[Commotion-discuss] Building a commotion network to support 2000 concurrent users

[Ben West]

Wow, that would be a lot of CPU and RAM behind a single 802.11n radio.
Given at host machine with that many resources, I think you may find the
USB dongle itself becoming a bottleneck far before the host CPU sees any
significant load.  The USB protocol stack itself (e.g. the ath9k_htc
driver) is going to impose limitations on throughput in and out of the
dongle, likely to be far less than the USB link speed.  Embedded nodes use
faster bus interfaces such like mini-PCI for this reason.

Also, you would be sacrificing some channel capacity if your USB dongle has
only 1 RP-SMA port (making 2x2 MIMO unavailable), or if it uses itty bitty
internal patch antennae.

For a node capable of hosting 30-50 clients, here is an ARM9-based single
board computer, with a mini-PCI slot:
http://www.gateworks.com/product/item/laguna-gw2388-4-network-processor

Likewise, here is a mini-PCI 802.11n radio from UBNT.  Two coaxial jacks
for antenna diversity:
http://shop.bizsyscon.com/ubiquiti-sr71-12-mimo-802-11b-g-n-2ghz-mini-pci/

This bug ticket does suggest at least one person has met moderate success
running both of these units together under OpenWRT:
https://dev.openwrt.org/ticket/13465

Also, there should be other options for single board computer  + mini-PCI
with OpenWRT support out there, if that is your host OS of choice.



On Sat, May 10, 2014 at 2:30 AM, Paul Liu <paulsc.liu at gmail.com> wrote:

> Hi Ben,
>
> Thank you for your feedback. We will review our overall deployment design.
>
> Here is some additional information. We will build a customized node. The
> prototype is using a dual core ARM cpu with 2GB ram, gigabyte Ethernet as wired
> backhaul. We will hookup USB WiFi dongle to service the clients.
>
> We do plan to test wireless backhaul and probably run it on 5.8GHz radios.
>
> Right now the design call for each node to support 30 to 50 clients. We
> will try to find out what kind of usage scenario is possible. Data only?
> with voice? with video? How will transfer large data affect the performance?
>
> Cheers,
> Paul
>
> If it is necessary, we can use quad cores or 8 cores ARM CPU.
>
>
> On Sat, May 10, 2014 at 1:10 AM, Ben West <ben at gowasabi.net> wrote:
>
>> My recommendation, from operating a mesh network with firmware very
>> similar to Commotion, that serves ~100 people daily, would be to focus on
>> how many mesh nodes you would need to deploy.  Likewise, since there is no
>> way to fit 2000 users on a single 2.4GHz channel, you would be needing to
>> segment such a large deployment into pocket meshes, e.g. a handful of nodes
>> in each mesh, with adjacent meshes programmed to non-overlapping channels.
>> Backhaul between these pocket meshes could be done with 5.8GHz radios, or
>> wired backhaul depending on your situation.
>>
>> To help with estimating how many nodes you'd need, it's fair to assume
>> each node could only support up to 5 (or possibly 10) simultaneous clients
>> before either the node itself exhausts its RAM (only 32Mbytes onboard
>> memory) or before the particular channel used by that ( node + its
>> neighboring nodes + all clients ) becomes saturated.
>>
>>
>>
>> On Fri, May 9, 2014 at 11:58 AM, Paul Liu <paulsc.liu at gmail.com> wrote:
>>
>>> Has anyone had the experience of building a commotion network that can
>>> support 2000 concurrent users?
>>>
>>> Any advice on how to build it, potential pit fall? total equipment cost?
>>>
>>> Best Regards
>>> Paul Liu
>>>
>>> _______________________________________________
>>> Commotion-discuss mailing list
>>> Commotion-discuss at lists.chambana.net
>>> https://lists.chambana.net/mailman/listinfo/commotion-discuss
>>>
>>>
>>
>>
>> --
>> Ben West
>> http://gowasabi.net
>> ben at gowasabi.net
>> 314-246-9434
>>
>
>


-- 
Ben West
http://gowasabi.net
ben at gowasabi.net
314-246-9434
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