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

john whelan jwhelan0112 at gmail.com
Wed Feb 3 16:16:25 UTC 2016

With fifty users sharing files you probaly want to use a couple of linked
hubs, that's where the TP-LINK MR3020 starts to shine.  I have one here and
one waiting to be picked up at the computer store to test but its freezing
rain here in Ottawa at the moment so there is a layer of ice on the
sidewalk, not so good for walking on.  However you can use two laptops
independantly and collate the files later on.

If you are texting only then one hub should be enough for fifty users, for
voice calls depending on the traffic it should just work since not everyone
will be using it at the same time.  For file transfer, depending on the
size of the files you might want to split the load over more than one hub.

For voice over more than one hub you need to link them so you need two or
more TP-Link devices with the special firmware.  Linked in this way you can
send a text to a device that is not available and in theory it will be
delivered when it comes in range next.

>From a practical point of view Paul's mesh extender combines a hub with a
small radio so you can link over longer distances.  It uses the same
frequency as a car garage opener to build the mesh.  It also comes in a
plastic box to keep the weather out.  Unfortunately it's not quite in
product yet but bug New Zealand's Red Cross and they should have some idea
of time frames.

If you're using a TP-LINK MR3020 it does require a power source, but
battery powered USB boxes are around to extend the battery life of a



It appears you can use any wifi hub that supports peers.  Note this isn't
quite the approach that the Serval team has been using up until now and I'd
need to play with the specific router to get the configuration sorted out
so stay with the specific Tp-link device or the win 10 hot spot and test it
before you go out in the field.

The portable wifi hub the TP-link is cheaper than a laptop, around $40
locally.  If you want to link them up then you need to flash them with a
different firmware.  I haven't done this yet but it is on the to do list
and it should be possible with a laptop but does require running some form
of unix on the laptop but that can be done under windows.  Once it is set
up then it takes a couple of minutes to update the firmware on the hub.
Want me to write up the process on how to configure one for stand alone
use?  Where would you like this written up?  Note different coutries have
slightly different rules for wifi etc. and a standard TP-Link hub
understands these so which country it will be used in is part of the setup
process.  Hopefully the linking firmware takes this into account.

Note there are other solutions than serval for sharing files, especially
using a hot spot from a laptop.  Essentially you can use the laptop as a
web server, in theory you just need the appropiate .html file(s) on the
laptop.  So you can link windows laptops together using this technique you
don't need serval for this.

If you use html5 code and have the downloads as .zips then you should be
able to click on the link and the file will download automatically.  I have
some simple sample html5 code floating around if anyone wants some.  I
think most smartphones can handle .zip files.

The other thing to note is that wifi devices such as Nexus 7 tablets can
use voice to smartphones running Serval.  In general wifi tablets are
cheaper than smartphones.

and you thought the HOT mailing list was just about mapping.

Cheerio John

On 3 February 2016 at 09:02, Mhairi O'Hara <mhairi.ohara at hotosm.org> wrote:

> Cheers John! We're collecting data on financial services, education and
> health facilities in Eastern Uganda and are looking for sharing solutions
> that don't involve the internet. With up to 50 students at times, sharing
> files via usb sticks and external hard drives is not ideal as it can be
> time consuming. Will look into the setup to see if it could work for us
> here.
> Mhairi
> On Wed, Feb 3, 2016 at 3:00 PM, Katja Ulbert <mail at katja-ulbert.de> wrote:
>> Thanks for this valuable information, John!
>> On 31/01/16 22:34, Pete Masters wrote:
>> Really interesting, John.... Thanks for the post. Just conducted training
>> in DRC on data collection and base mapping. We tried to focus as much as
>> possible on offline solutions. Wish I'd read this before we'd been, not
>> just after! ;)
>> Pete
>> On 31 Jan 2016 20:35, "john whelan" < <jwhelan0112 at gmail.com>
>> jwhelan0112 at gmail.com> wrote:
>>> I've been playing around with Serval software on Android.  Ideally it
>>> needs a wifi mesh set up using multiple firmware modified TP-Link MR3020
>>> portable routers with custom software connected to a small radio device
>>> which turns it into a mesh extender.
>>> The original concept was to turn the smartphone into a router but the
>>> latest Android software well anything above 2.2 denies access to do this.
>>> Besides which rooting the phone in this manner is not good from the
>>> security point of view.
>>> However if you are running Windows 10 and your Laptop supports it, most
>>> should, you can turn your laptop into a wifi hot spot that other devices
>>> can connect to. Note you should not need to be connected to the Internet
>>> for this to work.
>>> Translation Android smartphones running Serval within say 100 meters of
>>> the laptop  can now talk to each other.  I haven't tried a phone call, I
>>> don't have two Smartphones to hand, but messaging certainly works.
>>> You should also be able to transfer files certainly from one smartphone
>>> to another and if Serval doesn't support file transfer to the host laptop
>>> there are other apps around that do.  So things like the latest maps for
>>> Osmand etc can be brought down once to the laptop then propagated out to
>>> smartphones or a smartphone sent by mail, mule etc to the wifi hub can then
>>> connect and distribute files etc.
>>> I haven't looked at the implications of interconnecting laptops perhaps
>>> with cat 5 cables and although phone calls should be fine across one wifi
>>> hub theoretically each hub used in the hops adds a small delay so voice
>>> quality over multiple hops may not be ideal.
>>> Cheerio John
>>> _______________________________________________
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> Mhairi O'Hara
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> Email: mhairi.ohara at hotosm.org
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