A mesh network is a network topology in which each node relays data for the network. All
nodes cooperate in the distribution of data in the network.
A mesh network can be designed using a flooding technique or a routing technique. When using
a routing technique, the message is propagated along a path, by hopping from node to node
until the destination is reached. To ensure all its paths' availability, a routing network
must allow for continuous connections and reconfiguration around broken or blocked paths,
using self-healing algorithms. A mesh network whose nodes are all connected to each other
is a fully connected network. Fully connected wired networks have the advantages of security
and reliability: problems in a cable affect only the two nodes attached to it. However,
in such networks, the number of cables, and therefore the cost, goes up rapidly as the
number of nodes increases. Mesh networks can be seen as one type of ad
hoc network. Mobile ad hoc networks and mesh networks are therefore closely related, but
a MANET also must deal with problems introduced by the mobility of the nodes.
The self-healing capability enables a routing-based network to operate when one node breaks down
or a connection goes bad. As a result, the network is typically quite reliable, as there
is often more than one path between a source and a destination in the network. Although
mostly used in wireless situations, this concept is also applicable to wired networks and software
interaction.
Wired mesh network Shortest path bridging allows Ethernet switches
to be connected in a mesh topology and for all paths to be active.
Wireless mesh networks Wireless mesh networks were originally developed
for military applications. Mesh networks are typically wireless. Over the past decade,
the size, cost, and power requirements of radios has declined, enabling multiple radios
to be contained within a single mesh node, thus allowing for greater modularity; each
can handle multiple frequency bands and support a variety of functions as needed—such as
client access, backhaul service, and scanning—even customized sets of them.
Work in this field has been aided by the use of game theory methods to analyze strategies
for the allocation of resources and routing of packets.
Examples In rural Catalonia, Guifi.net was developed
in 2004 as a response to the lack of broadband internet, where commercial internet providers
weren't providing a connection or a very poor one. Nowadays with more than 30,000 nodes
it is only halfway a fully connected network, but following a peer to peer agreement it
remained an open, free and neutral network with extensive redundancy.
Zigbee digital radios are incorporated into some consumer appliances, including battery-powered
appliances. Zigbee radios spontaneously organize a mesh network, using AODV routing; transmission
and reception are synchronized. This means the radios can be off much of the time, and
thus conserve power.
In early 2007, the US-based firm Meraki launched a mini wireless mesh router. This is an example
of a wireless mesh network. The 802.11 radio within the Meraki Mini has been optimized
for long-distance communication, providing coverage over 250 metres.
This is an example of a single-radio mesh network being used within a community as opposed
to multi-radio long range mesh networks like BelAir or MeshDynamics that provide multifunctional
infrastructure, typically using tree based topologies and their advantages in O(n) routing.
The Naval Postgraduate School, Monterey CA, demonstrated such wireless mesh networks for
border security. In a pilot system, aerial cameras kept aloft by balloons relayed real
time high resolution video to ground personnel via a mesh network.
An MIT Media Lab project has developed the XO-1 laptop or "OLPC"(One Laptop per Child)
which is intended for disadvantaged schools in developing nations and uses mesh networking
to create a robust and inexpensive infrastructure. The instantaneous connections made by the
laptops are claimed by the project to reduce the need for an external infrastructure such
as the Internet to reach all areas, because a connected node could share the connection
with nodes nearby. A similar concept has also been implemented by Greenpacket with its application
called SONbuddy. In Cambridge, UK, on 3 June 2006, mesh networking
was used at the “Strawberry Fair” to run mobile live television, radio and Internet
services to an estimated 80,000 people. The Champaign-Urbana Community Wireless Network
project is developing mesh networking software based on open source implementations of the
Hazy-Sighted Link State Routing Protocol and Expected Transmission Count metric. Additionally,
the Wireless Networking Group in the University of Illinois at Urbana-Champaign are developing
a multichannel, multi-radio wireless mesh testbed, called Net-X as a proof of concept
implementation of some of the multichannel protocols being developed in that group. The
implementations are based on an architecture that allows some of the radios to switch channels
to maintain network connectivity, and includes protocols for channel allocation and routing.
FabFi is an open-source, city-scale, wireless mesh networking system originally developed
in 2009 in Jalalabad, Afghanistan to provide high-speed internet to parts of the city and
designed for high performance across multiple hops. It is an inexpensive framework for sharing
wireless internet from a central provider across a town or city. A second larger implementation
followed a year later near Nairobi, Kenya with a "freemium" pay model to support network
growth. Both projects were undertaken by the Fablab users of the respective cities.
SMesh is an 802.11 multi-hop wireless mesh network developed by the Distributed System
and Networks Lab at Johns Hopkins University. A fast handoff scheme allows mobile clients
to roam in the network without interruption in connectivity, a feature suitable for real-time
applications, such as VoIP. Many mesh networks operate across multiple
radio bands. For example Firetide and Wave Relay mesh networks have the option to communicate
node to node on 5.2 GHz or 5.8 GHz, but communicate node to client on 2.4 GHz. This
is accomplished using software-defined radio. The SolarMESH project examined the potential
of powering 802.11-based mesh networks using solar power and rechargeable batteries. Legacy
802.11 access points were found to be inadequate due to the requirement that they be continuously
powered. The IEEE 802.11s standardization efforts are considering power save options,
but solar-powered applications might involve single radio nodes where relay-link power
saving will be inapplicable. The WING project developed a set of novel
algorithms and protocols for enabling wireless mesh networks as the standard access architecture
for next generation Internet. Particular focus has been given to interference and traffic
aware channel assignment, multi-radio/multi-interface support, and opportunistic scheduling and
traffic aggregation in highly volatile environments. WiBACK Wireless Backhaul Technology has been
developed by the Fraunhofer Institute for Open Communication Systems in Berlin. Powered
by solar cells and designed to support all existing wireless technologies, networks are
due to be rolled out to several countries in sub-Saharan Africa in summer 2012.
Recent standards for wired communications have also incorporated concepts from Mesh
Networking. An example is ITU-T G.hn, a standard that specifies a high-speed local area network
using existing home wiring. In noisy environments such as power lines it's common that mutual
visibility between devices in a network is not complete. In those situations, one of
the nodes has to act as a relay and forward messages between those nodes that cannot communicate
directly, effectively creating a mesh network. In G.hn, relaying is performed at the Data
Link Layer. See also
Mesh network applications
Mesh network devices
Other topologies
References
External links Battelle Institute AoA Comparative Ratings
for popular mesh network providers, specific to mission critical military programs.
MIT Roofnet A research project at MIT that forms the basis of roofnet / Meraki mesh networks
WING Project Wireless Mesh Network distribution based on the roofnet source code
First, Second and Third Generation Mesh Architectures History and evolution of Mesh Networking Architectures
DARPA's ITMANET program and the FLoWS Project Investigating Fundamental Performance Limits
of MANETS Robin Chase discusses Zipcar and Mesh networking
Robin Chase talks at the Ted conference about the future of mesh networking and eco-technology
Dynamic And Persistent Mesh Networks Hybrid mesh networks for military, homeland security
and public safety Mesh Networks Research Group Projects and
tutorials' compilation related to the Wireless Mesh Networks
Phantom anonymous, decentralized network, isolated from the Internet
Qaul Project – Text messaging, file sharing and voice calls independent of internet and
cellular networks