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Has anyone designed a peer-to-peer communications networks system, which works almost like the internet, but wirelessly? I mean a system, which:

  • you can connect the transmitter to an usb port and operate it with a laptop
  • can be used to transmit data (for example, text messages)
  • units will connect automatically to nearest units of same system, and generate a routing table, and therefore you can send your message anywhere in the network, so that other units will relay your message forward until it reaches its destination.
  • The transmit power should be couple of watts (to get a range of couple of kilometers/miles per station) and the frequency band should be some legal band for free use (27 MHz, for example).

A purpose for this kind of device would be estabilishing a communications system in an area facing a natural disaster or to help people communicate in countries where government censorship prohibits using the internet.

As an electrical engineer, I know that this kind of system:

  • is possible to build
  • and the most hard part is to develop the protocol (communicating between two units is trivial, but how to get the message through multiple stations to its destination).

But has anyone done it yet?

Vesa Linja-aho
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  • What kind of data rates would you be wanting to achieve? – Oli Glaser Jan 08 '12 at 18:18
  • Data rates with this kind of system (low bandwidth) can not be dramatic - maybe few thousand bits per second. – Vesa Linja-aho Jan 08 '12 at 19:33
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    I am not going to push to have this question closed, but I would like to know peoples thoughts here: http://meta.electronics.stackexchange.com/questions/922/why-is-this-a-good-question – Kellenjb Jan 09 '12 at 12:56

9 Answers9

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units will connect automatically to nearest units of same system, and generate a routing table, and therefore you can send your message anywhere in the network, so that other units will relay your message forward until it reaches its destination.

What you are describing is a mesh network, or more specifically a wireless mesh network. So the short answer is yes, someone has done it already.

As others have pointed out, radio amateurs implemented this over 20 years ago in a system known as APRS. To use APRS on the amateur bands require one to be a licensed radio amateur however.

In the commercial space there are many companies offering mesh network devices such as Ruckus and Village Telco with their mesh potato for voice in the third world. Another vendor of low cost devices is Open Mesh.

For amateur radio, the latest incarnation for high speed mesh networking is HSMM-MESH -

HSMM-MESH™ is a high speed, self discovering, self configuring, fault tolerant, wireless computer network that can run for days from a fully charged car battery, or indefinitely with the addition of a modest solar array or other supplemental power source. The focus is on emergency communications.

In its current form it is built using the Linksys WRT54GL wireless router and operates on channels 1-6 of the 2.4GHz ISM band, which overlaps with the upper portion of the 13cm amateur radio band. Other platforms and bands may be supported as development resources permit.

JonnyBoats
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  • It also seems to me that if there were a few software layers added to the zigbee system they could satisfy this without any ham license required, much lower data-rate then many of your answers but the op posted a comment saying they only need a few kbps. – Kortuk Jan 09 '12 at 13:09
  • Kortuk: You are correct that zigbee, or virtually any radio, is capable if one implements the various software layers required. The devil is in the details of course and implementing a full stack is non-trivial. – JonnyBoats Jan 09 '12 at 13:15
  • @johnnyBoats, I meant that zigbee meets most of the requirements if you just design an uplink to the internet to be the zigbee master node(I forget the proper term) – Kortuk Jan 09 '12 at 13:26
  • @JonnyBoats Incidentally, APRS is built on top of AX.25... – vicatcu Jan 09 '12 at 16:02
  • The [wireless sensor network wiki](http://wsn.oversigma.com/) has some discussion of mesh networking protocols and custom hardware design. – davidcary Feb 16 '12 at 03:59
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I don't think X.25 is relevant here.

AFAIK various bands that are legal for speach are not legal for digital transmission. Check with a HAM specialist.

What you want is essentially an IP network with totally dynamic routing (the destination address holds no information about the location of the desination). In a non-radio (or directional radio) situation the problem is how each node should route its packets. It must basically have a routing map that has, for each destination, a direction (next hop) to send the packet to. This can be done, but the memory requirement in each node is linear in the number of nodes.

In a non-directional radio situation things get much more interesting. The question is not to which node a packet should be forwarded, but whether a station should re-broadcast a packet at all. That requires both knowledge of the direction in which the destination lies (compared to the previous sender and my own loaction), and knowledge of whether this particular packet has already been (re) transmitted recently. Interesting problem. An airtime-efficient solution requires a lot of memory.

Note that maintaining dynamic routing information is a hairy problem in itself. Think of the good-news-travels-fast but bad-news-dies-slowly problem. And how robuust should the system be against a single malfunctioning (or even malicious!) node?

A very simple (and robuust) implementation would 'flood' each packet through the entire network. This reduces the bandwith drastically, especially when stations are close compared to their range.

Wouter van Ooijen
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  • How can it not be relevant... it's a HAM data link layer protocol for Packet Radio networks... it may not be the "whole" answer, but it's certainly a part of it... – vicatcu Jan 08 '12 at 21:47
  • From what I know it is inteded for peer-to-peer communication, which is not what the OP wants. In the X.25 description I found no hints of routing, which is the main problem here. – Wouter van Ooijen Jan 08 '12 at 21:56
  • Actually just google AX.25 routing and you'll get a bunch of hits like http://homepage.ntlworld.com/wadei/nosintro/CH26.HTM... also from the wiki article "In practice, it is not uncommon to find an AX.25 data link layer as the transport for some other network layer, such as IPv4, with TCP used on top of that. Note that, like Ethernet, AX.25 frames are not engineered to support switching. For this reason, AX.25 supports a somewhat limited form of source routing. Although possible to build AX.25 switches in a manner not unlike how Ethernet switches work, this has not yet been accomplished" – vicatcu Jan 08 '12 at 22:21
  • Yes, I found and read that and based my conclusion on it. No built-in destination-based routing, let alone routing that supports roving and other issues that arise from using radio links in a non-peer-to-peer fashion. – Wouter van Ooijen Jan 09 '12 at 06:29
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I found this as I was trying to reconstruct my PACKET RADIO section of my HAM radio station. As a ham I have made digital connections to the MIR space station and then the ISS which is still in orbit at this time. It was VHF radio frequency and I have used the digital message box on the space station as it flies over. 1200 baud on 145.800 mhz. This is called Packet Radio. Ships at sea without satellite connections use packet on HF(shortwave) for email. It is a service. Now I am finding they use the computer's sound card and the production of Packet TNC boxes which run the radio/computer interface seems to be disappearing. Now, the hookup uses audio cable from sound card output thru a modem built into the radio. Many VHF radios sold now have this modem. I am finding that the PACKET BOXES or NODE CONTROLLERS did not make the jump to USB and since most computers now do not even have a serial port my TNC is not useable without some sort of work around. It is my understanding that AX25 was originally written for digital ham radio. We had a network over radio using AX25 that covered the world. This morphed into the internet, which is made of AX25. This protocol already has controls for RX/TX/Retries blah blah built in. You use it everyday.

Paul VE3SPP
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There are easy solutions which work for a very small percentage of geospatial problems. The more common problems (participants far apart, hills, trees, apartments, HOAs, cash shortages) require more difficult answers and planning.

I answered a similar problem with a plan based on a combo of off the shelf solutions and some script work. No automatic routing here but it does do text messaging over a hundred miles without commercial networks to route across, using off the shelf hardware and entirely on VHF/UHF ham bands.

See http://tarpn.net for shopping list and instructions as well as explanations.

Ka2dew
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There are various ways you could approach this, including just using adapted Wi-Fi (e.g. higher power, adhoc network)

Another option might be xBee, which (depending on module) can be used up to 80km and with speeds ranging from 9.6kbps to 250kbps.

Also there's packet radio (as mentioned by vicatu) although the speeds are pretty low. It would be fine for basic messaging though and probably cheap/easy to implement (should be able to get plenty of help from the amateur radio community)

Oli Glaser
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I have used this transmitter several times: link It works well and uses the DigiMesh protocol: link which is what you are looking for. I have built several systems that use it to network data over long distances.

Axis
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    Please add more to your answer. It is best for links to only supplement your answer, but not be required to understand what you are saying. You can add a bit more about the transmitter and the digimesh protocol and why it works for his needs. – Kellenjb Jan 08 '12 at 23:17
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There are sound card packet controller software's which will work over any frequency radio. 27 mhz is open so you could use it. there is UHF in the 400 mhz area assigned to Citizen radios. This is also possible. The software has controller and ongoing relay protocols built in.

Paul VE3SPP
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I think Netsukuku is pretty close to what you're looking for.

Dmitry Dzhus
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    Like I have told a couple other people, Please add more to your answer. It is best for links to only supplement your answer, but not be required to understand what you are saying. You can add more about the Netsukuku and why it is a good fit. – Kellenjb Jan 09 '12 at 14:15
  • To add to Kellen's comment: if that link dies your answer becomes useless. – Federico Russo Apr 25 '12 at 09:09
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This does not directly answer to my question, but tethr seems an interesting project for similar goals:

Vesa Linja-aho
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