Paging Service in Wireless Communication

In post the first service in wireless communications.This post continues to discuss 2nd service (paging service). It is similar  to broadcast, paging systems are unidirectional wireless communications systems. They are characterized by the following properties.

Principle Pager

• The user can only receive information, but cannot transmit. Consequently, a “call” (message) can only be initiated by the call center, not by the user.
• The information is intended for, and received by, only a single user.
• The amount of transmitted information is very small. Originally, the received information consisted of a single bit of information, which indicated to the user that “somebody has sent you a message.” The user then had to make a phone call (usually from a payphone) to the call center, where a human operator repeated the content of the waiting message. Later, paging systems became more sophisticated, allowing the transmission of short messages (e.g., a different phone number that should be called, or the nature of an emergency). Still, the amount of information was rather limited.

Due to the unidirectional nature of the communications, and the small amount of information, the bandwidth required for this service is small. This in turn allows the service to operate at lower carrier frequencies – e.g., 150MHz – where only small amounts of spectrum are available. As we will see later on, such lower carrier frequencies make it much easier to achieve good coverage of a large area with just a few transmitters.

Pagers were very popular during the 1980s and early 1990s. For some professional groups, like doctors, they were essential tools of the trade, allowing them to react to emergencies in shorter time. However, the success of cellular telephony has considerably reduced their appeal. Cellphones allow provision of all the services of a pager, plus many other features as well. The main appeal of paging systems, after the year 2000, lies in the better area coverage that they can achieve.