Overview

Cellular digital packet data (CDPD) is a standard for providing Internet Protocol (IP) data service over cellular voice networks. Although CDPD employs digital modulation and signal processing techniques, the underlying service is still analog. The media used to transport data consists of the radio channels typically used for Advanced Mobile Phone System (AMPS) cellular service. The CDPD infrastructure employs existing cellular systems to access a backbone router network that uses IP to transport user data. Personal digital assistants, palmtops, and laptops running applications that use IP can connect to the CDPD service and gain access to other mobile users or to corporate computing resources that rely on wireline connections.

Because CDPD leverages the existing $25 billion investment in the cellular infrastructure, carriers can economically support data applications and avoid the cost of implementing a completely new network, as most competing technologies would require. CDPD also offers a transmission rate that is two to four times faster than many competing wide area wireless data services, most of which are limited to 9.6 Kbps, 4.8 Kbps, or lower.

CDPD Applications

Although CDPD does not disallow long messages, it works best for data that can be transferred in short bursts rather than long sessions. Generally, cellular data applications fall into one of the following six categories: mobile office, financial transactions, telemetry, public safety, transportation, and Internet access.

• Mobile office. Increasingly, cellular data is appealing to companies that have increased the mobility of their work force. Armed with laptop computers equipped...