Demonstrating the Serval Rhizome Store-and-Forward MeshMS SMS Service

(Please take a look at our crowd-funding campaign at igg.me/at/speakfreely.)

Update: We trialled Rhizome on a training exercise in New Zealand recently.  Follow the link to read the blog post about it.

SMS messages on a cellular network get delivered via the cell towers and message centre infrastructure.

On a mesh, it is possible for us to deliver messages to other phones that are reachable on the mesh at the same time.  This works great, and we have had this capability in the Serval BatPhone software for a while now.

However, it does have some limitations, in particular, if there is no link all the way from the sender to the receiver on the mesh at the instant the message is sent.  This is rather unfortunate, as we usually think of SMS as being the most reliable fall-back on a mobile communications network.

So we set about replicating this resilience by creating a store-and-forward SMS-like service on top of the Serval Rhizome mesh file distribution framework.  We call this MeshMS, for Mesh Message Service.

This service uses direct mesh links if they are available by making use of the existing SMS capability in the Serval BatPhone software.  However, if there is no direct link, then it uses a store-and-forward scheme, that asks any passing phones to copy the message and distribute it to other phones on the mesh, until it (hopefully) eventually reaches its intended destination.  The cartoon below shows how this works.

The man wishes to send the message "Prepare the Zeppelin" to his hench-person, but there is no direct mesh link at that time due to the challenging topology.  The message gets picked up (stored) by the compatible phone in the pram, without any action on the part of the woman.  The woman then keeps walking along, and eventually the phone in the pram is able to automatically deliver (forward) the message to the ultimate destination, whereupon the minion knows to ready his master's zeppelin, to do the weekly grocery shopping, one trusts. Of course, there could be many intermediate steps, instead of just the one shown here.

The great thing about this approach is that it doesn't require a complete path to the destination at the time of sending, but can propagate progressively across the mesh as it is able, and can make use of nodes that move between otherwise isolated mesh networks, creating an asynchronous link between them where it would not otherwise be possible.

While the delay in such a service is huge, the bandwidth is also great, as potentially gigabytes of data can be transferred between nodes.  One side use of this protocol that we intend to exploit is to provide an efficient means of distributing updates to the Serval software suite, so that field updates can occur without dependence on infrastructure, and with much greater aggregate bandwidth than any single-cast cellular or wireless approach.  In fact, this will even allow the update of software, maps and other resources during a disaster.

We have even demonstrated it to deliver an SMS message between South Africa and Australia, using nothing but compatible phones to carry the message more than 10,000km:

This feature has profound utility in allowing the exchange of messages, files, and all manner of data in what are otherwise very difficult settings.

It also provides the capabilities required to enable disadvantaged communities, perhaps in remote locations, war zones or informal settlements, to create their own infrastructure, carrier and cost-free SMS networks using compatible handsets, so that they can enjoy the benefits of digital communications that many of us take for granted.

Kicking The Infrastructure Habit

Last weekend I delivered the inaugural Jim Bettison Memorial Oration at the biannual Adelaide Festival of Ideas. This was a great honour, and my presentation was well received by the audience, as was evidenced by the poignancy of their questions.

Here is the abstract of my oration:

Modern communications systems use extensive and expensive infrastructure to deliver services we could only dream of a few decades ago. This works for those who enjoy peace and sufficient wealth, but fails to reach the last billion people in poorer countries, as well as those in remote, emergency or disaster situations. Now modern mobile phones have the potential to communicate directly, to form networks without reliance on any infrastructure. The Serval Project based at Flinders University is turning this dream into a reality. It is working to make communications available to everyone, anywhere, any time especially to those who need it most.

You can listen to the oration by downloading the MP3 from the Radio Adelaide website.

You can also listen to an ABC Bush Telegraph interview about the oration that I recorded a few days prior to the oration.

Photos and Update from Nigeria - and introduction to Rhizome

We have a partner organisation working in Nigeria looking at citizen-sourced journalism and using our mesh network as the connectivity among a number of camera-equipped cell phones, so that citizen journalists there can make a short video or news piece and then have it distribute automatically over the mesh using our Rhizome protocol.

Rhizome is our mesh file distribution protocol that allows user-created content and software updates to spread hop-by-hop over the mesh.  This hop-by-hop approach elegantly solves many of the problems with mesh-wide file transfer, in particular bandwidth starvation and instability of long links.

We have called it rhizome because it is like the vegetable reproductive process of the same name, because we think it is a good analogy for the way that Rhizome allows data to spread by small hops, but such that over time it can spread over great distances.

We are busy working on making Rhizome do all that the team in Nigeria needs, but in the meantime, the team in Nigeria have sent us some photos showing the mesh in action.

First, they sent photographic evidence of 10 IDEOS U8150 phones forming a mesh with our software:

10 Serval BatPhones on the mesh (and a call in progress!)

They also sent us this picture which I really love, because it shows a community getting started with out technology thousands of kilometres from where we are writing the software here in Australia.  This is what it is all about, people using and benefiting from the software that we are creating and releasing.

Finally, just a week after they got 10 phones on the mesh, they sent this shot showing 15 phones on the mesh.  This was just a case of them getting 15 phones within range, as the underlying BATMAN mesh protocol should be able to handle a couple of hundred devices without any difficulty:

One of the challenges we are looking at solving with this group is auto-update of the mesh software, over the mesh.  That is, we want to be able to load a signed software update onto any one of the phones on the mesh, and have the phones on the mesh share it automatically with one another.

This is a great idea, and the Rhizome protocol will allow us to do this, however it introduces some security challenges.

In particular, we don't want someone or some party seizing or cracking our signing key, and then being able to spread a trojan update that destroys the Serval mesh.

One approach we are looking at is making the update require that the new version be signed by a majority of keys from a pool, where each key would be held by a different mesh-friendly organisation.   The pool of trusted keys could then be similarly updated by a majority vote of existing trusted keys.

This will allow us to spread the keys among countries and jurisdictions and provide the kind of distributed resilience that the Serval Project is predicated on, and even allows the software to continue to be refined and distributed if the Serval Project as an organisation ceases to exist.

If you think that your organisation might like to be one of our key custodians, let me know.

Why Serval is getting involved in the 802.11ah standards process

Serval is getting involved in the IEEE 802.11ah (WiFi on ISM bands below 1GHz) to try to make sure that it is well suited to infrastructure-independent ad-hoc and mesh networking at the IEEE meeting in Okinawa next week.

Here is our submission:

https://mentor.ieee.org/802.11/dcn/11/11-11-1138-00-00ah-packet-radio-mode-for-802-11ah-a-b-g-n.ppt

Basically we are asking for two things:

1. Improvements to ad-hoc mode (or provision of a new "packet radio" mode) that remove some of the problems currently faced when creating wifi-based ad-hoc mesh networks.

and

2. That the 802.11ah standard consider speeds below 1mbit and using cell phone baseband radios as a supported transport so that even cheap cell phones can form relatively long range mesh networks without any supporting hardware.

This second point is really important, because compared with 2.4GHz WiFi a mesh running in the ISM 915MHz band gains about +9db just from the change in frequency, which alone improves range by almost 3x.  If it supports lower bit rates, then further significant gains are possible, e.g., allowing 100kbit communications gives another +10db, for a total of 8x range versus WiFi.

There are some significant protocol challenges to be addressed, but if the standard doesn't support the use-case, then there will be no hardware and no chance.

These measures have the potential to push the indoor range up from WiFi's "about one house wide" to "about a block wide" and clear line-of-sight range up to a few km, which suddenly makes the formation of suburban ad-hoc mesh networks possible, which has profound impact for creating resilient infrastructure-independent communications solutions, for example for sustaining communications during disaster or enabling communications for rural and remote or developing populations.

We admit that we are very green to this process which we frankly find to be daunting.

But we feel compelled to try, regardless of what we perceive to be the odds of success.