Microwave data application in Dubus Magazine

Dubus is a quarterly magazine for technology, construction, DX and propagation on VHF/UHF and Microwave bands. It is edited in English and German languages by an international group of hams, printed in Germany.

I have blogged a few times before, on how the amateur microwave bands are so seldom used, and are our greatest allocation, as well as potential area for new development.

The problem is for the most part, the microwave bands sit idle, except for a few contests a year. Dubus is mostly what you'd expect, hams building microwave stations for the quest of a contact record.

I have never been that type, to each their own.

I am more interested in building infrastructure or something a number of hams can use. Which is why I like data networks, as I feel it can support a variety of applications while keeping some constant use of the frequencies.

Dubus 4/2006 - Microwave Japan Seiji Fukushima, PH.D, JH6RTO

High-speed IP connection on 5760 MHz by Hiroyuki, JH1UGF and Tsugno, JN1AYV

We report a 63 km high-speed IP connection on 5760MHz using ICOM ID-1's and modified transverters, UTV5600BIIP. The throughput was measured as about 100 kb/s at the application of layer .

Here are the details.

On the 29th of October, 2006, Hiroyuki, JH1UGF moved to Mt. Toogasa (altitude about 900 metres) and Tsugno, JN1AYV stayed at home in Chagasaki, Kanagawa for this experiment. The distance was 63km and both of us were within the line-of-sight. We used the same systems as follows. Our 1295MHz, digital transceiver was ICOM's ID-1 . To up/down-convert frequency, the 5760MHz transverters UTV5600BIIP were employed but some circuits were modified for this experiment. Since fast T/R switching is quite important, we removed the coaxial relay and added a circulator instead, as shown in Fig.1. In addition, two anti-parallel diodes were Inserted at the RX front end in order not to damage the preamplifier. These diodes cannot be seen In Fig, 1 unfortunately . The driver amplifier is MGF0904A and the final amplifier is 2xMGF1302, which outputs about 1W. We used a homebrew 25cm dish antenna with a horn radiator. Its gain was 25dBi.

We started our experiment. The voice QSO on FM was quite successful, RS 59+, as the distance was short enough . Then, we switched to direct digital mode for IP connection but the result was poor . Using a ping command of MS-DOS, Its connection rate was lower than 10%. Considering the multipath effect, we changed the frequency and/or antenna direction, but in vain. Lastly, Tsuguo moved his entire system , which was initially set in his room, to a balcony. Tsuguo had thought the experiment would have been successful even through a glass window since they had been within the line-of-sight. We got 100% ping connection after this trial.

Then we tried an application experiment. Using IP Messenger (IPmsg) software, Hiroyuki loaded an Tsuguo's image file into the Hiroyuki's PC. Look at our evidence of Fig. 2. The front is Hiroyuki and the back is Tusguo in the inset photograph. The 90KB file transfer took 6 or 7 seconds and, then, its application-layer throughput was calculated to be approximately 100kb/s . We learned that any thin obstacle in the path might make the multi-path interference at high-speed data communication. We would like to make the distance longer and to make the throughput higher in future.

What I did pay attention to in this article was that for the fast T/R switching they used circulators. I am not sure why this never occurred to me. I noticed this concept in 2006 Microwave Technology Letter, titled "Switchless Bidirectional Amplifier For Wireless Communication Systems."

So far this is the only microwave data application I have read in Dubus. I find that a bit odd, as there is a huge microwave data radio network in Germany and Europe.

If anyone else knows of good reading in these areas, I'd appreciate a note.

Flexibility of a HSMM network

KE7FTE, N7QQU and W9ERT show us the "drag and drop" flexibility of a HSMM platform. Offering reliable exchange of large image files, email, word-processing and other files that emergency responders and served agencies find invaluable.

The video does show what HSMM networks can provide for ARES. It should be clarified that this drag and drop flexibility is not exclusive to D-Star. It's a network file sharing protocol being employed between the laptops being used. Any TCP/IP based network can support this.

Yessj What's the range on this thing? It looks quite similar to a wireless peer to peer lan!

W7NWH

One big difference HAMS can use greater power with a upside of distance and robustness. Hams can use up to 1500 watts of power. Where your local wireless network is measured in millawatts to watts. With high gain antennas and lots of power ranges can exceed 50-80 miles. And that's peer to peer! Try that with your wireless LAN! Idea is this can provide emergency backbone for a LAN that is down in an emergency. Not super fast, just robust and proven!

Above are some of the youtube video comments. W7NWH is trying to make this pricey D-Star sound like it's fundamentally superior to common wifi. Yes hams can run more power, but that likely won't accomplish much more. Microwave propagation is microwave propagation. Height is the key item. If you don't have it, the 10 watt D-Star radios at 1.2 GHz won't yield much better paths than the under 1 watt paths that you could do with wifi. I don't know of any 1.2 GHz amplifiers to run more than the stock Icom ID-1 let you anyway. They have been several well publicized examples of 20-30 mile 802.11 links, and one 72 mile path!... One with a ham twist was published in the July 2005 QST, titled, "IEEE 802.11 Experiments In Virginias Shenandoah Valley."

One thing I've noticed is that command posts love telephones and fax machines. Pictured above you see an $30 analog telephone adapter. Talk about seamless to the emergency manager!

Another interesting and smart idea when it comes to repeater linking is to use analog radio adapters and link the repeaters over your HSMM backbone. Most repeaters are on decent tower sites already so linking such sites over microwave HSMM links should be very feasible. Now your linking channel is not just capable of voice, but can act as a high-speed back bone.

IRLP and Echolink linking are pretty prominent and well understood. In many cases there may be multiple repeaters in the same geographic area all linked (maybe even semi-permanently) using such common VOIP networks.

With HSMM backbones you can off-network link these. This is very emcomm friendly in the even a backhoe takes out internet to most of an area.

1.2 GHz HSMM with the Icom ID-1

Back in June 2004 we inquired about Icom's 1.2 GHz ID-1 D-Star solution for ham radio voice and data communications. We were fortunate enough to be able to evaluate it for a few months.

Our short documentation is located at:

http://www.qsl.net/n9zia/dstar-evaluation/

You can also read the Wisconsin Amateur Packet Radio review here:
http://www.qsl.net/kb9mwr/wapr/0204.html

We were most interested in the data performance and networking ability of the D-STAR system. The only radio that can do any significant data transfer is the 1.2 GHz ID-1. It's listed with a (theoretical value) transmission speed of 128 kbs. We clocked an effective TCP/IP throughput of 90 Kbs. Perfectly understandable considering protocol overheads.

We didn't have a lot of time to mess with it. Our initial path was a 4 mile hop, but that was just on the fringe due to the Packers stadium in the middle. We could communicate using the digital voice mode and analog FM, but not the digital data. A few more feet of height might have done it. We were at 60 feet at the remote end, and 40 at the other.

So we opted to test the data performance on a much shorter path with another local.

The lesson learned is even at 10 watts on 1.2 GHz, verses the 1 watt or less on 900 MHz or 2.4 GHz, microwave path loss doesn't change much.

So in our case for much, much less money we can accomplish the same paths at even higher speeds using other hardware. What would be interesting is to see how well the ID-1 would work mobile. I do believe it would work quite well for this compared to the alternatives.

{edit} Reports indicate that it takes a very solid signal into the Access Point/DD system to work well. And works good over a large area when non-moving, but motion/multipath tears it up. A continuous ping by with a 1.2 GHz radio would start working at very stop light, and stop as soon as was moving.

After having looked at the various documentation, the Digital Data (DD) mode of the 1.2 GHz Icom ID-1 is a rather strange design.

There is reason for concern on that the amount of overhead is huge (D-STAR header + Ethernet header + IP header), and that the FEC as implemented is a bit strange (why does it only apply to the D-STAR header, and not the Ethernet frame?). Further the protocol has no real mention of channel access concerns (collision detection, avoidance, etc). It really looks to me like DV with ethernet frames stuffed into the payload section (i.e. maybe it was somewhat of an afterthought).

All the DD mode appears to do is forward ethernet frames around. On its own, it does not do any acknowledgment/handshaking. This is all left to the upper-layer protocols (i.e. TCP).

It appears that if a collision happens then the DD packet is just lost, and there's no really mechanism to avoid collisions at the DD layer, either. It's up to the higher-layer protocol to do anything about it.

So you really have no indicator of channel quality when using it. The lack of this sort of thing seems like a major oversight. It looks like packet radio done badly, although with better speeds. If it were introduced 15 to 20 years ago we would have hailed it as the savior of packet radio, but now it looks like a poor imitation of WiFi.

To further, it doesn't help most of what you will read on the other D-Star Yahoo groups shows that the ID-1 isn't being used with good RF engineering practice leading to poor results.