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Wireless Performance by Design
Submitted by Firetide 2010/6/23

Transmission cabling can be tricky, which makes wireless video deployments attractive. Ksenia Coffman, Senior Marketing Manager for Firetide, discusses wireless mesh projects that deliver wired performance.

Transmission cabling can be tricky, which makes wireless video deployments attractive. Ksenia Coffman, Senior Marketing Manager for Firetide, discusses wireless mesh projects that deliver wired performance.

Wireless mesh networks are receiving more attention from the security industry. They allow security integrators to deploy network infrastructure where wire — cable or fiber — is either impossible or cost-prohibitive. But how do integrators achieve the performance they've come to expect from the wired networks?

This article provides tips and ideas on how to turn wireless projects into rock-solid deployments delivering wire-like performance for security applications.

Security deployments, especially in mission-critical situations, require high frame rates. Today's wireless networks based on 802.11n radios enable high throughput to support high-definition or megapixel cameras, so users don't have to settle for 5 or 10 fps. While fixed WiMAX systems deliver about 20 to 30 Mbps of capacity for the point-to-multipoint (PtMP) sector, MIMO 802.11n systems can deliver up to 300 Mbps of real-world capacity.

Law enforcement agencies require evidence-grade video for forensic investigations and prosecutions. Areas with fast motion such as intersections require 30 fps video at 4CIF resolution, even in nonlaw enforcement applications.

Unlike data applications which do not suffer from occasional delay and dropped packets, real-time streaming applications are sensitive to latency, jitter and dropped packets. If the wireless network is low performing, the resulting video will be pixelated or frozen, while excessive latency will prevent monitoring staff from operating PTZ cameras in real time. A wireless system must provide low latency, low jitter and end-to-end quality of service to make sure that delay-sensitive transmission receives priority.

Challenging Environments
Point-to-point (PtP) and PtMP systems require tall assets to place the base station in every sector of coverage. These systems will not be the right solution if the tall assets cannot be secured in sufficient quantities, such as rooftops of privately owned buildings. The same challenge applies to industrial facilities. Deploying mesh, with its ability to repeat the signal through a series of nodes, can be an alternative to constructing towers.

In dense urban environments, even with access to rooftops, the topology of urban canyons is such that you cannot achieve line-of-sight (LoS) from the rooftops to all the camera locations, which requires installers to go street level. Cities require street-level coverage with multihop, which can only be delivered by a mesh topology.

Compared to PtP and PtMP systems, mesh extends the reach of the network beyond the first hop. Wireless systems eventually run out of usable spectrum to achieve a clear LoS. At frequencies of 2.4/4.9/5 GHz, they are forced to radiate from at least one high point. This fills the airwaves with a chosen band of frequencies, which are limited.

Mesh avoids this issue by isolating the RF signal. Radios are typically mounted on street poles where the RF can be directed between buildings and trees in a given pathway back to a final destination, through a series of repeater nodes in a multihop configuration. Because the frequencies can be reused along the path, the limitations of PtP and PtMP solutions do not apply.

Cost Savings
Mesh is a superset of the available wireless topologies: PtP and PtMP. The best feature of mesh radios is that they are flexible in their configuration, whether as mesh, PtP, PtP daisy chaining (also called linear mesh) or PtMP. Having one piece of equipment not only simplifies installation and configuration, but is also great for sparing. Both are efficient and cost saving.

In an ironic but true statement, wireless mesh is sometimes not true mesh. The actual deployment topologies in the field vary greatly. Most often the end result is a "partial" mesh: some redundant links, some PtP and PtMP, and some linear mesh. An example of linear mesh would be mesh nodes strung together to reach into a neighborhoods or go alongside a key thoroughfare, which mostly used when the budget does not allow for 100 percent coverage of a given area.

Infrastructure mesh is not "Wi-Fi mesh" that went mainstream during the municipal Wi-Fi boom. With omnidirectional antennas and with an access point (AP) built in for client access, these devices were designed for low-bandwidth data.

The most advanced infrastructure for video is "infrastructure mesh." This features dual-radio IP infrastructure designed from the ground up for real-time high-bandwidth applications: voice, video and data. Trying to fit mesh APs in a video surveillance space is often a recipe for disaster. It requires many more mesh nodes in a given area, expensive wireless or wired backhaul and more complex network design.

Real-Time Mobile Video
Recorded video is fine for investigations after the fact. However, a real-time view into unfolding situations or the ability to know what's ahead is what transit agencies and industrial companies look for. Mobile real-time video is the wave of the future for city-wide public safety, industrial sites, campus environments, mining and transportation.

When applications need the ability to maintain real-time connections between fixed and mobile nodes moving at high speeds — without dropping packets and introducing latency or jitter — only wireless mesh will fit the bill. Wi-Fi access client mobility is enough to support noncritical low-bandwidth data, but is not sufficient to deliver real-time video streaming. Similarly, users cannot implement mobility with PtMP equipment, because the central command-and-control architecture does not allow for roaming. Mesh can support mobility with its distributed architecture and built-in intelligence, even for roaming across multiple meshes.

Considering Wireless?
Wireless can be as robust, secure and reliable as any wired infrastructure. For integrators, they should definitely look into wireless infrastructure or risk being outbid on a project. For end users, a properly implemented wireless system will save expense, time and headaches. The key is "properly implemented," so users should look for experienced integrators and perform due diligence on their technology of choice.

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