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Packet Cellular Technology. Cellular digital packet data (CDPD) technology is being developed and implemented by a consortium of 10 major cellular carriers, including AT&T Cellular and AirTouch. As a digital overlay of the existing analog cellular network that utilizes unused bandwidth in the cellular voice channel, CDPD is a logical extension of cellular data communications.

Because is based on an open design and supports multiple connectionless network protocols such as the Internet protocol (IP), existing applications require few, if any, modifications to run on CDPD. CDPD claims a bandwidth of 19.2K bps, although typical user rates are closer to 9.6K bps. Approximately 30 markets have access to CDPD technology.

Suitability of Packet Data Networks for Wireless Applications. Packet data networks offer several advantages, including:

  Reliable transmission of data.
  Cost- efficient transmission of short messages.
  Transparent roaming in the locations where the networks exist.
  Fast setup time.

Disadvantages of packet data technology include:

  High costs in certain situations (resulting from a per-packet charge).
  Slow transmission times for large data files (which is less the case for CDPD).
  More- limited coverage and availability than that of cellular technology.
  Limited bandwidth (here, again, CDPD is better than RAM or Ardis).

The suitability of packet data networks for wireless data applications depends largely on the application. The networks provide a solution for applications requiring instantaneous, unconnected delivery of small but valuable pieces of information that can save money or generate revenue. They are therefore used for single-transaction based applications such as remote credit-card authorization or rental car check- in. Use of packet data is more limited in cases of general sales force automation, database replication, E-mail with attachments, electronic software distribution, and multiple application requirements for mobile users.

CHOOSING AN ARCHITECTURE AND ACCESS METHOD

The first step in implementing wireless technology is to choose an appropriate communications architecture and access methodology. The many wireless and connectivity access methods available generally fall into three categories:

  Continuous extensions of desktop or local area network (LAN) systems.
  E-mail-based systems.
  Agent-based messaging systems.

A solution that fails to address the communications infrastructure of the wireless environment has both financial and systems implications. Although communications costs escalate dramatically with heavy system use and large numbers of users, support and resource costs increase as well.

Continuous-Connection Architectures

A continuous-connection architecture establishes and maintains a wireless connection so that a user can perform work while online to central computing resources, such as a desktop PC or LAN-based PC. This work is accomplished through remote access and file synchronization utilities. Although there are unique variations on how these utilities are implemented, organizations generally use one of two methods: remote node or remote control.

Remote node technology makes mobile users a node on the LAN network and allows them to perform work as if they were locally logged into the LAN, albeit usually more slowly. Remote control technology allows mobile users to connect and see a virtual copy of the remote PC’s screen or hard drive so that files can be accessed and applications can be run remotely.

Continuous-connection technologies offer the basic advantage of providing mobile users with access to their central LAN-based PCs and servers; the mobile computing device looks and acts as if it were the user’s local desktop PC. Unfortunately, this strategy is inappropriate for the majority of large mobile implementations for several reasons:

  Most field professionals are mobile or remote all of the time. They may not need LAN resources, understand local area networks or logically redirected disk drives, or have a dedicated PC at the central site.
  Even when the complexity of establishing connections is hidden from the remote user, communication time is lengthy and communication costs are high.
  Before performing work online, the user must leave the task at hand to initiate and establish a connection.
  Continuous-connection systems do not provide for communications management or for general systems management; as a result support costs are likely to increase.

E-mail Based Systems

E-mail based systems use E-mail as both the messaging application and as a general communications transport for other message types or transactions. The basic advantage of using E-mail as the access method for all communications is that it is a prevalent application that users understand.

However, use of E-mail as an access method for other applications is less than optimum because E-mail based systems:

  Lack integral systems management capabilities such as software distribution.
  Involve users with the information delivery process, which is not provided automatically by the application.
  Do not support applications that require queries into databases.

E-mail is clearly a popular application required by most mobile users. However, it should be considered an additional application that uses the available communications access method, rather than a communications transport or access method in and of itself.


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