The endless demand of delivering greater amount of data over longer distances
will continually increase as new information technologies continue developing.
To meet this demand researchers are working on technologies that will
enable simultaneous voice and data transfer applications. The technologies
that have been available up until now usually required obtaining a separate
hardware device, as in the ISDN and xDSL technologies, to transfer voice
along with data simultaneously; moreover this application was not favorable
in local area networks (LANs).
A group of researchers tried to find answers to the question of delivering
a mix of data that travels over a local network and voice on the same
medium without requiring any rewiring of the infrastructure.
As a result of these efforts and the leading role of Cisco, "Long
Reach Ethernet (LRE)" technology, which enables the transportation
of data that travels across a local network and voice together, on any
of two wires over long distances, was achieved.
The current local area standards enable data transportation over 4 wires.
In today's new cabling applications, a cable with 8 wires is used and
this is called CAT-5 cabling. This cable transports local area data at
a distance of maximum 100 meters. However, there are some shortcomings
of this widely used standard as for the designers of network infrastructures.
Disadvantages of this standard such as the distance over which you will
transport the local area network data is limited to 100 meters, or a totally
new cabling application is necessary since it uses 4 wires etc. LRE comes
up as a technology that overcomes the shortcomings and that creates the
suitable environment to simultaneously transport analog telephone calls,
data similar to ISDN, DSL and data traveling over a local area network.
Any of the 2 wires are used with Long Reach Ethernet contrary to the
typical standard application. By simply using the existing telephone wire
infrastructure in the buildings, it is possible to bring local area network
connection to the computers of all the users -without any interference
to their telephone calls- from the same connection. Three hardware devices
are needed to install LRE system.
The first one is a device that includes two standard RJ-11 telephones
at the side of the user end and a RJ-45 ethernet port. One of the telephone
sockets will be connected to the telephone of the user, the other socket
will be connected to the telephone wire in the wall if the current telephone
infrastructure is going to be used and RJ-45 socket will be connected
to the ethernet card of the user's computer. This device delivers two
groups of data below and under 700 kHz.
The information below 700 kHz is used by analog phone calls, ISDN, DSL
and similar technologies. The information is transported, without undergoing
any changes, to the telephone connection (or to any of the 2 wires that
are used). If the information is local area network data, the device modulates
the data used in the local network above 700 kHz and transmits it to the
receiver by using the telephone line in the wall (or any of the two wires).
This process enables the transportation of both voice and local network
data simultaneously over a long distance by simply using 2 wires similar
to that of telephone wires.
The second device is a splitter that separates the voice and data that
comes from the users. It transmits the local network data to the switch,
and it directs the voice and the signals under 700 kHz to the PBX system.
Since there is no software that runs on the splitter, it does not need
any configuration or console port.
The third and last device is a switch that will process the local network
data received from the splitter. Some of the ports of the switch contain
a standard RJ-45 connector to connect other servers and switches to the
device, whereas the ports where the local network data enters contain
2 wires. The device could provide a bandwidth up to 15 Mbps to each of
its ports without sharing. In this bandwidth, LRE can also transmit POTS,
DSL and ISDN signals to the receiver in addition to its own local network
The general structure of the whole system is given in Figure-1.
Figure-1: The general structure of LRE system
The bandwidth decreases in regard to the distance when the local network
data travels over two wires. When we think of the typical UTP data lines,
which are limited to 100 meters at 10/100 Mbps bandwidth, LRE technology
changes these limits as indicated on Table-1.