Powerline Networking for Surveillance Overview

Providing network connectivity to cameras in remote locations is a constant issue in the surveillance industry. Wireless gear can handle many applications, but line of sight and aesthetics may still be issues. Powerline networking has been in use for metering and SCADA applications for years, offering a potential solution without these issues. In this update, we'll examine the broadband over powerline (BPL) products of manufacturer Corinex, and their potential challenges and applications.

Product Overview

Explained simply, broadband over powerline is method of communication which allows electrical conductors to carry signal. This can be accomplished on both interior wiring, such as household circuits, and exterior wiring, such as low or medium transmission lines. The Corinex line allows for raw data rates of up to 200Mbps over these lines, and about 100Mbps usable bandwidth. The Corinex powerline system essentially consists of two components:

• Gateway: The gateway [link no longer available] is the heart of the system, containing an Ethernet input for connection to the network, as well as connections to up to three-phase power. The gateways vary in the number of adapters each may handle, as well as voltage handling capacity (in power transmission terms, low voltage refers to 400VAC and below, with medium voltage in the thousands or tens of thousands of volts). The gateway may also be used as a bridge to connect two disparate networks, or a repeater, connected inline to extend effective range. The high density gateway [link no longer available], the model most applicable to surveillance applications, has an MSRP of $479. 
• Adapter: The adapter is installed at the device location, and makes the conversion of broadband over powerline to 10/100 Ethernet. The latest model, the HD200, is a wall-mount device which plugs directly into an electrical outlet, with a pass-through socket, so the receptacle may still be used. Adapters are sold in a two-pack for $155.

The Corinex enterprise line contains some functionality that consumer adapters, such as the HomePlug-compliant devices offered by Netgear or Linksys, for example, do not. Consumer devices essentially create a "dumb" network, with all devices plugged in sharing bandwidth, without any sort of prioritization or management. The enterprise line, when configured with Corinex's PowerNet [link no longer available] management software, supports multicast, QoS, VLANs, AES encryption, and other features expected in enterprise networks. One of the key advantages of this is prioritization of specific adapters, so locations with multiple cameras may receive more bandwidth than a single-camera location.

Transmission Distances

The distance which broadband over powerline can be transmitted without repeaters varies depending on any number of variables, such as wire gauge, branches, and noise. While indoor wiring is generally in the range of 10-14AWG, the wire gauge used for exterior transmission lines can vary widely. The number of branches any given circuit takes is also a factor. On average, however, distances of up to 300 meters can be expected, dependent on the above factors.

Additional gateways can be connected in the BPL network and used as repeaters to extend these distances. Users should also be aware that signal will not pass directly through transformers, requiring a gateway to be installed on either side of the transformer to act as a bridge.

Potential Applications

Wide areas generally can't be served by BPL without numerous repeaters, due to distance limitations and the branching of transmission lines. Even with repeaters, BPL's 100Mbps speed may be insufficient for large camera networks, such as those seen in municipal surveillance. It may serve to fill out some areas where wireless is an issue, however, and be connected to wired or wireless backhaul.

Parking lots and parks may be a prime application. Powerline adapters may be able to serve many lots where typically trenching needed to occur to install copper or fiber. Wireless is often looked to for these applications, as well. Use of BPL eliminates the need to install antennas and maintain line of sight by trimming trees, which many users would prefer, aesthetically. Depending on the size of the area and circuiting of lighting, however, distances may require the use of repeaters. Especially in parks, however, if lighting is already installed, BPL may bring Ethernet to locations which have gone unserved due to cost or aesthetic constraints.

BPL's use in interior surveillance applications is more limited. Typically, cameras are not located near power outlets, as they are most often ceiling mounted or mounted much higher on walls. In open areas, such as warehouses, they may be of more use, as convenience receptacles are often located at each vertical column. This would allow the adapter to be plugged in low on the column, and only a short run of cable installed to the camera location, instead of long horizontal runs typically requiring substantial work on lifts.

Comparison to Existing Technologies

The main alternative options to the Corinex line in exterior applications are wireless and fiber. Wireless products such as the Ubiquiti NanoStation will be less costly to install, as a radio can be found online for below $70, making a link $140. Wireless also offers greater transmission distances than BPL's 300m limitations. However, if line of sight is an issue, wireless may not be an option at all. Or, if trees may be trimmed, some users may prefer not to deal with ongoing maintenance of vegetation to deal with line of sight, making BPL an option.

In general, fiber will be more expensive to install than BPL gear. While the cost of a fiber has come down in the past few years, now typically in the range of $0.60 or under for six-strand multimode cable, trenching, conduit, and electronics increase its total cost greatly. 1000' of fiber (~$600) may be competitive with a BPL link, but trenching for this distance is likely to drive cost close to or beyond $10,000, making BPL an extremely attractive option if electrical infrastructure exists.