FEATURE SWITCHES & ROUTERS
HD Video Over Multiservice Mesh Networks Instant Mesh By Wilson Craig, Director of Corporate Communications, Aruba Networks
When designed and deployed correctly, mesh networks enable organisations to combine voice, video and data networks onto a single network. The converged network is simpler to manage and operate, while the organisation retains control over the delivery of multiple services. In addition, fewer devices are required, so the network is less expensive to purchase and maintain. Modern mesh networks
A multiservice mesh is a multi-path, multi-hop wireless local area network and wide area network that is ideal for outdoor deployment. With a mesh, reliable networking can be established almost anywhere, without the cost and disruption of running cabling or fibre.
automatically discover the best route through the network and operate smoothly even if a mesh link goes down or a node fails. Because these networks are self-forming and self-healing, administration and maintenance costs are low. In addition, a wireless mesh overcomes the line-of-sight issues that may occur when a space is crowded with buildings or industrial equipment. Mesh networks, however, impose a unique set of challenges when used for delivery of high-definition video over long distances. The use of video surveillance is growing exponentially as businesses and the public want greater protection from a perceived increase in crime and terrorism. Real- time video surveillance has quickly become a preferred way to deter crime, improve incident response time and provide evidence. However, delivering high-quality
IP video over long distances with a wireless mesh network has traditionally been difficult. Problems with network latency, packet loss and jitter often result in pixilated images that are difficult to see clearly. That said, new techniques in video optimisation to enable mesh networks to deliver high-definition video in real-time, at broadcast-quality at up
to 30 frames per second. To deliver HD-quality video, mesh networks must be equipped to address a number of common impairments to high quality HD video delivery over mesh.
Finding MIMO
Multi-radio, multi-frequency architectures are a giant step forward in high-capacity mesh networks. Multiple- input and multiple-output (MIMO) is essential for fast download capabilities with reduced interference, which makes it possible to deliver high-quality video across the mesh. MIMO also delivers superior wireless coverage for smartphones, laptops and other mobile devices with low transmission power. In MIMO architecture, each 802.11n radio has multiple transmit antennas and paths. Using multiple antennas to transmit increases the effectiveness. This is because different Wi-Fi devices hear different signals more strongly in different parts of the coverage area, and they will use the best available signal for communications. The result is more uniform coverage and higher data rates. Unlike legacy 802.11a/b/g
technology, MIMO radio works especially well in a campus or city where buildings and moving people can cause high levels of RF reflection. RF reflections can cause transmissions to take different paths before arriving at their destination, which is known as multipath. MIMO leverages multiple paths between transmitters and receivers to improve network performance. Mesh networks are able to deliver
highest performance when the access network is separate from the backhaul network, i.e. when each mesh router has multiple radios dedicated to backhaul. With dual-radio systems, the backhaul is a shared network. With new innovations, the backhaul network is comprised of multiple point-to-point wireless links, with each link operating on a different channel. The best mesh routers on the
A mesh operating at Layer 3 provides intelligence that allows for optimal performance, scalability and reliability.
38 NETCOMMS europe Volume II, Issue 1 2011
market today support dual and quad radios with omni-directional or directional antennas. Each 802.11n radio can transmit at up to 300 Mbps in client, access or backhaul mode. Each mesh radio should also be able
to operate in multiple frequency bands – the unlicensed 2.4-GHz band, the 5-GHz band or the licensed 4.9-GHz U.S. public safety band. This allows organisations to deploy mesh routers using the frequencies, channels and maximum power allowed in each country. Specific techniques must be applied
to overcome the limitations imposed by Layer 2 networks, and to make the mesh more intelligent, scalable and resilient. The most advanced systems on the market today employ a distance- vector routing protocol (DVRP) that is purpose-built for both mobile and fixed wireless mesh networks. Some mesh products use Layer 3
routing in their architecture. These routing protocols, such as open shortest-path first (OSPF), were originally designed for wired networks. OSPF can easily flood the entire network when handling the rapidly changing conditions that are typical for a wireless network. Such frequent network-wide flooding causes serious performance, scalability, stability and convergence problems. In contrast, DVRP-equipped
systems are designed to minimise the unnecessary control traffic related to rapid and transient changes on a wireless network. These systems have lower overhead than other Layer 3 routing protocols, which leaves more bandwidth for user applications. Dynamic, adaptive routing also
improves network reliability. DVRP- equipped systems maintain multiple routes to each destination, and each router keeps track of connectivity to its neighbours and the devices connected to the mesh via Ethernet or Wi-Fi. Traffic is instantly rerouted around congestion or link failures. Delivery of high-quality video over long distances is currently a critical requirement for multiservice mesh networks. But not all mesh networks are up to the task. To ensure that your network is, and that it will remain so in the future, be sure to choose a network with a multi-radio architecture, layer 3 routing capabilities and advanced video optimisation.
www.netcommseurope.com
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