Wireless bridges are generally used in outdoor situations and are becoming more common in city surveillance efforts. Buildings and sites can be connected through point-to-point data links capable of high speeds and communication over long distances. Commonly used technologies include optical systems such as laser links, and radio frequency such as microwave links. For locations that are outside of the range of laser or microwave links, users have the option to connect wireless networks systems through satellite communication.
One way of using a wireless bridge is through a wireless mesh network, which is what Savannah used in its IP-based surveillance operation. A wireless mesh network offers multiple point-to-point data links creating a larger network within a well-defined area. Many cities are beginning to use wireless mesh networks as the framework for the communication networks. By establishing private wireless bridges that use radio frequency, cities have the ability to create secured wireless networks for city government use and city surveillance.
Wireless mesh technology is also easily scalable and reliable. The technology is based on nodes that transmit data to other nodes. Each wireless node is connected to the network. If one node drops out, the transmitted data is sent to the next available node and the system remains intact. Plus, additional nodes can easily be added to existing systems.
Wireless mesh systems function well in difficult environments and offer practical solutions for cities like Savannah looking for coverage in challenging environments and rough terrains. Because wireless mesh systems do not rely on existing infrastructure and the labor intensive installation of cabling through city centers, they can easily be set up for permanent and temporary surveillance efforts.
Fast and Flexible Installation
Three-months prior to the St. Patrick Day Parade, Savannah officials discussed the possibility of creating a temporary wireless surveillance installation with systems integrator NetMethods.
City leaders had partnered with the Louisiana-based company on a previous wireless network installation in a small area of town just a few months prior and experienced initial success. They wanted to continue that success and build a larger wireless system that would scale to the project at hand – and quickly as the Parade was around the corner. One-month prior to the Parade, Savannah officials approved the wireless surveillance project, and NetMethods began an accelerated planning schedule for wireless installation.
The target area for the proposed temporary wireless installation was the historic Riverfront area and its side streets. NetMethods worked with its partner, Tropos Networks, and designed a system that overlaid Axis Communications wireless network cameras on a Tropos MetroMesh network. The installation included the AXIS 232D, a network pan/tilt/zoom (PTZ) dome camera with day and night function; the AXIS 221, a fixed-view network camera with day and night function; and the AXIS 214, a PTZ network camera. The project ran on On-Net Surveillance Systems Inc. (OnSSI) software and tapped directly into the City of Savannah 's core PC servers for video management. Police officers and public safety officials were able to remotely view surveillance footage through IP-enabled laptops in squad cars or by logging on with computers to a secured connection. In addition, officials were able to quickly task employees with constant surveillance of high-traffic areas during the festival weekend.
NetMethods deployed a team to install the proposed wireless system in Savannah with less than two-weeks to go before St. Patrick's Day. When the team took a closer look at the planned camera locations, they realized that some installation points were no longer viable. For example, there were limited mounting assets and power supplies from what they originally anticipated; foliage in between camera points was much thicker than they thought; and nearby water threatened to change the way signals were received from node to node. However, because officials chose a wireless system affording greater flexibility, the team was able to find alternative options on the spot and the installation was able to proceed with minimal disruption to the original timeframe.