[HOT] Smartphones using wifi in the field If you ain't in the field or techie ignore this post.

Eric Christensen eric at christensenplace.us
Fri Feb 12 03:33:48 UTC 2016


On Monday, February 08, 2016 06:54:55 PM john whelan wrote:
> I'm seeing different groups have different requirements here and cost is a
> major driver.

I used to be a network engineer and still do a fair amount of network 
architecture.  That said, I fully agree with your statement regarding 
solidifying the requirements at the very beginning.

There are many solutions available to build wireless networks.  Some are more 
expensive than others, obviously, and expense does not equal quality or ease 
of use.  I'm fond of the Ubiquiti network gear for building point-to-point 
links using their proprietary TDMA protocol (prevents blind-transmitter and 
stations trying to talk over one another).  These devices also support 
traditional WiFi (802.11abg...) for point-to-multipoint connections to the 
clients.  Since WiFi is pretty much ubiquitous on our consumer devices this is 
likely the easiest way to connect to computers and smartphones.  Mesh networks 
are also nice as they provide additional availability options although not all 
mesh protocols are equal.

The next fun is the applications.  My gut reaction is to suggest all open 
source software and stick to what people know.  You can always use postfix and 
dovecot for email, owncloud for sharing and managing files, and httpd for 
websites (and asterisk for voice communications and jabber for IM and...).  To 
me it's very important to keep this data as local as possible.  The last thing 
you want to do is tie up your WAN connection (wide area network: connection 
between cities or backhaul to the Internet) for data that is simply going 
between local computers.  Keep your WAN connection for exchanging information 
between disparate local area networks (LANs).  You should be able to host 
email, owncloud, and httpd on a small laptop or desktop computer locally to 
help keep the traffic on the WAN to a minimum and provide faster access to data 
locally.  Also, you want applications on the smartphones and computers that 
can cache changes locally and sync them later when network connectivity is 
available.  I know that OSMAND allows you to hold changes and notes offline 
until you are ready to upload them.  This is a bit plus when you are out and 
about without network connectivity.

I guess my greatest curiosity would be committing data to and retrieving data 
from the OSM network.  Is there a way to easily host this data locally, 
accepting changes from clients, and then send diffs back up to the OSM servers 
and also receive diffs of changes from OSM.  Again, with everyone needing to 
update their maps with the latest changes I think this would be very 
important.  Having all the mapping data available on the LAN for whatever app 
they are using means only having to download the data once over the WAN saving 
the valuable bandwidth.  It also improves speeds for the users.  I just don't 
know how to do this piece of the puzzle.

FWIW, the One Laptop Per Child (OLPC) folks developed a pretty neat mesh 
networking system that is built into their OLPC laptops.  They laptops create 
a mesh network on their own and if one laptop has access to the master server 
or the Internet those resources are automatically shared with everyone else.  
I don't know anything about the protocol or implementation (it's on my todo 
list) but it's developed to just work; always nice for a emergency/tactical 
network.

--Eric
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