Automation of buildings without wires.
Why are wireless solutions used in buildings?
Because they offer building owners many advantages: the operation service and maintenance personnel can monitor processes in the building, wherever they are.
If a building is undergoing renovation or new construction, wireless technology can save on cabling costs and improve the performance of multiple systems using a single wireless solution.
With careful planning, a wireless system can be used to control lighting and HVAC while monitoring the building's fire and security systems. Future changes to the building, such as moving walls or remodeling, can be greatly simplified.
Network compatibility
Traditionally, the various networks in a building (wired or wireless) have been separate, each with its own hardware. For example, one network for building automation and control (LON or BACnet), another for basic IT purposes, and another for voice over IP (VoIP). Using a single network for all of these purposes would significantly reduce the cost of building and maintaining them. A wireless network with sufficient bandwidth and Quality of Service (QoS) for all applications would make this possible.
Most modern network topologies and protocols use TCP/IP. In a TCP/IP wireless network, many applications such as VoIP, video, and BACnet/IP can operate and be supported using the same network infrastructure. BACnet/MSTP and LonWorks protocols can be transformed into IP data packets and transmitted over the same wireless network. By creating a broadband wireless network, it is possible for several systems to operate simultaneously. For applications with real-time data requirements, the QoS scheme ensures that the tasks are performed.
Increasing throughput
Typically, building automation controllers operate at speeds of tens to hundreds of kbps. The main building automation protocols have the following data transfer rates: 10 Mbps for Ethernet, 156 kbps for ARCNET, up to 76.8 kbps for MS/TP, and 78 kbps – 1.25 Mbps for LonWorks. Thus, when several networks are connected together, the requirements for the system’s throughput as a whole increase several times.
Let’s consider wireless solutions
Wired building automation systems have been used for many years and have proven their reliability. Wireless solutions have only recently entered the field and have established themselves in the market due to their increased reliability and reduced costs. Today, there are many situations where wireless technology is justified and even preferable: hard-to-reach places in a building for wiring, or where wiring entails increased costs, communication between several buildings, the need for mobility. Ultimately, the economic feasibility of using a particular solution is considered, if it satisfies all technical parameters.
Conducting building inspections
A building inspection is performed to assess the coverage area and network capacity, determine the required number of routers, antenna locations and their orientation to ensure a good quality signal in all required directions of the building. A building inspection also addresses issues such as signal-to-noise ratio (SNR) and packet retransmission counter (the number of attempts to retransmit packets for successful reception). There may be areas in a building where the signal quality is strong, but interference or overlaps may prevent the radio from decoding the signal, and the number of packet retransmissions will increase.
Interference Mitigation
Wireless Local Area Network (WLAN) 802.11.b/g uses the 2.4 GHz frequency, while WLAN 802.11a uses 5 GHz. Both frequencies are open and do not require special licenses.
Interference from microwave ovens, cordless phones, satellite systems, and other radio devices, including radio-controlled lighting and nearby wireless networks, can significantly impact your network. The simplest preventative measure is to use a channel with minimal RF interference. At the MAC (media access control) layer, the standard CSMA/CA protocol helps avoid packet “collisions” by detecting them early and slowing them down before resending them.
Building Mobility – People, Walls, and Actions
One of the key benefits of a wireless system is the ability to provide mobility to people and devices, as well as the ability to reconfigure. Mesh networks (mesh networks, data networks that provide the ability to transmit information between two points along different paths) are the key to providing such mobility. People move around in a building; walls, offices, desks and equipment change their location. A wireless network design created for one environment may not be suitable for another environment due to changing RF conditions in the surrounding environment.
A mesh network can adjust itself to redistribute the changed state of a building. The technology developed by Kiyon is called «wireless host routing», which can recognize a weak client connection and find an alternative with a stronger signal, which leads to minimal delays.
RF environment inside a building
The wireless coverage area is complex and often uncontrolled inside buildings. Compared to radio transmission in open areas, where the signal strength decreases proportionally to the square of the distance traveled, the conditions of propagation of an indoor radio frequency signal are more complex and dynamic. The signal transmission loss through concrete depends on the physical properties of the fences and is usually in the range of 6 dB at 2.4 GHz. In some cases, the loss can be up to 21 dB. In addition to the loss of signal strength, interference can also occur on reception due to the geometric features of the interior.
Operation of a radio system in a closed environment is much more complex and often difficult to predict. Using more powerful transmitters is not always possible and often does not produce results. There are several techniques that an installer uses to set up a wireless network in a building — proper placement of routers and antennas, use of the appropriate type of antennas, placement of wireless devices, avoidance of metal obstacles and other factors make a successful wireless network deployment.
Security
The security mechanism is described in the 802.11 standards and is called WEP (Wired Equivalent Privacy). Although widely used, WEP is known to be vulnerable to prepared hacker attacks. A hacker's kit contains tools that allow him to crack the encrypted key and obtain data packets. To improve security in wireless systems, a new specification, 802.11i, was developed, which uses more complex encryption algorithms. It is also known as WiFi Protected Access+2 (WPA+2).
What is a mesh network?
Wireless technologies are created in various configurations and have different architectures.
For example, a hub-based network, where a wireless hub or access point serves all client devices. Another example is a mesh network, where any device on the network can communicate directly with other devices outside its own range, “hopping” through intermediary devices.
Access Points
The figure shows a classic point-to-multipoint or hub-based network architecture. In such a network infrastructure, the wireless hub is called an access point (AP), which provides control over the network and often serves as a gateway to another network, such as the Internet. Each AP requires a cable connection to the network and operates independently. APs are often used in most home networks and commercial networks based on 802.11 technology.
Multihop Mesh Network
While hub-based networks are simpler and more commonly used in home WiFi networks or access points, mesh networks have a more flexible architecture that can cover larger areas while providing greater capabilities. Mesh networks are less susceptible to outside interference, environmental conditions and provide a higher quality of service (QoS).
Multi-hop mesh network
Choosing an antenna
An alternative in industry
IEEE 802.11 access points or mesh networks are a cost-effective solution for many building automation applications, especially where high throughput is needed.
ZigBee The ZigBee standard and its underlying technology
802.15.4 was developed for personal area networks (PANs).
The maximum data transfer rate assumed by the IEEE 802.15.4 standard is 250 kbps (for North America) and lower rates for use on other continents. Since this technology consumes less power, it is suitable for various battery-powered applications (e.g. wireless sensors, light switches, thermostats, etc.).
Closed Protocols (800-900 MHz and Other Frequencies)
In general, systems operating in the low-frequency range — 800 MHz (for Europe) or 900 MHz (for the USA) — do not require licenses and provide a longer range, but at the expense of lower data transfer rates.
This technology is closed and requires support from equipment manufacturers to promote it on the market.
Antenna Usage Options Each wireless router has a whole system of antennas. The correct selection and placement of the antenna can reduce the number of routers needed. To select an antenna, you need to know: the size of the coverage area, what the building structures are made of, the height of the ceilings, internal barriers, and existing installation options.