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Couple of technical questions

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km5l
km5l's picture
Couple of technical questions
I've a couple of questions, first some backdrop. I'd like to stir up some interest in east Dallas. Problem being that this area has mature pecan and oak trees. I want to reach out to east Dallas hams but would like to have an idea on how we could organize first.

So, first question: With the trees, will we have to have line of sight, clear of leaves and branches? This question for all bands, including 900 mHz? Or, is it possible at a certain distance to get through branches and leaves with a directed antenna and short dx? In east Dallas there's a lot of hams, so it's possible we could get some density too. What would you recommend?

Second question - just curious is all - I have some networking background - in terms of OLSR... Does each and every device hold a table in memory with cost of each node and path? Does OLSR run on every device, including the smaller 802.11n clients? And then if A-B is broken, does it stop transmitting those packets on that route and just then begin a transmission to A-C? In other words, the RF part of this is IP smart and doesn't transmit unless the route is active with interesting traffic?

Thanks again and 73 Patrick KM5L
K6AH
K6AH's picture
Thanks for the post Patrick,

Thanks for the post Patrick, and welcome to AREDN.  

First of all, AREDN is not BBHN, and it is quite possible to construct links of 40-50 miles, so I wouldn't discount the real possibility of connecting up with the group west of you in Ft. Worth.  I would personally recommend 3GHz, for longer haul links and 2GHz (channel -2) for the "last mile".

Yes, the routing protocol updates the node's tables constantly.  Node A has a list of each other node's IP address.  So if node B is 3 hops away, Node A looks up Node B in its own routing table to determine which of its own "first hop" neighbors to pass the message to.  With the first hop compete, that node also determines which of its own neighbors to send it to for the "second hop"' etc.

So the RF path keeps pretty busy updating OLSR information.  It also maintains RF link quality data.  When there are multiple paths to node B, then it evaluates which is the best path based on the sum of link quality metrics.  You learned about that in my YouTube video.

All nodes running AREDN software do exactly the same thing... I'm not sure what you meant by "smaller 802.11n" clients.

Unfortunately, Any sort  of vegetation in the path (actually the expanded envelope called the Frenzel zone) will kill the signal.  The 900 MHz band should theoretically give you some relief from this.  Water towers, tall buildings, towers are pretty much a necessity, unless you're lucky enough to have hills/mountains.

I hope this helps.  You will find many helpful people on this forum.  Don't hesitate to ask questions.

Andre, K6AH
 

km5l
km5l's picture
Hey back again
Hey Andre, thanks for the reply. The info on the protocol detail is much appreciated.

I don't want you to think I'm just asking questions, I spent a chunk of time reading several docs but still have an important strategy question. I'm sure it's no accident that most of the City of Dallas is not covered with any Mesh solution (I'm using this term to cover AREDN, BBHN, et. al), and also not a surprise that most of the coverage is in fact in areas where vegetation is MUCH lower - newer burbs or additions. The DFW/North Texas area is also an East-West line that begins to separate highly forested eastern from west Texas plains.

So, we need a solution for the masses. I would frankly love to be part of the solution if there's one to be had, but if it's an impossible uphill battle you might just let me know. From what I gather about your own personal location you are not "dead in the water" right from the start - you do have hills and mountains to contend with, but your trees are no 75 feet tall and not dense, correct? So that's what a lot of us work with. Don't get me wrong, most of the time there are "holes" to be found out of the neighborhood, but there's going to be a lot of work to match the holes up.

I looked but just can't find a document with a simple drawing of two hams connecting.  Can you point me to one. Referencing the DtDLink document, just so I can wrap my head around it, say I find a visual hole to another ham a half mile away. I could connect to him via a Nanostation M2 (and he as well via an M2), right? That's a mesh? Now then we both have our own LANs and can have apps, voip, cams, or whatever for each other? See basic drawing attached.

Am I missing something or would that be the basic thing? I know you said AREDN is not BBHN but all I'm trying to do is establish an intitial useful foothold/presence. From that we can go from there.

What are my options for the switch in the picture? Does it need to be able to do VLANs?  I know I'm asking basic questions, not finding just the right document.

Thanks,
Patrick KM5L
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AE6XE
AE6XE's picture
Patrick,
Patrick,

Yes, 2 people can build a 2 node network per your drawing.   I usually say it this way, and it's more complicated with caveats than this, but the basic idea is this.    Think of the mesh node as if it was the cable modem from your internet service provider. But this is our ham radio private internet.  It's a black box on how data passes to someone one else's house to their cable mode.  When we use an application, voip phone, etc. and send traffic to the IP address on the other end, this black box network just gets it there (with OLSR figuring it out).   For both AREDN/BBHN, any set of mesh nodes that have a usable RF link or DtDlink cable between them are now this black box network.   As long as there is a daisy chain path of links to the end destination you want to get to, the links are usable, then the end-to-end applications can communicate to each other over this network.

Yes, you do need an 802.1q (vlan) switch to extend the physical ports of mesh nodes, except the AirRouter that has 5 ports built in.  It's as cheap to get the AirRouter as a vlan switch, so I've started advising new mesh'ers to get the pre-configured AirRouter (and add a dumb switch if they have even more devices).

In the context of not-BBHN to clarify.  Protocol wise these are 100% compatible.  This basically means we can DtDLink between a BBHN and AREDN device to link together and extend the mesh network across both.  (It could be done on ch 1 to 6, but everyone figures out quickly to run away from these channels given the significant noise.)  not-BBHN primarily means:  outdoor packaged and can do 40+ mile high speed link every day of the week.  We have a permanent link over the noise rich LA Basin area that demonstrates this with just a NanoBrige 3Ghz. Andre, myself, and others are building backbones with higher gain RocketDishes.    

For  flatlanders, what you'd be looking at doing is identifying these tall structures to put the backbone links in/out of, then provide local Sector or Omni coverage.   Here's a picture of such a setup:

https://sites.google.com/site/orangecountymeshorganization/orange-county...

In the mountain peak locations, we think of backbone across these peaks with a downlink to "mid-mile" or cell areas.  For flatland, you'll probably just have backbone primary links between towers/building-tops where opportunistically available and each is a local cell coverage area.

Joe AE6XE
km5l
km5l's picture
Thanks Joe
That's exactly what I needed. I totally understood the concepts but needed a nudge on what AREDN is doing differently in terms of a "neighborhood" network.
73,
Patrick KM5L
km5l
km5l's picture
On your picture
Joe, one the picture you sent: https://sites.google.com/site/orangecountymeshorganization/orange-county...

There are two or three tall buildings (10 or so stories) within two miles of here. For most of us there's going to be a tree in the way, again, these trees can be 75 feet tall - great for shade though. So, on the honest honest, if the building is within a couple of miles is there any chance a directional antenna at a ham's house can get through the one tree and hit the omni on the building? (900 mHz even?)  I realize we can just try it but that could frustrate a lot of talent. Better to plan our best probabilities.

73,
Patrick KM5L
AE6XE
AE6XE's picture
Short answer, no.   The only
Short answer, no.   The only time I've seen microwaves or 900mHz getting through more than a few leafs is just recently.  A local ham was 0.5 miles away and happened to be directly inline with a Rocketdish 5Ghz w/ 30dBi on a roof pointing to a mountain.   He pointed back a ~22dBi nanobridge through many trees--it probably is  bouncing around them somewhere :) with a 100% LQ/NLQ.  This is such low power that leafs will absorb all the energy.   We'd probably have to fry birds flying by with enough power to get through any non-trival foliage. 

If it were me, I'd try to find a way to get a <1 lb Nanostation on a pole strapped to and raising just above the tree line with a 100+ ft cat5.  The NS is a 90deg sector so one doesn't have to be very precise trying to mount it.

Joe AE6XE
km5l
km5l's picture
Hi Joe -
Joe, you have my interest peaked on that response (pun intended :) )

You're saying I might consider mounting a lightweight (less than 1 lb) Nanostation on a tall tree, above the tree line; and because it has a 90 deg. sector it doesn't matter if the tree is moving/swaying?  That's an interesting idea. Which Nanostation for example?

73,
Patrick KM5L
K6AH
K6AH's picture
Filling in a couple gaps on Joe's very fine answer...

There are three VLANs that the node uses to split specific communications functionality out from a single Ethernet port:

​VLAN1 - WAN: This is the Gateway and is generally connected to the Internet, although it is often left open when not passing Internet traffic to the mesh.
VLAN2 - DtD: Used to connect 2 or more nodes back-to-back.
VLAN10 - LAN: This is for local computers connected to the mesh like the laptop you use to connect to the node’s graphical user interface.  It’s also used for computers which run services you advertise to others on the mesh (like email server, web servers, etc.)

Smart switches can be used to separate these VLANs into individual physical Ethernet ports.  But even if you don’t use a switch, the VLAN10 is the default and you can throw a dumb switch on the node’s port and connect as many devices as you have configured your node’s DHCP service for.

Similarly, you can also connect VLAN2 (DtD) devices directly onto the node’s port because VLAN2 is tagged, meaning other nodes will recognize traffic using this tag and know it’s to be treated as DtD data.

There’s more on DtD in the following article:  http://www.aredn.org/content/device-device-linking-dtdlink

I hope this helps.

Andre, K6AH

km5l
km5l's picture
Thanks Andre
Stupid question but when you say "internet" you mean the private ham internet, correct?
73,
Patrick KM5L
K6AH
K6AH's picture
"Internet"
No, I mean "Internet".  Served agencies can have many bonifide uses for Internet connectivity.  The AREDN software has a Gateway function that, when turned on, connects the mesh to an Internet default route.  This is not meant to encourage the use of the mesh for general Internet access, but AREDN certainly wouldn't exclude this served-agency business use case.
 
KA5TYW
AREDN -- Richardson, Texas
Hi, Patrick.

This may be of interest to you:
 

There is now a special presentation scheduled for the afternoon session of the Raspberry Pi SIG.

Please join us on Saturday, July, 16, 1200-1500 at University of Texas at Dallas, for a presentation on, and demonstration of, high speed MESH networking using the K5UTD Amateur Radio Emergency Digital Network (AREDN) project.   Given by Andrew, KE5GDB, the presentation will will include assistance with node setup (hardware, software, firmware) and operation.

AREDN is an adaptation of Broadband-Hamnet firmware to Ubiquity wireless products on the 900Mhz, 2.4, 3.3 and 5 Ghz amateur bands.  AREDN has the potential to provide extraordinary digital communication capabilities for RACES/ARES and public service operations.

Whether you are just curious about AREDN or are already mesh-ready, this presentation will be an excellent opportunity for learning and sharing.  If you have node gear (radio, antenna, laptop, etc.), please bring it.

For meeting location, visit http://brandenburgtech.com/

73,

Paul -- KA5TYW
 

km5l
km5l's picture
Hi Paul
Paul, thanks, yes I knew about it, unfortunately I can't make it - I have a ministry mission I'm working on and that will eat up the whole day.

I did ask on the FB rpi dallas page if someone could audio record it, that would be awesome.

73,
Patrick KM5L
AE6XE
AE6XE's picture
reply to #8 - mounting NS at top of swaying tree

Paul,  all of the Nanostations (M2, M3, M5) and Nanostation Loco (M2 only) would have some possibility to work.   The exception is the Loco M5 which is an 'XW' and not yet firmware supported .    They all have different beam widths both horizontal and vertical.  The best for wind motion would be the M2 loco - 60deg sway up/down, 60 deg left/right and still in the beam pattern.   But this has the lowest power output and antenna gain--with clear line of sight this would probably work great 2+ miles range.   On the other end is the NSM5 which is ~41deg left/right and only 15deg up/down.

However, there's no whiplash spec :) ,   what kind of sway are we talking about?  If the sway is an arc and rotating 45 deg left and right, misalignment of the polarities could lower SNR on the receiver and degrade the link in/out of useable. 

I've hoisted up a NSM3 on a ~20'+ painter pole with it swaying back and forth up to 2' at the top establishing a link ~8 miles and it worked fine.

Joe AE6XE

N8NQH
N8NQH's picture
loaner kit

We have a "loaner" kit with two nodes and detailed instructions... to help ease fears of those in our area who aren't quite sure if they are interested in Mesh... or if they can even connect to our local grid.

I also have some web pages up, with basic How-To:P
www.tim-yvonne.com/ham/mesh


and a local "recommendation" page for ones first QTH node:
http://tim-yvonne.com/ham/mesh/first/index.htm

though it's area specific.

FYI, if you use a VoIP phone model that has a built-in switch (like the Grandstream GXP1630)... you can have both the phone and your computer connected at the same time... without the need for an additional hardware.
 

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