A Virtual Pipe
Sufficient throughput is critical, especially with the advent of HD video. “Video surveillance requires an extensive amount of bandwidth, especially with the new megapixel and HD cameras. Without enough bandwidth, cameras cannot deliver evidentiary-grade video or support video analytics,” Coffman said.” The video security system is only as good as the network that enables the transmission from the cameras to the command center. That is why transmission can become the Achilles' heel of a project if cameras need to be deployed in areas where no networking infrastructure exists.”
“With the advent of products based on 802.11n technology, wireless transmission can achieve throughput speeds in excess of 100 Mbps and, therefore, can satisfy even the high-bandwidth requirements,” Mahishi said.
“The latest breakthrough in wireless infrastructure is MIMO-based mesh, enabling fiber-equivalent throughput over a reliable, self-healing network,” Coffmanadded . “ The high throughput (up to 300 Mbps) makes wireless mesh an ideal solution for professional security networks — from video surveillance to access control and mass notification devices,enabling extensive municipal, transportation and industrial security networks.” The high-bandwidth capabilities of a MIMO mesh make it an ideal solution for voice and video, the most bandwidth-intensive and latency-intolerant applications on the network.
Selection Criteria
The wireless technology used in a system is essential to its success; choppy or granular video caused by the network is a critical flaw when it comes to surveillance, Coffman said. “Not all wireless technologies are created equal, and extensive due diligence should be a part of any technology selection process.”
The most important criterion for choosing a wireless network should be the TCO, Mahishi said. “TCO includes cost of equipment, cost of installation and cost of maintenance. Low-power, short-range access points (APs) are generally cheaper than high-power, long-range APs, but may eventually cost more as more of them are needed to provide coverage in a given area.”
When considering IP-based or HD systems, throughput consumption should be considered. Mesh and MIMO wireless systems provide more throughput for bandwidthhungry devices like megapixel and HD video systems, Damato said. “The number of turbo-mode channels should be identified and used when throughput capacity is a key component of the wireless solution specified for a megapixel or HD streaming video project.”
“Other important criteria include support for standards; routing protocol (speed of convergence); quality-of-service support for video/ voice; support for reliable video multicast; and interference mitigation mechanisms as video is very susceptible to latency which could be introduced especially in challenging RF environments,” Mahishi said.
According to Coffman, some other key factors to evaluate are:
1.Video performance: Video applications can eat up bandwidth quickly,and any wireless infrastructure should have plenty of room to grow — even if current requirements appear limited.
2.Security and privacy of video streams: The most secure systems offer end-to-end encryption supporting WPA2 and WEP. Encapsulation schemes can also be used to add another layer of security, where only the mesh nodes can see the encapsulated packets.
3.Multiservice networks: The transmission medium must give appropriate priority and quality of service to mission-critical applications among various video, voice and alarm signals.
4.Ease of setup: Wireless negates the need to pull cable, drill holes or disrupt day-to-day operations. Unlike a PtMP system, any mesh node can act as a “head end,” allowing multiple command centers to be set up at any point on the network.
5.Multicasting: Multicasting enables video feeds to be sent to multiple destinations for simultaneous viewing and recording. Multicasting is essential for monitoring by multiple decision makers, but can minimize the impact from bandwidth requirements.
Environment First
When connecting via wireless, environmental conditions have an impact on the reliability and over-the-air throughput potential, Damato warned. “But there are several ways to maintain sufficient wireless links to help guarantee the pipe needed over the air.”
“LoS between antennae will become more critical if the distance increases.The presence of other possible interfering sources can also limit the distance transmitted or throughput gained in a wireless environment,” Damato said. “An open area should be available so that the entire Fresnel zone is free of obstructions, especially for streaming video over wireless. Clear LoS is necessary to pass the RF to obtain maximum signal strength and data rates.”
High-gain directional antennae are recommended to increase the signal strength and attempt to overcome noise. This would be similar to raising your voice to talk to someone across the room while music is playing or there are other people in the room who are also creating noise, Damato said. “Increasing the gain of the antenna can help overcome some limitations of wireless systems.”
Other options include configuring megapixel cameras to lower frame rates or other settings to reduce the overall throughput need on the mesh, Damato added. “Streaming IP video is different from standard Ethernet data packets, which consist of bursts of traffic when packets are accessed over the link. With a constant video stream with changes in the picture or the entire M-JPEG video frames, the traffic is a nonstop flow of throughput consumption with potential data bursts as well. A mesh network that can handle this form of throughput consumption is recommended for integrating a wireless mesh network for streaming video and management software.”
The availability of frequencies in a particular wireless environment should also be taken into consideration. License-free wireless transmission utilizes RFs and power output ratings allowed by the US Federal Communications Commission and other regulatory domains, Damato said. Different frequency bands are allowed for use for different industries.
However, the frequencies used for industrial, scientific and medical applications in the U.S. can also be shared by many consumer electronics, as well as commercial and industrialgrade devices, Damato cautioned. “For instance, radar technology can interfere with RF devices operating on the 5-GHz frequency band. Environments that contain signs of interfering sources and/or physical obstructions to LoS are places where wireless is the last-resort alternative, as certain requirements may be necessary to deal with the environmental restrictions.”