Many jurisdictions around the country are realizing the benefits of public-safety mobile data systems. "Mobile data" refers to a vehicle-based computing device that communicates wirelessly with a host computer system. Installing computers in police vehicles gives law enforcement personnel access to "silent" dispatch and status messages; local, state and national crime database information; vehicle-to-vehicle text messaging; and report writing and processing. Likewise, fire and EMS personnel can use mobile data for dispatch and status messaging and automated vehicle location as well as accessing pre-fire building plans, inspection history, HAZMAT information or other database information. In short, wireless mobile computing provides access to more complete and timely information, which enables police, fire and EMS staff to perform more effectively.

Since wireless networks are a critical component of mobile data systems, public agencies must decide how best to connect users in the field to host computers. Until recently, the decision was clear: Construct a private-data radio network -- vendor built, and government owned and operated -- to be used exclusively by a single agency or department. Today, commercial-data radio networks are becoming viable for law enforcement use. Government agencies now have the option of leasing a wireless network infrastructure and services, much as they would lease a wired network from the telephone company.

As with any technology investment decision, there are important factors to consider in assessing whether to build a private wireless data network or lease a commercial one: Cost, performance, security, flexibility and priority access must be considered.

What Is a Private Mobile Data Network?

Private wireless data backbones provide a dedicated network tailored to the specific needs of a public safety community. This approach requires your agency or jurisdiction to construct and operate its own wireless data network backbone, with responsibility for implementation, funding, operations and maintenance of the backbone infrastructure. You would also be responsible for licensing frequencies to be used for mobile data transmissions. Design and construction of a private-network infrastructure entails significant initial costs. However, these may be reduced through the strategic use of existing infrastructure, such as radio sites and towers.

Mobile data applications are typically implemented together with the private network as a single, integrated solution, although some systems integration is required for computer-aided dispatch and records-management systems (CAD/ RMS). Current private networks provide up to 19,200 bits per second (bps) data throughput per channel, sufficient for most text-based public-safety applications. They are designed to be secure and provide priority access to public-safety users. Private networks have a proven track record for public safety; most public safety mobile data systems operate on private wireless networks.

What Is a Commercial Mobile Data Network?

Commercial mobile data networks provide wireless data access to subscribers, including governmental and non-governmental organizations, using a variety of communication technologies, including specialized mobile radio (SMR), spread spectrum, cellular digital packet data (CDPD), satellite and others. Each relies on a terrestrial network for connectivity with host computers.

By using a commercial wireless provider, your agency avoids investing significant cost and time constructing a fixed, private infrastructure (for most private systems, the fixed infrastructure can account for 40 percent to 60 percent of the total one-time costs of a wireless data system). However, commercial wireless networks entail significant monthly subscriber fees per user. These recurring costs typically lead to higher system lifetime costs.

Many commercial wireless networks employ open protocols, support a variety of user devices and are easily scalable to allow for expansion. Nevertheless, significant systems integration is required to develop interfaces among applications and between the wired network infrastructure and the commercial wireless network.

One of the distinct advantages of commercial wireless networks is the increased bandwidth and data throughput they provide (up to 28,800 bps throughput per channel). Since commercial networks typically have more sites and channels than a private system, the design of