Darwins Wireless Mesh CCTV System Evolves

DARWIN’S street camera project required Security & Technology Services to integrate 47 existing CCTV cameras deployed at hotspots – mass passenger transport systems as well as bus interchanges – with 62 new IndigoVision 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 fibre optic cable, STS needed a highly reliable wireless network to allow NT Police personnel to monitor the 109 cameras, control them remotely and record high-resolution vision of any incidents that are of a quality fit for use in a court for prosecution purposes.

Major challenges of transmitting high definition video streams from the cameras to 3 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 highly redundant, high performance wireless network to integrate the Darwin Street Camera system. STS also deployed an optical fibre ring network to augment the system’s high-capacity 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 best self-healing network architecture for the Darwin Street Camera project, which covers a total of 6 square kilometres.

MIMP selected network equipment from Strix Systems, a US-based global leader in wireless mesh networking. Strix Systems exclusive distributor, Wireless Tech (Australia) supported MIMP with pre sales engineering design support in the project. The Strix Access/One 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 optimise 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 rich 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 multi-subnet architecture to route video data streams over diverse data paths via multiple subnetworks. This design effectively created three standalone mesh networks with a fibre backbone.

MIMP general manager Allan Aitchison said the multicast mesh structure gave the Darwin wireless network both resilience and redundancy. “To our knowledge, this is the first multicast mesh network in Australia,” he said.

“A multicast mesh network provides the richest connectivity and is very robust, because it self-heals if devices disappear off the network. 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.”

Aitchison said the Strix equipment also handled the demanding Darwin environment including heat, humidity, lightning and vandalism. “Strix equipment is in the highest category for handling lightning strikes,” he said.

“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.”

MIMP designed, configured and tested the network at its Adelaide head office before sending it to Darwin where it was installed by STS. MIMP technicians then commissioned the network, which went live in December 2009.

Installation of the CCTV system was funded under the Territory Government’s Anti-social Behaviour Initiative and the Australian Government’s Safer Suburbs Plan. As well as the MIMP-designed multicast mesh multi subnet network, STS chose an IP-based camera system from Scottish IP video security specialist IndigoVision.

The CCTV system is operated by a dedicated police monitoring team located in a real-time CCTV control room at the Joint Emergency Services Communications Centre 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, 7 days a week. Each day, the 109 cameras deliver hundreds of gigabytes of new vision for storage at 2 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.

NT Police CCTV Project Administrator Shane Moten said the CCTV network had assisted police to more proactively manage and reduce anti-social behaviour on the streets of Darwin.

“Since the system has been live, we have generated hundreds of additional incidents that we might otherwise have missed,” Moten said.

“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 more experienced with identifying developing problems, they are able to proactively look for certain things at hotspots for anti-social behaviour and alert police to intervene before a situation becomes bigger.”

STS Managing Director Greg Ireland said the MIMP multicast mesh network had been a critical part of the CCTV system’s success.

“The NT Police are very happy with the system,” Ireland said. “The CCTV system has proved to be very user-friendly. It also provides police with high quality images that they have been able to use to reduce anti-social behaviour and improve community safety.

“We chose MIMP based on their previous experience and the fact that they’d delivered similar projects elsewhere. We had good feedback on the reputation of their company. While it’s fair to say you always have some teething problems, MIMP’s commitment to solving those problems has been very good.

“We also chose MIMP for a similar project in Alice Springs, which says a lot about what we think of them.”