Home automation systems usually reside on standard communication protocols. The most used standards are EHS, BATIBUS, EIB, KNX (for the European market) LONTALK, HAVI, CEBUS, X-10 (for the American one) and HBS (Japan). Those standards were the results of the efforts of several companies that joined together for defining some common rules for letting their devices communicate with each other.
EIB (European Installation Bus) is a protocol developed by a group of companies called EIBA (European Installation Bus Association). EIB is an open standard and it can be implemented on the telephone line, electricity, Ethernet, IR or radio waves. It follows the seven layers of the OSI model.
EHS (European Home System) developed EHSA (European Home System Association) derives from the European project ESPRIT (European Strategy Program for Research & Development in Information Technologies) were experts from several companies, with government collaboration, define the way that electrical devices can communicate between them, using every kind of media available. It’s an open standard that requires a product certification.
A system implemented with the EHS standard can manage millions of devices and offers Plug & Play functionalities. It also has a service developed for granted the system’s strength versus communication errors and faulty devices.
BatiBus is an open standard developed by BatiBus Club International that uses the telephone line as the transmission medium. It supports several network topologies: star, ring, bus, tree as well as their combinations. The telephone line permits data and command transits between CPUs, sensors and actuators.
The Konnex Association is a result of a union of three distinctive associations: BCI (BatiBus Club International), EHSA (European Home System Association), EIBA (European Installation Bus Association). The aim is to spread the knowledge and the adoption of the Konnex (KNX) protocol as a unique standard for home (and building) automation applications.
KNX is an integrated solution based on the EIB standard that integrates the configuration mode and the transmission media of BatiBus and EHS. It is a distributed system where the computation resides on each single device.
X-10 is a historic home automation standard, introduced in 1976 in the USA. It gained a large diffusion in Europe too and, thanks to the numerous devices available in the market, it maintains a good position in the collection of home automation systems.
It’s made of a central entity that sends commands to the peripheral devices using conveyed waves on the power line for data transmission, thus providing a great reduction of costs. The commands transmission takes place by sending pulses from a control panel. It is possible to connect up to 256 devices and to send commands to several devices simply assigning them the same address. However, it can happen to have communication difficulties due to noise on the electric network. This is usually solved by placing some filters by the devices that are causing noise.
A market research showed that X-10 compatible products could be found in over 10 millions houses in the USA, and this thanks to the advantages that they have compared to the competitors:
- Low cost (due to the use of existing wires)
- Easy of installation
- Amount of compatible products
- Standard’s longevity
CEBus stands for Consumer Electronics Bus and was developed in 1984 in the USA by EIA (Electronic Industries Association) with the initial purpose of standardizing the infrared signaling used for the remote control of devices, for avoiding incompatibilities issues and interferences. This effort grew into the development of the CEBus standard for home automation.
The characteristics of this standard, aside from the flexibility and the relatively low cost, are:
- Possibility to introduce automation in preexisting houses
- Usage of a distributed communication strategy so as not to necessitate a central controller
- Possibility to add devices to the network without interrupting its functioning, requiring a minimum configuration by the user
The CEBus standard defines several communications media:
- Electric power line
- Twisted-pair wires
- Coaxial cable
- Infrared signals
- Radio frequency signals
- Fiber optics
- Audio-Video bus
With this variety of transmitting media it’s possible, as an example, let the devices communicate to each other by the powerline (without any new wire), while using IR or radio signals to communicate with a remote controller. Of course this versatility permits to utilize the protocol in already existing houses.
The LonTalk protocol was developed in 1988 by Echelon. The network operates thanks to the Neuron Chip, a component realized to provide control functionalities to low cost devices. This chip has the ability of communicate and run applications. The standard main characteristics are:
- Transmitting media independence
- Possibility to support 32.385 devices
- Direct, broadcast or group communication
- Minimization of installation and management costs
- Ability to easily reconfigure the links between the devices
HAVi stands for Home Audio/Video Interoperability, and its purpose is to define an architecture for the interconnection of audio and video home devices.
In the 1998, the HAVi consortium published the standard’s specifications, describing how the future electronic devices could communicate to each other trough a network. The main characteristics of this protocol are the ability for the devices to interact between them and the manufacturer’s interoperability. Within a HAVi network is possible to exchange high quality audio and video, having a wide band available.
In a HAVi network there’s no central controller: every device is designed to control and be controlled by the other devices, regardless of its position.
Jini is an interconnection technology presented by Sun in the 1999. The main purpose of a Jini based system is to join together users’ groups and resources (hardware peripherals and software applications) in a house.
A Jini system is composed by:
- A set of components that provide an infrastructure to connect the services in a distributed system
- A programmable model that supports the production
- A set of services
A Jini system aims to:
- Let a user to share services and resources in the network
- Provide an easy access to resources to the user, wherever he is
- Simplify the building management, and the modification of the peripherals, software and users network
In general, the devices in a Jini network are equipped with memory and a CPU. It is possible, however, to connect devices without these characteristics if other devices will control them.
Ethernet is the default local-area network (LAN) technology for PCs and perhaps the most widespread and well-known LAN technology used in corporate and enterprise networks. Its installation and configuration are simple and familiar, and it was expected to play an important role in home networking, before the advent of Wi-Fi. Ethernet is a good example of a technology with “new wiring” requirements: tough some houses could already have Ethernet cables, they are probably not enough for controlling several devices, so some wiring is still required.
Bluetooth is intended to serve as a universal low-cost, user-friendly, air interface that can replace the plethora of proprietary interconnect cables between a variety of personal devices. Bluetooth is a short-range (10 cm to 10 m) frequency-hopping wireless system providing up to 1 Mbit/s in the unlicensed 2.4 GHz band. The Bluetooth wireless technology supports both point-to-point and point-to-multipoint connections. Currently up to 7 slave devices can communicate with a master radio in one device by forming a “piconet”. Several piconets can be linked together in an ad hoc networking mode; this allows extremely flexible configurations to be established such as might be required for meetings and conferences. Of course the low bandwidth capability permits only limited and dedicated usage, and prevents Bluetooth being used for in-house multimedia networking.
Z-Wave is a radio technology realized by ZenSys AS. The purpose of this technology is to realize wireless networks in a home environment, but to access the specifications a subscription to the Z-Wave Alliance is needed. The Z-Wave solution by ZenSys is optimized for the energetic consumption but shows several limitations in respect of the network scalability (maximum 200 devices), the limited data rate (9600 bit/s) and the poor predisposition of its protocol stack for industrial environments. The average transmitted packets payload length is below 10 bytes, while it uses the UHF band. Z-Wave’s chips are product directly by ZenSys. That’s why, in contrast to other technologies, Z-Wave can’t be considered a real standard: the devices’ interoperability is granted by the presence of a unique chipmaker rather than by the realization of a technological standard.
ZigBee is a radio frequency communications standard based on IEEE 802.15.4. The ZigBee coordinator is responsible for creating and maintaining the network. Each electronic device (i.e. Washing Machine, Television, Lamp etc.) in the system is a ZigBee device managed by the coordinator. All communication between devices propagates through the coordinator to the destination device. The wireless nature of ZigBee helps overcome the intrusive installation problem with the existing home automation systems identified earlier. The ZigBee standard theoretically provides 250kbps data rate, and as 40kbps can meet the requirements of most control systems, it is sufficient for controlling most home automation devices. The low installation and running cost offered by ZigBee helps tackle the expensive and complex architecture problems with existing home automation systems.