Published in the May 2005 issue of Today’s Facility Manager
Like several systems, video surveillance has moved into the digital age. For many years, the standard in video surveillance has been the use of coaxial cables and fixed monitors. While these analog video systems are still in use in numerous facilities, digital video surveillance is on the rise. Furthermore, digital cameras that are part of a network enable the surveillance system to be accessed on any computer screen and transported across the computer network.
This development not only brings new functionality and flexibility to the facility manager, but it also poses quite a technical challenge. Facility managers have reported difficulties when implementing digital video surveillance systems.
Before considering these challenges, a facility manager should examine the benefits of digital video surveillance. For those not familiar with digital video systems and their differences from analog, here is a primer:
In an analog system, cameras send a signal over coaxial cable to a receiver and a multiplexer which display images on television screens. Data travels a dedicated path to the viewer. In a digital network system, cameras encode the video signal into a stream of digital packets sent through a computer network. The digital packets are then assembled at their destination and presented as a video image.
This means more cameras operate on less cable. A single CAT5 cable (a lot like a phone cable, but thicker) can handle the transmission of hundreds of times more digital video than a similar coaxial cable. As a result, the system will need fewer physical cables for the same number of cameras. The facility manager may be able to save a substantial amount on the cost of cabling on a new installation by using CAT5 instead of coaxial.
Digital video is also very flexible, because once the video image is on a computer network, it can be viewed on any computer on that network. This is possible as long as the viewing software is loaded, and the person has the proper ID and password. Using this type of system, the facility manager no longer needs to confine viewing cameras to a single desk. This gives security personnel more flexibility, even enabling users to view the imagery from any location via the Internet. Security guards can also be given tablet computers (like a laptop, but just a screen with no keyboard) with wireless LAN cards, which allows guards to walk through the facility while viewing live feeds on the tablet.
The fact that the signals in a digital network video surveillance system are sent across a computer network offers another benefit: it is sometimes possible to connect the cameras directly to the facility’s existing Local Area Network (LAN). This can be a major savings over installing new cabling, but it can also cause problems if not done correctly with enough capacity on the network.
Some facility managers have noticed that digital video signals appear jerky or sometimes seem to pause and then speed up. In these cases, the system is actually catching up, because the video signal is delayed on the network. This happens because each information packet sent through a digital network has a numerical address and is routed to the appropriate destination by the network switches and routers. Packets from many origins with different destinations mix together on the network.
Heavy loads can cause packets to be delayed. For example, opening a very large file located on a network server causes a sudden spike in traffic. The network will try to send the packets for this large file in a group, and this can cause a delay in other packets behind them. On an administrative LAN, a slight delay like this is usually not a problem, because it only lasts from between a fraction of a second to several seconds. That is okay for typical network activities like sending e-mail, but digital video is a live stream, and any interruption of the video is immediately noticeable. This is what causes the video image to be jerky or to pause and then speed up.
The best defense against this problem is to have the LAN assessed by a certified network expert (such as a Cisco CCNA certified person) who has experience in digital video. Network administrators may assert the network is capable. However, digital network video is very different from normal LAN traffic, and it is prudent to consult a LAN expert.
LAN experts use specialized traffic sensing software to determine the existing network traffic. They will track this over a period of days (or sometimes even weeks) to get an accurate sampling of the existing traffic. Then they will analyze the loads that will be introduced by the new video signals. The facility manager will need to get accurate information from camera manufacturers they are considering about the network traffic that those cameras will generate. (This is not identical for all systems; some manufacturers have built in compression that can dramatically reduce camera traffic.)
With this information, the LAN expert is able tell whether or not the network can support the increased traffic from digital video. The expert may not be able to conclude that there will be no problem at all, because he or she cannot predict exactly what users will do on the network. For instance, systems can get bogged down because employees e-mail a funny video to each other without realizing that the traffic they are creating is crippling the system.
Even if the LAN expert finds the network is not capable of supporting the additional video, the facility manager may not need to install a completely new one; there are techniques for improving speed and capacity. For example, upgrading the network switches often dramatically increases speed and capacity without having to replace cabling, which can translate to savings. In the recent past, CAT5e cable was installed in many facilities with equipment transmitting at 10 megabits per second (Mbps). By replacing network switches and routers, it is possible to increase speeds to 100 Mbps. It is also possible to increase to 1,000 Mbps, but this requires the cabling to be very tight. All terminations must be extremely well done and cabling must not be positioned too close to electrical wiring or equipment that can cause electromagnetic interference (EMI).
If facility managers find that the existing network will not support digital video, they will need to add some cabling and switches to handle the traffic. Facility managers should coordinate with their IT staff on this; very often, it makes more sense to upgrade the entire network at the same time, instead of installing a new cabling system just for video.
Facility managers have always needed to stay on top of new technologies, and digital video network surveillance is just the latest one. With proper planning, a facility manager can successfully make the transition.
Condon, a Facility Technologist and former facility manager, is a contributing author for BOMI Institute’s revised Technologies in Facility Management textbook. He works for System Development Integration, a Chicago, IL-based firm committed to improving the performance, quality, and reliability of client business through technology.