[see allso  PLCBUS Technology]

Technology in the Smart Home Service

Today it is possible to convert any existing home to a smart home, at a low cost,
without destroying any walls [Subject to electricity feeds]
and within a short period of time. The following article explains the
revolutionary technology principles and how it is possible to implement
it to serve the smart home.
By actually using this technology, any customer can install a system to
control the lighting, shutters, etc, according to his requirements.
Use of the existing electricity network for the management and control
of the smart home and for transferring communications is a field that has
developed tremendously in recent years due to the many advantages embedded
in this technology.
The choice to transmit communications on power lines is preferred over various
types of carriers and standards such as wireless communication and this is due
to a number of obvious reasons such as the simplicity of installation,
availability and accessibility to alternate voltage of 230V, high power,
relatively low cost, system reliability and high data security.
This field has been highly researched in the last few years and a number
of technologies and standards were marked as leading in the field.
At the end of the seventies, the first standard was released for a smart home
called X-10.
It used the existing electricity network for transmitting communications between
various controllers that were located in the end units and provided an answer for
controlling various consumers such lighting circuits, electrical sockets and electric
shutters, all this by using carriers on existing power lines.
This standard was in use for many years, but was characterized by several technical
problems that required a significant change in the technology.
The main problems were connected to the reliability of the system that had a success
rate of about 80-85% and with the installation of suitable filters, it was possible to
reach up to 96%.
In addition, the communication protocol of this technology is one-way and does not
enable receiving confirmation of a command that was sent to the controller,
i.e. after giving any command to a specific controller, there is no possibility
of knowing if the command actually reached the controller and if so, whether the
controller executed the required command.
Another finding that disrupted the quality of communication was connected to the fact
that the technology of the X-10 is analog and not digital.
In this method encrypting data that is modulated on power lines is less precise and
more errors are made.
Over the years, new methods were developed and improvements were entered in these
technologies.
This field has undergone a significant change and today, the technology presented
to the world has an amazing performance level, high reliability and structured data
security. This technology is called – PLC-BUS.
The PLC-BUS technology – Power Line Carrier – constitutes a huge improvement from
all aspects compared to the old-fashioned technologies that came before it.
The improvement and the innovation in this method is expressed in a number of areas,
where the main one is that it is a digital technology, which ensures us higher reliability.
One is aware that encrypting data that is modulated on an electricity network
that is executed by a receiver is much simpler and is performed much more successfully
when we deal with digital data, and indeed, the success rate of this technology is
much higher and meets our steep requirements.
Contrary to the old technologies, this technology provides success rates of about
99.95% (that is a deviation of 5 times for 10,000 operations).
Another innovation in the PLC BUS technology is the capability to transmit a two-way
communication. This innovation is extremely important especially since we are dealing
with home automation.
The significance of the two-way communications is the capability of the controller
at the end point to return an answer (Ack) to the transmitting unit and therefore,
to receive confirmation from the controller that the command was received and executed.
This capability enables us, amongst others, to keep the status of the controller at
any moment and to monitor the system status at the home in general.
So how does the method actually work?
The PLC BUS standard is a technology that uses alternate current that flows on the
power lines and is currently used in every structure.
The alternate current is based on the sinus wave, and in  the UK home electricity
network provides a voltage of about 230V at a frequency of 50Hz.
The significance of the electric current’s frequency is that every second,
50 cycles of the sinus wave are received.
The communication transmission of a specific signal in general, and the communication
transmission of the electricity network, especially, requires a carrier wave.
Without a carrier wave, it will not be possible to transmit data to the desired
distance and the signal will get lost on the way.
In order to transmit data, the PLC BUS technology modulates the data signal on the
sinus wave of the electricity network and uses it as a carrier wave, so as to transmit
the data to the desired distance and to actually reach each of the end points in the home.
The technology uses a modulation method called PPM – Pulse Position Modulation.
The data that we wish to transmit is encoded according the location of the modulated
pulse, where the location is determined according to time intervals between the
electric pulses.
In order to modulate the data on the carrier wave, pulses are used with time intervals
between them.

 

Where the modulation of each pulse appears as follows:

 

 Pulse modulation on the sinus:

 

After the single has been modulated on the sinus, a signal is received that is composed
of the carrier wave and the pulses that are composed on the sinus wave.

 

The data encoding method according to the PLC BUS protocol is based on a frame that
is found every half cycle of the sinus wave, close to the location where the wave
crosses the zero line (zero crossing).
The frame is divided into four parts where the location of the pulse in each one of
the four parts represents two bits, In this manner, in every two half cycles,
or alternatively, in every complete cycle, four bits are encoded and in every two cycles
of the sinus, 8 bits are encoded which is a communications byte.
As you may recall, the current in uk flows at a frequency of 50Hz which enables
communication at a rate of 200bps.
This rate is enough to enable the transmission of commands to the end controllers.

 

The communication frame according to the PLC BUS protocol is built of a preamble
byte that precedes the data frame and prepares the transceiver that communication is
about to be received.
Immediately following this, five bytes of header information arrive that contain data
such as the command source, network name, address of the recipient controller and the
length of data.
The content of the command is packaged in a variable number of bytes that can reach up
to 25 bytes.
The frame is supported by a checksum byte whose purpose is to detect errors.

 

In this manner, full communication is enabled with the end controllers based on the
electricity network.
The communication rate and the data encoding ability in the communication frameworks
provide the ability to implement a smart command system and automatic control actually
in every structure in which a designated infrastructure has not been previously done.
The communication method on the existing electricity network currently constitutes a real
revolution in the field of smart control systems around the world in general and
especially in the U.K.
The technology enables us to enter an existing home and in a matter of hours,
turn it from a home that controls its electricity conventionally into a home that is
completely managed by a smart automatic control system.