Power over Ethernet in IP Based Security Applications
What is Power over Ethernet?
Power over Ethernet (PoE) is a revolutionary technology that integrates data, voice and power over standard LAN infrastructure. It is the means to supply reliable, uninterrupted power to Internet Protocol (IP) telephones, wireless LAN access points, network cameras and other Ethernet devices, using existing, commonly used Category 3 (4 pairs) and Category 5 cable infrastructure.
Power over Ethernet technology saves time and cost of installing separate power cabling, AC outlets and wall warts, as well as eliminates the need for a dedicated UPS for individual devices. The power delivered over the Ethernet infrastructure is automatically activated when a compatible terminal is identified, and blocked to legacy devices that are not compatible. This feature allows users to freely and safely mix legacy and PoE-compatible devices, on their network.
The PoE technology is to be designed in a way that does not degrade the network data communication performance or decrease the network reach.
There are two main implementations of Power over Ethernet:
- The Endspan - PoE enabled Ethernet switch. Power is supplied directly from the data ports.
- The Midspan - A patch-panel like device, residing between an ordinary Ethernet switch and the terminals, often referred to as a "Midspan". Power is added on the spare wires, with data uninterrupted.
Figure 1: Architecture of Power over Ethernet Midspan in the Enterprise
The Revolution of Ethernet Based Security Systems
A closed circuit television system (CCTV) is a television system which operates on a closed loop basis, unlike the Television at home which is a public system available to anyone with a suitable receiver. CCTV images are only available to those connected to the closed loop.
The main function of the CCTV system is to allow surveillance and remote viewing, typically from several cameras, back to one location within the same building. Usually, it is part of an overall integrated package operated by security personnel that includes access control, alarms, intrusion detection and communications.
The typical surveillance system comprises four components: camera, video network, recorder, and monitor.
Over the last 15 years, one by one, these four components have been digitized.
- Digitization of the Camera
Around 1990, digital cameras replaced analog tube cameras. These CCD cameras were partly digital, and still used analog connections of coax cable. Recording was still done to analog VCR tapes.
- Digitization of the Recording
Around 1996, the DVR's recording function become digital. No more changing tapes, recording quality was consistent and recorded event searches became much more efficient. The DVR was an analog-digital hybrid. It still had analog coax inputs and an analog output for the monitor.
- Digitization of the Monitor
The monitoring station was digitize through employing a PC. In the last few years, DVRs come equipped with a network or modem interface so that the recorded images can be monitored remotely, via monitoring software, using a standard PC.
- Digitization of the Video Network
To complete the CCTV digitization, the link from the camera to the DVR was digitized using IP Network cameras and video servers. Digital imaging, combined with networking, enables a whole new range of system-level functionality and cost efficiency.
Security systems are only useful if they can communicate and control the environment they secure. The video streaming from the CCTV system is meant to be watched and/or recorded, otherwise it is useless. Access control devices enable access to authorized personnel, while restricting others and must have a central personnel database. As such, the use of the readily available and cost effective Ethernet infrastructure was imminent.
Once end devices, such as a network camera or an access control terminal are up and connected to the Ethernet infrastructure, they still require power to run. It is here that Power over Ethernet has a role. Power over Ethernet technology enables Ethernet devices to be powered over the network-cabling infrastructure, thus avoiding the need for separate power and data cable infrastructure and costly AC outlets near cameras. This eliminates the need for licensed electricians from the installation team thereby cutting costs to the overall installation.
Network cameras are traditionally installed in open high places, such as corridor ceilings, airport or lecture halls, etc. The adding of power infrastructure was a costly and long affair, requiring dedicated electrician teams for pulling of power cables and conduits. These changes also needed to be recorded in building plans for safety approvals.
Once operating, each device was connected to a specific electrical branch, which if down, meant an appearance of unacceptable "holes" in the security coverage. By allowing the Network cameras to be installed where they are most effective and not where the AC sockets are, the actual number of cameras may also be reduced, further reducing the surveillance implementation costs.
Figure 2: Architecture of Power over Ethernet in the Enterprise
There are additional key benefits for Power over Ethernet in the Security market:
Installing a Network Video System using Power over Ethernet
- Simple Means for Resetting IP Cameras. IP Cameras, as complex devices, may need to be reset from time to time. A "dark" camera, once discovered to require a reset, forces the IT manager to locate the network camera, reach it, and then reset it. By using Power over Ethernet, resetting becomes a trivial matter, enabling reset via the camera's respective PoE port (instead of climbing up high ceiling installations).
- Easy Changes to Camera Positions as Needed. Altering a camera position, no longer requires a new AC installation. It is even possible to experiment the camera position to achieve ultimate coverage results.
- UPS Backup for the Security Network. By backing up of the Power over Ethernet Midspan in the communication room, the entire camera network can continue operation during a power outage. This is a real must for a high-end surveillance system. With PoE, the security system can be backed up with one single network.
- Assured Safety With Advanced Line Terminal Detection. Line detection is the technology, which enables safe installation without worrying about high voltage damages to laptops, desktops and other non-power ready devices, due to a misplaced connection. A faulty camera or an access control terminal can be detected and shut down preventing damage to expensive switches and patch panels in the Ethernet network. The line detection is one of the reasons the Power over LAN midspan is much more than an intelligent power source.
Network Video systems are being installed today in many different environments.
Most common among these:
- Transport terminals, Airports
- Large retail stores, Shopping malls, Casinos
- Law enforcement surveillance in public events
- Government and Security facilities CCTV
- Universities, Schools remote monitoring
There are differences in the requirements from the Surveillance system for each type of environment. For example, a Train Station installation, with a high camera count and the need for minimum maintenance, is very different from a warehouse installation, with difficult accessibility and the need for durability. This paper focuses on the approach to optimize the IP Video network with Power over Ethernet. Fortunately, most Network devices installations, in most environments, share a very similar infrastructure design.
The Ethernet lines run from the network switch, sometimes through a patch panel, out of the communication room and connect to the digital cameras and analog to digital video gateways (See Figure3). Adding Power over Ethernet enables the cameras to be powered through the same cabling infrastructure, providing the most cost effective solution.
When the switch is already installed, the simplest means to add Power over Ethernet is by adding a dedicated Power over Ethernet midspan.
Figure 3: Installing Network Video system using Power over Ethernet Midspan