Page 230 - Handbook of Electronic Assistive Technology

Chapter 8 • Assisted Living 219

A field bus system is a linked network of devices, sensors and actuators, all with imbed-
ded intelligence. ‘Bus’ refers to the cable used to connect the devices within the network.
The terms ‘sensors’ and ‘actuators’ refer to device types but can also be considered generi-
cally to refer to system ‘inputs’ and ‘outputs’, respectively. The local intelligence originates
from a local microprocessor and a unique physical address for each device, making it a
node within the network, and the fact that all the devices communicate more or less as
equals as they share information continuously over the network. This approach allows
environments to be monitored intensively and real-time responses to complex situations
to be made, and importantly with a high level of redundancy and consequent safety.
The technology for intelligent building control systems clearly had potential for use in a
domestic environment, and so developments in home automation followed, with a strong
focus on the high-end market. Before reviewing the development of smart home systems
it is helpful to have a contextual reference for defining the operation of such networked
systems. This is provided by the Open Systems Interconnection (OSI) reference model
(ISO standard 7498), which provides a design template for data communication standards.

ISO OSI Model of Data Transmission

For complex networks to be understood a standard way of describing how they commu-
nicate is required. The OSI model provides a hierarchic model of system communications.
It consists of seven layers, with standards defined for each layer covering areas such as
physical characteristics, the network protocol and interaction with the outside world. This
allows divergent systems to communicate freely within a layer and define ways of com-
municating across layers. Not all systems need to utilise all the layers. The model will be
referred to when describing the various systems. Standardisation is an extremely impor-
tant matter and has been a central issue within the evolution of all systems. The ability to
offer compatibility and continuity is critical to creating a viable market for an ecosystem
and in facilitating and ensuring connectivity with the wider world.

KNX

There were three primary competitor technologies within the European home automa-
tion market: BatiBus, European Home System (EHS) and European Installation Bus (EIB).
BatiBus was developed by Merkin Gerin in France and BatiBus Club International was
formed in 1989. EHS was developed by Philips, Thomson and AEG out of a European-
funded Esprit II project and the European Home System Association was formed in 1990.
The EIB was developed by a German consortium consisting of Berker, Gira, Jung, Merten
and Siemens AG, and the European Installation Bus Association was also formed in 1990.
Over time it became apparent that the existence of three major competing technologies
was hampering rather than fostering commercial development within Europe. It was rec-
ognised by the three competitor technologies that they would need to work together to
prevent technologies from outside Europe dominating the European market. This led to a
lengthy convergence process from 1996 to 2002, the outcome of this being the formation