Where’s the Wire?
Wireless mesh technology, improved security and reduced radio frequency obstructions are some of the developments that have increased the appeal of wireless building automation controls.
CSE: What are the main advantages of wireless controls?
MUNSON: The big benefit is the ability to deploy devices in difficult settings, especially in existing structures or remote locations. Also, mobility and rapid deployment are high on the list of advantages, as well as lower costs from reduced infrastructure wiring requirements.
HOFFMAN: There are certainly cost savings from not having to pull wires between controllers and sensors. But I think the main advantages of wireless controls are expandability and flexibility. Businesses need to be more flexible than ever. A company has to morph as its needs change. This is the right environment for wireless controls, particularly occupant space equipment like sensors. Adding sensors, whether temporarily to diagnose a problem or permanently to improve control, is much easier.
HENDRIX: Wireless also means that sensor placement can be optimized to ensure sensing is being done in an area most representative of the space. In the past, sensors were typically located wherever it was easiest to wire. This was frequently the case in large commercial office spaces with many cubical offices. But now, wireless not only allows sensors to be easily moved, but also allows more sensors to be used for better input to the automation system.
Another benefit is that wireless simplifies retrofit projects by eliminating the need to tear up walls and ceilings to run conduit and new wiring. This is especially true when the wireless control devices are either battery-powered or use some other power source already present so that a new power trunk is not required.
CSE: How has this affected installation?
HENDRIX: I think wireless simplifies coordination between various construction trades. For example, a room sensor can be mounted and commissioned toward the end of the project and doesn’t have to be coordinated with multiple trades through the various project phases. In retrofits, it’s also less disruptive to occupants.
In addition, wireless controls allow for a staged migration of legacy systems to meet budgets and schedules. Frequently the wiring being used by legacy systems cannot be reused by new systems. Consequently, it has to be run, and the old network upgrade must take place, all at once. This typically results in the entire network having to be taken down and everything transferred to the new network at the same time. However, with a wireless link, controls can be replaced and connected to the new system one by one without affecting the remaining legacy devices.
CSE: What obstacles still stand in the way of wireless controls?
HENDRIX: One issue is that many wireless control devices, such as sensors, require batteries that need to be changed out multiple times over the life of a device. However, as the power requirements of wireless control devices decrease, battery technologies improve and power scavenging techniques become more widely used, this will become less of an issue.
MUNSON: Another obstacle is a lack of confidence that the system is secure from malicious intrusion and interference from other electrical devices. Essentially, the general end-user perception is “Can I trust the system to be reliable, and if not, what is the fail-over mode when it does fail?”
RUIZ: That’s the perception, and given the advances in technology, a dated one. In fact, well-designed wireless control networks are now as reliable and secure as wired ones. And new technologies like frequency hopping, mesh networking and spread spectrum are being embedded into wireless control networks to make them even more reliable and secure.
WILLIAMSON: With any new technology, the adoption rate increases as the technology is proven. The manufacturers have devoted a large amount of R&D resources over the last three years to make sure wireless solutions address reliability, security and response standards set by the end user. The technology has now reached a maturity level where these goals can be met at an attractive cost point for a wide range of applications.
HENDRIX: Still, the fact is that, in most cases, the cost of additional wireless electronics is still greater than the installation costs they eliminate. But this is quickly changing, as more radio electronics migrate to a single chip, the price of which drops significantly each year.
Also, the lack of interoperability between wireless control devices is of concern. Work will need to continue in the standards area to address this issue.
CSE: An argument can be made for wireless controls for just about any facility, but which building types are most suited to wireless?
HOFFMAN: Generally, wireless controls are a natural fit in facilities that inhibit wiring. This can be for cosmetic reasons, health concerns or installation expense. For example, when a sensor must be installed in a glass-enclosed showcase area, wireless sensors are the best option. And when network wiring would have to be passed through an area contaminated with asbestos or trenched underground, wireless networks are cost-effective.
WILLIAMSON: For all projects, there need to be good methods in place to plan a wireless network, with an understanding of how physical obstacles and building materials affect wireless networks. But there are four types of facilities where a wireless solution is particularly attractive: city buildings, cleanrooms, historical buildings and difficult-to-wire and remote buildings.
For example, cleanrooms need to maintain precise climate and pressure conditions, so any penetration into the production area decreases performance. For historic buildings, it’s important that the structure’s historical integrity be maintained. This means that wires cannot always be run in a straight path. Thus, wiring a network to the next room may mean running 1,000 ft. of cable vs. a 10-ft. wireless path. Finally, trenching a network cable to a remote building or the penetration of brick, glass or cement walls may be difficult and expensive.
HENDRIX: Offices, schools and universities, as well as manufacturing and other industrial facilities, offer potential for wireless applications. Facilities that are fairly open can be ideal because there are minimal radio frequency (RF) obstructions.
MUNSON: In addition, facilities with a large number of individual workstations are ideal candidates. In fact, individual space control should be the prime motive for wireless controls. Personal comfort and the feeling of individual space control can increase a company’s bottom line by creating happy and content workers.
CSE: So, in the future, how should building infrastructures be set up in order to facilitate the adoption of wireless control technologies?
RUIZ: It’s good to consider RF-friendly materials. Wireless controls typically work best in open environments that do not interfere with or absorb RF energy. In these environments, signals can travel up to 300 ft., making wireless ideal for room temperature and humidity sensing. The controllers are normally 30 to 60 ft. from the sensors, just above the ceiling tile.
Porous materials like wallboard, ceiling tile and cement block have less of an effect on wireless signals than materials like metal and concrete, in which RF will travel less than 100 ft. Surprisingly, metal ductwork sometimes helps wireless signals, because it acts as a wave guide and bounces signals between controllers.
WILLIAMSON: One newer technology, wireless mesh, actually offers the benefit of not requiring an infrastructure to be in place. The way it works is each mesh node contributes to building a strong wireless network.
Wireless mesh differs from wireless Ethernet, which is a point-to-multipoint network that relies on the strategic placement of access points. In the wireless mesh model, each node has multiple connection paths and knows about all its nearest neighbors. As a result, daisy-chain wiring becomes a thing of the past. If one node is disconnected or the current path is blocked, the network heals itself by finding its next nearest neighbor to reconnect messages. Since a wireless mesh doesn’t require creation of an infrastructure, cost savings over wired networks is easily realized.
HENDRIX: That’s right, mesh networks use a grid-like topology to provide multiple redundant communication paths with each node functioning as a sender, receiver and router. Mesh networks can route around obstructions, and each node only needs to communicate with two or three of the neighboring nodes.
WILLIAMSON: As a matter of fact, the IEEE 802.15.4 wireless mesh standard offers a much better wireless solution for controls over WiFi and Bluetooth. The wireless mesh networks are self-forming and do not require an infrastructure or access points and routers, although repeaters may be used.
CSE: Besides wireless mesh, what are some other recent technological advances in wireless controls?
HENDRIX: Power requirements are getting lower and lower, allowing devices to run for a long time on battery power.
HOFFMAN: One of the latest trends is the adoption of distributed antenna, or DA, systems. These systems guarantee coverage for all of the wireless systems within a building including cellular phone, wireless LAN, VoIP phone and building controls. They also improve security, since they can be engineered to ensure wireless hot spots inside and dead spots outside a building.
Designers of wireless systems are also adopting military technologies. For example, to reduce interference, wireless control networks are using frequency hopping—dynamic frequency selection. They’re also using spread spectrum transmission, which is distribution of a signal across a frequency band. Advanced encryption algorithms are also being embedded into the radio hardware to improve the security of control networks. These technologies have been used in military radios and are now economical for wireless control networks.
CSE: How do you envision the world of wireless controls 10 and 20 years down the line?
MUNSON: I see all devices being wireless IP addressable with a minimum of 1 GB of bandwidth communications capable.
HENDRIX: I predict that wireless will be the low-cost infrastructure of the future. Power requirements will continue to decrease, and alternative power or power harvesting strategies will be employed allowing devices to run forever with no maintenance. RF electronics will be embedded into all devices. Sensors and RF electronics will shrink to a fraction of the size that they are today and will be incorporated into all kinds of devices that could be monitored for predictive maintenance, comfort, life safety and security. BAS control devices will also utilize the larger ubiquitous wireless infrastructures that will exist. Each building will contain a warehouse of information that can be mined and monitored via the Internet or automatically for optimal control, energy efficiency and occupant comfort.
RUIZ: We expect the evolution of wireless building controls to follow the cell phone and WiFi networking markets in terms of adoption and as an enabler for more distributed, less hierarchical control systems. Due to cost and reliability, cell phones filled a niche market until the mid 1990s. As technology evolved, costs fell, reliability improved and customers came. Today, there are more than 1.5 billion wireless subscribers, and the WiFi networking industry showed the same kind of growth. In addition, the WiFi networking industry demonstrated another thing: Wireless installation does not have to be performed by an expert. The technology is so advanced that wireless networks can be installed by an end user in one afternoon. The same thing is expected of building controls; within 10 years, wireless control networks will be the preferred installation method in commercial buildings.
With the installation of wireless networks based upon standards, like WiFi and Zigbee, the current hierarchical architecture of control systems will change. End devices such as sensors and actuators will become smarter, leaving less need for a supervisory controller. They will do onboard alarming, trending and scheduling, as well as providing a user interface. Integration between different systems will also become more commonplace. For example, a time clock will be able to tell the HVAC and lighting system when a building is empty and when it will be occupied again.
WILLIAMSON: With time, buildings will have an ever-increasing proportion of wireless-to-wired controls inside them. Just as an office has a combination of wireless hot spots and wired offices for Ethernet connectivity, there may also be some level of wired controls networks within a facility. Wireless controls will become common and will include peripheral devices such as sensors—for occupancy, door contacts, intrusion point and temperature.
Open protocols such as ASHRAE’s BACnet will adopt a wireless standard as an optional fieldbus within the standard. With wireless communications standardized for controls, it will be possible for products from multiple vendors to share a common wireless mesh network while interoperating with each other.
Between the reduced installation costs of wireless mesh control networks and the freedom of choice offered by open protocols, building owners are looking at a future where they can provide safe, comfortable and efficient indoor environments with the minimal effort and expense.
Tom Munson, RCDD, Principal
TLC Engineering for Architecture Orlando
Jay Hendrix, Manager, SBT Wireless, Buffalo Grove, Ill.
Terry Hoffman and John Ruiz, Johnson Controls, Milwaukee
Jon Williamson, Marketing Manager, TAC North Andover, Mass.
Evolution of Wireless Standards
Any new technology poses a challenge for codes and standards to keep up. And, it’s generally up to code groups and industry alliances to work as diligently as possible, while pushing biases and corporate interests aside, for the sake of building occupants.
“Unfortunately, squabbling and market positioning often stand in the way of needed products getting to market in timely fashion. Standards committees continue to struggle with when to stop tinkering and pull the trigger on ratifications,” observes Tom Munson, principal, TLC Engineering for Architecture, Orlando.
As far as what’s happening in the world of wireless controls, it appears as though the crux of standardization efforts are being spearheaded by the Institute of Electrical and Electronics Engineers and the ZigBee Alliance, a group of controls manufacturers working to promote wireless networks based upon an open global standard.
According to John Ruiz, program manager of wireless building systems at Johnson Controls, Milwaukee, “The IEEE has standardized on a low-power, moderate-bandwidth and license-free radio called 802.15.4. This standard has also been adopted by the Zigbee Alliance as part of the Zigbee 1.0 standard.”
As far as what’s on the boards, Ruiz adds, “Zigbee is adding features in version 1.1 of the standard to improve the reliability of the radio network by adding mesh networking and advanced encryption. Also at ASHRAE’s January 2006 meeting, a working group was formed to determine how to add Zigbee to the BACnet communications standard.”
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