MESH, D-STAR, etc.


Griff Hamlin <griff@...>
 

Hi fellow CMRA members,

Fred, KD0PAI, mentioned Mesh networking would be a good topic for a CMRA program. I also think it would be very interesting. Michael's (AC0G) recent email reports he has Linksys routers working with HSMM-MESH firmware. You may be aware that HSMM-MESH is used in:

1. St Louis ARES (stlares.org). There's power-point presentation at http://stlares.org/Docs/HSMM.ppt. It's an interesting overview of HSMM-MESH and how it might be used in emergency communications.

2. Collin County Texas, for the Amateur Radio Communications Health-care Emergency Services (ARCHES). See http://kb9mwr.blogspot.com/2010/08/hsmm-mesh-network-in-texas.html

It would be nice if the HSMM-MESH firmware ran on some of the newer 802.11G equipment that is designed for outdoor mounting, uses higher transmitter power, is capable of being used on 13cm ham-band frequencies that are not also unlicensed part 15 802.11 frequencies (minimum interference), and can use reduced bandwidth (5mhz) for increased range, at the expense of data-rate.
I believe the hsmm-mesh organization only makes it available for WRT54G Linksys equipment. Several hams (kj6dzb, n8lbv, ..) have requested on the hsmm-mesh.org forum that hsmm-mesh firmware be created for Ubiquity and other modern 802.11 products. Hsmm-mesh is essentially the OLSR mesh
(www.olsr.org) routing protocol running on top of the OpenWRT system. OpenWRT is a compact distribution of the Linux operating system suitable for the flash memory of embedded CPUs as found in most 802.11 equipment. Since OpenWRT runs on many devices, and since OLSR reported by it's authors to be highly portable, the hsmm-mesh.org group reported last June they are working on porting hsmm-mesh firmware to other devices.

Mesh networks are a way to overcome the limited range of 2.4ghz low-power (part 15) equipment. In years past I have made "digital repeaters" (like hams use in VHF packet networks) to increase the range on 2.4ghz. I connected two 802.11 devices connected back-to-back, on different RF channels, each with it's own directional antenna pointing in different directions. More recently, the much more sophisticated SMESH mesh network (see smesh.org) similarly uses multiple radios at each node on different channels.
Using multiple radios avoids the problem with most mesh networks that each "hop" cuts in half the
effective data-rate (3 hops cuts data-rate to 1/8th).

Another interesting mesh network idea is the "Mesh Potato" (http://villagetelco.org/mesh-potato/. A mesh-potato is a Wifi radio plus an Analog Telephony Adapter (ATA), built together.
You can plug in any ordinary analog telephone into the ATA and you have telephone service over the mesh's coverage area, without wires. Emergency communications personnel should like that since everyone already knows how to use a telephone. VillageTelco uses the open-source "Asterisk"
digital PBX software on a computer attached to their mesh-potato network to provide a telephone PBX system. See villagetelco.org/2009/07/mesh-potato-tests/ and the David Rowe, VK5DGR, webpage: www.rowetel.com/blog?page_id=1100. I believe this mesh network uses B.A.T.M.A.N routing (see www.open-mesh.org) instead of OLSR. A couple of companies are starting to sell inexpensive
mesh-potato routers. See www.open-mesh.com for the OM2P mesh-potato, $59. Meraki mini wireless mesh routers ($49 to $149) were introduced in 2007.

Griff W5VWP