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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
Gateway
Point-to-Multipoint Network
Master
Not 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
MESH TYPE
Attributes
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
No
No
Yes
Yes
Yes
Multi-Use
No
No
Multiple peer-to-peer
apps
Yes
Yes
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
Light mesh in less densely
populated areas
Mesh Network Adaptability
—
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
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.
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: [email protected]
abb.tropos.com
1KHA - 001 280 - SEN - 1001 - 7.2013 © Copyright 2013 ABB. All rights reserved.
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.