Radio over IP gives state responders a common platform

Washington use of WAVE software links legacy systems statewide

For the past 25 years, Washington state has relied on the On-Scene Command and Coordination Radio (OSCCR) network, as its primary interagency communications channel.

“The frequency has been offered up to everybody who works with us,” said Don Miller, telecommunications manager for the state’s Emergency Management Division.

OSCCR has a statewide Federal Communications Commission license to operate on the 156.135 MHz channel, and EMD has authorized 24,000 radios in federal, state and local law enforcement and emergency response agencies to use the channel.

“That’s the de facto band we were using for primary interoperability,” Miller said.


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The system works, but it has limits. It supports only voice communications with no data capability, and direct access has been limited to radios operating in the very-high-frequency band. Three counties with radio systems operating in the 800 MHz band used cross-band patches that connect them with OSCCR talk groups. The routing and bridging infrastructure lacked flexibility and voice clarity. “It was really a nightmare managing it,” Miller said.

Several years ago, EMD took a cue from a regional interoperability project started in 2001 in the state’s Olympic Peninsula — the Olympic Public Safety Communications Alliance Network — and adopted radio over IP as a system to bridge not only radio systems but also cellular and landline telephones. Along with desktop and mobile IP devices, it created a single interoperable domain.

The division is using WAVE communications software from Twisted Pair Solutions and has established 16 repeater sites throughout the state, with gateways to perform analog-to-IP conversion, routers in eight communications centers and dispatch console software at 23 agencies. The system connects existing radio systems without the need to replace or upgrade the radios. They still work radio to radio, but when they need to communicate with another agency in an emergency, the gateway moves the traffic into an IP system to connect with other systems.

“They can all talk to each other,” Miller said. “It gives us interoperability between primary state agencies that have radio operations, and we can also communicate over mountaintops.”

This is an important consideration in a state with more than 71,000 square miles, which includes the Coast Range, Olympic Mountains, Cascade Mountains and Rocky Mountains. The most common emergencies that Washington agencies respond to each year are wildfires in the state’s forested areas and the annual floods on the west slopes of the coastal mountain ranges caused by the moist winds of the Pineapple Express coming in from the Pacific.

“Dec. 5 is a date that I dread every year,” Miller said, because it inevitably heralds two or three weeks of 13-hour days caused by the flooding. But the new communications system is giving him better command and control on the scenes of fires, floods and other incidents.

NEXT: What changes in the radios?

Radio VOIP

WAVE is a software-based radio-over-IP system. Originally it stood for Wide Area Voice Environment, but the company has abandoned the acronym and now uses it as a stand-alone name.

“It is fundamentally VOIP with a specialization for radio,” said Twisted Pair marketing manager James Mustarde. “We have a large library of radio systems that are embedded into the software, so all you have to do is bring a radio into the system.”

WAVE supports the codecs needed to code analog audio signals from a variety of radio systems into digital format so that IP can be used as the intelligent transport for the traffic. Most radio voice traffic is still analog, Mustarde said. “With new digital radio systems, the data already is IP,” he said. But the digital data signal usually is an add-on to a system that still uses analog signals for voice traffic, and that needs to be converted to digital.

Radios, whether IP or analog, need no software to use the system. “We don’t change the native functionality of radios,” said Joe Groen, Twisted Pair's director of product marketing. They need only to connect with a radio gateway that is linked to a media server to convert the signal.

A management server is used to set up a WAVE system, called a domain, and administers the components in that domain. A media server does digitizing, mixing and audio-transcoding of the RF signals coming in from a gateway. The server also can be linked with the public switched telephone network to bring cellular and wired phone traffic into the network.

Desktop Communication software brings Windows PCs into the system, allowing them to make and take IP phone calls and support instant messaging via the WAVE radio channels. Mobile Communicator is a lightweight application that brings smart phones into the WAVE domain, supporting push-to-talk capability over the system and allowing access through any cellular connection. Equipped phones can make secure point-to-point calls to other devices in the system using Advanced Encryption Standard 256 encryption.

The Dispatch Communicator is a software console for dispatch centers, giving dispatchers full access to the system.

Virtual radio channels are set up through the management server, which typically contain similar devices or some other logical grouping. A standard channel connects human-operated devices and a trunk channel connects nonuser components, such as servers and gateways. Other channels can be used for multiplexing, IP phone paging and other tasks.

Channels have distinct transmit and receive points with their own IP addresses. WAVE sessions join devices in audio conferences and can be used to create ad hoc talk groups that can link entire channels, individual devices or other sessions. Session traffic is given a multicast IP address and devices in the talk group can pull off the traffic.

“The VOIP has given us flexibility,” Miller said, and the digital channels provide clearer audio signals than analog RF.

NEXT: What's the next step?

Phasing In

The system is being phased in and expanded as money and resources are available. An initial management server and the radio repeaters linking to WAVE gateways were set up in the first phase, and additional servers and dispatch consoles were added in a second phase. The state now is looking for money for a third phase of expansion, linking more radio systems to the WAVE gateways. The project will go after low-hanging fruit first, linking to counties that already have their own radio repeaters.

The system supports only voice traffic, Miller said. “We’re exploring the use of data, but that requires money and time to do it.”

Even without data, WAVE is an improvement over the previous system. It not only gives responders in the field better communication with one another but also provides better coordination because dispatchers and others have the ability to monitor the traffic and communicate with those on-site. In the past, dispatchers who had to stay on their standard radio channels were not able to easily monitor what was happening on OSCCR, but the software console allows them to stay in touch via the WAVE system.

Reader Comments

Fri, Jul 30, 2010

All fine and dandy as long as the towers stay upright, the power stays on, and the fiber stays intact. But I hope they also kept some RF-only backup frequencies and equipment, so they have at least SOME interagency comms if the IP system goes down. Emergency comms is a belt and suspenders sort of thing- you always need a Plan B.

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