Wireless communications

INTRODUCTION
Wireless communications are becoming increasingly popular in today’s fast paced world. Mobility, portability, and instant access (via the Internet) to unlimited information have become the mantra of businesses and individuals alike. The evolution of wireless communications has been incredibly quick and the future of this technology is unlimited. The impact of this technology on our lives will be tremendous and allow us to do things we never imagined.

What Is Wireless Communication?


The two main wireless services in use today are cellular and private packet radio. The service that is chosen will depend on the application(s) that a company or individual wants to run.

Cellular

Cellular technology is commonplace in both the business and private sector.
There are two types of cellular technology: 1) circuit-switched cellular, and 2) Cellular Digital Packet Data (CDPD). One of circuit-switched cellular’s biggest advantages is its nationwide availability. Another advantage is the ability to send voice and data over the cellular phone network. Circuit-switched cellular is ideal if the application requires the exchange of long text messages, large files, or faxes because it typically charges by the minute of connect time, not by the number of bytes transferred. A practical application for this technology is the transfer of data from a laptop by means of a cellular modem and phone. The initial cost to outfit a laptop to connect to a cellular network is about $400. A disadvantage of this type of service is the long set-up time each connection requires (about 30 seconds).
Cellular Digital Packet Data is best suited for transaction processing and database queries. This service offers fast call setup (about 5 seconds), and is inexpensive for short messages, such as sending e-mail. The main disadvantages of CDPD are the expense of large file transfers, and the limited availability of the service (currently it is available in about 40 cities nationwide).

Private Packet Radio
Private packet radio, though not as common as cellular, offers businesses widespread connectivity. The two major private packet radio providers in the U.S. are Ardis and RAM Mobile Data. These services can be connected to from virtually anywhere in the country. Private packet radio offers quick call setup and is well suited to communications that generate short, bursty messages, such as e-mail, database queries and point of sale applications. Since private package radio has been around for several years, there are many applications that use the network. Some of the commercial applications being used handle messaging, scheduling, electronic filing of expense reports, and even allow for insurance agents to process accident claim forms from a customer’s house or office (Salamone 96). The disadvantage with private packet radio, like CDPD, is that it is expensive for large file transfers.
The fundamental problem that wireless communications faces is that none of the major wireless data services is ideal for all applications. The stumbling blocks to widespread adoption of data connections for laptops and personal digital assistants (PDAs) include the lack of compatibility between services, the cost of the services, and the size and price of wireless modems.

History of Wireless Communications
Radio telephones have been used for decades, but have not been widely available due to limited system capacity. The breakthrough that addressed this capacity problem was the development of the cellular concept, which allows frequency reuse. Needless to say, the use of wireless communications has increased exponentially since that breakthrough. The evolution of wireless systems can be divided into several stages: 1) the preprevailing stage, 2) the first generation analog system, 3) the second generation digital system, and 4) the third generation system (to be discussed later). The promised services, the required technologies, and the developmental timetable are summarized in Table 1 (see appendix A).

Preprevailing Stage

The preprevailing stage occured during the 1950’s and the 1960’s. Land Mobile Radio systems such as police communication and taxi dispatch systems were developed. Navigation radio for ship and aircraft, and portable radio telephone for the battlefield were other applications. The sending and receiving equipment was bulky and expensive in this early stage of development.

First Generation System
The first generation wireless system is based on analog technology and was developed in the 1970’s and 1980’s for public use. The price of the hardware was reduced rapidly and the demand for wireless services grew quickly in this stage.