Challenge or Opportunity?

Wireless mesh is changing the name of the game

• By Ksenia Coffman
• Apr 01, 2010

Wireless has been in the physical security space for years, especially with point-to-point bridges. But the newcomers— especially in the field of wireless mesh—are changing the game. Will wireless be as ubiquitous for outdoor deployments as cable or fiber?

There is still skepticism in the physical security community regarding wireless as a go-to solution for security and surveillance. Will the signal be jammed? Will there be enough capacity? How difficult is it to design and install? Do you need to have specialized expertise, or even a sub-contractor, to deploy it successfully? What is hype and what is reality?

Wireless: Niche or Mainstream?

Wireless transmission is still considered “niche” by many industry watchers; however, they believe that wireless is an excellent option that is gaining acceptance among integrators and end users. The advent of multiple input/multiple output wireless mesh technology will accelerate this trend, as it delivers a fiber-equivalent throughput of up to 300 MBps with 0.9 ms latency.

The benefits of wireless are well documented. Wireless connections have a much lower cost of installation compared to trenching and digging—as low as one-tenth the cost of fixed infrastructure. End users will avoid lengthy architectural approvals and many of the disruptions associated with closing streets, re-routing traffic and unsightly construction. In indoor settings, wireless is often the solution for historic buildings where drilling and running cable would create a business disruption.

Paradoxically, wireless can be more reliable than fiber, if a network specifies redundant paths. Fiber can be cut either accidentally or maliciously.

But consider the downsides of wireless as well. Wired infrastructure has standard performance over a specified distance. On the other hand, wireless systems operate in a dynamic, changing environment, both physically—e.g., seasonal changes due to foliage or new construction— and regarding RF disruption.

Key Considerations

All wireless technologies are not the same, and extensive due diligence should be part of the technology selection process. Wireless technology is essential to a system's success, so make sure to consider the following points:

Capacity. Without sufficient bandwidth, cameras cannot deliver evidencegrade video or support video analytics. With the advent of megapixel, HD and thermal imaging cameras—all of which require up to 35 MBps per megapixel camera—a wireless network must be able to withstand increased traffic.

Multicasting. Multicasting enables video feeds to be sent to multiple destinations for simultaneous viewing and recording. Multicasting is essential for monitoring, but it can severely burden a wireless network. Many of the analog cameras, when attached to the IP network via encoders, appear to be sending multicast traffic. Even without a formal multicasting requirement, a system needs to be able to transport multicast packets without killing the throughput.

Security. Wireless technologies— point-to-point, point-to-multipoint or mesh—used for video surveillance are not cellular, nor are they Wi-Fi accessbased, so they do not expose the users to the same vulnerabilities. The most secure systems offer end-to-end encryption supporting WPA2 and WEP. In addition to encryption, encapsulation schemes also can be used to add a layer of security.

Flexibility. The technology should make it easy to gradually grow the network, as funds become available, new departments come on board or there is a need to cover new areas.

Ease of setup. This is especially critical for temporary installations, where the installer may have only a few hours to get the system in place. Even in fixed installs, the cameras often need to be repositioned as conditions change.

Multi-hop capability. This is ideal for navigating around obstructions, resulting in less dependency on wired or wireless backhaul of point-to-multipoint systems. In a city, point-to-multipoint systems may not be able to reach into the urban canyons. Look for systems that support five to 10 hops before backhaul is needed. This will lower your cost for backhaul links, fiber or dedicated point-to-point wireless.

End-to-end quality of service and traffic prioritization. This is crucial for video that is extremely sensitive to variations in latency. Excessive delay will result in the system being unresponsive to the PTZ commands, while jitter—packets arriving out of order— will cause the video to freeze or drop out. Access-point-based systems, along with mesh APs, are especially subject to these limitations.

On the business side, check for verifiable successes in the field and look at comparable deployments. Wireless often has difficulty scaling; a technology that can handle a dozen cameras may not scale up to 50. Beware of data rates listed in vendors' marketing literature. These are theoretical and, as a rule of thumb, usually translate to 30 to 50 percent of real-world throughput.

Taking Connectivity to Moving Vehicles

Real-time visibility into trains, buses and industrial machinery is a frequent customer requirement. Recorded video is fine for investigations after the fact, but many transit agencies and industrial companies are looking for real-time surveillance of unfolding situations, or the ability to know what's ahead.

One of the first large-scale wireless video surveillance deployments is Seoul Korea's subway system. After 198 people perished in the Daegu subway fire in 2003, the Seoul Metropolitan Rapid Transit Corp. began investigating realtime wireless video surveillance systems to help protect subway riders and transit workers against potential fires, accidents, thefts and other incidents. SMRT has a ridership of more than 2 million daily and involves a total of 201 subway trains at 148 stations.

The Daegu fire was caused by an arsonist who set fire to a car train that was stopped at the Jungangho station. The fire then spread to a second train that had entered the station from the opposite direction. After the incident, SMRT wanted a system that allowed train operators to have access to video of the station before entering.

The ability to stream video from a station's cameras to a monitor in a train moving at speeds of 50 mph was critical. Wireless mesh technology was the only option to transmit video to and from subway cars, as it provided seamless handoff and roaming along the fixed wireless infrastructure. The subway environment is particularly harsh for RF communications because of the refl ective metal surfaces, noise, vibrations and high voltage electric power.

A total of 1,000 mesh nodes will be deployed for all four SMRT subway lines, along with 350 cameras in the stations and 300 in the trains. The wireless infrastructure delivers 20 MBps of capacity, enabling real-time streaming video at 30 frames per second to and from the trains moving at 50 mph. In addition to providing video surveillance from the station to train operators, the network also provides video surveillance from inside the passenger trains to a monitoring center. When completed this year, it will be the world's first real-time, high-bandwidth mobile wireless video surveillance subway system, costing an estimated $60 million.

Mobile real-time video is the wave of the future for city-wide public safety, industrial sites, campus environments, mining and transportation. To maintain real-time connections between fixed and mobile nodes moving at high speeds— without dropping packets or introducing latency or jitter— only wireless mesh will fit the bill.