How Wireless Mesh Networks Work


Courtesy Motorola A node on a streetlight.
Courtesy Motorola A node on a streetlight.

Wireless mesh networks, an emerging technology, may bring the dream of a seamlessly connected world into reality.

Wireless mesh networks can easily, effectively and wirelessly connect entire cities using inexpensive, existing technology. Traditional networks rely on a small number of wired access points or wireless hotspots to connect users. In a wireless mesh network, the network connection is spread out among dozens or even hundreds of wireless mesh nodes that "talk" to each other to share the network connection across a large area.

Mesh nodes are small radio transmitters that function in the same way as a wireless router. Nodes use the common WiFi standards known as 802.11a, b and g to communicate wirelessly with users, and, more importantly, with each other.

Nodes are programmed with software that tells them how to interact within the larger network. Information travels across the network from point A to point B by hopping wirelessly from one mesh node to the next. The nodes automatically choose the quickest and safest path in a process known as dynamic routing.

The biggest advantage of wireless mesh networks -- as opposed to wired or fixed wireless networks -- is that they are truly wireless. Most traditional "wireless" access points still need to be wired to the Internet to broadcast their signal. For large wireless networks, Ethernet cables need to be buried in ceilings and walls and throughout public areas.

In a wireless mesh network, only one node needs to be physically wired to a network connection like a DSL Internet modem. That one wired node then shares its Internet connection wirelessly with all other nodes in its vicinity. Those nodes then share the connection wirelessly with the nodes closest to them. The more nodes, the further the connection spreads, creating a wireless "cloud of connectivity" that can serve a small office or a city of millions.

Wireless mesh networks advantages include:

  • Using fewer wires means it costs less to set up a network, particularly for large areas of coverage.
  • The more nodes you install, the bigger and faster your wireless network becomes.
  • They rely on the same WiFi standards (802.11a, b and g) already in place for most wireless networks.
  • They are convenient where Ethernet wall connections are lacking -- for instance, in outdoor concert venues, warehouses or transportation settings.
  • They are useful for Non-Line-of-Sight (NLoS) network configurations where wireless signals are intermittently blocked. For example, in an amusement park a Ferris wheel occasionally blocks the signal from a wireless access point. If there are dozens or hundreds of other nodes around, the mesh network will adjust to find a clear signal.
  • Mesh networks are "self configuring;" the network automatically incorporates a new node into the existing structure without needing any adjustments by a network administrator.
  • Mesh networks are "self healing," since the network automatically finds the fastest and most reliable paths to send data, even if nodes are blocked or lose their signal.
  • Wireless mesh configurations allow local networks to run faster, because local packets don't have to travel back to a central server.
  • Wireless mesh nodes are easy to install and uninstall, making the network extremely adaptable and expandable as more or less coverage is needed.

In this article, we'll explain how wireless mesh networks work, how they increase network access for a wide variety of industries, and how they might make our dream of a seamlessly connected world come true.

Wireless Mesh Technology

Wireless mesh network
Wireless mesh network

The graphic below shows how a wireless mesh network functions when sharing an Internet connection across a Local Area Network (LAN). As you see, only one node in the wireless mesh network needs to be directly wired to the Internet. That wired node shares the Internet connection wirelessly with the nearest cluster of nodes, which then share it with their nearest cluster of nodes and so on.

That means that each individual node doesn't need to be wired to anything. It only needs a power supply such as traditional AC plugs, batteries, or solar panels if outdoors. Outdoor nodes are encased in a weatherproof, protective shield and can be mounted anywhere including telephone pools, roofs, etc.

Wireless mesh networks are effective in sharing Internet connectivity because the more nodes that are installed, the further the signal can travel. And the more nodes you have, the stronger and faster the Internet connection becomes for the user.

How does the Internet connection become stronger and faster?

  • If your laptop computer is in the broadcast range of four nodes, you're tapping into four times the bandwidth of one traditional wireless router.
  • Distance plays a huge role in wireless signal strength. If you reduce the distance between your computer and the nearest wireless node by two, the signal strength is four times as strong.
  • Nodes can also provide Internet connectivity to wired devices within the network like VoIP phones, video cameras, servers, and desktop workstations using traditional Ethernet cables. Most nodes come with two or more Ethernet ports, and through a technology called Power Over Ethernet (PoE), the node can provide power to stand-alone devices like surveillance cameras without having to plug the camera into an electrical outlet.

Now let's look at some real and potential applications of wireless mesh networks.

Applications for Wireless Mesh Networks

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Cities and Municipalities

With wireless mesh networks, cities can connect citizens and public services over a widespread high-speed wireless connection.

A growing number of downtown areas are installing public WiFi hotspots. Mesh networks allow cities to inexpensively and simply link all those hotspots together to cover the entire municipality.

Some advantages of municipal mesh networks:

  • Commuters can check their e-mail on the train, in the park, at a restaurant.
  • Public works officials can monitor the diagnostics of the city's power and water supply by installing wireless nodes in water treatment facilities, sewers and generators. There's no need to dig trenches to run cables.
  • Public safety and emergency workers can access secure virtual networks within the larger network to keep communication lines open, even when regular phone or cellular service is down. With mesh nodes mounted on streetlights and stop lights, police and firefighters can remain connected to the network, even while moving.

According to a report by MuniWireless.com in March 2007, 81 U.S. cities have already installed citywide or region-wide municipal wireless networks and 164 more are actively building such networks. The report also says that 38 U.S. cities already have municipal wireless networks for the exclusive use of public safety and city employees.

Not all existing municipal wireless networks are mesh networks, however. Some are powered by a technology called WiMAX which has the ability to broadcast signals over large distances using powerful microwave transmissions. Other municipal networks use a combination of mesh, WiMAX and others.

Developing CountriesWireless mesh networks are useful in countries without a widespread wired infrastructure, such as telephone service or even electricity. Solar-powered nodes can be connected to one cellular or satellite Internet connection, which could keep a whole village online.

Isolated Locations, Rugged TerrainEven in developed countries, there are rugged locations too far off the grid for traditional high-speed Internet service providers. Wireless mesh networks are being considered for these areas. A series of nodes would be mounted from the nearest available wired access point out to the hard-to-reach area.

EducationMany colleges, universities and high schools are converting their entire campuses to wireless mesh networks. This solution eliminates the need to bury cables in old buildings and across campuses. With dozens of well-placed indoor and outdoor nodes, everyone will be connected all the time.

Mesh networks also have the capacity to handle the high-bandwidth needs required by students who need to download large files.

Students can connect anywhere.

Schools can also rig their entire public safety system up to the network, monitoring security cameras and keeping all personnel in constant communication in emergency situations.

HealthcareMany hospitals are spread out through clusters of densely constructed buildings that were not built with computer networks in mind. Wireless mesh nodes can sneak around corners and send signals short distances through thick glass to ensure access in every operating room, lab and office.

The ability to connect to the network is crucial as more doctors and caregivers maintain and update patient information -- test results, medical history, even insurance information -- on portable electronic devices carried from room to room.

HospitalityHigh-speed Internet connectivity at hotels and resorts has become the rule, not the exception. Wireless mesh networks are quick and easy to set up indoors and outdoors without having to remodel existing structures or disrupt business.

Temporary VenuesConstruction sites can capitalize on the easy set-up and removal of wireless mesh networks. Architects and engineers can stay wired to the office, and Ethernet-powered surveillance cameras can decrease theft and vandalism. Mesh nodes can be moved around and supplemented as the construction project progresses.

Other temporary venues like street fairs, outdoor concerts and political rallies can set-up and tear down wireless mesh networks in minutes.

WarehousesThere is simply no effective way to keep track of stock and shipping logistics without the types of Ethernet-enabled handheld scanners used in modern warehouses. Wireless mesh networks can ensure connectivity throughout a huge warehouse structure with little effort.

Future ApplicationsThe U.S. military, which helped develop wireless mesh technology, foresees a day when thousands of microchip-size mesh nodes can be dropped onto a battlefield to set up instant scouting and surveillance networks. Information can be routed to both ground troops and headquarter personnel.

Carmakers and telecom companies are working to develop Intelligent Transport Systems (ITS) powered by street and highway-based wireless mesh networks. Using an automated network of surveillance cameras and in-car sensors, public safety officials can tightly monitor traffic accidents and dangerous road conditions.

PC Magazine reports that there's even technology in the works that would alert a driver when a nearby car deploys its airbag. Mobile mesh networks also promise upgrades for in-car entertainment options like digital music and movie downloads.

Chipmakers and network software developers like Ember Corporation already sell automated home and automated building solutions that employ mesh networks to control and remotely monitor surveillance systems, climate control and entertainment systems. The future applications for wireless mesh networks are limited only by our imaginations.

Read on for much more information about wireless mesh networks and technologies that make them work.

Related HowStuffWorks Articles

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How Municipal WiFi Works

How Home Networking Works

How Power-line Networking Works

How Phone-line Networking Works

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How Routers Work

How Virtual Private Networks Work

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More Great Links

Wireless Philadelphia

Tibetan Technology Center

Microsoft's Wireless Mesh Research Page

Firetide: Multi-Service Mesh Networks

Ember: Zigbee Wireless Semiconductor Solutions