what is paging ?

Topic:- Paging

fig:Working of paging System

Paging Systems are wireless communication systems that are designed to send brief messages to a subscriber. It's a one-way messaging system in which Base Station send messages to all subscribers. The Paging System transmits the message also known as Page, along with Paging System access number, throughout the service area using Base Station, which broadcast the page on a radio link. 

Types of Paging Systems

• Manual Paging System: In a manual paging system, a message is sent to the paging operator through telephone call by the caller. The message is then delivers to the pager through paging network by the operator.
• Automatic Paging System: In an automatic paging system, the incoming requests are automatically processed by the paging terminal and then this information is delivers to the pager. Automatic Paging Systems are mostly used.

Messages in Paging Systems 

One of the following four types of information messages can be delivered in a Paging System.

• Alert Tone Message
• Voice Message
• Digital String Message
• Text String Message

Alert Tone Message: In the alert tone message, a dedicated telephone number is assigned to the receiver, which is also known as Tone Pager. The pager is triggered by dialing the number. To generate tone-type messages, the advantage of tone paging is that it utilizes a small amount of airtime. 

Voice Message: In the voice message, a voice message can be transmitted in some tone paging systems after the beep.  

Digital String Message: In digital string message, the receiver is a Numeric Pager. The string can be the telephone number of the caller or a coded message. This coded message is generated on request of the caller by the paging center and is decoded by a codebook built into the pager. This type of paging takes less amount of airtime.

Text String Message: In the text string message, the receiver is an Alphanumeric Pager, which has large screen to display the text strings. This type of messaging is becoming more popular than numeric messaging. 

Paging System Architecture

The Paging System network consists of six basic elements.

• User Terminal Equipment (Input Devices)
• Paging Terminal
• Operation and Maintenance Center (OMC)
• Base Station Controller (BSC)
• Base Station (BS)
• Pager

User Terminal Equipment (Input Devices): Terminal equipment is used by the caller to send messages. The equipment can be a telephone handset, a computer with modem and a specific input device. A telephone handset is used to generate alert tone or numeric type messages and is delivered through the Public Switch Telephone Network (PSTN), while alphanumeric messages are generated by the computers and are delivered through the Public Switch Digital Network (PSDN). 

Paging Terminal: The messages are sent to the paging terminal through user access interface. A paging terminal can supports 1 million pagers and is connected to a central office of PSTN. The paging terminal also maintains a database of the customer which conations information such as page number, pager code etc. 

Operation and Maintenance Center (OMC): The OMC is used for operation, administration and maintenance functions of a paging network. The customer's database which is stored in terminal paging can be accessed by the OMC to add or delete new customer's records. 

Base Station Controller (BSC): The paging terminal and base stations are connected by the BSC by powering up the base stations. In transmitting mode, the BS consumes the high power and when it is in idle mode it consumes low power. 

Base Station (BS): The messages to the pager are broadcasted by the BS over radio links. The BS and its pagers have dedicated paging channels. The messages from the paging terminal to the BS are transmitted by using transmission technologies, which are leased telephone lines and satellite based networks. 

Pager: A pager includes four basic elements.

• A Receiver: To receive and demodulate the paging signals, the receiver is tuned to the same radio frequency (RF) as the BS.
• A Decoder: The binary information is decoded by the decoder.
• A Control Logic: The control logic provides control for duplicate messages, locking messages and freeze messages.
• A Display: A display is used to read messages.

Paging Systems have ultra-reliable coverage, high infra structure, high complexity and high hardware cost.

Categories

Pagers themselves vary from very cheap and simple beepers, to more complex personal communications equipment, falling into eight main categories.

Beepers or tone-only pagers

Beepers or tone-only pagers are the simplest and least expensive form of paging. They were named beepers because they originally made a beeping noise, but current pagers in this category use other forms of alert as well. Some use audio signals, others light up and some vibrate, often used in combination. The majority of restaurant pagers fall into this category.^[12]

Voice/tone

Voice/Tone pagers enable pager users to listen to a recorded voice message when an alert is received.

Numeric

Numeric Pagers contain a numeric LCD display capable of displaying the calling phone number or other numeric information generally up to 10 digits. The display can also convey pager codes, a set of number codes corresponding to mutually understood pre-defined messages.

Alphanumeric

Alphanumeric pagers contain a more sophisticated LCD capable of displaying text and icons. These devices receive text messages, often through email or direct connection to the paging system.

Response

Response pagers are alphanumeric pagers equipped with built-in transmitters, with the ability to acknowledge/confirm messages. They also allow the user to reply to messages by way of a multiple-choice response list, and to initiate "canned" messages from pre-programmed address and message lists. These devices are sometimes called "1.5-way pagers" or "1.7-way pagers" depending on capabilities.

Two-way

Two-way pagers are response pagers with built-in QWERTY keyboards. These pagers allow the user reply to messages, originate messages, and forward messages using free-form text as well as "canned" responses.

One-way modems

One-way modems are controllers with integrated paging receivers, which are capable of taking local action based on messages and data they receive.

Two-way modems

Two-way modems have capabilities similar to one-way modems. They can also confirm messages and transmit their own messages and data.