Wireless Sensor Networks
Nick Baker
Walter Woods
Adaptive Wireless Solutions Ltd
Copyright© 2013 Adaptive Wireless Solutions Ltd
Adaptive Wireless Solutions
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Specialists in monitoring and control solutions using wireless mesh sensor
networks for over 8 years
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Offer systems integration and equipment supply for numerous wireless and
wired technologies driven by customer requirements
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Distributor for ECOMM and Wireless Sensors in UK and Europe
Certified System Partner for HMS Industrial Networks (Netbiter) in UK
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Can help you integrate and manage your data gathering, monitoring and
control activities
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Complete solution design, supply and support
Wireless technology consulting and advice
Programme and project management
Technical and wireless architecture design
Equipment and software supply from multiple vendors
Integration with other systems
Installation and commissioning
Maintenance and Support
Copyright© 2013 Adaptive Wireless Solutions Ltd
Customers and Projects
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Mesh Wireless projects in BMS extension, energy management, industrial
plants, IT environments, commercial offices, universities and colleges, hotels
and apartment complexes, warehousing, recycling plants, food companies
and national utilities.
Customers in UK, Ireland, Italy, Netherlands, Belgium, Hungary, Israel, Saudi
Arabia
BOMBARDIER
Copyright© 2013 Adaptive Wireless Solutions Ltd
Business Advantages of Mesh Radio
Economic and operational advantages vs. wired sensors
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Up to 90% lower installed costs
– Lower cost of required equipment and supplies
– Much quicker installation = less on-site time and less disruption
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Monitor and control in:
– harsh environments (lots of metal and interference)
– “wire unfriendly” situations where wires are difficult or undesirable
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Low cost and speedy retrofit to existing buildings, equipment and processes
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Monitors mobile or rotating equipment
Easy optimisation of sensor position in process for a better result
Cost-effective diagnostics in uncertain or temporary situations
Multiple sensor types with standard wireless nodes on a single network
Remote, ‘PC-less’, monitoring from anywhere on the internet
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Wireless Network Types
Older, less flexible, less reliable technologies
Direct Connection
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Wire replacement
Point to point, highly specific
Engineered to suit application
Star
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One central routing and control point
Single-hop - point to multi-point
All data flows through central point
Newer, more flexible, more reliable technology
Mesh
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Multiple data paths
Multi-hop
Can operate as star or hybrid star/mesh
Self configuring, self healing
Highly flexible, highly reliable
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Gateway
Mesh node
Sensing
node
Operational Advantages of Mesh
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Multiple Pathways
– Stronger connectivity
– Self-Healing, Self-Managing
Transmit Around Equipment
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More robust
More flexible
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Extend Network Range
– More robust
– More capable
Secondary
Primary
Out of Range
Primary
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Core Mesh Wireless Product Ranges
System
Monitor/
Inputs
Control/
Outputs
Key Strengths
ECOMM
Yes
Yes
Large scale networks, multi-channel I/O,
direct equipment/meter integration
Wireless
Sensors
Yes
No
External TRH sensors, RTD’s, battery
operation, device packaging
Copyright© 2013 Adaptive Wireless Solutions Ltd
Copyright© 2013 Adaptive Wireless Solutions Ltd
ECOMM direct integration with Modbus meters
• The following electricity meter types are currently supported by
direct integration via Modbus RS485 connection to the ECOMM
WC21 radio unit
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Schneider E 5600
Schneider ION 8600
Schneider PM 710/750
Schneider PM 9C
Schneider ION 6200
Carlo Gavazzi EM24
Veris H 8036
EIG Shark 100
Continental Controls Wattnode
• Other meter types can be added as needed (at a modest cost)
Copyright© 2013 Adaptive Wireless Solutions Ltd
Copyright© 2013 Adaptive Wireless Solutions Ltd
Remote Monitoring and Control
Copyright© 2013 Adaptive Wireless Solutions Ltd
Solution Architecture – Netbiter remote monitoring
Wireless range to cover large sites, highly reliable digital mesh radio, not affected
by interference. Scales from 1 to 100’s of points. Netbiter transfers data off-site to
Netbiter Argos remote monitoring portal. Web API available to integrate data to
other applications
Remote off-site
monitoring using
Netbiter Argos
Netbiter is Modbus
TCP proxy
Wireless
mesh
Gateway
Typical Sensors and I/O devices
Battery and/or line powered
Temperature sensor
Temperature and humidity
Occupancy, door contact
Light
Pulse counting
Dry contact inputs
Up to 32 inputs per radio: contact, NTC, 0-5V, 0-20mA
Relay and analogue outputs
Multi-stage thermostat controller
Modbus RTU bridge
Copyright© 2013 Adaptive Wireless Solutions Ltd
Although we specialise in mesh radio we also use
GSM/GPRS and Narrowband radio systems
when needed to meet customer requirements
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Typical Solution Architecture Overview (1)
Copyright© 2013 Adaptive Wireless Solutions Ltd
Typical Solution Architecture Overview (2)
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Example Projects
Integration type
Sector
Description
OPC / Remote
Asset
Management
Supermarket refrigerator, freezer temperature monitoring, HVAC and outside
temperature monitoring. Expansion of trial site to 10 further stores
Modbus TCP / Remote
Energy
Electricity consumption monitoring on 7 floors of Dept. Health, London office, 8
meters per floor in risers. Wireless installed and commissioned in 2 days.
Modbus TCP into BMS
Asset
Management
Electricity feeder pillar status and generator status monitoring and control with
battery UPS-protected wireless network across 100 acre government laboratory
site.
Modbus TCP
Building
Management
Temperature and Humidity monitoring across 5 warehouses in large warehouse
complex for Nestle
Modbus TCP/ BMS
Building
Management
Wireless temperature monitoring and window damper, heating valve and air
recirculation damper controls. Historic university building. Demonstration project
for Irish government.
BMS
Energy
Wireless boundary gas meters pulse transfer to BMS outstations on hospital site
Modbus TCP / SCADA
Pharma
Laboratory refrigerator, freezer and warehouse monitoring at Johnson &
Johnson facility. Validated environment.
Direct I/O
Asset
Management
Remote generator status monitoring into site SCADA system
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Application example – Westfield Shopping Mall BMS
integration for temperature control
55,000 Sq Metres on
two floors with Atrium
49 Air handling units on
roof
1 Wireless network
18 Mesh repeaters
30 Sensing nodes
Ambient Temperature
input to HVAC zone
controls via Modbus
TCP
Installed in 2 days to
resolve critical
operating requirement
£6,100 equipment cost
Copyright© 2013 Adaptive Wireless Solutions Ltd
Application example – Large Data Centre
Monitoring Solution
7,500 Sq Metres
Floor 3
4 Floors
Floor 2
Control Room
Viewers
Primary Server
Main Mission Critical
Data Centre
Console
Floor 1
Basement
Common
Ethernet
Network
Remote Business
Continuity Centre
Other
Viewers
Secondary Server
Remote Disaster
Recovery Centre
Secondary
Console
Copyright© 2013 Adaptive Wireless Solutions Ltd
Phase 1 - 2008
6 Wireless Subnetworks
22 Mesh repeaters
178 Sensing nodes
Ambient TRH
Phase 2 - 2009
100 additional TRH
sensors on two
floors
4 more wireless
sub-networks
Phase 3 - 2010
Being planned now
Electrical Power
Chilled water
BMS / SCADA Integration
• We have supplied systems to clients providing integration to existing
BMS’ and SCADA / software systems via:
– Modbus TCP and RTU
– Direct analogue and digital connection
– ODBC, OPC and SQL connection
• BMS’ that have been integrated with our systems include:
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Trend
Siemens
Schneider
Andover Controls/TAC
Honeywell
Priva
• Numerous SCADA systems have also been integrated
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Network Performance and Reliability
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Industrial Wireless Sensor Networks
Industrial WSN OEM Adoption Inhibitors
Source: ON World, Inc.
10%
Node Size
20%
Education
43%
Dev Cycles
Battery
53%
58%
Ease of Use
Standards
67%
92%
Reliability
0%
20%
40%
60%
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80%
100%
Building Automation Wireless Sensor Networks
Commercial Building WSN Adoption Inhibitors
Source: ON World, Inc.
Guest Room
4%
23%
Node Size
44%
Ease of Use
52%
Dev Cycles
Education
53%
55%
Battery
63%
Standards
70%
Reliability
0%
20%
40%
Copyright© 2013 Adaptive Wireless Solutions Ltd
60%
80%
Wireless Sensor Network Reliability
RF Interference
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Common interference sources:
– Multipath interference
• Occurs when the RF signal interferes with itself
• Reflections off surfaces of all types
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• Can interfere with original signal and even cancel it out
– Interference with other transmitters
• ISM band 2.4 Ghz wireless is increasingly common
• Signals can be affected by other sources
• Data slows down (more retries) or even stops
• A good way to avoid it is to ‘frequency-hop’
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Examples of other transmitters in the 2.4 GHz band can be WiFi nodes,
microwaves, cordless phones, Bluetooth devices, RFID, and other
wireless sensor networks.
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How can it be avoided?
Copyright© 2013 Adaptive Wireless Solutions Ltd
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Wireless Sensor Network Reliability
Interference Avoidance
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Typical methods:
– Direct Sequence Spread Spectrum (DSSS) modulation
• Part of the IEEE802.15.4 radio standard
• Spreads the signal over a wider bandwidth
• Reduces the chance of blocking the whole signal
• NOT part of the IEEE802.15.4 radio standard
• Uses a range of base frequencies
FREQUENCY
– Frequency-Hopping Spread Spectrum (FHSS) modulation
• Transmitter and receiver periodically hop to a new frequency
TIME
• Acts more like a narrowband radio for very short intervals
• Very unlikely that all channels in the band are interfered
• Not a modulation technique
INTERFERENCE
Signal strength
– Dynamic channel hopping
• Enhances simple FHSS modulation by dynamically detecting
persistently busy channels and avoiding them
2.40GHz
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The best mesh radio systems use all three techniques
Copyright© 2013 Adaptive Wireless Solutions Ltd
NOISE FLOOR
frequency
2.48GHz
Wireless Sensor Network Protocols
How do they affect performance?
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Two main options:
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Carrier Sense Multiple Access
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Time Synchronised Protocols
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These minimise or avoid collisions and transmission re-tries
Time synchronisation allows the use of channel-hopping
TDMA (Time Division Multiple Access) is an example
Also called ‘slotted’ protocols because each device has a ‘time slot’
The benefits of synchronised traffic and channel-hopping are:
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Collision-based protocol
Uses collision-avoidance (CA) or collision detection (CD)
Most WSN protocols use CA to avoid network overhead
Network communication is not time-synchronised
Pseudo-random ‘Back-off and re-try’ mechanisms are used
Collisions within the network escalate as networks get larger
ZigBee is based on this CSMA-CA approach
Better performance (fewer collisions/retries)
Increased battery life (fewer retries)
Better interference avoidance (channel-hopping)
The most sophisticated systems use adaptive dynamic channel-hopping
Copyright© 2013 Adaptive Wireless Solutions Ltd
Protocol Standards?
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802.15.4-based market offerings are
differentiated by proprietary protocol stacks with
different design goals
Network layers of the protocol
are not standardised
There are many trade-offs in protocol design
There is room for several feature-specific protocol variants
using the IEEE 802.15.4 base standard
It is important that hardware remains 802.15.4 compliant
‘Standard protocols’, if they ever become available, will not
mean that proprietary protocols become obsolete or
unnecessary.
ZigBee is not a standard and has serious reliability and
performance limitations in industrial and commercial
environments. ZigBee equipment from different vendors
does not interoperate – one of the key goals of a standard.
Copyright© 2013 Adaptive Wireless Solutions Ltd
Application
Application Interface
Network Layer
Data Link Layer
MAC Layer
MAC Layer
PHY Layer
IEE 802.15.4
Proprietary
Application
Contact Details
Adaptive Wireless Solutions Ltd
91 High Street
Prestwood
Great Missenden
HP16 9ER
Tel:+44 (0) 1494 865992
www.adaptive-wireless.co.uk
Nick Baker
Director
Mobile: 07968 352875
nbaker@adaptive-wireless.co.uk
Skype: adaptivewireless
Copyright© 2013 Adaptive Wireless Solutions Ltd