Calling All Nodes
Editor / Provider: a&s International | Updated: 5/24/2011 | Article type: Tech Corner
We now live in a world where wireless technology has become a “way of life” for many. Traditionally considered a last resort in security applications, wireless transmission has come a long way in signal reliability and resilience — in some cases, it is even the only option.
“Where we're going, we don't need roads,” said Dr. Brown in the 1980s' blockbuster Back to the Future. While we are far from eliminating roads today, technology has allowed us to remove something comparable — wires.
Three key wireless topologies exist today, namely point-to-point (PtP), point-to-multipoint (PtMP) and multipoint-to-multipoint (MPtMP). The flexibility of mesh allows it to be deployed in many scenarios for complete redundancy, said Ksenia Coffman, Senior Marketing Manager at Firetide. “Some deployments start as PtMP and then are reconfigured into a mesh topology when security needs call for ubiquitous coverage later on. Some integrators deploy mesh equipment in a PtMP topology, with ‘mesh on the edges' to provide reach into remote areas.”
Where the Wires End,Life Begins
The Americas and EMEA regions' combined market for wireless infrastructure used in video surveillance was estimated to be worth around US$175 million in 2009, with an estimated growth rate of nearly 20 percent in 2010, according to IMS Research.
Wireless transmission for security is getting adopted across a broad spectrum of use cases, said Manju Mahishi
, Director of Wireless Products Strategy at Motorola Solutions. “Most notable is mass transit with trains and buses, where a wired network is not even an option, and perimeter security at large facilities, where wiring would be cost-prohibitive.”
Two of the key vertical markets with strong demand are government and public safety, Mahishi continued. “Other key markets for wireless mesh networks include manufacturing (such as petrochemical), transportation (airports, seaports) and construction (large sites/projects).”
“Three vertical markets where demand for wireless infrastructure for video is especially strong are government (city surveillance, homeland security, emergency preparedness, critical infrastructure), transportation (mass transit, railways, highway systems) and industrial (plants, construction, oil and gas, utilities),” Coffman added.
“Ease of deployment and low cost of ownership are the main advantages of using a wireless video surveillance system,” Mahishi said. “There are no disadvantages in using a wireless system if it is deployed correctly.”
For security applications, wireless transmission is often utilized in outdoor settings, where a wired infrastructure
is nonexistent, cost-prohibitive or impractical, Coffman said. “Wireless networks are also ideal for temporary installations from days (such as special events, fairs, rallies) to months (construction sites). Wireless installations are much faster and do not require major construction or cause the disruptions that fiber installations do. We've seen wireless deployed for indoor surveillance in cases where it's impossible to wire, such as monuments with historical value.”
Wireless is best suited for locations with established infrastructure such as roads, parking lots and buildings, where trenching is cost-prohibitive, added Jeremy Damato, Technical Support Manager at KBC Networks. “It's also a cost-effective solution for systems requiring remote transmission from locations that exceed standard cable limitations.”
Wireless networks for video surveillance must be reliable. A wireless mesh network typically utilizes the 802.11 standard and provides redundancy and multiple paths to ensure tolerance for failure of individual points within the network. “The advantage of wireless mesh networks is that redundant links eliminate single points of failure associated with conventional wireless networks, with multiple paths overcoming line-of-sight (LoS) issues,” Coffman said.
“Mesh systems allow for redundant paths in the event the signal is obstructed by a mobile object or if a competing device is turned on in the vicinity of the primary path,” Damato added.
Mesh networks are also designed to provide several different options, Damato continued. “Based on the radio integrated into the mesh node, the system can offer multiple frequency bands and networking parameters to better equip the system in harsh radio frequency (RF) environments. For this reason, wireless mesh systems are becoming more popular in traditional PtP environments, such as apartment complexes.”
“Today's multi-in-multi-out (MIMO, 802.11n) wireless mesh networks have already been deployed to support HD and megapixel video surveillance. One limitation compared to fiber continues to be throughput — wireless mesh is not yet capable of providing gigabit (Gbps) speeds,” Coffman said. “However, with up to 90-percent reduction in cost, this trade-off is often acceptable to our customers.”
Wireless mesh is essentially a companion technology to cellular broadband, Coffman continued. “For example, our customers build out mesh backhaul to connect the cameras (in lieu of fiber), and then use a cellular broadband technology to provide access to the feeds from the field (such as via cellular routers). So, the two technologies complement each other. To illustrate the point, wireless mesh provides 100 to 150 Mbps of user throughput per hop (essentially equaling wired Ethernet and approaching fiber). Cellular broadband, in contrast, provides an average of 5 Mbps for download and 1 or 2 Mbps for upload. Latency is also much higher in cellular broadband technologies.”
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.
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.
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.”
Depl oyment Chall enges
High-performance wireless infrastructure is not easy to design and deploy, and professional wireless equipment is a considerable investment, Coffman said. “To ensure the success of any wireless surveillance installation requires intelligent planning from the start. You must perform site surveys, for example, to determine any issues involving LoS obstructions, RF environments, distances and access to camera sites.”
Major challenges in implementing wireless mesh networks include deployment and training, Mahishi said.
Deployment often requires coordinating resources that are not under the direct control of the customer or integrator, such as public utilities, telephone, cable and private companies, Coffman said. “From a technical point of view, ensuring LoS between nodes is essential. Design work may occur in the winter months when foliage is minimal; the spring-time foliage, however, can obstruct LoS. Such issues can be dealt with by going around obstructions; some projects call for the construction of a tower or mast.”
Securing power and gaining access to camera locations can also be challenging, if the customer does not “own” the light poles or buildings where cameras are to be mounted, Coffman continued. “Solar or power generators may be required to power remote installations. When allocating budgets and finalizing network design, the provider should consider all contingencies and discuss them with the end user.”
The learning curve for deployment of a wireless mesh network is longer than general wireless apparatus, Damato added. “Previous wireless and IT management experience, as well as previous experience with a particular manufacturer's mesh system, will assist with how to properly use specific diagnostics tools.“
Mesh topologies can involve redundant path scenarios which will require configurations to eliminate loops in the communication, Damato continued. “If a mesh system manufacturer does not simplify the interface for setup, it can be more difficult to integrate the system. On the other hand, if they simplify it too much, it becomes easier to cause loops. There should be tools and diagnostics within the GUI with which a user can determine the correct route(s) for the wireless c ommu nication with in the network.”
No Interoperab ility
Currently, there is no industry stand a rd for wire less mesh networks. All mesh solutions are proprietary, and wireless gear from different providers cannot be properly integrated together, Mahishi said. “However, IEEE 802.11s is very close to being ratified by IEEE and may provide this support in the future.”
No Silver Bullet
Most of the confusion and unrealistic expectations from wireless mesh networks arise from confusion between data rate and throughput; real throughput in noisy environments; throughput as the number of mesh nodes increases; and backhaul link throughput.
“Throughput across the wireless network is a common misconception. If the node has two radios, users assume that there is 100 Mbps combined. In reality, in turbo-mode channels, each radio can independently offer up to 50 Mbps, depending on the frequency, environment and local regulations,” Damato explained.
“The specifications should be closely examined. Often, a ‘signal rate' is thought to be the throughput over the air. The signal rate refers to the speed of connection between radios, whereas the throughput is the overall pipe capacity based on specs such as the signal rate, signal strength, possible interfering sources and other environmental factors,” Damato said.
Vendors should articulate clearly real-life performance metrics under various deployment scenarios to minimize confusion for their clients and better educate end users on realistic expectations in real-life settings.