Video surveillance is adopting wireless transmission methods when needed; one area of strong uptake is in municipal video surveillance.
Photo credit: Image courtesy IndigoVision
One of the many benefits of IP Video surveillance technology compared with traditional analog video equipment is that digital video is compressed and streamed across standard Ethernet networks using the Internet Protocol (IP). This is exactly the same protocol as used on corporate networks and the internet. Digital video can therefore be transmitted across any broadband network connection: cable, fiber or wireless.
There are a number of wireless technologies that allow digital surveillance video to be easily transmitted across large urban areas and from remote locations. As far as the IP video system is concerned the wireless interface is transparent and is simply a replacement or extension of the standard wired IP network. Connecting to a wireless network is the same as connecting to an Ethernet switch.
Benefits of Wireless IP Video
Combining IP video surveillance with wireless networks can provide the user with a number of significant benefits:
- No cable -- eliminating the need for costly installation works.
- Less disruption -- with less cable to install, project timeframes are significantly reduced and business disruption is minimized.
- Lower transmission costs -- no expensive fixed lines required.
- Expansion and migration -- legacy surveillance systems can easily be extended using wireless IP Video and provide a cost-effective solution for migration to fully digital systems.
- Remote monitoring -- surveillance of remote locations over large distances.
- Mobile applications -- live and recorded video from remote surveillance cameras can be viewed while on the move using 3G mobile phone networks.
- Heritage protection -- in many historic buildings installation of cable is prohibited, wireless is the only alternative.
Wireless Broadband Networks
Wireless broadband typically operates in the unlicensed frequency spectrum and provides high-speed wireless internet and data network access over a wide area.
For IP video applications wireless broadband networks can be deployed in a number of configurations:
- Point-to-point, often known as an Ethernet bridge: A simple link between two networks.
- Point-to-Multipoint: This topology allows several locations to be connected to a single network.
- Mesh wide-area network: This is a communications network made up of radio nodes organized in a mesh topology. They are in effect a router network minus the cabling between nodes and they create a high-bandwidth network over a specific coverage area. Surveillance cameras with a wireless interface can be located anywhere within the mesh, allowing them to be repositioned as the environment changes or to be temporarily installed in crime hotspots around an urban area.
Different network technologies, both wired and wireless, are often deployed together to achieve very wide area coverage. Chihuahua State in Northern Mexico has deployed such a system based on distributed IP video technology. Covering nearly 100,000 square miles, Chihuahua is the largest of Mexico's states. Its capital and largest city has the same name, Chihuahua, and it includes eight other major cities. The truly distributed nature of the system allows an operator in the state capital to view video from any other city in the region from a PTZ camera that they can control. The surveillance systems in each city are deployed using point-to-multipoint wireless networks. Additionally, each city is connected to the state capital via fixed network links.
WiMAX (Worldwide Interoperability for Microwave Access) is a telecommunications technology that supports wireless broadband access over large distances as an alternative to cable and DSL. It is different from Wi-Fi, which is a shorter range system (coverage over hundreds of feet); as opposed to WiMAX that provides wide area coverage over many miles.
An example of this technology is in place at the Acuicola Marina fish farm in the Spanish Province of Castellon on the Mediterranean coast. The business offices and a warehouse are located at Burriana, two miles inland, with the fish farm facilities are sited six miles offshore. The valuable fish stock is a target for poachers and Acuicola Marina has always found it difficult to police the offshore facilities. To overcome this, they deployed an IP video system with a wireless network infrastructure consisting of a local Wi-Fi network covering the offshore facilities with a 7 Mbps WiMAX radio link back to the on-shore offices, eight miles away. As well as providing security for the fish stock it also offered them operational benefits with submersible cameras monitoring fish stocks and food distribution.
Mobile Wireless Broadband
This provides high-speed internet access through existing 3G mobile phone networks. It is an established technology that many of us use on our phones to access the internet while on the go. It can be a very powerful tool for law enforcement officers to monitor live and recorded footage from surveillance cameras on a laptop mounted in police vehicles.
This can be demonstrated by the fully integrated municipal video surveillance system that has been developed in the city of Lansing, Mich. In Lansing, the video is streamed at 30fps across various network technologies including SHDSL (single-pair high-speed digital subscriber line), fiber, mesh wireless and mobile 3G broadband. The police department has equipped 60 vehicles -- each with a laptop and with high speed mobile wireless broadband 3G technology that allows officers to view and control any camera in the system.
Satellite broadband access is an expensive communications solution, but is often the only technology available to connect remote areas. Since the data must travel approximately 20,000 miles to reach its destination, latency (or delay) can be more of an issue than with standard radio-based wireless networks. They can also be affected by weather and climatic conditions. However, where traditional network infrastructure is not available, satellite broadband can often be the only solution.
Satellite is part of a surveillance system at the Grand Canyon West Resort in Arizona, and is used to tie together disparate locations of the resort. A distributed IP video system has been deployed at multiple sites, providing an integrated surveillance solution across a wide area. Grand Canyon West is a popular tourist destination on the west side of the canyon owned and operated by the Hualapai tribe. The resort includes Skywalk, which allows visitors step out on a horseshoe-shaped glass bridge that overhangs the Grand Canyon.
Several sites, including Eagle Point (the location of the Skywalk), Guano Point, a hotel, fuel depot and airport, are all centrally monitored from the airport terminal building. The facilities are located several miles apart and are completely standalone with no cabling or infrastructure between them. All the sites are powered by their own generators, and each local IP network is interconnected using a satellite broadband network.
Wireless networks typically have far lower bandwidth than wired networks. A wired network can have an available bandwidth of up to 700 Mb/s, whereas wireless networks typically offer no more than 25 Mb/s. It is therefore paramount to minimize the amount of data transmitted across the wireless portion of the network. This can be achieved by ensuring that the IP video system deployed has the best compression available, is based on a distributed architecture and has features that ensure the minimum amount of video is transmitted at all times.
Deploying H.264-based video compression technology can make a significant difference to the performance of the wireless IP video system. This is particularly important when using increasingly popular high definition (HD) cameras with their higher resolutions and higher bit rates. The data rates from different manufacturers' cameras can vary significantly, even when comparing cameras implementing H.264. With the limited bandwidths available from wireless networks, this is an important consideration.
There are typically two different architectures used by IP video systems: centralized and distributed. A centralized architecture uses a master database usually located in the central control room or head office. A distributed architecture spreads the data around the security management system, and this model generally locates the data close to where it is produced or needed. Normally much more data is transferred across the network to the centralized video and storage servers than would be the case with a distributed system, where video workstations and network video recorders (NVRs) can be located at the edge of the network. Well-designed distributed systems reduce need for large amounts of data to travel large distances, e.g. between the central network and the edge components.
IP multicasting is an extremely powerful networking feature that allows video from the same camera to be efficiently viewed and recorded by multiple operators at the same time, with the same network bandwidth requirement as would be for a single operator. Using multicasting on a distributed system is an efficient solution for IP video systems.
Motion Detection Analytics
Real-time analytics running in the cameras at the network edge can be used to reduce the amount of video that is streamed across the wireless network. When a scene is inactive, there is no point in transmitting full-frame video. Motion detection analytics can be used to detect a change in motion in a scene and automatically modify the video output stream from low frame-rate to maximum.
Cameras on some IP video systems are capable of dual streaming, that is outputting two separate video streams at different frame-rates. Typically, this could be used to transmit a lower frame-rate stream across a wireless network, while using a full frame-rate stream for recording on a local NVR.
Often, IP video systems will have a set of tools for bandwidth management. These allocate bandwidth to each camera stream based on a pre-configured maximum available for a particular network setup. These tools would typically work on a WAN connection, not on the local network. In the case when the WAN connection is wireless, this can be a very useful tool for ensuring the available bandwidth is not exceeded and works well alongside features such as dual streaming, mentioned above.
The benefits of using wireless networks with IP video systems are clear and can sometimes be the only solution available for large or remote areas. However, the overall performance of the network -- and hence the surveillance system -- is very dependent on the performance, features and capability of the IP video system itself and the selected wireless technology.
About the author: Oliver Vellacott founded IndigoVision in 1994. He was previously a product manager with a background in intelligent camera products; he holds a degree in software engineering from Imperial College London and a PhD in electrical engineering from Edinburgh University.