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How Municipal WiFi Works

        Tech | Connectivity

Wireless Network Applications and Public Safety

A municipal network can provide low-cost, high-speed access to the general population. Some cities have used this to justify the expense of the network. In theory, people who are no longer spending money on a high-speed connection will be able to put that money back into the local economy.

Organizations have created wireless networks in developing nations to provide Internet access in locations where traditional networks are impossible. Some U.S. cities hope to use their networks to close the digital divide. Philadelphia, Pennsylvania plans to supplement its network with low-cost computers for low-income families. Plans also include training teen-agers to provide tech support to the people in their communities. You can find out more about these plans through Wireless Philadelphia, the nonprofit organization overseeing the network.

Free or low-cost Internet access is great, but it's only a fraction of what a municipal network can do. In rural areas, wireless networks can give farmers real-time access to security cameras and controls for irrigation and other systems. Networks can make inexpensive Voice over IP (VoIP) phone calls more practical, which can save money for people, businesses and the government. Networks can also make city workers' jobs substantially easier with applications like automated meter reading. Building, fire and restaurant inspectors can file reports without returning to the office, cutting down on their travel time. This is another way that cities can see a return on their investment in the network - they save money on travel, equipment and fees paid for existing communications networks.

Networks can also give police and firefighters remote access to security cameras, blueprints, criminal records and other necessary information. They can let officers show witnesses mug shots or "virtual line-ups" at the scene of a crime. For applications like this, American cities can apply for funding from the Department of Homeland Security.

Public Safety Most people connect to a wireless network using the 2.4 GHz band of the radio spectrum. Public safety personnel can do this as well, using secure, encrypted connections. But they also have another option -- the 4.9 GHz band of the spectrum. This band is licensed. Not just anyone can get on it, and it's for public safety use only. Putting public safety traffic into its own channel keeps it from getting bogged down during heavy use of the network. Wireless transmitters must have separate 4.9 GHz radios to use this frequency.

Public safety networks also have additional options in the radio technology they use. Motorola's Mesh Enabled Architecture (MEA®) systems originated from battlefield technology. MEA gives police officers, firefighters and others capabilities above and beyond an ordinary network.

MEA radios can create an ad-hoc network. MEA allows Multi-Hopping® -- a signal can move from user to user in the network rather than from the user to a node in the network. Each radio automatically detects the other radios, and a network automatically forms between them. The radios themselves act as routers or repeaters to pass the signal along. This means that officers with MEA-enabled radios can go into an area with no access to the rest of the network and still have access to one another. Media access control (MAC) filtering and encryption measures keep the network secure.

Vehicle-mounted modem
Vehicle-mounted modem
Photo courtesy Motorola

Imagine a town in which a tornado destroys the light poles that house the network's wireless routers. Power and phone lines fall as well. Ordinarily, this would severely limit communications. But with MEA radios, officers with vehicle-mounted modems can drive into the area and form a network with one another. Portable devices, like ruggedized laptops and PDAs, can use MEA-enabled wireless cards to communicate with the ad-hoc network. If one of these radios can connect to the ad-hoc and the mesh networks, it can form a bridge and connect the two.

MEA card
MEA card
Photo courtesy Motorola

MEA-enabled equipment has some other capabilities, too. Most wireless networks can't determine the location of a specific user within a network. This is why many experts caution consumers about placing 911 calls from WiFi phones. But MEA technology grew out of battlefield technology that allowed the military to track soldiers' locations, even if they were out of the line of site of the GPS satellites.

MEA radios can measure the length of time it takes for an officer's signal to travel to three nodes, called time of flight. It then triangulates the officer's location. This can significantly reduce the amount of time it takes for crews to find firefighters who are still in burning buildings or to zero in on injured policemen. The process works on vehicles, too.

Finally, most wireless radios can maintain a signal at speeds up to 30 or 40 miles per hour (48-64 kilometers per hour). Many of these public safety radios can transmit at speeds of up to 250 miles per hour (402 kilometers per hour). Similar systems have been used in racing to send vehicle telematics to the pit crew.

Municipal networks are so new that there's no one standard or method for creating and using them. Not every network has separate parts of the spectrum for public safety, and not every network allows public access at all. Check out the links on the next page for more information on wireless networks on related topics, as well as links to sites where you can learn about the latest network deployments.


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