Technical information

1393/10/17 14:43

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Introduction to Power over Ethernet (PoE)

• Power over Ethernet or PoE technology describes a system to safely transfer electrical power, along with data, to remote devices over standard data cables in an Ethernet network (Cat3/Cat5/Cat5e/Cat6 ).

• The original IEEE 802.3af-2003 standard version of PoE supplies up to 15.4 W of DC power (minimum 44 VDC and 350 mA) to each device. Only 12.95 W is assured to be available at the powered device (PD) as some power is dissipated in the cable.

• No effect on network performance of 10/100/1000 Mbps links to the PD.

• Power is remotely supplied from a central location (e.g. wiring closet) for distances under 100 meters without the Ethernet devices having to be individually powered by an AC outlet.

• PDs include IP Phones, Wireless LAN Access Points, IP Security Cameras and various other network devices

• IEEE 802.3af-2003 standard specifies Power over Ethernet (PoE) technology in two different methodologies:

   – Power-Supplying Equipment (PSE) may use either End-Span or Mid-          Span

   – Powered devices (PD’s) accept power from either type of power                 source

• Over 70 million PoE PSE ports shipped in 2008

PoE Key Benefits

• Installation Cost Savings

    – Eliminates the need for electrical outlet installation

    – Dramatically reduces cost of deployment – savings up to $1,000 per          PD

    – No need for bulky AC power adaptors

• Simplifies Installation

   – Uses a single Cat5/5e/6 cable for both data and power

• Centralized Power Backup

   – Continuous operation during power interruptions

• Centralized Power Management

   – Devices can be remotely powered down during periods of low usage or for security purposes

• SAFE Power

   – Will not damage Non-PoE devices or legacy peripherals



PoE Switch = PSE End-Span

Power Originating from an End-Span

(Ethernet Switch)

End-Span technology -Power originates from a powered port on an Ethernet Switch and is super-imposed on data transmission wire pairs 1,2,3, and 6


Switch + PoE Injector = PSE Mid-Span



Power Originating from an External

Mid-Span Device



Power over Ethernet PDs




Splitters for PoE

Active PoE Splitters allow PoE power on non-PoE devices



PoE Splitters Application Example



IEEE802.3af Distance Limitations



PoE Market Size

Projected 25+% growth rates for PDs and PSEs



Market and Competitive Analysis

• Ethernet Switch Ports: This report estimates that global shipments of PoE-enabled ports in enterprise switches are expected to reach over 132 million ports in 2012. By 2012, PoE ports will represent one quarter of all enterprise Ethernet ports.

• Mid-Spans:. Mid-Span shipments will be healthy over the next several years as people who have not yet deployed PoE or PoEPlus switches will still want to take advantage of PoE benefits without having to purchase new switch gear.

• PDs: In 2007, shipments of PoE-enabled business IP phones exceeded 10 million units. VDC expects shipments of enterprise wireless LAN access points to grow to 11.2 million units in 2012.

• PoE Controllers: There are only two vendors who have any significant market share of PSE controllers, Linear Technology and

Microsemi. The PD controller market is a bit more fragmented, with several companies having significant market share in 2007.

PoE Original Standard (802.3af-2003)

• IEEE802.3af (15.4W/port)

  – Approved in 2003 for PDs up to 12.95W (350mA) at 48V DC

  – PoE requires handshake before applying power

  – Power Sourcing Equipment (PSE) transmits power over 2 pairs (4 of 8       wires) on Cat5/5e/6 cable

   – Connect/disconnect protocol for applying/disconnecting power

• Detect device that needs power

• Determines power needed

• When to turn on power

• Detect device disconnect (AC and DC disconnect)

• When to remove power

   – Physical layer mechanism for PSE’s to characterize power demand of        individual PD’s and thus manage power delivered per port.

The Ultimate PoE Vision

PoE Powered Notebooks, Netbooks,Thin Clients and Kiosk PoE at Every Conference Room, Hotel Room & Home


The PoE Challenge

Engineers created this Power over Ethernet Shaver!

What PoE Device can  you Design?

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