How Wi-Fi, EnOcean, and Bluetooth Contribute to Building Internet of Things Goals
Second of a three-part article explaining the pros and cons of wireless standards.
3. Wi-Fi. The most widely used wireless technology, of course, is Wi-Fi, under IEEE 802.11. Wi-Fi is often used in information technology systems. It operates in ISM (industrial, scientific, and medical) frequency bands and is capable of data rates up to 300 megabytes per second for the 802.11n standard. The newer 802.11ac standard offers data rates up to 1 gigabit per second. As such, Wi-Fi can be used to support even large building automation systems.
“For devices sending large amounts of data, the building may need a Wi-Fi solution,” Szcodronski says. “But the device will consume more power and the battery does not last very long.”
Wi-Fi is best for “large data streaming applications,” agrees Grimard.
However, Wi-Fi’s incredible capabilities come with a large price tag. And Wi-Fi’s distributed antenna system of transmission is relatively more complicated to apply.
In return, Wi-Fi offers significant data benefits. For example, Wi-Fi can map traffic patterns in different building layouts over time, allowing facility managers to optimize layouts. And it can combine a building occupant’s personal preferences for lighting, comfort, etc.
“If set up properly, Wi-Fi also is more secure than wired systems,” says Szcodronski. “Wi-Fi comes with built-in encryption and port security. But if it’s not properly set up, all bets are off.”
4. Bluetooth, now and future. The biggest difference between different wireless options is their throughput vs. range, explains Szcodronski. “If a sensor needs to send an update every hour, giving a status, that would be a prime candidate for a low bandwidth, low energy solution such as Bluetooth.” Provided the bridges and gateways are secured, encryption of Bluetooth addresses security issues. The data transmission rate for Bluetooth 4.0 is 25 megabytes per second.
Currently, Bluetooth is commonly used for location-based services, explains Szcodronski. “Bluetooth is practical for one-direction communications, such as whether or not the conference room is occupied.”
In late November, Bluetooth announced that it was very close to its own mesh technology. This action changes Bluetooth from a point-to-point, star-based network topology to a true mesh network configuration.
“The benefit of a wireless mesh network is that it can find new routes to get information on communication failure where it is needed,” says Grimard.
Bluetooth Smart devices operate in the same bands as ZigBee and Wi-Fi. The Bluetooth mesh network should allow large groups of devices, such as smart lights or temperature sensors, to operate across a large area. Devices can be grouped and messages or commands sent only to a predetermined group (e.g., third floor lighting) or to specific devices (e.g., office 4 on the third floor).
Attempting to spread out from the home market to commercial applications, Bluetooth Smart does not need a special hub or even an Internet provider connection, though it will use gateways built to Bluetooth’s mesh standard.
The Bluetooth mesh network working group recently released version 0.9 of the new specification to its members to start prototyping products. The goal is to facilitate machine-to-machine communication via the mesh. And, by adding nodes, the new system will be scalable as needs change.
“We can track assets in buildings and materials through a manufacturing process via the mesh. We can create truly smart facilities. You have an umbrella of mesh networking coverage in your facility,” posted Steve Hegenderfer in Bluetooth’s blog.
5. EnOcean. Like Zigbee’s Green Power option, EnOcean relies on energy harvesting rather than batteries. The difference is that EnOcean’s energy harvesting solution is patented. In operation, an EnOcean light sensor uses light energy, while flow or movement sensors tap kinetic energy from the environment. EnOcean’s data transmission rate is 125 kilobits per second.
EnOcean communicates in a low frequency range. This allows for longer transmission distances and separates their communications from other nearby devices.
Second-generation interfaces allow bidirectional communication with BACnet actuators and controllers. Typical applications for EnOcean technology focus on energy conservation measures such as lighting and HVAC controls. The technology is offered through the EnOcean Alliance’s 120 member companies.
“EnOcean devices alleviate the problem of batteries through its proprietary grid network,” says Thompson.
Energy harvesting solutions that provide their own power are evolving very rapidly, according to Grimard. Currently, the solar cells that harvest power for lighting wireless sensors and controls have a 25-year or more life expectancy.
Pitfalls to avoid
After choosing the right combination of wireless and wired solutions, facility managers also must decide whether or not one wireless solution is best for the whole building. For device-to-device communications, a building might use Zigbee back to a gateway. Location-based needs are probably best served by Bluetooth, because it is not bidirectional in the marketplace yet.
“Wi-Fi is probably best whenever you need a higher throughout communication,” says Szcodronski, “for example, from the gateway to the building network system, which is controlling higher functions or multiple devices.”
“Define your goals,” stresses Thompson. “What do you need to control in real time? Do I really need to control that device from anywhere in the world?”
Thompson estimates that first costs of wireless systems generally range from $3 to $30 per controllable device. “The next cost is implementation, integration, getting online, and controlled access,” he says. “The third cost is administration. What are your efficiency goals? The fourth cost is exposure and cyber security, which are on-going costs.” Facility managers also need to add in the costs of making sure these wireless devices are locked off and maintained. That includes a budget for buying and replacing batteries, he says.
Be aware of hacking concerns, advises Grimard. “Use consultants and work as a team to know what applications are secure enough to give you the data and information you need to run your building,” he says.
Also, remember that all wireless systems have gateways or access points that need to be secured. “Even Wi-Fi systems require network updates and periodic security patches,” observes Grimard. Annual wireless supplier service and support subscriptions to make sure everything runs as designed could add up to 10 to 15 percent to the cost of the system, he adds.
Rita Tatum, a contributing editor for Building Operating Management, has more than 30 years of experience covering facility technology.
Email questions to firstname.lastname@example.org.