PLC Network Characteristics
the realization of numerous short network segments within a PLC access network is the
interference between the nearby segments. Therefore, a wider frequency spectrum has
to be used and divided between network segments, which leads to the reduction of the
common network capacity such is the case in low-voltage networks with multiple PLC
The installation of the repeaters and gateways causes additional costs that can be
avoided if the network stations, conveniently positioned in the network, also take the
repeater or gateway functional. In the extreme case, each network station can operate
simultaneously as a repeater, dividing a PLC network into very short network segments,
which significantly decreases the necessary signal power and electromagnetic radiation
(Solution proposed by the former company ONELINE, Barleben, Germany). However,
network stations with the repeater function are more complex and their application requires
a complicated management system to enable frequency or time-slot allocations within a
PLC network. Furthermore, repeater devices cause additional propagation delays because
of the processing time needed for the signal conversion. Therefore, the common number of
repeaters, as well as gateways applied to a PLC access network is expected to be limited.
3.1.3 Structure of In-home PLC Networks
As was mentioned in Sec. 2.3, there are three possibilities for realization of the PLC
· An in-home electroinstallation is used as a simple extension of the PLC transmission
medium provided by a low-voltage supply network.
· An in-home PLC network is connected via a gateway to an access network, which
can be realized not only by a PLC system but also by any other access technology
· An in-home PLC network exists as an independent system.
In the first case, the in-home electrical network is a part of a homogeneous PLC access
network. A communications signal transmitted over a low-voltage network does not end up
in the meter unit and it can also be transmitted through the in-home installation (Fig. 3.9).
In this way, the connection to the PLC access system is available in each socket within
the house. An internal electroinstallation, as an in-home part of the PLC access network,
also keeps the same physical tree topology, as is recognized within low-voltage supply
In-home PLC networks can also be connected over a gateway to any access network
(Sec. 2.3). In this case, the gateway acts as a user on the site of the access network
and as a main/base station for the in-home PLC network. If both access and in-home
networks use PLC technology, the gateway is placed within the meter unit. This is also a
point where all three current phases can be easily connected to each other, making PLC
access available in each part of the internal electroinstallation. Accordingly, this is also a
favorable place for the gateway if the access network is realized by other technology.
Independent in-home PLC networks include a base station that incorporates a master
function for the entire home PLC system. It can be assumed that the base station of an
independent in-home PLC network is also situated in the meter unit (Fig. 3.9). Independent