Hi Nico Greeting from JA,
And, here is another noise from floor expecting your comments.
To mitigate the dilemma of message size and required power you and Joe
described, It is a common practice to provide the variable code rate feature
(from current FT8 fixed r=0.5). The benefit of this feature is able to avoid
system incompatibity from the information length difference (among FT8, FT8+,
WSPR…) if the system provides the identification flag.
Does FT8+ have already considered this?
Regards,
take
de JA5AEA
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
________________________________
From: Nico Palermo <nico...@microtelecom.it>
Sent: Friday, August 31, 2018 7:04:31 AM
To: WSJT software development
Subject: Re: [wsjt-devel] WSJT-X 2.0 possible new mode/protocol
Furthermore there is no need to improve a protocol just to cope with energy
limits when a really variable medium, as the ionosphere is in the HFs, is the
limit itself. Of course we could think to a new mode in which a 2-way QSO
between two antipodal points on earth would require 50 mWatts instead of 100
mWatts at the same information rate. But is there really any old man out of
this world who can't afford a 100 mWatts transmitter? The situation is much
different from the situation EME stations have to cope with, which is much more
demanding and where it would be really nice if we could gain yet some other
dBs. But who is really concerned about power requirements on HFs? Aren't the
current HF modes already fast enough? Would it be really important if a QSO
were carried out in 30 seconds instead of 60? And if it were, what prevents to
do double the transmission rate simply by doubling the transmitter power?
Nico / IV3NWV
Il Gio 30 Ago 2018, 21:37 Joe Taylor
<j...@princeton.edu<mailto:j...@princeton.edu>> ha scritto:
Hi Igor,
Earlier this month you made suggestions for a possible new protocol for
minimal weak-signal QSOs. I have been away on vacation since that time,
so have not had a chance to respond.
Of course there are many possible ways to make design trade-offs
involving message size, duration of transmissions, sensitivity,
bandwidth, undetected error rate, coding and modulation scheme, and so
on. In the modes implemented in WSJT, WSPR, and WSJT-X we have made
choices that I believe provide close to optimum solutions for a wide
variety of different Amateur Radio activities.
By all means, if you think your ideas have merit you should proceed to
develop a new mode along the lines you outline. But I should point out
that the particular goal your message seems to favor is close to that of
the "WSPR QSO Mode" that I introduced in May, 2008. A brief description
of this mode was published in the proceedings of the 13th International
EME Conference, held in Florence, Italy, later that year. A link to
this article may be found as Reference 11 here:
http://physics.princeton.edu/pulsar/k1jt/refs.html
"WSPR QSO Mode" reached a sensitivity of -29 dB and the required
bandwidth was only 6 Hz, but the mode never became popular. One reason
is surely that the supported message types (in 50-bit packets) were too
restrictive. Another reason is that the 2-minute T/R sequence length is
too long: QSOs were necessarily verrrry sloooooow. Scaling the
transmissions to 15 s sequences would make the bandwidth about 47 Hz and
sensitivity -20 dB. FT8 has about the same bandwidth, better
sensitivity, and a much wider range of supported message content. WSPR
QSO MOde was an interesting idea, but FT8 is far better.
-- 73, Joe, K1JT
On 8/8/2018 2:29 AM, Игорь Ч via wsjt-devel wrote:
> Hello Joe and all,
> .
> We all have been missing JT65 mode sensitivity and proposed WSJT-X 2.0
> new FT8 approach with 0.2 dB sensitivity penalty can make things even worse.
> .
> I would like to ask you to consider a new protocol where callsign hash
> would be used instead of the real callsign in all messages but CQ and
> incoming call, this way we can get back to -25..26dB SNR sensitivity
> although will get more limited with the free message length.
> .
> CQ message: 28 bit callsign1 + i5bit + 12 bit CRC = 45 bit
> incoming call: 10 bit call1 hash + 28 bit callsign2 + i5bit + 12bit CRC
> = 55 bit
> report message: 10 bit call2 hash + 10 bit call1 hash + i5bit + (10 bit
> call3 hash for DXpedition) + 6 bit report + 12 bit CRC = 43(53) bit
> roger+report message: 10 bit call1 hash + 10 bit call2 hash + 6 bit
> report+ i5bit + 12bit CRC = 43 bit
> 73 message: 10 bit call2 hash + 10 bit call1 hash + 15 bit GRID + i5bit
> + 12bit CRC = 55 bit
> RR73 message: 10 bit call1 hash + 10 bit call2 hash + 15 bit GRID +
> i5bit + 12bit CRC= 52 bit
> .
> Spare bits can be used for nonstandard(special) callsign transmission in
> CQ message. call1 hash could be omitted in the incoming call message if
> this message is originated by the nonstandard(special) callsign.
> .
> Probably we can optimize protocol even better while a main idea is to
> transmit a full callsign only once per each QSO and to transmit not more
> than one full callsign in the message.
> .
> 73 Igor UA3DJY
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