WiFi Here and Now

Imagine a world where all the security devices in your building can communicate with the HVAC devices, which in turn communicate with all the lighting controls, and there is not a single piece of wire between them. As you near the entrance, a motion sensor detects your presence, the system recognizes your credential, unlocks the door, and turns on the lights and HVAC.

Imagine a world where you can add security devices, lighting control modules or building automation devices without the inconvenience or cost of running wire. The office can be rearranged quickly and inexpensively. Any wireless device added will automatically become part of a wireless personal area network and can be configured from any PC on the corporate LAN.

These scenarios now exist only in our imaginations, but given the pace at which wireless technology is moving, they may be reality sooner than we think.

In the Rear View
In the mid 1980s, wireless burglar alarm systems became popular, with models like the Ademco 5700 series. They were bulky, had reduced battery life and were purpose-built for security applications, but they were pretty reliable. Door contacts, motion PIR, glass-break detectors, panic push buttons and smoke detectors also joined the wireless ranks during this time.

By the mid 1990s wireless devices had become smaller and had more battery life because of lower power consumption. Their advanced circuitry also allowed for longer transmission ranges. But the existing technology still had limitations.

Burglar alarm systems

    No compatibility between different manufacturers’ products.
  • Frequencies of transmitter and communications protocols were unique to each manufacturer, resulting in no sharing of devices.
  • No compatibility even between various versions of the same product by the same manufacturer. CCTV
  • Point-to-point wireless video transmission only.

Access control

  • Wireless card reader communications back to the field control panel limited by functionality and distance.
  • Little in two-way communications.

What did these systems offer?

  • Purpose-built receivers—Typically a burglar alarm receiver that could communicate directly with the burglar alarm panel. This receiver was powered by the panel and did not depend on self-contained batteries for its operation.
  • Purpose-built transmitters—Door contacts, motion detectors, glass break detectors, panic/hold up buttons and even smoke detectors for residential applications.
  • Built-in batteries offered long life.
  • Remote key fobs allowed for remote arming and disarming of the system.

The principal objective of wireless security was to limit the cost and increase the speed and simplicity of installation. Tom Rosback, vice president of engineering and technology for Honeywell Automation & Control Solutions, says that when Ademco (now a Honeywell subsidiary) produced its wireless burglar alarm system in the early 1990s, it reduced the average installation time from 20 hours to four hours.

You Are Here
In the past five years a plethora of sophisticated wireless solutions has hit the market. Many proprietary systems have started providing monitoring points and control outputs for other systems, making them more flexible. Some manufacturers have taken the readily available PC wireless connectivity standards 802.11.g and 802.11.n as the foundation of a more generic product range. Increasing sophistication allows for increased security of signals, encryption of data and security of devices—linking or pairing Tx with Rx and eliminating errant signals affecting security.

Access control and CCTV wireless implementations have up to now been in large measure point-to-point “wireless elimination” solutions rather than fully wireless solutions. That changed with the advent of wireless LANS, which allow for more complicated connections. New wireless technologies include:

  • Peer-to-peer or point-to-point, with network gateway access
  • Bluetooth
  • Mesh
  • ZigBee

Point-to-point communications have evolved into sophisticated service offerings. Initially most point-to-point solutions involved application-specific proprietary communications, like burglar alarm and CCTV wireless links. A number of companies have started making generic wireless input/output devices to allow for the easy transmission of alarms and controls from point “A” to point “B” without using cables. Some of these solutions include connections to gateway controllers that allow for further connection to other, more sophisticated systems.

The solutions in this area include those made by Kele Inc., which has taken the novel but sensible approach of not designing or building its own radio, but rather buying a ready-made, proven device from one of the leading vendors in the wireless/radio marketplace. Kele elected to focus its efforts on building a robust field I/O device. Transmitters have a wide range of available inputs, including temperature, 0-10v dc, 4-20 mA; and receivers have a wide range of outputs available including relay, triac, 0-10v dc, and 4-20 mA.

Kele is one of a number of companies that realized that a point-to-point wireless solution on its own has a limited market appeal, so the engineers at Kele added a flexible generic gateway device to the wireless network that can communicate in a number of readily available standards, like LonWorks, BACnet and Serial ASCII. This allows for interfacing with many of the currently available building automation and facilities management packages.

Most of the field I/O and repeaters must be AC powered, thus reducing the system flexibility. Point mapping of inputs and outputs is easy, and there is even a Palm-based portable programmer. Repeaters increase the transmission range. The advent of IEEE 802.11 wi-fi communications has expanded opportunities greatly, and with the creativity of a number of manufacturers, the original 100-meter transmission range has been expanded by 10 to 20 times. The basic system architecture allows for device-to-device communication on a PC-PC basis, but is limited in its ability to connect discreet status I/O like door contacts without a lot of additional hardware.

Initially conceived to connect cellular phones and earpieces, PDAs and printers, Bluetooth technology has matured to the point where it can be used for more demanding applications. Since most commercial solutions’ main purpose is allowing increased user mobility, ease of connectivity has been a much larger issue than security.

By using built-in security features, however, it is possible to build a secure system. Using 128- or 256-bit encryption together with 79-channel random frequency hopping (changes 1,600 times per second) and the AES III NIST encryption module, it is possible to make a secure protocol. Device authentication under these conditions is typically set with “link keys” invisible to the network.

Bluetooth’s limitations are the low power of the transmitter (100mW) and the limited number of devices that can be connected to a single access point. Both these limitations are being addressed, and with a high-gain external antenna it is now possible to transmit to more than 5km. Battery life is not normally a problem, since in most non-consumer applications the device is powered from a locally available PSU or outlet.

Early adopters of Bluetooth include IMAG Technologies Inc., which has developed a full range of Bluetooth-to-Ethernet products aimed at the access control market. Doug Stevens, vice president of sales at IMAG, said recently, “Everything can be wireless. The difficult issue is to decide which area of business to go after. ROI on development and potential sales volumes are the deciding factors.”

Mesh is one of the most exciting of the newer wireless opportunities in that it allows for a truly scalable and flexible solution. The basis of mesh technology is that although the individual transmitters are low powered, each device acts like a transmitter as well as a receiver, and the system allows the strongest transmission path to be used at all times. Every wireless point can be an input device, an output device, or a combination of both depending on its configuration.

The devices are ideal for short-range transmission applications. Applications like VAV control for HVAC in accessible ceilings and burglar alarm door monitoring work well, while remote parking lot control does not. Repeaters are not very common, since the mesh devices will always find the strongest signal. Power is typically not a problem either, since the mesh devices are normally powered off the equipment they are connected to.

Mesh networks include three classes of nodes:

  • Gateway—a single personal area network coordinator. This acts as the network controller and interface to the rest of the controlled environment.
  • Router—full-function device. This can be used to pass packets along to its final destination and may also act as an endpoint.
  • Endpoint—reduced-function device. This is designed to be the lowest cost device, does not propagate packets across the network, uses less power and monitors one or more sensors.

One of the leading contenders in the mesh networks arena is Millennial Net, which has successfully transformed some very creative ideas conceived at MIT into a market-related product offering. Tom Cunneen, vice president of sales at Millennial Net, said recently, “The limiting factor with wireless products is the decision of which solution to implement first.”

ZigBee, an emerging wireless standard, aims to provide a low-cost, low-power, high-reliability, high-security embedded wireless network based on IEEE 820.15.4, focusing on an area of connectivity not covered by other standard wireless technologies. It aspires to offer low cost (

ZigBee can be applied to such areas as lighting, HVAC, industrial process control, precision agriculture and cargo monitoring as well as security. It also works with a wide array of sensors, including temperature, pressure, contact closure, chemical gas and motion. The secret to ZigBee low power consumption is a low duty cycle and the rapid ability of the radio to “go to sleep” and “wake up” when an event occurs. A 10mW active power and 10µW standby unit with a duty cycle of 0.1% using a 750mAh AAA battery will work for 37,000 hours (four years and three months).

ZigBee adopts 128-bit AED security for all wireless communications. To prevent the loss of communication due to atmospheric conditions, metal barriers or interference from microwave generators, the 820.15.4 protocol uses direct sequence spread spectrum to transmit signals. This methodology greatly improves the signal-to-noise ratio.

ZigBee network nodes—which come in three classes, similar to Mesh nodes—operate in a number of different network configurations. Star is the simplest, mesh offers the best reliability, and cluster tree is best in large-scale networks.

Amongst the many early adopters of this technology are companies like Dust Networks, Helicomm and Senicast Systems.

A new era of wireless connectivity has begun. Our traditional approach to solving a connectivity problem is rapidly becoming outdated and difficult to justify. In many respects the personal computing industry is far more advanced in the wireless endeavor, and building automation is catching up fast. Security manufacturers should take note of what is happening with wireless technology.

Lionel Silverman, PE, is vice president of business development for Facility Robotics Inc., a nationwide systems integrator specializing in building automation and security systems for larger multi-location and prestigious clients. He is a member of IEEE and ASIS.