Wireless Video: the Good, the Bad and the Ugly
Security Magazine: What do you see as wireless video advantages?
Lawrencer: The demand for increased security in schools, communities and businesses can be quickly seen by observing the extremely rapid growth of the surveillance industry around the world. To support the high demand, wireless technology is quickly becoming the preferred alternative for timely and cost effective deployment of video surveillance and security applications.
One of the greatest advantages of a wireless solution is the flexibility in camera placement. Not only is the material and labor cost of a wired infrastructure sometimes prohibitive, but it is often impossible to place wired cameras in desired locations due to right of way and other issues.
The benefits of a wireless solution are numerous, including lower overall cost, flexibility of placement, faster deployment times, dramatic savings in material and manpower costs and more efficient use of security personnel through remote monitoring and mobile distribution of video and alarms, to name a few.
Security Magazine: But there are challenges.
Lawrencer: Unfortunately, while wireless solutions are an obvious choice, there are also numerous challenges with video over traditional wireless networks. To better understand some of the more important issues, here’s a quick educational lesson.
Take a look at how video is transported across a typical wireless network: First, the camera’s image is converted into digital signals which are then encoded into a series of Internet Protocol (IP) packets and sent out over the network as a data stream. At the destination, the receiver re-assembles these packets back into the original video stream. The reconstructed video can then be viewed, stored, searched, replayed, or retransmitted to virtually any location anywhere in the world.
This sounds simple, but IP video is a totally new area with significant technological and integration challenges.
Video requires large amounts of bandwidth, as well as highly reliable, predictable delivery mechanisms. Unfortunately, typical wireless networks are not designed to provide this level of service and video packets are frequently dropped during transmission mostly because of interference from other radio frequency sources operating in the area and other uncontrollable factors. Unmanaged, this causes phenomena known as latency and jitter, which is seen as frozen, jerky or pixilated video on the viewing screen. In many wireless networks a 20-40 percent packet loss is not uncommon. This is clearly unacceptable for commercial video surveillance applications.
Security Magazine: What are the implications for wireless networks?
Lawrencer: The lousy nature of the 802.11 (and other wireless technologies) amplifies the effects of these factors. We have seen that the challenges in deploying video over wireless networks stem mainly from issues related to interference and link quality.
To overcome some of these challenges, wireless manufacturers have introduced a variety of solutions designed to mitigate the effects of link quality and interference. One common approach is simply to employ highly directional antennas between the sender and receiver. The idea is that by limiting the “beam width” of the radio signal, there will be less interference from other sources. While this is true, this approach also limits the flexibility of placement of the transmitter/receiver which may increase the cost and negate some of the other benefits of wireless networks.
There are also some changes in 802.11 (WiFi) technology that are designed to overcome these issues. 802.11n, for example, uses multiple antennas in an attempt to route the wireless signal around potential problem areas. Other approaches include configurable quality of service parameters which enable the user to establish different service levels for different types of traffic on the wireless network. On the surface, this sounds like a good solution; however, since most of the packet loss problems are caused by interference, simply assigning a higher priority to video traffic often results in transporting a lossy video stream before other traffic is sent.
The result is still poor quality video at the receiver. Overall, these technologies actually do little to improve the situation in a typical commercial outdoor wireless surveillance environment.
Security Magazine: And your conclusions?
Lawrencer: Wireless video surveillance is getting tremendous attention in the physical security world because of its lower cost, rapid deployment and flexibility. Yet, as seen, high quality full motion video delivery over ordinary wireless is a complicated problem because of dramatic and frequent changes in the quality of the underlying wireless channel. In order to gain the most benefit from wireless video surveillance, we must find new, innovative solutions that improve the reliability of video delivery, without increasing the cost and complexity of the system or requiring proprietary, incompatible technology.