Hello David, please find below answers to your many questions.
Le 16/06/2019 à 19:08, David Ranch a écrit :
- I see in the advanced guide that the system "IDs" itself every 2-6
seconds but what mode is that done in. In line with the symbol and spectrum limitations that the US amateurs have to deal with, IDing is also something to deal with. Is your system able to send non-NPR transmissions? http://www.arrl.org/part-97-text --> 97.119 Station identification . There is some discussion about this on the Hackaday comments section but there doesn't seem to be a conclusion about it.
ID'ing (sending callsign) is of course only done in "NPR" protocol. I've not read your "part 97" rules. Let me know if it matches your local regulations; but if AREDN, DSTAR, C4F and DMR are OK with that, NPR should be OK also.
- In the current firmware, I don't see any mention of a watchdog if
the system crashes. Is it possible to add one?
No watchdog currently. Here in France, we use a "remote modem" in association with a R-Pi, for remote access. The R-Pi is programmed to reboot the modem once every day. I will see if it's possible to add a standalone and efficient "watchdog". I don't know if my microcontroller has such hardware feature, I will check.
- I see in the docs and videos the details about client to master but
with this design, can say client #1 transfer data to client #2 via the master? Can client #1 automatically wake up client #2 and send data (assuming there is an IP server to connect to?
Of course, 2 clients can communicate together via the Master. But the Master or one client cannot wake-up another client. Only the Master has an "active/listening standby" mode, and can be waken-up by a client. Finally, if the Master is switched OFF, then the clients only send rare "connexion requests", which occupy in total less than 1% of the timeslots.
- Your advanced document mentions that due to weakness in the FEC
algorithm, maybe using modes "11, 20, or 21". I see there isn't any mode "10" for the 56kS/s symbol signaling rate. Is this a limitation of the modem chip?
I have not provided "mode 10", because my protocol is really not appropriate for such very low datarates. With my current protocol, you would have to wait a very long time in order for one clinet to connect to the Master, because the "discovery slots" do not occur frequently.
- Your Introduction PPT mentions a upcoming kit. Any ETA and cost on
that? On the Hackaday page, you mention you would ship to the EU but does that mean you WON'T ship to the US? Making at least the PCBs, sheet metal and a parts BOM would be a huge help for us in the US.
We are organizing sale to Europe. Today, I'm still not sure if we could sell to US. It would be a great help if someone could organize a sale in the US directly. The BOM is easy to provision, it's given in the documentation. I can help if you have question.
- Interference on 433Mhz is always going to be a challenge but do you
think it would be possible to add a "scanning" feature to the NPR system so it could go out and listen to X frequencies for Y seconds and come back with a report if those frequencies are quiet? This is something that Wifi has had on it's "channels" and it can be hugely helpful. In an amateur radio deployment, I don't that we would ever want a auto-channel selection feature but being able to initially listen and pick a frequency would be a huge help. The only other option here would be for the operator to deploy an SDR and listen in.
Scanning is possible, the SI4463 has such feature. But I'm not sure I will program that. Like you say, SDR software already exist, and easier to use. And automatic channel selection will not match ham-radio needs.
- With the lower bandwidth design, do you think enhancements could be
made to support full duplex using two radios? Aka.. each transmitter could use multiple time slots for higher performance? I do understand how that makes the overall setup a lot more complex.
It could be possible... but difficult. My design is in the spirit of minimalism. At least, we could develop a "FDD" version, with the Master-repeater station being duplex, and the client stations being half duplex, like 2G/3G phones. But it will add a lot of complexity. I can add this feature to the "wish list", and see if people want it or not. It can be helpfull if you put an NPR Master on a tower which already has a 70cm repeater, full duplex with frequency split. Aggregating several channels : I will not program that, because I don't see the need. If you need more datarate, just use higher symbol rate! If your idea is to strictly respect the "56kBaud" rule of the FCC, then that's a non-sense in my opinion, too crazy. In my opinion, the "occupied radio bandwitdh" rule is much more important than the "Baudrate" rule. I don't see the meaning of a "baudrate" limitation.
- You mentioned that NPR doesn't support IPv6 which is ok for small
deployments but there isn't any mention of MTU. I assume this system supports a RAW MTU of 1518 bytes but maybe it can support smaller or larger MTUs to better deal with the BER rate of the connection?
MTU is 1500, like with Ethernet. In order to be compatible with "lots of things" (IPv6, other IPv4 architectures, static IP, backbone links), I plan to add a "pure ethernet" mode in the following months: the radio protocol will carry "Ethernet frames" instead of currently "IPv4 packets".
- I see on the Hackaday page that it looks like the expansion from 7
clients to 15 clients might need different hardware. Would it be a good idea to socket the STM board so the upgrades could be "plug and play"?
That's not possible. The Nucleo L432 board, which I currently use, is already the most powerfull with this "form factor". If I propose a new microcontroller, it would probably be directly integrated to the PCB (LQFP package), so PCB assembly should be made by "automatic PCB assembly" services, or by human with very good soldering skills.
- I see you have email lists other community links posted on the
Hackaday page. Would be good to add those links to the end of the Introduction PDF
OK, thanks, I will do that.
- Maybe this Q&A and some of the other points from the Hackaday
comments section would all be well suited to start a FAQ?
I plan to add that later.
Anyway, thanks again for your efforts here and making it available to the world!
--David KI6ZHD
On 06/16/2019 06:30 AM, f4hdk wrote:
Hello.
I have updated the firmware of my NPR (New Packet Radio) project with 2 expected features, mainly for America: * New modulations (11, 12, 20, 21) for lower datarates, lower bandwidth. Symbol rates: 56kS/s (complies with FCC) and 120kS/s. You now have the choice between 9 modulation parameters, in order to adapt to lots of situations and needs. * Frequency range extended to 420-450MHz instead of previously 430-440MHz
I have updated all the documentation accordingly. https://hackaday.io/project/164092-npr-new-packet-radio/
Several people here expected these features. I hope you will enjoy it!
73, Guillaume F4HDK _________________________________________ 44Net mailing list 44Net@mailman.ampr.org https://mailman.ampr.org/mailman/listinfo/44net