Fig. 1 Communication over power-line grid
The standards and technologies used in the PLC
control schemes include X10 [8], CEBus [9], LonWorks
[10, 11], Insteon [12, 13], HomePlug [14, 15], and some
others. They are described as follows:
1. X10 was developed in 1975 by Pico Electronics [8], is
an international and open industry standard for
communication among electronic devices used for
home automation. In the X-10 protocol, transmissions
are synchronized with the zero-crossings on the AC
power-line. A binary ‘1’ is represented by a 1mS long
burst of 120 KHz, near the zero-crossing point of the
AC. A binary ‘0’ is represented by the lack of the 120
KHz burst (fig. 2). The X10 protocol is quite slow,
data rates are around 20 bits/s, so it takes roughly 3/4
second to transmit a device address and a command. It
lacks also the support for encryption, and can only
address 256 devices.
Fig. 2 Data format of X10 signal.
2. CEBus (Consumer Electronics Bus) also known as
EIA-600, was released in September 1992 by the
Electronic Industries Alliance (EIA) [9], is a set of
electrical standards and communication protocols for
electronic devices to transmit commands and data. It
is suitable for devices in households and offices to use,
and might be useful for utility interface and light
industrial applications.
The CEBus standard uses spread spectrum modulation
on the power line. A binary ‘1’ is represented by a
100 microseconds long burst, and a binary ‘0’ is
represented by the absence of burst that lasts 200
microseconds, the average data rate is about 7,500
bits/s.
CEBus supports a flexible topology, thus a device
may be located wherever convenient, and the control
is distributed among the CEBus appliances and media
routers (fig 3).
Fig. 3 Example of CEBus topology [9]
3. LonWorks is a networking platform specifically
created to address the needs of automation control in
industrial, home, transportation, and buildings systems
such as lighting and HVAC. The platform is built on
a protocol LonTalk created by Echelon in 1999, and is
defined by ANSI Standard ANSI/CEA 709.1 [10, 11].
The LonWorks is an open, but proprietary technology
and is not subject to use power line as media
.
C
ommunication between devices may be either
peer-to-peer (distributed control) or master-slave
(centralized control) (fig. 4).
Fig. 4 Example of LonWorks network
4. INSTEON is a dual-mesh RF & power line home
automation networking technology designed by
SmartLabs technology in 2005 [12, 13]. This
technology was designed specifically to address the
inherent limitations in the X10 standard but also to
incorporate backward compatibility with X10. Under
the network topology, all Insteon devices are peers,
meaning each device can transmit, receive, and repeat
any message without requiring a master controller or
routing software (fig. 5). The data rate is up to 13,165
bits/s on wire and 38,400 bits/s on air.
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