cost HF/VHF Ionospheric Simulator. This kind of testing allows accurate testing with repeatable data which is often difficult or impossible to duplicate over the air. Those interested in seeing details on Tom Whiteside's N5TW simulation effort and protocol comparisons should check out https://winlink.org/content/ionos_simulator 73, Rick Muething, KN6KB
On 1/17/2021 5:45 PM, Tony wrote:
All:
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Graham
Its unclear as to why the simulator results where so wrong and now so right , applying to just one mode, where as other's remain, apparently, unaffected ?
What was identified as causing the discrepancy ? 73 -Graham g0nbd
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Andrew O'Brien
The article is very interesting Andy K3UK
On Thu, Jan 21, 2021 at 10:42 AM Graham <g0nbd@...> wrote: Its unclear as to why the simulator results where so wrong and now so right , applying to just one mode, where as other's remain, apparently, unaffected ? --
Andy
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Andrew OBrien
and I will add ... The pactor modes still hold up as very effective under various conditions but I think it is ironic that after the written and verbal "beating" that Jose received for his ROS mode software , Jose deserves huge credit and thanks for his VARA work. The results mentioned in the article are truly outstanding! Both HF and FM VARA . Wide VARA and Narrow VARA. The article appropriately references Rick's pioneering work with WINMOR and ARDOP. I especially enjoyed the early WINMOR experiments on air.
Andy K3UK
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Graham
Yes , Quite agree Andy ,
The vara modem started years before it broke the surface , in many variations, the fully odfm version was and remains radical , the mfsk front end to the HF version, signalled the limitations to psk modulation .. perhaps echoing the MT63 , progression to Olivia in terms of s/n In reality , 'we' as in data mode users are now 10 years behind the times , Ros HF , introduced , 'efficient use of bandwidth' whilst maintaining QSO integrity and equal channel access for users at minimal s/n levels . To day , as already commented , non coexisting transmission formats are spreading along the dial Only need to observe the psk-map 11 meter band , when there is a opening , to observe , the traffic level supported in a single voice channel , by non ham users , demonstrating the validity of the designe .. and the far sightedness of the SS Trial group , who also came under fire , 73-Graham g0nbd
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Rick Muething
Graham, I think I missed the first part of the discussion. Is this referring to the Winlink/ARSFI Ionos Simulator project/simulator? There is a pretty complete write-up of the effort and examples of simulation runs at: https://winlink.org/content/ionos_simulator Tom W. N5TW, Tom Lafleur KA6IQA and I were working on the effort most of last year during the development and verification of the simulator and testing common popular protocols. If interested I can provide more detail. 73, Rick Muething, KN6KB Winlink Development Team.
On 1/21/2021 10:42 AM, Graham wrote:
Its unclear as to why the simulator results where so wrong and now so right , applying to just one mode, where as other's remain, apparently, unaffected ?
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Graham
Rick
Test via HB9AVK 592 km 7,050 MHz DIAL
Term 1
*** Completed send of VARA message JE2O4B0QBRP2 *** Sent 1 message. Bytes: 20230, Time: 01:03, bytes/minute: 19030
*** Completed send of Pactor message MATG09PBPW98 *** Sent 1 message. Bytes: 20218, Time: 03:11, bytes/minute: 6332
Term 2
*** Completed send of VARA message 6Z4SZQFPRIJL *** Sent 1 message. Bytes: 20213, Time: 02:16, bytes/minute: 8870
*** Completed send of Pactor message 2XWY9G2MCS0N *** Sent 1 message. Bytes: 20219, Time: 02:07, bytes/minute: 9517
Term 3
*** Completed send of VARA message TC67GB6RLZ1S *** Sent 1 message. Bytes: 20213, Time: 02:46, bytes/minute: 7301
*** Completed send of Pactor message Z6PSHUFB8HZ3 *** Sent 1 message. Bytes: 20217, Time: 02:21, bytes/minute: 8573
Term 4
*** Completed send of VARA message K9K11XBW9D3F Vara WL2K *** Sent 1 message. Bytes: 20215, Time: 02:37, bytes/minute: 7692
*** Completed send of Pactor message 58KVLSL4OUSX fast QRM Disconnecting Timeout *** Sent 1 message. Bytes: 20219, Time: 05:24, bytes/minute: 3740
Result:
VARA Mean Value: 10723 P4 Mean Value: 7040
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Rick Muething
Graham, During the development of the Simulator there were many mods to
the code doing the audio processing. Specifically my initial code
(and some of the initial tests) did not correctly model the
multipath (created by the delay and modulation (with a randomized
Real + Imaginary veector) of the audio. This was found to be due
in part to problems with the C++ implementation of the narrow band
(~3 Hz) multipath filters which were implemented using IIR
filters. It took a couple of months to get the implementation to
match/track other simulators (hardware and software). Also the
latest simulator firmware versions (2.03) gave users the option
of using 1 path (WGN), 2 path multipath or a 4 path multipath. The
results published in Tom W's testing writeup: use only 2 path multipath (two I + Q paths) along with the most
recent revisions of VARA, Pactor 4 and the Winlink Express client
program. Some mods in the Winlink Express modem drivers allowed
slightly (10-15%) more throughput in both Pactor 4 and VARA. VARA
2.8 KHz BW was not available for testing. That should allow
slightly faster throughput at High S:N levels (> 25 dB) . In
practice however it is rare (without Linears or high gain
antennas) to often see digital connections > 25 dB S:N. The simulator of course does not know or care what protocol it is
processing it simply takes the audio from the modem/sound card,
checks to make sure it is not overdriving the simulator ,and
processes the audio at the requested simulator bandwidth (300-3300
Hz or 300-6300 Hz) and then mixes WGN at the requested S:N and
the desired level of multipath (using the recommended path delay
values by the CCIR/ITU ) . The extensive testing showed
repeatable results [net throughputs for long (5-15 minute) ARQ
sessions] for all protocols. The Ionos Simulator also computes and displays the Crest Factor
which can help determine the optimum drive level for the
transmitter. With very low crest factors (< 2:1 or < 3dB)
it is quite possible to drive most amateur SSB transmitters to
exceed its thermal limits even if it is not driven to maximum
rated PEP. With high crest factors (>5-6 dB) most amateur
transmitters will be PEP limited before thermal limited and this
will result in lower net Energy per bit and therefore lower
throughput for a given PEP drive level. The main value of the simulator is that it allows duplicating statistically similar paths (S:N and multipath) that are almost impossible to do using using over the air testing. This is why they have been used extensively in testing and characterizing protocols such as Mil STD 188 and STANAG. 73, Rick KN6KB
On 1/22/2021 9:17 AM, Graham wrote:
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