[CQ] Reality check on Amateur Mesh Networking

[Michael Shiloh]

Hi Bruce,

Thanks for the wonderful report. This is facinating and great.

Is Jason aware of the Open Hardware Summit and effort? We should 
certainly connect his work to that.

Michael Shiloh
KA6RCQ

On 10/16/2010 06:42 PM, Bruce Perens wrote:
> I attended Jason's talk at Pacificon today. It seemed to me that there
> was a concatenation of optimistic assumptions in the talk.
>
> To get a reality check on mesh networking, please take a look at David
> Rowe's "Mesh Potato" effort and his deployment of a mesh telephony
> network in Dili, Timor Leste. In the post at
> http://www.rowetel.com/blog/?p=652
> Rowe discusses why a commercial Wimax device works well, even in Timor
> Leste, when his own mesh network doesn't.
>
> Also note that Rowe has created a 100% open mesh wifi design and is
> having it manufactured, and has a history of success in manufacturing
> Open Hardware - his Blackfin Asterisk PBX is great.
>
> Jason showed a 150 mile wifi link as an example. While these things are
> possible when all of the conditions are met, it's more the case that the
> average ham won't achieve line-of-sight to even one other node. This is
> the main reason that hams are still using D-STAR, AX-25, etc. We can do
> better than D-STAR, potentially, with spread spectrum on lower
> frequencies than those proposed.
>
> Jason discussed mobile use of the mesh hardware. Has there been any
> testing? I suspect that the multipath and fading issues might be
> underestimated.
>
> Jason offered TDMA as a cure for the hidden-node problem. While a good
> algorithm for doing TDMA in a mesh is probably possible, it's not at all
> clear that we have one yet. The RTS algorithm used on WiFi hasn't worked
> well in practice on Rowe's mesh, in an area that didn't have much "Part
> 15" operation to interfere with it. Phil Karn KA9Q designed most of the
> algorithm that was adopted in the WiFi standard, and I'm trying to get
> him interested in why it's failing. I suspect that the well-working
> examples have a star topology.
>
> It's likely that we will lose 44 net in the coming IPV4 address panic.
> Given the use we are making of it presently, it would be responsible of
> us to give it up. Starting with IPV6 would make our lives easier over
> the long run, there is an old TAPR paper on encoding Amateur callsigns
> in IPV6 headers. If your local equipment only does IPV4, run NAT or map
> the Amateur IPV6 subnet to a bank of net 10 addresses.
>
> Codec2 was mentioned as a potential audio payload. Please note that the
> 7 byte Codec2 frame is tiny compared to the IP+TCP/UDP/RTP/STCP header
> overhead, and that you either end up wasting most of the packet or
> having really high latency because it takes 4 seconds of speech to fill
> a packet. So, it turns out that a codec with less compression works
> better over IP, Codec2 is intended to run with only one header per
> transmission over the radio link.
>
> I think there are some difficult, unsolved problems that should be
> acknowledged in future talks. It might be best if the potential quoted
> is what you achieve in your own testing.
>
>       Thanks
>
>       Bruce Perens K6BP
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