Since the terrorist attacks of Sept. 11, 2001, emergency communications have taken on stark importance. The need for public safety agencies — fire, police and EMS — to be able to communicate with each other has never been so important.

Better radio communication could have saved some of the 343 firefighters lost in the collapse of the World Trade Center towers, contends the Uniformed Fire Officers Association, a union representing 2,500 New York City fire captains, lieutenants and battalion chiefs. According to the union, one Fire Department of New York staff chief gave an order to evacuate the North Tower 56 minutes before the tower collapsed, and no one heard the order.

Communication confusion reigned at the Pentagon that day as well. A recent report on communications lessons learned from the Pentagon attack issued by the Public Safety Wireless Network maintains that 900 personnel representing 50 secondary agencies responding to the scene just minutes after the attack had no means of direct radio communications with first responders.

The World Trade Center and Pentagon radio anomalies are not unique. The PSWN report also estimates that across the nation, public safety officials have trouble communicating in operational situations at least one-third of the time.

However, the ability of agencies to speak to one another requires communications interoperability, the ability of disparate agencies to communicate with each other without using a dispatcher. Unfortunately, true interoperability cannot be achieved with existing technologies.

Currently public safety entities at all levels of government compete for limited radio spectrum, are hobbled by meager public safety budgets, and face challenges in keeping pace with advances in technology. Moreover, public safety officials operate separate tactical communications networks.

The good news is new communication systems have emerged that are capable of tying all public safety communication together under the same network umbrella. Now every agency — whether local, state or federal, police, fire or EMS — can operate on the same virtual radio network and communicate with each other no matter what type of radio frequency or protocol they happen to be using.

The technology changing the public safety communications landscape is Internet Protocol. With IP, true scalable, available, cost-effective interoperability is no longer a dream.

“It's unusual for a need to arise just as a cost-effective technology has evolved to address it, but that is exactly what's happened in public safety communications,” said John Vaughn, vice president and general manager of M/A-COM Wireless Systems, formerly Com-Net Ericsson, a provider of wireless communications systems for public safety agencies.

IP technology is based on the concept of packet switching. Traditional voice networks (telephony or land mobile radio) are circuit switched, which means users share an exclusive connection (a circuit or radio channel) for the duration of the conversation. With circuit switched technology, one call ties up the whole dedicated circuit.

On the other hand, packet switching information is divided into segments called packets, discrete units of data with address labels that direct them to their final destinations (end-user devices). Multiple users share access to a circuit or radio channel by taking turns placing their packets onto the channel. In the case of public safety communications, every user device on the network has an IP address (so that packets know where to travel), and calls are routed to their destinations by a combination of network hardware and software.