Linking emergency networks

The US pushes to connect its communications

Even before the terrorist attack on the US on 11 September 2001, federal, state and local public safety agencies knew they should improve their emergency communications with each other. But the need to do better was brought into sharp focus that day by the death toll among emergency workers at the World Trade Center.

The New York City police officers at the scene, equipped with emergency radios operating on one frequency, received the order to evacuate the towers when collapse looked imminent. But firefighters and other rescue personnel, using a different radio system, never got that message.

Communications interoperability is the priority
for the US government

Sixty police officers lost their lives when the towers fell but more than five times that number of firefighters were killed. If all emergency workers had been able to hear the evacuation message at the same time, that death toll might have been substantially reduced.

Communications interoperability – the ability of public safety agencies to talk with each using different radio systems – has now become a priority for state, local and federal governments. Public safety officials understand that they need to be able to talk to each other in the event of another terrorist attack, a police situation (like the sniper attacks that terrorised Washington DC area a few years ago) or natural disasters. The need for action was dramatically re-emphasised when Hurricane Katrina struck the city of New Orleans and several counties in the state of Mississippi in 2005.

State and local jurisdictions have been exploring their options and several have begun to set up systems to make interoperability possible. The US Department of Homeland Security’s Office for Interoperability and Compatibility (OIC) has even established a special program, SAFECOM, which is charged with researching, developing, testing and evaluating tools and systems to help make interoperability a reality.
 
It’s an almost overwhelming task. There are 2.5 million public safety first responders in the US, working for more than 60,000 state, local and federal departments and agencies. They use a wide variety of radio equipment, including conventional, trunked, VHF, UHF (700 and 800 MHz) systems. This equipment may be 20 to 40 years old and most often incompatible with that of nearby jurisdictions.

There are 2.5 million public safety first responders in
the US, working for more than 60,000 state, local
and federal departments and agencies

Even different agencies within a single jurisdiction (police, fire, and emergency medical services) usually have different radio systems that are incompatible. And the newer digital equipment has actually made the problem worse because it is designed with manufacturers’ proprietary spread-spectrum systems, so emergency personnel using one brand of radio can’t communicate with colleagues using another brand, even when they’re both operating on the same channel. In addition, public safety communications are spread among 10 different and often crowded frequencies.

To overcome these incompatibilities, the various jurisdictions often use gateways, which are hardware interfaces that can connect existing networks, “patching” them together. Gateways use either traditional circuit connections or, more recently, internet protocol (IP) connections. With circuit-switched technology, used in traditional voice networks, such as telephones and land mobile radio, the users share an exclusive connection as they are talking.

IP gateways, on the other hand, use a network to transfer data. Despite their name, IP gateways do not always operate over the internet; they simply use internet-style technology (transmission control protocol/internet protocol or TCP/IP) to send messages out. Every device, be it radio, telephone or computer, on this network has a distinct IP address.

When a rescue worker transmits a message on a radio connected to an IP network, the audio is digitised, compressed, encoded and packaged into IP packets by a server. It is then sent out to the desired IP addresses, which can be IP gateways or any IP-enabled device such as a mobile phone or a computer. These devices reverse the packaging process so that the message is heard as audio once again. The IP gateway is considered a more robust link than traditional circuit-based links, because it distributes the message routing function across many different paths. This improves the chances of the messages reaching their destination.

Even different agencies within a single jurisdiction (police,
fire, and emergency medical services) usually have different
radio systems that are incompatible

IP networks offer several advantages to jurisdictions looking for interoperability. They enable agencies using both digital and analogue technologies and even different frequencies to communicate over the air. They can be made with off-the-shelf-components, so they are relatively inexpensive to set up and operate. They provide “scalability,” that is, the ability to support a large number of agencies, users and dispatch stations.

One disadvantage, however, is the vulnerability of the IP infrastructure or network. During a natural disaster like Katrina, for example, IP infrastructures may be severely damaged, hampering emergency communications efforts. There are also some concerns about the level of security of such IP networks.

The state of Florida chose an IP system for the backbone of its interoperability (IO) network. It had two goals for its system, which it began building in 2004. The first was to: “Provide network connections between Florida dispatch centres and install an interoperability tool to connect users on any [emergency] radio system to any other radio system on the network,” according to Florida’s IO Network.

The second goal was to build nine mutual aid channels throughout the state. These channels: “Provide radio service to first responders outside the range of their local system or when they need to communicate with users not on their local system. The mutual aid build-out will substantially increase their geographic coverage, ensuring that wherever they go, Florida’s first responders will have radio communication capability,” says the network.

Motorola won the bid for both parts of the system. Its solution was the IP-based Motorola Soft Switch Radio Network, known as Motobridge. Its components include two servers (redundant, constantly synchronised, and located geographically apart so that one can continue to function if another is knocked out by some disaster) and seven Session Initiation Protocol (SIP) servers located throughout the state that set up the patches between the various emergency radio systems.

At the local level, the system includes radio gateway units (RGU), which are voice and data switches that connect the system’s radios to the network and workstation gateway units (WSGU) that connect a dispatcher application to the network and to other dispatch centres for intercom and conferencing. Each dispatch centre can support a minimum of four simultaneous patches.

The radio interfaces that the WSGUs use vary according to the equipment used by their local systems. The Florida network includes systems from EF Johnson, M/A-COM and Motorola in UHF, VHF and 800MHz frequencies for land mobile radio (LMR) systems.

The network itself is closed, and each connection is protected by a firewall. The audio that travels over the network is encrypted to protect against electronic eavesdroppers. The network is scalable, and can support up to 2,048 patches involving 4,096 talk groups or channels.

As of April 2006, 225 dispatch centres, including fire rescue, emergency medical services and law enforcement, and the Statewide Emergency Operations Center are linked to Florida’s IO. The second part of the system, the mutual-aid build out, continues to be constructed.

The Florida IO network passed its first real emergency test in January 2005, when fire rescue trucks from one Florida county, which used a legacy VHF radio system, successfully used the network to request assistance from another county that used an 800MHz system.

Florida has also established a Statewide Law Enforcement Radio System (SLERS) that provides a shared 800MHz radio system to over 6,500 users with 14,000 radios. The state’s partner for this initiative is M/A-COM, a subsidiary of Tyco Electronics. The radio system is M/A-COM's digital trunked EDACS system. To date, the system has performed unfailingly during Florida’s turbulent hurricane season. While local systems and cell phone systems were failing at the height of the storms, the SLERS continued to operate.

Although most jurisdictions think of radios when they talk about interoperability, those in the greater Washington DC metropolitan region have chosen to link through a wireless virtual private network (VPN) that allows users to communicate via a Web browser.

Using the Capital Wireless Integrated Network (CapWIN) members of public service agencies in the District of Columbia and neighboring states Maryland and Virginia can take part in online discussion groups (accessible only to those in the network) or use instant messaging for one-on-one communication in an emergency situation. The Web browser can reside on personal computers, personal digital assistants (PDAs), wireless phones and police radios.

The CapWIN system also provides for data sharing, allowing users to access law enforcement data bases from all three jurisdictions. This is especially valuable to police officers who can easily check if someone they’ve stopped has any outstanding arrest warrants or other problems in adjoining areas.

Eventually, users that have enough computing capability on their equipment should be able to access web services and other databases that will help them handle their day to day activities and critical situations more effectively.

CapWIN uses the IBM WebSphere MQ Version 5.3 to allow communication between the agencies’ various computer systems. Wireless communications are maintained using the IBM WebSphere Everyplace Connection Manager 5.0. The system went live in June 2005 and one year later has 47 participating agencies representing 1,754 total users.

While public services today are using networks to link their disparate communication systems, developments in radio technology itself could alleviate the need for gateway-based interoperability in the future. Software-defined radio subscriber equipment (SDR) can change transmitter and receiver characteristics, so they can operate on multiple frequencies as needed.

With SDR equipment, members of an emergency agency such as a fire department can use the frequencies they prefer when talking among themselves, but could easily switch to a common frequency when they needed to work with people from other agencies at the site of an emergency. So far, however, the technology has been used primarily by the military and by cell phone providers, but has not yet been adapted to emergency communications radios.

SDR equipment uses digital signal processing (DSP) chips for modulation and filtering. These chips can be modified, their software upgraded, via over-the-air broadcasts. While the technology shows promise, there are problems. The very ease with which changes can be made to SDR equipment could also leave it vulnerable to malicious attacks.

SDR equipment could also cause interference problems with existing equipment currently operating on various radio frequencies. Finally, for SDR equipment to be useful to emergency responders, it will have to be made using open (instead of proprietary) standards, so the equipment made by one manufacturer will be able to communicate with that made by another.

SDR is just one example of the type of innovative thinking and state-of-the-art technology that will be required to solve the interoperability dilemma in the US. While some real progress has been made towards allowing all first responders to communicate with each other in an emergency, public safety officials have a long way to go before reaching the goal of complete interoperability.