Pitfalls of Mesh: Bandwidth Issues
The radio bandwidth of the mesh transmitters is usually a couple of megabytes. The integrator and end-user need to look at the expected frame rate and quality of the video to be sent back to the central station for recording. An experienced system integrator can look at the bandwidth of the system to see if it can work. It is really a mathematical equation — how large is the pipeline and how much bandwidth do you need to accomplish your goals.
Which can lead to one of the hottest products on the market today — megapixel cameras. These cameras are designed to provide the highest level of resolution for live and forensic review. But they are bandwidth hogs and as such may not be suitable for use in most wireless mesh network installations.
“The number of cameras an end-user may want to add to a system could be limited by the nature of a mesh network,” says Jim Coleman, president of Operational Security Systems in Atlanta.
“Bandwidth limits mean that the number of cameras cannot be increased exponentially,” Coleman adds. “So when an end-user wants to add a camera here and a camera there, that changes all those mathematical equations that were worked out to start the project. You just can’t keep adding cameras without affecting performance.”
Another bandwidth problem may result from the crowded radio spectrum in many cities. Seth Ferrier, of Salt Lake City-based Alpha Security, says that became a problem with a system the company installed for the city of Sandy, Utah.
Alpha installed a 14-camera system using the public safety network on the 4.9-gigahertz spectrum. But the population of other frequencies in the locations where Alpha had installed antennas was so heavy that Ferrier was limited in what frequencies he was able to select for the city. “Within the certain range, we were limited to the number of channels and bandwidth accordingly,” Ferrier says. “So we had some hurdles to overcome there.”
Koorsen’s Powell agrees with Ferrier that that crowded airwaves can be a serious problem for an end-user wanting to transmit video over a wireless mesh network. “In Indianapolis, we have the city police, state police, the FBI — everybody and his brother making demands on the available frequencies,” he says. “There are a lot of people using those same frequencies, and in a lot of cases, there is so much traffic that our systems can almost die on us.”
Looking at some of the potential problems, it may seem as though transmitting video via a wireless mesh network is not worth the trouble and expense. But there are some tremendous advantages that make it a valuable security tool.
Ferrier says that Alpha Security had a Utah light rail customer that put off installing a security camera system along its entire line when a cost estimate for fiber transmission reached $10 million. When Alpha estimated a wireless mesh system could be installed for one-tenth the cost, the project won approval.
Here is a hypothetical example: If a city wanted to install a 30-camera public safety camera system over a 30-block area, the cost and inconvenience of trenching for a fiber backbone would likely be prohibitive. A wireless mesh system would be not only less costly, but also less disruptive to traffic.
These examples are not meant to imply that a wireless mesh network will always be significantly less expensive than a system with a fiber backbone; but, as Powell notes, there are some projects — such as a security system for an Ohio racetrack that his company recently completed — where getting a signal from certain locations to a central station is impossible by fiber or a point-to-point wireless system. Only a wireless mesh network will work.
Unlike a point-to-point wireless system, a mesh network offers redundancy. If one node fails, the others still communicate directly or though intermediate nodes so that the video transmission continues uninterrupted. And it is important that the redundancy continues to the backhaul — the radio that sends the signal from the network to the central station. A mesh network should be designed with multiple connection paths back to the recorder. That way, should one backhaul fail or be tampered with, the system will continue to transmit vital video and/or other data.
Another major advantage of a wireless mesh network is its ability to add mobile cameras to meet immediate needs. A public safety or corporate security department can take its mobile command center to the site of an emergency, access the network and begin sending video to the central station within minutes.
Getting it Installed
When it comes to choosing a provider to design and install a wireless mesh network for video, there are two different ways to go, according to Coleman. “Folks that are in the networking and infrastructure businesses have been putting these things in for a while,” he says. “They look at life as just providing a communications path from points A to B. What (system integrators) are doing is utilizing that technology to help provide solutions that are security solutions. We are going to have a whole area of expertise that has to do with security that an infrastructure business is not going to necessarily have.”
Wireless mesh is not always the right answer for all situations. You put fiber inside a building where you need high bandwidth; but, if you have remote locations where cabling is too expensive or just impossible, then wireless mesh is the way to go. It is not a matter of going with the latest technology to future-proof your installation. It has to do with each individual application.
Look for hybrid systems — those blending fiber and wireless mesh networks — to be a very common way for government and corporate organizations to move video from the camera to the recorder in the near future. Also, look for the number of wireless mesh networks to continue to grow.
Rick Allan is the IT director of Burnsville, Minn.-based VTI Security, which also operates offices in Colorado and Wisconsin. VTI is also a member of Security-Net, a network of 24 leading independent international system integrators providing clients with a single source for all electronic security needs. The group serves clients in commercial, industrial, education, government, financial and public sector facilities across North America, the United Kingdom, Brazil, Japan, Australia and the Dominican Republic. For more information, visit the Security-Net Website at www.securty-net.com.