Wireless Mesh Networks Improve Safety

For example, in parking structures as in other types of industrial environments, carbon monoxide (CO) is one of the most abundant contaminants and poses significant safety concerns. Heavy machinery and vehicles using these structures generate CO that must be controlled or ventilated when concentrations approach unsafe levels. There are various gas detection monitors available for use in parking structure applications that control the use of exhaust fans and the air intake devices in order to provide fresh, clean air to prevent the build-up of toxins and maintain safe CO levels.

By using GreenPeak's low power wireless radio technology to eliminate the need for expensive wiring, and by introducing a self-forming network installation procedure, Honeywell was able to drastically reduce the installation and maintenance costs of their wireless gas detection product line for carbon monoxide monitoring.

The Honeywell-Vulcain wireless gas detector system uses highly sensitive gas sensors communicating via GreenPeak's wireless RF signal transmitters to detect carbon monoxide (CO) in parking structures. The gas detector exchanges data with the controller over a wireless mesh network using a secured 128 bit encrypted communication protocol. Because of its reliability and extremely low power requirements, it can operate for several years without maintenance or battery replacement. In contrast to traditional gas detection networks, this system offers greater flexibility and operational reliability together with significant installation and operational savings.

Without the need to hardwire the monitors for connectivity and power, installation costs are drastically reduced. The sensors are simply wall-mounted, turned on and ready for operation. Once activated, they auto-configure to the controller and are fully operational within seconds. This 'plug and play' approach enables technicians to execute a 100% correct installation without the need for special training regarding the complex technical aspects of setting up a wireless network. The system essentially sets up its own network.

The mesh network communication allows for quick installation of site-wide wireless coverage throughout a facility without the need for dedicated base stations or routers. Each wireless sensor acts as a router for neighbor devices. Self-installation, self-healing and redundant communication paths result from the mesh topology.

Unlike point-to-point or point-to-multipoint communication, if the communication path fails, if the signal quality decreases, or if the infrastructure changes, the system can automatically establish an alternative route. This self-healing network feature enables continuous contact, even in harsh environments or when structures change. In a warehouse or large parking, a large truck may move into place, blocking the signal path. The mesh network then instantaneously finds a new path around the obstruction.

The inherent network integrity minimizes false alarms and ultimately trims operational costs. To further enhance the reliability, periodic 'heartbeat' signals throughout the network ensure that all transmitters are continuously active and guaranty full network and building coverage.

In addition, by using a Low-Power-Routing (LPR) communication stack, none of the devices require powering from the mains power supply, which allows for battery operation for all the nodes in the system. This is achieved by using smart power-up/power-down and synchronization techniques that enable all mesh nodes to operate in a low-power mode without a battery or power cabling.

Wi-Fi vs Bluetooth vs ZigBee/IEEE 802.15.4
All three of these wireless technologies target different applications. Wi-Fi was conceived as an alternative to wired Ethernet PC communication: high data rate networks with a base station at the center and PCs nearby (i.e. a star-network topology). In order to achieve high data rates in a local area, Wi-Fi consumes a fair amount of power, usually sourced from a laptop battery. With Wi-Fi, data rates rapidly degrade as distance to the base station increases.

Bluetooth was conceived with the mobile phone as the center of the universe: it connects the phone to an earpiece, to a GPS device and to a laptop. The Bluetooth data rate of 1 Mbps is high enough to carry voice, but is at least one order of magnitude smaller than that of Wi-Fi. In return, the power consumption is lower, most often sourced from a mobile phone battery. In general, the communication range is also shorter than that of Wi-Fi, which reflects the fact that the phone is usually in the vicinity of the earpiece, the laptop and the GPS device.

Sensor applications have totally different requirements, particularly with regard to power consumption. Sensors often have to work for years on a coin cell battery, or on energy harvested from the environment through a solar panel or vibration harvester. The battery cannot be recharged like a laptop or a phone battery. Other sensor-specific requirements are governed by factors such as reliability, communication range, the large number of nodes that may need to be supported in a single network, and the need for automatic network organization. In return, a lower data rate is generally acceptable, as most sensors generate fairly small amounts of data, and generally not on a continuous basis. For wireless sensor transceivers, the dominant and probably only real standard is the IEEE 802.15.4 specification. The first version was ratified in 2003, with an update in 2006.

There have been efforts to use Bluetooth and Wi-Fi for sensor applications. In both cases, Bluetooth and Wi-Fi were used in a pseudo-standard way, interweaving the principles of IEEE 802.15.4 into their native implementation. However, it is now widely accepted that IEEE 802.15.4 offers the best solution for the development of wireless sensor applications.

However, not all technology suppliers adhere to the IEEE 802.15.4 standard. Some have chosen to build proprietary transceivers with the goal of reducing complexity and cost. It remains to be seen if these proprietary solutions will achieve the volume needed to actually reduce cost. Moreover, reducing complexity often goes hand in hand with sacrificing performance, thereby limiting the range of applications for these solutions.

Regardless of specific technology, we now live in a world where minimizing energy requirements while ensuring reliability is becoming very important. By eliminating the need for networking cables, power lines and constant battery replacement, developers can create wireless sense and control networks that can safely function for months, if not years, without maintenance.

About the Author
Cees Links is CEO and Founder of GreenPeak Technologies