Power Over Ethernet (PoE) is a
revolutionary technology,
which had changed the way
of deploying various advanced IP
based technologies in the
premises. To name a few are VoIP
(IP-based telephony), Wireless LAN
and IP-based security systems. This
technology enables the delivery of
power over normal Ethernet
cables. The standard for PoE is
called as IEEE 802.3af which comes
in the forces in 2003. PowerDsine
had contributed more than 70 per
cent in forming this standard. To
name some of the advantages of
deploying PoE technology is, huge
cost saving, improved network
reliability, ease of deployment,
safety and compatibility.
As per the standard there are
two types of Power Sourcing
Equipment (PSE) available. One is
called as End span (Switches) and
the second is called as Midspan.
The equipment, which get
powered up with these PSEs are
called as PD (Powered Devices).
* PD - PoE-enabled TE (for
example, IP Phone, WLAN AP)
* PSE - PoE-enabled Ethernet
source:
* Endspan - PoE-enabled Ethernet
switch
* Midspan - Power injector
residing between the switch and
the PD.
The typical PDs, which are
available today are IP telephones/
wireless access points/ IP security
cameras and so on. The typical
power consumption of these
terminals is in the range of 6-12 W.
IEEE 802.3af standard which is a
ratified standard of PoE at present
can safely defined to power the
devices up to 13 W. The typical
power consumption by various
terminals can be shown as follows:
* VoIP phones 3-7 W
Get a dial tone even during power
outage. By connecting a UPS to a
Power over Ethernet midspan in
the communications room, the
entire network, including the
remotely located resources, are
capable of continuous operation
during a power outage.
* Wireless LAN access points 8-
12 W
Wireless LAN infrastructure is
dramatically simplified by
eliminating the need for separate
electrical wiring systems and
allowing wireless hubs to
be installed in previously
inaccessible locations.
* Security cameras 7-12 W
You do not need an electrician
to install AC sockets in hard to
reach places.
* Security access devices 8-12 W
* Video IP phones 10-12 W
The PoE process basically can be
divided in various parts as follows:
* PD detection is performed to
decide whether the terminal is
PoE-enabled
* PD classification determines PD’s
consumed power level prior to its
ignition
* Gradual startup to avoid data
interference of high frequencies
* Real-time protection and power
Management during operation to
ensure system safety
* PD disconnection is followed by
a fast power shutdown.
....CONTD
