Practical Mesh Mobile Telephony
Paul Gardner-Stephen, Founder/Software Developer, Serval Project
Cell phones have changed the world, but they have an Achilles Heel:
They rely on big infrastructure to communicate. Big infrastructure is
great during good times, when you have plenty of cash, when there is
no war, when there is no disaster, and when you stay close enough to
the big infrastructure. The trouble is, that probably leaves out two
or three billion people at any one time. Thus big infrastructure
telecoms, as an exclusive model, has a few problems.
First, the poorest two billion just can't afford to access big infrastructure. It has been estimated that the cost of running a cell tower in off-grid Africa as being about $250,000 a year. That tower might support a thousand or so phones at any point in time. That means you need to extract hundreds of dollars from each subscriber each year, just to run the cell tower, let alone cover the cost of calls and the rest of the network. But what if your annual income is only a few hundred dollars a year? What about the millions who have cell phones according to the statistics, but cannot afford to use them on a regular basis? So cost is problem number one.
First, the poorest two billion just can't afford to access big infrastructure. It has been estimated that the cost of running a cell tower in off-grid Africa as being about $250,000 a year. That tower might support a thousand or so phones at any point in time. That means you need to extract hundreds of dollars from each subscriber each year, just to run the cell tower, let alone cover the cost of calls and the rest of the network. But what if your annual income is only a few hundred dollars a year? What about the millions who have cell phones according to the statistics, but cannot afford to use them on a regular basis? So cost is problem number one.
Second, during disaster, emergency or unrest big infrastructure often
fails when it is needed most. We saw this in Haiti. In regional
Victoria in my home country of Australia, we had devastating bush
fires that killed hundreds. These fires destroyed communications
infrastructure, complicating an already horrific situation. The
Australian Red Cross were unable to contact some teams for up to three
days during the fires due to the lack of communications. You can
imagine how worried they were. You can imagine how worried their
families were. So fragility is problem number two.
Third, big infrastructure requires big enterprise. Big enterprise are
legally obliged to maximise benefit for their investors, not for
subscribers or for society as a whole. Big telcos may not provide
coverage to small or poorer communities, even if the lack of
communication is part of why those communities are small or poor. So
dependence on big enterprise is problem number three.
The trouble is that people haven't had any alternative, because mobile
telecommunications with cell phones requires big enterprise and big
infrastructure.
This is what we have changed at the Serval Project by creating the
Serval BatPhone software that works on off-the-shelf cell phone
hardware, allowing them to form multi-hop meshed mobile telephony
networks that allow dialling using ordinary phone numbers, and can be
connected to the global PSTN.
This approach is complementary to the big infrastructure approach, and
while it doesn't offer any service guarantee, the same range or
various other properties of that approach, does allow communities to
solve their own communications problems, and provides the possibility
to communicate in many circumstances where it is not currently
possible, at a price point that is not currently possible, and with a
resilience to adversity that is not possible while depending on
centralised infrastructure or enterprise.
The latest Serval BatPhone experimental software will be demonstrated
during the presentation, including the ability to share the software
from phone to phone, allowing for rapid dissemination of the software,
e.g., after a disaster has struck, thus solving a significant
logistical problem in disaster response.
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