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Wireless mesh is a network topology having at least two nodes connected with two or more paths between them. It provides communication through radios with high reliability and redundancy, and utilizes mesh clients, routers, and gateways. The current generation (third) uses CSMA collision for mesh links with maximum performance and no bandwidth degradations. It is characterised with decentralized management, self forming, and self healing resulting in economic solutions in areas including: cities and municipalities by providing high speed wireless connection; developing countries without wide infrastructure; education; healthcare; hospitality, temporary venues; ware houses. IEEE defines 802.11s as standard for wireless mesh networks which has over 70 routing protocols; however, it is still under development. IEEE 802.11s expands the IEEE 802.11 MAC Standard with the protocol that supports Broadcast Multicast and Unicast delivery using "Radio-Aware Metrics over self-configuring multi-hop topologies. There are 18 patent owners for IEEE 802.11s including companies like Motorola, Apple, Intel and Cisco. These companies work in different fields related to WMN including broadband Internet Access, Extending 802.11 WLAN coverage, connectivity, and mobile internet support. Besides current applications such as VOIP, Wireless Mesh Networks also provide promising future applications like battlefield applications that are funded by the Defence Advanced Research Projects Agency and intelligent transport system by car makers and telecom companies.
An Introduction to Mesh Topology
A Network Topology in which there are at least two nodes connected with two or more paths between them is called Mesh Topology. (Available at knowledgerush.com)
The following diagrams compare mesh topology construction with various other network topologies.
In a Mesh Network at least one node connected to another provides full connectivity to the entire network as each node forward packets to the other nodes in the network as required. It does not require a full physical layer connectivity and the Mesh protocols automatically finds the best possible routes within the network and can also reconfigure the link dynamically if it breaks. (Available at belairnetworks.com)
Wireless Mesh Networks
Wireless Mesh Networks provides Network Communication through radios which require minimal configuration and infrastructure by arranging nodes in a Mesh Topology. A mesh network is very reliable and offers redundancy. (Davis et al, 2006) Wireless mesh networks consists of mesh clients, mesh routers and gateways. When one of the nodes is not functional, the rest of the nodes can still communicate with each other, directly or through one or more in-between nodes. Wireless mesh networks can be implemented with a range of wireless technologies which includes 802.11 and 802.16. (Available at en.wikipedia.org)
It has the characteristics of Self Forming and Self Healing which skips the need of centralized management as the relation between mesh nodes fulfils this requirement. (Hay, 2006)
Why and where we need Wireless Mesh Networks?
Cities and Municipalities:
Wireless Mesh Networks can be deployed by the Cities and Municipalities to provide a high speed wireless connection for citizens and public services so the commuters can use their own devices to check the e-mails while on the train, in the park, at restaurants, etc. (Roos, 2007)
Countries without widespread wired infrastructure like telephone service or even electricity needs wireless Mesh Networks to benefit with the Internet or Network Sharing facilities. Nodes can be powered with the solar power generators and connected to a single cellular or satellite Internet connection such as VSAT which can make the whole village online.
Even in the developed countries Mesh Networks can be considered in the rural areas where there is a community with no internet and live far from the grid station, wireless nodes can be connected to each other all the way from the wired access point to the area where wired infrastructure is hard to reach. (Roos, 2007)
Colleges and Universities are considering implementing Wireless Mesh Networks to get rid of cabling issues across the campus. Having installed Wireless Mesh nodes indoor and outdoor make all students to connect to a high bandwidth network at all time and that resolve their large file download issues too. (Roos, 2007)
Many old built hospitals were not made according to the idea of having computer wired networks. Wireless Mesh Nodes can be installed around different parts of the buildings to ensure the connectivity to every corner of the building even through the thick glasses. As the high bandwidth connectivity is important to update patients information like test results and medical history. (Roos, 2007)
High speed internet connection is a requirement in hotels and resorts. Without changing the existing structure of the building and interrupting the business Wireless Mesh Network setup is easy to deploy indoor and outdoor. (Roos, 2007)
Wireless Mesh Network can easily be deployed and removed on the construction sites to give connectivity to the Architects and Engineers to their office. Surveillance cameras can also be installed over WMN setup for security reasons on site.
Other temporary venues like concerts, fairs, political events etc. WMNs can be setup and removed quickly. (Roos, 2007)
Wireless Mesh Networks can be installed in the huge warehouses where it is difficult to keep records for the stocks and wired setup is impractical as wires hanging around stocks could be dangerous. (Roos, 2007)
History of Wireless Mesh Networks
Wireless Mesh Network started initially with the Single-Radio structure explained and illustrated with the help of the figure bellow.
First Generation: Single-Radio gives connection to individual user devices and backhaul (links across the mesh to the wired or fiber connection), that creates wireless congestion at each node. In this type only two radio "hops" possible between connections to the wired or fiber Ethernet. Video and Voice applications performance is very poor as Clients and the backhaul share the same radio, there is RF interference issues too from other radios operating on the same frequencies. (Available at meshdynamics.com)
The above figure illustrates the Single, Dual and Multi-Radio structure. (Source: meshdynamics.com)
Second Generation: Dual-Radio: To Solve these WMN congestion problems the Dual Radio was developed by having two radios in each node. A combination of IEEE Standards '802.11 b/g' service radio and '802.11 a' as backhaul radio. With the Dual-Radio type it was a slight performance improvement but with heavy user demand the congestion problem with the backhaul link stayed there as the Dual-Radio doesn't have a dual- radio backhaul. The issue of RF Interference can only happens if a radio operating on unlicensed backhaul frequency and therefore the whole network need to switch channels, which is impractical in the real world. (Available at meshdynamics.com)
Above figure illustrate the functionality of Multi-Radio Mesh Setup.
Third Generation: Multi-Radio Mesh works as unique pair of dedicated radio on each end of the link so unique frequency is being used for each wireless hop and therefore a dedicated (CSMA) Carrier Sense Multiple AccessÂ collision domain. This is the best Mesh link with maximum performance and no bandwidth degradation and without adding latency. Therefore quality performance can be achieved on Voice and video applications. In third generation type one of the mesh nodes dedicates one of the radios to perform like a station and connect to the neighbour node Access Point radio. There are no RF interferences as each backhaul is split into two radios, which works on two different channels. (Available at meshdynamics.com)
The Elements shown in the figure below Influenced for the designing of routing Protocols (Davis et al, 2006)
VoIP is one of the very important and useful applications used to make wireless local telephone calls through Wireless Mesh Network management support by using Quality of Service method. This type of infrastructure can be decentralized (with no central server) or even centralized (with a central main server); both methods are very reliable, resilient and economical too. (Whazup, 2009)
Nodes in this topology perform as routers and transmit data from nearby nodes to peers that are far to reach in one leap this makes the network to cover long distances. Mesh topology is very reliable as each node is connected to other if there is a hardware failure or any other reason makes the node disconnected from the network, neighbour nodes find the best route using advance routing protocols. (Whazup, 2009)
The concept is just like wired internet in which the packets travel around, the data hop from one device to another until it reaches the destination. Dynamic routing method is applied in each device to communicate routing information to other device. Now each device finds out what to do with the data it received either pass it to next device or keep it, according to the protocol. These routing protocols applied ensure the best and the fastest route to the destination. (Whazup, 2009)
There are more than 70 Routing Protocols for WMNs. Below is the list of some mainly used Intelligent Protocols. (Available at en.wikipedia.org)
Ad hoc On-Demand Distance Vector (AODV) Routing
Optimized Link State Routing Protocol (OLSR)
Dynamic Source Routing (DSR)
Open Shortest Path First (OSPF)
Destination-Sequenced Distance-Vector Routing (DSDV)
Better Approach To Mobile Networking (B.A.T.M.A.N)
Order One Routing Protocol (OORP)
Temporally-Ordered Routing Algorithm (TORA)
Hazy-Sighted Link State (HSLS)
Infrastructure Wireless Mesh Protocol (IWMP)
Predictive Wireless Routing Protocol (PWRP)
Ad Hoc on Demand Distance Vector (AODV) Routing Protocol is designed for mobile Ad Hoc Networks (MANETs) and other wireless ad-hoc networks in Nokia Research Centre, University of California, Santa Barbara and University of Cincinnati by C. Perkins, E. Belding-Royer and S. Das. The main capability is unicast and multicast routing and reactive routing that establish the route to destination only on demand. So that means the Network remains silent until a connection is required. (Available at en.wikipedia.org)
The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol used for mobile ad-hoc networks and can also work with other wireless ad-hoc networks. It uses Hello and Topology Control (TC) messages to find out and then distribute link state information all over the mobile ad-hoc network. Each node in the network uses this topology information to figure out next hop destinations for every node in the whole network using shortest hop forwarding paths. (Available at en.wikipedia.org)
One of the main reasons for having too many protocols is Lack of Standard set by IEEE for WMNs, which defines its operations. (Davis et al, 2006)
IEEE Standard 802.11s for Wireless Mesh Networks
The Development of IEEE 802.11s
IEEE 802.11s started as a Study Group in September 2003 then became a Task Group in July 2004 since then many joint proposals have been submitted and some of which were accepted and formed a shape of Draft. The final Draft was approved by Working Group (WG) in March 2009 but IEEE 802.11s is still under development and many issues still need to be resolved. (Available at en.wikipedia.org)
The Concept of IEEE 802.11s
IEEE 802.11s expands the IEEE 802.11 MAC Standard with the protocol that supports Broadcast Multicast and Unicast delivery using "Radio-Aware Metrics over self-configuring multi-hop topologies". (Available at en.wikipedia.org)
Relatively different to the existing Mesh Devices, 802.11s makes a transparent 802 broadcast domain that supports any upper layer protocol and offers frame forwarding and path selection at (layer -2) Data Link Layer. (Hiertz et al, 2007)
The default Routing Protocol for IEEE 802.11s is Hybrid Wireless Mesh Protocol (HWMP) inspired by Ad-hoc On-Demand Distance Vector (AODV) Protocol and Tree Based Routing. HWMP has the combination of On Demand and Proactive Routing which discovers the routes only when they are required which has some pros and cons as low routing overhead and extra route discovery delay and data buffering. (Sengul, 2009)
HWMP- On -Demand:
Loop Freedom is supported by using a destination sequence number and when a link error is detected, a route error is sent by unicast. Route errors are rate controlled, that's how route is maintained. (Sengul, 2009)
Proactive Routing keeps each node to maintains routes to all reachable destinations at all times which have some pros and cons too as Low Delay and high Routing overhead. (Sengul, 2009)
Advance mode with Multi-Radio, Multi-Channel:
The Multi-Radio ability Creates Alternative Paths and there is a Framework for Flexible Channel Selection Algorithms ahead of the Standard Scope. (Sengul, 2009)
HWMP- The Tree Based Routing:
Proactive Route Request Mechanism:
In this mechanism Root issues a broadcast Route Request (RREQ), the Mesh Points (MP) may respond with Unicast Route Reply (RREP), so it's a Two Way Handshaking. (Sengul, 2009)
Proactive Root Announcement Mechanism:
In this mechanism Root issues a broadcast Root Announcement (RANN), Mesh Points responds with a Root Request and Root responds with a Root Reply, so it's a Three Way Handshaking. (Sengul, 2009)
IEEE Standards Association
There are Eighteen Patent Owners for IEEE 802.11s and their date of registration is listed below. (Available at standards.ieee.org)
Apple Computer, Inc. 11-Oct-2005
Trapeze Network, Inc. 16-Nov-2005
Intel Corporation 22-Dec-2005
Cisco Systems, Inc. 12-Jul-2007
Symbol Technologies, Inc. 24-Jul-2006
Huawei Technologies Co., Ltd. 20-Jun-2007
Microsoft Corporation 20-Jun-2007
Qualcomm Incorporated 7-Jul-2007
Research in Motion Limited 17-Jul-2007
Fujitsu Limited 10-Sep-2007
Toshiba Corporation 29-Oct-2007
InterDigital Technology Corporation 8-Feb-2008
INRIA (Institut National de Recherche en Informatique et en Automatique) 25-Feb-2008
NTT DoCoMo, Inc. 5-Mar-2008
Thomson S.A., Thomson, Inc. 14-Jul-2008
LG Electronics Inc. 24-Dec-2008
Companies Actively Involved In the Development of Wireless Mesh Network and its Products:
The list of companies working in different fields related to Wireless Mesh Networks and the development of its products is given below. (Available at ece.ncsu.edu)
Broadband Internet Access
Lam Tech (Acquired Radiant Networks)
Ricochet Networks Inc.
Trilliant (Acquired Sky Pilot)
Telabria Wireless Networks
Extending 802.11 WLAN Coverage
Intel Wireless Mesh Networks
NoCat - Authentication System for Seattle Wireless
Mobile Internet Support
Mesh Networks (Acquired by Motorola in Nov.2004)
Motorola's Intelligent Wireless Mesh Networks Devices:
IAP 4300 - Intelligent Access Point (Source: motorola.com)
This IAP 4300 device works as a bridge between wired Networks and Wireless Mesh Networks. It has two models with single radio configuration works at 2.4 GHz WiFi radio (802.11 b/g) or two radio configuration with an additional 5.8, 5.4 or 4.9 GHz (802.11 a) radio. (Available at motorola.com)
Mesh Wide Area Network AP 7181 (Source: motorola.com)
The Access Point 7181 is a very high-performance, Multi-Radio 802.11n with Motorola's unique and exclusive intelligent Advanced Element Panel Technology (ADEPT) Antenna System. It can achieve the data rates up to 300 Mbps. This product for Wireless Mesh Networking has been developed after many years of research and specially made to fulfil the external network requirements of municipal agencies, transit systems and at enterprise level. (Available at motorola.com)
IAP 6300 - Intelligent Access Point (Source: motorola.com)
Intelligent Access Point 6300 is used in MOTOMESH Solo networks by Motorola, works as a Transition (Change-over) Point from wired to wireless networks. It has the ability to achieve the data rate up to 6 Mbps which gives excellent performance to voice and video data communications. (Available at motorola.com)
IAP 7300 - Intelligent Access Point (Source: motorola.com)
IAP 7300 Access Point works as wireless Gateway link between MOTOMESH Quattro network and the wired networks. It has got 802.11 (WiFi) radio and Motorola's two very popular Mobility Enabled Access MEA mobile broadband radios. One WiFi and MEA radio set works over an unlicensed 2.4 GHz band and the other set works over 4.9 GHz public safety band which is licensed. (Available at motorola.com)
VMM 4300 -Vehicle Mounted Modem for Mobile Wireless Connectivity (Source: motorola.com)
Motorola's VMM 4300 wireless mesh Network device support broadband data rates at highway speeds. It can be mounted over any vehicle as train or bus to obtain secure and reliable broadband connectivity. (Available at motorola.com)
Mesh Wireless Video Camera (Source: motorola.com)
This Motorola's Mesh video camera can be used wirelessly for fixed and mobile video setups. It can work on 4.9 GHZ licensed or 2.4 GHz unlicensed frequency. It has the ability to work either on standalone basis or as a part of Mesh Wide Area Network. A high quality video can be achieved wirelessly even at highway speeds. (Available at motorola.com)
One Laptop Per Child
OLPC XO-1 (Source: wikipedia.org)
One Laptop Per Child is a non profit organisation registered in Delaware USA and funded by its member Organisations AMD, Brightstar corporation, Ebay, Google, Marvell, News Corporation, SES, Nortel Networks and Red Hat, each company detonated 2 million dollar for this project.
At a primary school in Kigali, Rwanda in 2009 (Source: wikipedia.org)
The main idea is to provide 100$ worth rugged, low-cost and low-power Laptops to children in the poor developing world which contains self-empowered learning software. This laptop is manufactured in Taiwan by the company called Quanta Computer.
Internet Access through Wireless Mesh Networking (Source: wikipedia.org)
This Fedora based Operating System laptop has the ability of Mobile Ad-hoc Networking based on the 802.11s Wireless Mesh Network Protocol which allow students to work together and share their activities and Internet access from one single connection (such as VSAT). This laptop has much more wireless range and battery life as compared to usual laptops and has the cranking ability to recharge. (Available at wikipedia.org and laptop.org)
Microsoft's Self Organizing Wireless Mesh Networks:
Microsoft is researching to create wireless Mesh Networks which can connect neighbourhood and has many advantages which are listed below:
There is no need to have an individual gateway at each home for internet access. A fast speed Internet can be shared through the locally distributed gateways in the neighbourhood. Data travels dynamically using advanced Wireless Mesh Networking Protocols hoping from one node to another around the neighbour's until reaches the gateway.
Backup tools can be deployed mutually on the neighbourhood systems to avoid losing data in case of disk disasters.
This setup allows data produced locally to be used locally rather than sending data through internet.
Comparing the Wireless Mesh Networks with DSL and Cable modem System setups which are centrally controlled systems whereas WMN is not centralised everyone in the neighbourhood has a share in contributing the network resources and cooperates.
However privacy and security may still be an issue in such type of networks which requires a lot of research to be done. (Available at research.microsoft.com)
Locust World offers Mesh Open-Source Software:
Locust World offers an open source Fedora (Linux) based Operating System software which turns any x86 processor based computers to Mesh Network Client, Repeater, Gateway and Access Point. To support the Mesh Routing functionality this MeshAP provides Remote Management, Security and Access Algorithms. (Webb, 2003)
The Future of Wireless Mesh Networks
Think of a battlefield in a war situation under attack with thousands of acoustic sensors dropped from an airplane, they observe all sounds even from a whisper to sniper's rifle. All sensors communicate with neighbouring sensors through radio using wireless Mesh Network Technology, recording every single moment and sending all information's and alerts through GPS to the Collection Points.
These battlefield applications are funded by the Defence Advanced Research Projects Agency. (Rupley, 2003)
Parking Meters Invented in 1935, finally getting upgrade by the Street Line San Francisco Based Company in USA. As we all know they accept coins but the newer models do accept Debit and Credit cards. Street Line is working with the city officials to add Wireless Mesh Network Technology component to the Parking Meters. By Using a Smart phone you connect to the meter and pay, for example you have paid for an hour and are still away, the phone will say after 55 Minutes your time is about to expire would you like to add another half an hour and you will say yes and it goes straight to the meter. So there is no question that the space is paid or not and you don't actually need to be there to put coins in the meter.
Street Line is developing another Vehicle Sensor called Bump, equipped with the Wireless Mesh Technology helps driver to locate an empty parking space. This sensor is on the street and detects if a car is parked or not on a parking space. If there is an empty space it gives a Map on the screen of your phone and marks it as green but once it's occupied it will highlight it as red. So you can actually plan your trip before leaving home. This will reduce a substantial amount of traffic in the city; in fact, city officials estimate that drivers just looking for parking make up 30 percent of the traffic congestion in cities. These sensors are under testing stage at the moment in San Francisco and coming out soon to other states too in USA. (Dykstra, 2010)
Â 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. (Available at slideshare.net)
Mesh Networks Chief Technology Officer Peter Stanforth is working with U.S. Car makers on a certain application that alerts the driver when a car in front of him deploys its airbags, gives few precious seconds to avoid serious crashes. (Rupley, 2003)
Wireless Mesh Networks is an economical and very useful technology which can be used at various places in a variety of scenarios. Many corporations are continuously working to achieve a smooth platform on the basis of new standard IEEE 802.11s. The future appears promising when this technology gets mature.