ranges cannot talk directly to each other. For many public safety users in Indiana, incompatible frequency ranges have made communicating very difficult.

Trunking is another voice radio alternative being considered by Indiana. Trunking channelization is a newer technology that supports a large number of users on a group of channels, achieving spectrum efficiency through channel sharing. Trunked radio systems operate in the VHF, UHF, 800MHz and 900MHz bands of the radio spectrum and are ideally suited to meet the needs of large or regional systems that have many users from different agencies. When a user makes a call, the system automatically selects an available channel from a set of pooled frequencies. The intelligence of the trunked system then transparently tunes the user's transmitter to that channel while directing the appropriate receivers to switch to the same channel. As a result, trunked systems provide users automatic access to all available pooled channels, thus reducing wait time and increasing channel capacity. While these systems often are more technically complex and higher costing than conventional systems, trunking supports the direct interoperability critical to public safety success. Currently, there are several agencies throughout Indiana that utilize trunked systems; however, these systems were developed by different manufactures that support incompatible technologies. As a result, these wide-area communication systems currently do not support interoperable communications, even though they provide coverage to overlapping geographical areas.

Other voice alternatives include leased-service providers that offer both terrestrial and nonterrestrial communications systems. While agency-owned conventional and trunked radio systems are the most commonly used alternative for public safety communications, leased-service availability of trunked radio systems, referred to as Specialized Mobile Radio (SMR) and Enhanced Specialized Mobile Radio (ESMR), is becoming an increasingly popular option.

In addition, satellite-communication services are becoming more prominent and can provide communication paths for public safety personnel in remote areas without requiring buildout of a land-based system. These types of leased services can provide immediate communications for agencies without requiring large up-front capital costs necessary for procuring a radio system. Also, upgrades and maintenance to the system backbone are the responsibility of the system owner. However, priority access, potentially high recurring costs and limited coverage of SMR systems are possible disadvantages.

Mobile-Data Alternatives

Mobile-data technologies are rapidly being adopted for use in public safety services and include support for functions such as data inquiries, status messaging, field reporting, e-mail and automatic vehicle location. As is the case with voice radio, various infrastructure alternatives exist that support mobile-data transmissions. Depending on whether the infrastructure is owned by the operating agency or leased from commercial service providers, agencies have several data-transmission alternatives.

A dedicated mobile-data network is a system owned and maintained by an agency and designed to facilitate data transactions between mobile units and fixed-host computer systems. While some agencies operate dedicated mobile-data networks or support data on their trunked voice system, not all have been designed to share information seamlessly with neighboring agencies. Rather, these networks function as separate islands of information available only to their host agencies. Historically, dedicated networks have been implemented in parallel with voice radio communication systems and provide overlapping coverage using primarily conventional technology. Dedicated mobile-data networks have typically been selected to support large numbers of users with high-volume data application requirements. These networks offer the benefits of dedicated use over a secure infrastructure, but can be costly to install, upgrade and maintain.

Several commercial alternatives exist to agency-owned mobile-data infrastructures. Instead of building a new network, agencies can lease service where costs are generally based on a per-unit connection, air time or data-transmission volume. circuit switched cellular, cellular digital packet data, spread spectrum, SMR and satellite technologies are just a sample of commercial mobile-data-transmission alternatives that can free agencies from the radio-frequency requirements, administration and maintenance responsibilities and high initial costs normally associated with private infrastructures.

Agencies throughout Indiana are excited about the prospect of statewide interoperability among public safety communications systems. Having gained considerable momentum since the most recent governor's summit, the Indiana Legislature recently and unanimously passed HB 1869 that formally established an oversight committee to organize the governance for this project. Indiana residents, through implementation of the statewide initiatives of ILEC and Project Hoosier SAFE-T, are moving closer to realizing the benefits of integrated communications.

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Brian Hudson and John Green are consultants with The Warner Group, a Woodland Hills, Calif.-based management consulting firm specializing in the public sector. Additional information about Project Hoosier SAFE-T is available by contacting them at 818/710-8855 or online.

Portions of this article first appeared in the March issue of Actionlines, a monthly publication of the Indiana Association of Cities & Towns.