MIMP Wireless Network Connects Australian City Surveillance System

In 2009, the Northern Territory Government and the Australian Government committed US$8.612 million to establish a surveillance system to equip NT Police to monitor and reduce antisocial behavior on the streets of Darwin.

After a competitive tender, the NT Police Fire and Emergency Services Department chose Darwin-based security company Security & Technology Services (STS) to deliver the project.

The Darwin Street Camera project required STS to integrate 47 existing surveillance cameras deployed at “hotspots”, mass passenger transport systems as well as bus interchanges, with 62 new PTZ cameras. These cameras are installed at popular congregation points at Casuarina, Palmerston and Darwin.

Due to the prohibitive cost of connecting all the cameras with fiber optic cable, STS needed a wireless network to allow NT Police personnel to monitor the 109 cameras, control them remotely and record vision of any incidents that are of a quality fit for use in a court for prosecution purposes.

Major challenges of transmitting HD video streams from the cameras to three police stations, plus a fourth remote storage facility, were to avoid network congestion from the large volume of data traffic and to eliminate the risk caused by single points of failure.

The demanding Top End environment delivered difficulties including high year-round heat and humidity plus thousands of lightning strikes a day during the turbulent Wet Season. Another issue was vandalism.

STS selected Australian network specialist MIMP connecting solutions to design and deliver the redundant, wireless network to integrate the Darwin Street Camera system. STS also deployed an optical fiber ring network to augment the system's wireless backhaul.

To meet the demanding Darwin climate and operational challenges, MIMP decided the wireless network needed to be self-healing, so it would keep working if part of the network went offline.

MIMP searched internationally to identify the self-healing network architecture for the Darwin Street Camera project, which covers a total of six square kilometers.

MIMP selected network equipment from Strix Systems, a US-based wireless mesh networking provider. The outdoor wireless system is a modular, in-the-field upgradable system that delivers high throughput and low latency levels.

Strix technology provides high redundancy by using a multicast mesh structure with self-healing capabilities to optimize performance and availability. Multicast mesh is a highly distributed network model where any device can accept and pass on a data packet, even if it's not on the shortest path from sender to receiver. This connectivity maintains data delivery even when devices or even parts of the network became unavailable.

With 128-bit data encryption for security, the system also uses a multisubnet architecture to route video data streams over diverse data paths via multiple subnetworks. This design effectively created three standalone mesh networks with a fiber backbone.

“The multicast mesh network provides the richest connectivity and is very robust, because it self-heals if devices disappear off the network,” said Allan Aitchison, GM of MIMP. “By designing the network so each device accepts messages, even if the device is not on the shortest path from a camera to the police station, it routes data around any disrupted areas, so there's no single point of failure. Further robustness is added by the use of multiple subnets, so the second and third subnets can continue operating even if one area goes down.”

“Lightning is a huge issue in Darwin during the wet, when there are as many as 3000 strikes a day, which all tend to hit the top of buildings. As well as lightning protection in the antenna and the equipment itself, Strix wireless units have a heat shield over the radio unit, which also protects them from vandalism,” Aitchison said.

Installation of the surveillance system was funded under the Territory Government's Antisocial Behavior Initiative and the Australian Government's Safer Suburbs Plan. As well as the MIMP-designed multicast mesh network, STS chose an IP-based camera system from Scottish IP video security specialist IndigoVision.

The surveillance system is operated by a dedicated police monitoring team located in a real-time control room at the Joint Emergency Services Communications Center in Berrimah. As well as video data being recorded at this secure remote data storage facility, surveillance capabilities are available at police stations in Casuarina, Darwin and Palmerston.

Cameras are monitored 24 hours a day, seven days a week. Each day, the 109 cameras deliver hundreds of gigabytes of new vision for storage at two locations, one of which is a central repository with 30 terabytes of data storage. Most video data is destroyed after 30 days, although some is retained as evidence for police investigations and prosecutions.

“The surveillance network had assisted police to manage and reduce antisocial behavior on the streets of Darwin,” said Shane Moten, NT Police CCTV Project Administrator. “Since the system has been live, we have generated hundreds of additional incidents that we might otherwise have missed.”

“It has helped to solve problems that range from recovering stolen property, dealing with assaults and vandalism to identifying multiple persons on different occasions with concealed weapons, which enabled us to direct police to intercept these persons before incidents occurred.”

“As the video operators become experienced with identifying developing problems, they are able to look for certain things at hotspots for antisocial behavior and alert police to intervene before a situation becomes bigger.”

“The surveillance system has proved to be very user-friendly. It also provides them with high quality images that they have been able to use to reduce antisocial behavior and improve community safety,” said Greg Ireland, MD for STS.

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