The pursuit of interoperability

Safety of life and property can only be assured when public safety agencies can easily communicate with one another. All too often, the different systems they use preclude them from communicating at all. Agencies must have high-quality, interoperable communications at their disposal to ensure effective and timely coordination of disaster responses. Recent high-profile incidents, coupled with the events of Sept. 11, have drawn into sharp focus the need for voice radio interoperability both for routine day-to-day use and during emergencies.

What is interoperability?

A good definition of interoperability can be found on the Advanced Generation of Interoperability for Law Enforcement program Web page (www.agileprogram.org): “Interoperability is the ability of two or more parties (e.g., public safety agencies) to exchange information, when and where it is needed, even when disparate communication/information systems are involved. Information may be exchanged among fixed facilities, mobile platforms and portable (personal) devices.”

Providing interoperability

To be most effective, interoperability needs to be available for daily operations and for emergency use. Additional considerations include suitability for disaster sites as well as fixed-station use, ease and speed of deployment, central control capability, network capacity of the system and cost. Communications interoperability can be obtained with:

Consoles — Communications consoles in many LMR systems can interconnect different agencies’ radio channels. This can provide day-to-day interoperability, but console operators can become quickly overloaded during emergencies. Additionally, only those agencies whose channels are accessible through the console can be interconnected, precluding important agencies whose participation is crucial during emergencies, particularly agencies that are brought in to deal with specific situations.

Mutual aid channels — Many city and county LMR systems have a mutual aid channel available that is useful for daily interoperability. Disadvantages for emergency use include difficulty of usage coordination and the fact that field radios may not contain the mutual-aid channel. Only those agencies with access to the mutual-aid channel can be interconnected, which can leave out important agencies whose participation is needed during emergencies.

Collocated communications devices — Interoperability may be handled at the scene of a disaster by an officer operating a number of different radios while relaying messages between radio channels. Although inexpensive and quick to deploy at a disaster, the operator’s inability to deal with simultaneous conversations is a major system limitation.

Cellular and landline phones — Telephone service can be a convenient means of providing day-to-day interoperability. However, during disasters, cellular service may be unavailable because of circuit overload; landline circuits can be similarly affected. Landline phones can’t reach officers in the field, and telephones don’t provide a dispatch-type operating environment.

Trunked radio systems — Trunked radio systems provide excellent daily and disaster communications interoperability among talk groups in the system. Agencies “foreign” to the trunked radio system can interoperate through the trunked system with the aid of a cross-connect gateway.

Cross-connect gateway — A cross-connect gateway operates by transparently interconnecting radio audio paths so that agencies can patch into each other’s radio channels in real time. This modular, off-the-shelf unit is designed to implement flexible interoperability systems and includes the capability not only to interconnect radio transceivers, but also landline and cellphones. A transportable version housed in a rugged case is available for use at disaster sites. The entire system can be easily controlled from a central point using a computer running controller software. Using this software, rapid set-up and tear down of cross communications paths can be made as needs arise, with quick set up of individual talk nets involving multiple agencies.

Cost-effective interoperability

Trunked radio and cross-connect gateways are two methods that have the flexibility to provide seamless interconnectivity with few disadvantages. Of these two, the cross-connect gateway is the quickest and cheapest to deploy. This is because it works with existing radio infrastructure, allowing agencies to use radios, repeaters and frequency allocations that are already in place. A cross-connect gateway can interconnect 24 radio channels and can be installed and up-and-running in hours at a cost less than $25,000 for a single site.

Using the gateway and a network extension unit (a VoIP device), a multisite statewide inter-operability network can be deployed site-by-site as funding becomes available. This type of system is currently being deployed in Maryland.

Implementation of a trunked radio system in most cases requires the complete replacement of an agency’s radio infrastructure with deployment times measured in months to years and costs in the millions of dollars. Also, the trunked system still may not include all the agencies that must respond to an emergency, particularly those brought in to deal with specific situations, such as a hazardous spill or a terrorist situation.

A cross-connect gateway is a low-cost option to provide inter-operability even when plans include the eventual installation of a trunked radio system. The gateway also works well within existing trunking systems, where it can provide compatibility with legacy radio systems and help fill in coverage holes.

Pflasterer is president of JPS Communications, Raleigh, NC.