Police departments and other city agencies weave web to conduct business.
An officer with the Ripon Police Department in California uses his patrol car laptop to view real-time video of a separate area of the city. The images are sent via Ripon’s mesh network system.
Law enforcement agencies are benefiting from mesh network technologies developed originally for military use. Private industry is modifying versions of these types of communications systems to allow police and other public workers to share vital information more quickly and reliably than through cellular communications. The benefits are evident. While cellular communications rely on a central tower to relay messages that can become backlogged in emergency situations, mesh networks avoid this inherent problem by employing multiple routers set up around an area that allow messages to find alternative wireless paths to recipients.
The Defense Advanced Research Projects Agency (DARPA),
Other requirements included a position location capability that was not dependent on a global positioning system (GPS), which requires line of sight to the satellites to work effectively. “They wanted to use the inherent architecture to get the relative location of every node in the network,” says Rick Rotondo, former vice president of technical marketing for MeshNetworks, which licensed the rights to market mesh network technology commercially. Motorola acquired MeshNetworks in 2004, and Rotondo is now the director of marketing for the Mesh Networks Product Group at Motorola,
Cities across the country now are purchasing products such as Motorola’s Motomesh to enhance the effectiveness of their first responders and other public workers. Motomesh creates a communications mesh over a city. Information passed via the system hops from wireless router to wireless router, unlike cellular systems’ central tower arrangement.
“The whole concept of mesh networking is this concept of hopping,” Rotondo explains. Messages transfer—or hop—among a series of routers that are set up around a city on structures with power sources. Radio signals hit the routers and the routers pass the signal along. If one router is busy, the signals can take an alternate path through different routers.
Motomesh also features intelligent access points (IAPs) that connect the wireless network back to the wired network. When Motomesh users want to access information on the Internet—to find city maps, for example—they connect to the IAPs through the routers. The use of routers extends the range of the access points, spreading coverage over a city. Using Motomesh, radio users can connect directly to one another through the routers, forming an ad hoc network, or they can connect to the Internet through the routers and an IAP.
Placing routers throughout a city moves the messages along faster than other configurations because as distance decreases, speed increases. “It actually comes down to physics,” Rotondo says. He adds that three factors influence wireless data transmission—power, distance and data rate. Developers have to work within this “iron triangle” to increase transmission speed. The Federal Communications Commission (FCC) limits the amount of power that can be sent through the air, and for any given amount of power as distance increases, the number of bits that can be sent through the air decreases. Or, the farther the signal travels from the origin, the slower its speed. So, to increase the transmission speed and stay within FCC limits, Motomesh reduces the distance each signal has to travel by using the routers to hop the signal along. “In a mesh network, we cheat a little,” Rotondo says.
By hopping the data through distributed routers, the data rate stays high end-to-end because it travels only short distances. The technique is similar to running a relay. Each runner— in the case of Motomesh, each signal—can give a strong burst of energy over a short distance to increase the total speed of the race. Runners trying to finish the race without teammates would have to pace themselves to cover the entire distance.
Mesh networks operate on broadband rates so more bits per second are sent, making downloading faster. For public workers, these downloads can include files, videos, e-mail and pictures. “Primarily in the public safety space, even in municipal broadband space, the devices you’re connecting to are PDAs and laptops,” Rotondo states.
Those devices can connect on two different bandwidths. All public workers as well as emergency services and basic services personnel can operate on the 2.4-gigahertz (GHz) band. A new band, 4.9 GHz, has been introduced for first responders only. Agencies have to apply to use this bandwidth and do not pay for the spectrum.
According to Hamilla, each router comes with four radios—two Wi-Fi and two MeshNetworks Enabled Architecture (MEA). One of each type is for use on the 4.9-GHz band, and the other is for use on the 2.4-GHz band.
Regardless of whether a first response agency uses the 4.9-GHz band, using the wireless broadband system prevents the messages from being disrupted by a backlog in the system. In a major emergency such as a natural disaster, these open communications channels will allow first responders to continue operating even if other systems experience interference from overuse.
In more common situations, installing a mesh network gives emergency and law enforcement personnel such as a police force more time on patrol and better situational awareness. For example, the city of
Ripon also has installed cameras in potential problem areas such as a local truck stop. Officers and dispatchers can monitor the activity in those areas while performing duties in other vicinities. “We have a fairly low crime rate,” Bull says. “This is just another tool to assist in keeping it low.”
A major consideration in purchasing the mesh network was officer safety, according to the chief, so the department uses the system in patrol cars. “Part of what we did was install a digital mobile vision in-car camera system that operates over our mesh wireless system,” Bull states. The system allows devices connected to the network to follow events in real time. Officers can provide backup remotely by monitoring situations such as a traffic stop via the network. While on the street, Ripon officers also can use the network to look up fingerprint records or to validate a driver’s license.
|The wireless routers in Motorola’s MeshNetworks products can be placed on any structures with access to electricity. Setting up routers around an area such as a city creates a wireless, interconnected communications tool that does not experience the backup that can occur with cellular communications.|
In addition to safety, the mesh network facilitates office administration. Incidents are recorded and sent wirelessly through the system for storage. Bull says storing records digitally saves time and space. Another advantage of the system is that it allows law enforcement personnel to file reports through the network, cutting down on time spent at headquarters and maximizing time spent on patrol. The remote filing increases officers’ productivity as well as their visibility in the community. “Anything they could do on a desktop in the police department they can do in the patrol car now,” Bull explains. “We want our police department to be highly visible and seen by the public. This is just one way to get them more street time.”
Another law enforcement application for the system partners the police with the local business community. Several banks and hardware stores in the city have installed surveillance cameras in their buildings that can be activated as an alarm. The cameras and alarm are connected to the mesh network. When the alarm is activated, a notification and video are transmitted to the dispatch center. The dispatch center staff and officers can hear and see what is going on inside the buildings. “It gives a lot of security to the people inside,” Bull says. “It gives a lot of security to our officers responding.”
One method through which the system can provide extra security to officers is by tracking people. According to Rotondo, situational commanders can determine the precise locations of their personnel. Instead of having to radio their location in to their commanders, the commanders can see these individuals and tell them to move more to the left or right, for example. “With mesh, you could actually see a dot of that person and know exactly where they were,” Rotondo says. “It’s all about situational awareness.”
Another possible use for the system is in obtaining search warrants. Officers detecting something suspicious at a crime scene such as a weapon could send video or pictures of the object to the district attorney to determine whether the threat is obvious enough to validate in court a search without a warrant. Or, the officers could take video evidence from the system with them to court. “It can change the way processes and procedures work,” Rotondo asserts. Hamilla also touts the video capability of the mesh network. “Video surveillance is a big part of crime prevention and also status and monitoring,” he says.
The variety of applications for the mesh network influenced Ripon to purchase the technology. Along with the practical uses, the integrity of the system provides the force with a benefit, too. “Our number one goal is to have a safe, secure system that in the case of an emergency, we wouldn’t have to worry about it getting overridden,” Bull states. The city has tried to compromise its own system without success. Bull says the mesh network is invisible. “We tried to hack into this system; we can’t even find it,” he explains. “We can’t even find it with regular 802.11 devices.”
According to the chief, the mesh network has advantages over the 802.11 system. Unlike that tool, which can require adjustment, the mesh network remains stable and connected. Since the city installed its system late last summer, the network has not required any tweaking. Bull says the city values not having to hire a full-time information technology employee to maintain the network.
In addition to improving police force functionality, the system improves homeland security activities such as monitoring well sites and infrastructure. The U.S. Department of Homeland Security awarded Ripon a $75,000 grant to assist with its purchase of the Motorola Mesh Network solution. Bull estimates that in two to three years the city will have a return on its investment. Ripon saves an estimated $150,000 to $200,000 a year on data storage and personnel costs using the network.
Since integrating the system into the work process, Bull has received positive feedback from his staff. “They really like it, especially the dispatchers,” he says. “It’s one thing to take a 9-1-1 call; it’s another thing to call up a camera and see what’s going on in real time.”
City officials researched the purchase of the system for two years before deciding on the Motorola product because they wanted a tool they could use daily that would allow all units to communicate on one system and that could be easily set up. In addition, they were interested in a system that they could expand after installation.
More potential uses for the network are being worked out. Bull says the police department is looking at placing license plate scanners in different areas to track stolen cars. In the public works sector, the city may develop wireless meter reading. The mesh network allows the city an opportunity to adapt the system as it needs. “It makes it very easy when you have a wireless system in place to just add another device to the system,” Bull explains.
Other capabilities for Motomesh include mine and railcar monitoring, says Hamilla. He adds that as people become accustomed to having the additional bandwidth, they will make demands for its uses. He echoes Bull’s statements about the flexibility of the product. “It’s software,” Hamilla explains. “The physical layer in the hardware is something we build right now, and where we add capability is software.”
That flexibility leaves the product open to even greater applications. Hamilla says, “I think the growth and applications are yet to come.”