Posted by bboyes
on July 21, 2005 at 11:44 AM PDT
802.15.4-2003 contemplates, but doesn't fully specify, a mesh network for low rate wireless personal area networks (LR-WPANs), and now there is work to formalize a mesh network using 802.11 wireless media.
This article in Infoworld: http://www.infoworld.com/article/05/07/20/HNmeshnetworks_1.html?source=NLC-TB2005-07-20 reports that 15 competing proposals will be whittled down to create the new IEEE 802.11s specification.
What's so great about a mesh network topology? A mesh network is a network in which the routing of messages is performed as a decentralized, cooperative process involving many peer devices routing on each othersâ€™ behalf.
"Mesh networks reduce the need for wired connections in wireless LANs by letting multiple access points carry each others' traffic. Whereas a conventional wireless access point needs its own wired link to a backbone network, with a wireless mesh there can be just one wire for many access points. Traffic that is destined for the Internet can hop from one access point to another until it reaches the one wired connection." - Bilel Jamoussi, director of strategic standards at the Chief Research Office of Nortel Networks
So you can imagine a mesh in a building, or a university campus, or formed by a group of mobile nodes - PDAs, or vehicles, or robots, which would enable reaching any connected node through a path of other mobile nodes. Personally I'm more interested in peer mesh networks which may not even have a wired internet connection, and are just used for local communications.
There are apparently two competing 802.11 mesh alliances: WiMesh (including Nortel) and SEEMesh (Simple, Efficient and Extensible Mesh) which includes Intel Motorola and NTT DoCoMo.
Another area of mesh network progress is in low-rate personal networks. The 802.15.4 spec and its associated ZigBee Alliance have considered mesh a key enabling feature from day one, though the mesh specification has been only recently defined, and I was not able to find a reference to the actual spec for this blog. 802.15.4 defines the physical and MAC layers of an application, and ZigBee defines the network/security layer, application framework and, in some cases, the application profile. ZigBee provides a simple, low-cost global network that supports a large number of nodes with extremely low power consumption, making it very practical for battery operation.
(At the Zigbee Alliance website you can download the Zigbee specification - currently "ZigBee Document 053474r06, Version 1.0" dated both Dec 2004 and June 2005, but this document does not include any mesh specifications per se.)
Where this all leads us is that very shortly there should be accepted standards for mesh networks on a variety of media layers - 802.15.4 and 802.11, for starters. This makes it possible to think about practical distributed control and communication applications utilizing standardized wireless communications. Mesh-based systems are a better fit for many applications than current star or tree topologies. Mesh networks can be more easily self-adapting and healing, especially when typical nodes are ephemeral. These are exactly some of the issues which would be faced by large robot swarms.