Hi, Take. Greetings from Italy :-)
A variable transmission rate would be appreciable indeed but we often
forget that the main purpose of the WSJT-X modes was that of allowing some
reliable amateur communication in the "energy limited" part of the channel
capacity/energy per bit plane given some real channel model.
This is what I understood from Joe's work at least.
Flexibility comes always at the expense of something else: a more flexible
system would not be as optimal, as i.e.FT-8 is, from the energy point of
view as you would need to transmit some more information to instruct the
receiver at what rate the transmitter is using and this takes more energy
than that a fixed rate system requires.
The larger the number of the possibilities a receiver has to understand and
cope with, the least the signal to noise margin is.
If you are not so sure about this fact try to decode a signal in which,
besides the usually unknown time delay between the transmitter and receiver
clocks, besides the unknown frequency offset and drift, you add some other
parameter, unknown to the receiver, which a receiver must necessarily
estimate in order to decode with some success what has been transmitted.
But ok, history doesn't stop in 2018 and I'm not so pessimistic. I think
that we will continue to see something new and possibly even more amazing
:-)
73
Nico / IV3NWV
2018-08-31 14:04 GMT+02:00 Tsutsumi Takehiko <ja5...@outlook.com>:
> 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> 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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