[HamWAN PSDR] 1.2GHz to Paine [was: 44.x.x.x HamWAN network at Paine]
Bart Kus
me at bartk.us
Wed May 28 20:27:09 PDT 2014
Well yeah, you can't have ping without arp first, unless you configure
static arp entries. :)
So it looks like the protocol does support 1/2 FEC, and also enforces an
FCS (CRC). The FEC starts after clock recovery and frame synch, which
is optimal.
Forget the FM receive thing, all I really wanted to know is what the SNR
of the 1.2GHz signal you get from Paine? If the ID-1 doesn't tell you
this, an RTL-SDR should. Does the link work in 4.8kbit mode? I'm
assuming you have both sides set for 128kbit right now.
--Bart
On 5/28/2014 7:20 PM, Dean Gibson AE7Q wrote:
> See http://www.arrl.org/files/file/D-STAR.pdf - pages 3-5 describe the
> DD-mode (data) packet.
>
> The ID-1 apparently doesn't know whether or not the Ethernet frame is
> corrupt. From the TX/RX lights for both the radio and the Ethernet
> connection, it appears that every received packet from one end, goes
> out the other.
>
> When conditions are right and I receive about 10% of the packets from
> a PING (like last Monday), it seems clear from observed behavior that
> once an ARP response is received, then quite a few PINGs get through.
> I haven't tried listening on FM to a DD packet, but I can try that on
> Thursday, when I am at the DEM. I'm not sure what the point of that
> would be, though.
>
> On 2014-05-28 17:12, Bart Kus wrote:
>> This is some really broad strokes. Are there specifics on ID-1
>> protocol / framing somewhere?
>>
>> --Bart
>>
>> On 5/27/2014 4:59 PM, John D. Hays wrote:
>>> ID-1 simply encapsulates an Ethernet frame behind a D-STAR header.
>>> The header has some correction, but the Ethernet frame is not
>>> corrected by D-STAR.
>>>
>>> ------------------------------------------------------------------------
>>> John D. Hays
>>> K7VE
>>> PO Box 1223, Edmonds, WA 98020-1223
>>> <http://k7ve.org/blog> <http://twitter.com/#%21/john_hays>
>>> <http://www.facebook.com/john.d.hays>
>>>
>>>
>>> On Tue, May 27, 2014 at 4:28 PM, Bart Kus <me at bartk.us
>>> <mailto:me at bartk.us>> wrote:
>>>
>>> There's no protocol I'm aware of that implements these features
>>> on top of ID-1. You'd need the ability to receive corrupt
>>> frames from the ID1 to allow the use of FEC. How does the ID1
>>> handle corrupt frames? Is there a CRC or something in the
>>> framing? For ARQ, you could keep the TX retrying until it hears
>>> an ACK or times out. Custom software would be needed, or
>>> perhaps pppd can do such tricks, I dunno.
>>>
>>> Did you hear any signal when you listened with an FM receiver?
>>> Can you use an RTL-SDR or equivalent to see if there's any
>>> signal present?
>>>
>>> --Bart
>>>
>>> On 5/24/2014 8:36 PM, Dean Gibson AE7Q wrote:
>>>> That's what I figured ("features [that] are common to all WiFi
>>>> systems"); it just made sense (although that is not always
>>>> determinative!).
>>>>
>>>> So, my next question: Is there an available tunneling protocol
>>>> that employs those features?
>>>>
>>>> Note that with the ID-1 in the *one watt* setting (same omni
>>>> antenna), I can use the 1.2GHz KB7CNN repeater 35 miles away on
>>>> East Tiger mountain, with no noise in the FM signal. The link
>>>> to Paine (5 miles away) was tried at max power (ten watts) on
>>>> both radios. I tried two different frequencies (that's the
>>>> beauty of being able to control both radios from one
>>>> location!): 1.250GHz and 1.249GHz (I listened on both in FM
>>>> mode), with no significant difference. So, in my opinion, it's
>>>> a path problem.
>>>>
>>>> On 2014-05-24 13:13, Bart Kus wrote:
>>>>> Wow that sucks. :( Is the signal level just too low? Is it
>>>>> a matter of interference?
>>>>>
>>>>> And yeah, I can confirm that the microwave stuff we use
>>>>> includes both FEC (at up to 1/2 rate) and an ARQ system (look
>>>>> at "hw-retries" setting). These features are common to all
>>>>> WiFi systems too, and they're just carried over into our NV2
>>>>> TDMA system.
>>>>>
>>>>> --Bart
>>>>>
>>>>> On 5/24/2014 10:19 AM, Dean Gibson AE7Q wrote:
>>>>>> Scott Honaker and I have moved forward on this project:
>>>>>>
>>>>>> 1. We have installed a gateway (Linksys BEFSR41) between the
>>>>>> ID-1 and the internal ARES/RACES subnet (not 44.x.x.x) of
>>>>>> the DEM.
>>>>>> 2. We have installed a Digi "AnywhereUSB" box to give us
>>>>>> remote access to the ID-1's USB port, and thus remote
>>>>>> control of the ID-1 radio. This not only allows multiple
>>>>>> use of the ID-1 (which has useful 1.2GHz FM and digital
>>>>>> voice modes as well as Ethernet data), but provides for
>>>>>> remote frequency agility and a diagnostic capability.
>>>>>> This works beautifully (eg, to search for and use a
>>>>>> low-noise frequency)!
>>>>>>
>>>>>> Unfortunately, what does not work very well, is the RF
>>>>>> portion of the connection. PINGs failed at a rate of over
>>>>>> 99% when using the 1.2GHz antenna at the 70 ft level on the
>>>>>> tower, so we swapped the antenna with the one used for the
>>>>>> Icom 1.2GHz repeater (which wasn't seeing any action anyway)
>>>>>> at 100 ft. That made a "dramatic" improvement, as PINGs now
>>>>>> only fail at a 98% rate (depends upon the time of day, etc)!
>>>>>>
>>>>>> Antenna comparison between 1.2GHz and 5.9 GHz for the two sites:
>>>>>>
>>>>>> 1. On 1.2GHz, both antennas are omni-directional.
>>>>>> 2. At the DEM, the 1.2GHz antenna is now at the 100' level,
>>>>>> whereas the 5.9GHz antenna is at 150'.
>>>>>> 3. At my home, the 1.2GHz antenna is about 10' above the
>>>>>> 5.9GHz antenna, and it's on the same line-of-sight path.
>>>>>>
>>>>>> Note that voice communication between the two sites using the
>>>>>> two ID-1 radios, is fine (there is a slight bit of noise on FM).
>>>>>>
>>>>>> The big difference, in my opinion? I'll bet that the
>>>>>> wireless protocol used by the MikroTik radios includes an
>>>>>> aggressive error correction and retry protocol, whereas the
>>>>>> ID-1 is like a piece of Ethernet cable, and thus relies on
>>>>>> the standard TCP/IP retry mechanism. The TCP/IP protocols,
>>>>>> while "unreliable" in the technical sense of the term,
>>>>>> require a higher overall reliability than a typical raw
>>>>>> wireless connection.
>>>>>>
>>>>>> What this says (and I'm a bit surprised to note this), is
>>>>>> that sites considering using ID-1 radios for data
>>>>>> communications, may find that even with the tighter siting
>>>>>> requirements of 5.9GHz, that the latter may be more
>>>>>> successful (whether or not part of HamWAN). In addition to
>>>>>> being a lower-cost radio with a much higher data rate, the
>>>>>> MikroTik radios offer a built-in router, which can obviate
>>>>>> the need for a separate router.
>>>>>>
>>>>>> -- Dean
>>>>>>
>>>>>> ps: The callsign and digital code filtering features of
>>>>>> D-Star that we previously discussed, are not available
>>>>>> (greyed out in the software) for digital *data* mode. Huh?
>>>>>> Another fine example of software of the "seven last words" of
>>>>>> poor program design: *"Why would you want to do that?"*
>>>>>>
>
>
>
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