Wireless Mesh Networks

Wireless Mesh Networks,

Definition

"A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. Wireless mesh networks often consist of mesh clients, mesh routers and gateways.The mesh clients are often laptops, cell phones and other wireless devices while the mesh routers forward traffic to and from the gateways which may but need not connect to the Internet. The coverage area of the radio nodes working as a single network is sometimes called a mesh cloud. Access to this mesh cloud is dependent on the radio nodes working in harmony with each other to create a radio network. A mesh network is reliable and offers redundancy. When one node can no longer operate, the rest of the nodes can still communicate with each other, directly or through one or more intermediate nodes. The animation below illustrates how wireless mesh networks can self form and self heal. Wireless mesh networks can be implemented with various wireless technology including 802.11, 802.16, cellular technologies or combinations of more than one type.

A wireless mesh network can be seen as a special type of Wireless Ad-Hoc Network. A wireless mesh network often has a more planned configuration, and may be deployed to provide dynamic and cost effective connectivity over a certain geographic area. An ad-hoc network, on the other hand, is formed ad hoc when wireless devices come within communication range of each other. The mesh routers may be mobile, and be moved according to specific demands arising in the network. Often the mesh routers are not limited in terms of resources compared to other nodes in the network and thus can be exploited to perform more resource intensive functions. In this way, the wireless mesh network differs from an ad-hoc network, since these nodes are often constrained by resources." (http://en.wikipedia.org/wiki/Wireless_mesh)

Description

Explained by the Wikipedia at http://en.wikipedia.org/wiki/Wireless_mesh_network

Wireless mesh networking is mesh networking implemented over a Wireless LAN.

"This type of Internet infrastructure is decentralized, relatively inexpensive, and very reliable and resilient, as each node need only transmit as far as the next node. Nodes act as repeaters to transmit data from nearby nodes to peers that are too far away to reach, resulting in a network that can span large distances, especially over rough or difficult terrain. Mesh networks are also extremely reliable, as each node is connected to several other nodes. If one node drops out of the network, due to hardware failure or any other reason, its neighbours simply find another route. Extra capacity can be installed by simply adding more nodes. Mesh networks may involve either fixed or mobile devices. The solutions are as diverse as communications in difficult environments such as emergency situations, tunnels and oil rigs to battlefield surveillance and high speed mobile video applications on board public transport or real time racing car telemetry. The best mobile networks are those that provide a seamless handover between the mobile device and the fixed infrastructure points." (http://en.wikipedia.org/wiki/Wireless_mesh_network)

"In basic terms, the mesh provides an alternative to established methods of linking computers together and connecting them to the internet. In practice, it can be used to build large networks far more quickly and cheaply than has previously been possible. As a result, wireless networks are viable in unexpected places. New Orleans, still without a phone service after Hurricane Katrina, recently began building a free, citywide network using mesh technology, while the whole of Macedonia is now one big wireless hotspot. Networks are also providing web connections to people in the parts of the UK untouched by phone-based broadband, as well as in developing countries that have never had effective telephone networks". (from Times Online, quoted by http://www.smartmobs.com/archive/2006/01/28/wireless_mesh_n.html)

Example

From http://www.worldchanging.com/archives/003133.html :

* CUWiN

"CUWiN -- the Champaign-Urbana community WIreless Network -- brings together a bunch of worldchanging ideas into one useful package: Free/Open Source software to create ad-hoc municipal wireless networks using recycled old PCs. The software -- which can be downloaded from cuwireless.net -- just needs to be burned onto a CD, which can then be used to boot a PC (even something as old as a 486) with a wireless card. Once the system boots, the software configures itself, looking for other nodes to connect to; the CUWiN system uses "ad hoc networking" principles to link machines together to reach the computer that's actually connected to the Internet." (http://www.worldchanging.com/archives/003133.html)

From Magnus Lawrie:

* DjurslandS.net

DjurslandS.net in Denmark is among the largest CWNs in the world).

250 volunteer built radio stations share fast internet connections with over 5000 remote rural households in an area of 3360 sq/km (Neilsen, 2007, p.3).

The Djursland peninsula, extending East from Jutland, is encircled by a fibre-optic backbone. At the end of the 1990s, despite the proximity of this communications ’trunk road’, most Djursland homes fell into the ’last mile’ of connectivity, where broadband was technically inoperable. For incumbent telecom providers, extending coverage was financially unjustifiable - market failure had occurred. By now Djursland had been in economic decline for some years. The closure in 1998 of Djursland’s only regional newspaper was the motivation to set up an internet information portal. Boevl, the computer enthusiasts’ group who took up this challenge had engaged in socially-active projects since 1992. With grant aid they had established a free access computer workshop, undertaken computer recycling and instigated fifteen similar projects in Lithuania and Kazakhstan. By practical steps of widening access to information and services, Boevl developed their vision of the ICT-Society in Djursland and from January 2001, worked with a decision making board towards the ideal of ”lightning fast internet access for a fixed price all over Djursland” (Neilsen, 2007, p.7). A phased development programme followed, with the pilot project expected to receive EU support. However, an obscure funding process resulted in the ruling that (even in the absence of competition) government intervention in the market was not allowed. As the options for external support dwindled, by increments Djursland’s network - built on DIY pragmatism more than Free Software idealism - became self-sustaining.

Through economies of scale and hobbyist-led technical innovations costs reduced, whilst individuals worked to greatly expand the network. Members of DjurslandS.net provided themselves fast internet access, at one-third of the subscriber fees in more ’economically viable’ urban areas.

* Freifunk:

Freifunk was established in Berlin in 2002 to create independent, community-based, non-commercial, open and uncensored data networks (Freifunk, 2004). Freifunk has done this using wireless technology, operating on unlicensed segments of the radio spectrum. Technical efforts have centred on adapting OpenWRT – Free Software run on consumer wireless routers.

The resulting ’firmware’, developed by a small team of volunteers, manages bandwidth allocation in order to maintain an equal flow of data throughout a wireless network; Regardless of network size, traffic, or the relative locations of two communicating points, data will be exchanged with equal priority.

A flexible ’mesh’ networking arrangement (many nodes connecting to many neighbour nodes) invests control of the network in the end devices, not an additional layer. By sharing technology and experiences, several Freifunk networks were established in Berlin. These were connected through wireless links known as the Berlin Backbone (BBB). Although the linked networks continued to operate independently, the BBB could be seen as an administrative layer which takes control away from end devices, whilst enhanced possibilities for local audio and video applications such as free radio, internet telephony and webTV advance the case for uncensored data and net neutrality. Freifunk’s social aim has been to strengthen existing organization and to develop e-democracy and grass roots structures appropriate to the digital era. Balances between social and technical participation in Freifunk networks is achieved by the absence of privileged nodes; horizontalism remains built in the network, whilst the hobbyist aspect of the organization keeps the network free to use and free of commercial interests. A diversity of participants and agendas is maintained through router firmware designed to put control with users." (http://ditch.org.uk/download/commons_wireless_autonomy.pdf)

Typology

Magnus Lawrie:

"Two types of wireless mesh network exist. These we have seen in two distinctive CWNs: infrastructure (with a separate administrative layer) and ad-hoc (where control is ’in’ the network). These principles extend more or less easily to describe user participation in the network. An organizational hierarchy is more discernable in Djursland, whereas such distinctions are not so clearly deliniated in the Freifunk community. The case studies show cultures where organizational questions (technical and social) are always informed by a view where ”architecture is politics” (Kapor, 2006). Contrasting legal and technical systems for Free Content distribution present alternative models for dealing in scarce natural resources and cheap-to-copy data. Keeping Boyle’s objections in mind, we might consider the fate of software and public good in the Global Commons to be intertwined. Certainly, in this context, much thinking is being redefined. To this extent such hitherto arcane fields as economics and law are being opened to scrutiny, and even celebrity. In 1989 political rhetoric concentrated on the grand themes of Left versus Right. Today opposing sides are drawn less by political lines, more by pragmatic aims. The diversity of CWN membership, as well as recent Intelectual Property case law, suggests it is now far more a matter of incumbents versus newcomers. Participants in CWNs may be recognized as empiricists, not ideologues (Lessig, 2001, p.69), driven by rough consenus and running code (Clark, 1992). The ’viral’ and self-organizing characteristics of CWNs however suggest both a culture and economics of autonomy, which values the Free Software Definition." (http://ditch.org.uk/download/commons_wireless_autonomy.pdf)

Discussion

Why Open Mesh Networks are beneficial

Mark Cooper:

"The technologies at the heart of the digital revolution are also at the heart of the deployment of open wireless networks in the spectrum commons. The potential spectrum carrying capacity has been the direct beneficiary of the convergence of progress in digital technology and the institutional development of networks. When users add radios that help by cooperating in receiving and forwarding signals, i.e. act as repeaters, carrying capacity of the network increases. Smart nodes get their expanding brainpower from decentralized computational capacity to communicate seamlessly, utilizing embedded coordination protocols.

Smart technologies in mesh networks cooperating to deliver messages also show the beginning of anti-rivalry characteristics. The ability of each node to receive and transmit messages, even when they are neither the origin nor the destination, expands the capacity of the network. This intelligence is the key to mesh networks’ immense capacity.

The Spectrum Commons in which these networks exist exhibits the characteristic of inclusiveness, since the more nodes on the net-work, the greater the value to users. The denser the nodes in the commons, the greater is the commons’ communications capacity. The combination of digital technology and network organization has turned the old logic on its head; adding users on a mesh network improves performance. Mesh Networks allow devices to share their resources dynamically, allowing more communications to take place with less power.

However, even with new technology, there is still the challenge of how to ensure cooperation among users. Since cooperation is the key to the capacity gain, if users chose not to cooperate, the mesh network will not work. Therefore, more devices are transitioning to “embed coordination” to ensure cooperation. For example, radios become smart by embedding intelligence – algorithms – that take on the functions necessary to transmit a signal after listening to the spectrum and finding available frequencies to use and determining the power necessary." (http://cyberlaw.stanford.edu/system/files/From+Wifi+to+Wikis+and+Open+Source.pdf)

More Information

Essay: Wireless Networks as Techno-social Models. By Armin Medosch.

See also the entry on Hive Networks