White Paper All mesh networks are not created equal Over the last decade or so, wireless mesh technology has been developed to provide ubiquitous wireless coverage across small to large geographical areas. Today, wireless mesh networking is used for applications as varied as reading utility meters, accessing the Internet, wireless video surveillance, and home area networking. This document provides an overview of wireless mesh networking technology, differentiates between wireless mesh technologies used for various implementations, and provides some guidance on how a wireless mesh can effectively be applied to a many different applications. All mesh networks are not created equal.
Mesh networking concepts The original concept of a mesh network was developed for military applications by DARPA (Defense Advanced Research Projects Agency) in the 1980s. It was designed for battlefield data communications between moving vehicles and used an architecture optimized for vehicle-to-vehicle (peer-to-peer) communications. This basic architecture had to be adapted to be efficiently used for today s wireless communications environments. Today s modern mesh networks all follow the same basic design principles. Data packets are forwarded through one or more free-standing radios or nodes until they reach a gateway with backhaul a radio that is connected to the core network. This backhaul can be a wired, fiber, or point-to-point wireless connection. Many mesh network architectures allow clients, such as Wi-Fienabled smartphones, to connect to the network in addition to serving to interconnect many other kinds of devices such as AMI collectors and video cameras. Because a large number of applications reside on the Internet or in the core network, many mesh designs are optimized for the most efficient connection from each client to the core network where the application or communications server resides. A mesh network delivers a number of advantages over a direct client connection over wire or fiber and over a point-to-multipoint wireless network: Reduced infrastructure costs. Because only a small percentage (often 5-10%) of the radios in a mesh network function as gateways, the network s wired backhaul costs are dramatically reduced. Improved wireless coverage. Working together, the radios in a mesh network provide many non-line-of-sight connection paths between clients and the gateway locations. Mesh networks can effectively transmit data around corners to avoid obstructions such as buildings. With appropriate design, city-wide coverage in excess of 90% has been achieved. 2 All mesh networks are not created equal
Highly resilient. Mesh network architectures are inherently resilient, since each node typically has multiple available paths to choose between and can dynamically re-route or adapt its path based on changing conditions in the radio environment. The basic topology, combined with dynamic mesh intelligence, can deliver a selfconfiguring, self-healing infrastructure that can provide up to 99.999% availability, if implemented appropriately. Topology Comparison Wireless Mesh Network Point-to-Multipoint Network Gateway Master t all meshes are created equal Several of the best known wireless mesh network systems have been developed for specific applications. Advanced Metering Infrastructure (AMI) is an example of a smart grid application that often takes advantage of the enhanced coverage provided by multi-hop radios. Mesh networks for AMI, commonly referred to as a Neighborhood Area Network (NAN), benefit from the resiliency of a mesh architecture with its multiple wireless paths to each endpoint. The AMI application has relatively low throughput requirements (meter reads have a payload of 50 to 100 bytes of data and data is not highly time sensitive) making use of low frequency spectrum desirable. Meter reading intervals are measured in hours, and often reads take place only once or twice per day, therefore network latency of several seconds to several minutes is acceptable for the AMI application. Above all, the low cost requirement for the deployment of millions of radios restricts the processing power and intelligence that can be built into each mesh node. NAN products invariably use basic mesh repeater technology and are lower in cost. The table below compares a range of different types of mesh networking technologies and the typical requirements of the applications for which they are most often used as the application requirements drive network requirements or attributes. 3 All mesh networks are not created equal
Attributes MESH TYPE Multi-Hop Repeater Home Automation Mobile Military Enterprise Infrastructure Metro-Scale Broadband AMI Demand Response Appliance Control Battlefield Communications Internet Access Enterprise Applications Video Surveillance Smart Grid Video Surveillance Intelligent Transportation Systems, Mobile Workforce Applications Automation Public Safety Public Hot Zones Throughput Low (50-100 Kbps) Low (<50Kbps) Medium (0.1-1Mbps) High (10-100 Mbps) High (10+ Mbps) Range Medium (400ft) Low (30 ft) High (1mile) Medium (50-250ft) Varies (200-2,000ft) Latency Moderate (100ms-few seconds) Moderate (sub-second) Low (sub-10 msec) Low (sub-10 msec) Low (10 msec) Scalability Service area scale (1000s mesh radios) Local (10-20 mesh radios) Limited (1-50 mesh radios) Campus scale (10s mesh radios) Metro-scale (1000s mesh radios) Coverage Neighborhood In-building Convoy-wide Campus City/Region+ Mobility Multi-Use Multiple peer-to-peer apps Wireless technology 400-900MHz ZigBee; Z-Wave; Short range Wi-Fi; Special Licensed 2.4GHz/ 5GHz Wi-Fi 2.4GHz/ 5GHz Wi-Fi In contrast to AMI that is typically based on a multi-hop repeater network architecture, many metro-scale and enterprise infrastructure applications have requirements that can be better characterized as ubiquitous wireless broadband. Applications such as public safety and mobile workforce automation, fixed and mobile Internet access, video surveillance and utility distribution automation require data speeds measured in Mbps along with millisecond latency. Many need high speed, pedestrian or vehicular roaming, and all benefit from ubiquitous coverage and extremely high resiliency. For nearly all of these deployments, the ability to run multiple applications at different Quality of Service (QoS) and security levels is essential. Since 2000, ABB Tropos Wireless Communication Systems has been delivering large-scale broadband mesh infrastructures built upon industry standards and based upon its exclusive, patented meshing technology. Tropos mesh technology A Tropos metro-scale mesh network infrastructure is comprised of relatively small radio routers typically mounted on street furniture such as lampposts, traffic lights, and power poles. Although mainly using unlicensed Wi-Fi spectrum, these radios are very different than typical indoor wireless access points. For a start, they are much more powerful. In the USA, the FCC allows the use of up to 4 Watts of transmitted power outdoors (compared to a typical access point at 100 mw), and the Tropos radios can use all of this. They have the industry s best receive sensitivity (they listen better), and they are built to withstand extreme weather conditions heat, cold, storms, event tornados and hurricanes. Each radio contains a very powerful processor which utilizes the patented Tropos distributed routing protocol, the core intelligence of Tropos mesh technology. 4 All mesh networks are not created equal
Dynamic routing When the radios are deployed and turned on, they communicate with each other and automatically configuring themselves into an optimum mesh infrastructure. By measuring the quality of the wireless connectivity between each router, they collectively work out the best way of passing data from any end point to one of the gateway radios on the backhaul network. This path evaluation process is repeated up to 5 times per second, enabling the network to constantly monitor and optimize itself. New radios are easily added they automatically participate in the mesh optimization process. Continuous optimization also makes the mesh self-healing. Because the radios are so powerful, each radio can see many others, so if any radio or backhaul connection fails, the routers reconfigure themselves to cover the gap. This process occurs quickly enough to compensate for localized or transient interference. Performance optimization Network resiliency is enhanced by several unique Tropos features: Automatic band and channel selection. Most multi-band mesh technologies reserve frequencies for specific tasks: 5.8 GHz for internode connection, 2.4 GHz for client access, for example. Tropos multi-band radios switch bands as part of the optimization process, automatically using the band with the best connectivity. The mesh can also optimize the operating channels within the band. A huge advantage of using unlicensed 802.11 is the availability of around 500 MHz of spectrum in the 2.4 GHz and 5.8 GHz bands (compared to a typical 50 MHz WiMAX license, for example). Although this spectrum can be, and is, used by others, the ability to dynamically automatically select the least-used band and channel creates a wireless infrastructure that is proven to be more reliable than typical limited bandwidth, licensed deployments. Dynamic power control. The distance between the mesh radios varies widely, sometimes within the same deployment, and depends on a number of factors: the environment (urban, rural, open country), the terrain, and particularly the type of application and the client radios accessing it. The Tropos routers automatically adjust to these conditions by transmit power management. Each packet of data transmitted between the Tropos radios and to their clients is sent at the optimum power level, removing potential self-interference from the Tropos routers themselves, and significantly improving the connectivity of lower powered clients. Multi-application support. Nearly every Tropos customer uses their network for support of multiple applications. For example, several utility customers use the network to aggregate data for AMI, as critical connectivity between distribution and substation control devices (Distribution Automation and Substation Automation), and as a mobile data network for their mobile field workers. All of these applications have different operational and security requirements which are met with Tropos. 5 All mesh networks are not created equal
Tropos uses industry standard network virtualization techniques to separate, prioritize and secure data traffic for each application. VLAN data separation is extended from the core wired network throughout the wireless infrastructure and enables each application s data traffic to be bandwidth controlled and prioritized. Different security policies can be applied across each of these VLANs, enabling security to be tailored to each application s requirements. Tropos satisfies the latest industry-specific security standards such as NERC CIP for the utility industry, and is certified for FIPS 140-2 compliance, the standard for US government homeland security systems. Standards-based implementation facilitates common security and QoS policies across the entire network infrastructure. Heavier mesh in more densely populated areas Mesh Network Adaptability Light mesh in less densely populated areas Scalability. Tropos distributed architecture delivers unlimited scalability, both in terms of coverage and performance. The communications overhead for inter-router traffic never exceeds more than 5% of the total available throughput, and the network can scale linearly to tens of thousands of radios, and beyond. Manageability. A fundamental requirement for the operation of metroscale networks is an effective Network Management System (NMS). Tropos Control is a utility/carrier class NMS that provides advanced monitoring and management of the entire wireless infrastructure. Map-based monitoring of network health allows real time identification of faults and wireless performance problems, and identification and location of specific client issues. Simplified bulk provisioning and asset management delivers real time operational control of all network components. A comprehensive reporting system delivers long term performance analysis for network optimization. Tropos Control is standards-based, and often forms the core of an integrated Network Operations Center. 6 All mesh networks are not created equal
Summary Mesh networking technology has been used for nearly 20 years to deliver ubiquitous wireless coverage over large areas. Different forms of mesh networks have been developed, some for specific application environments, but many applications benefit from the performance, capacity and coverage of a broadband, metro-scale mesh infrastructure. ABB Tropos Wireless Communication Systems has been an industry leader in the development of mesh technology and its adaptation for very large scale networks. A Tropos mesh infrastructure is built on a standards-based foundation: it facilitates network access from hundreds of millions of available Wi-Fi clients, while delivering industry standard security and network facilities that allow the delivery of multiple applications at enterprise, carrier and utility class service levels. This combination enables solutions at a practical price/performance level that has made Tropos the technology of choice and the market leader for the deployment of very large scale, broadband mesh network infrastructures. 1KHA - 001 280 - SEN - 1001-7.2013 Copyright 2013 ABB. All rights reserved. For more information please contact: ABB Inc. Tropos Wireless Communication Systems 555 Del Rey Avenue Sunnyvale, CA 94085 Phone: +1 408.331.6800 E-Mail: tropos.sales@nam.abb.com abb.tropos.com