PAGING SYSTEM

PAGE:

            " Its a short message sent to subscriber over wireless network ".

PAGING SYSTEM: 

                                This system is used prior to telephone system .

In this system a brief message is sent to subscriber , depending on the type of service the message may be either a numeric message , an alphanumeric message,or a voice message. But in modern paging systems news headlines , stock quotations and fax can be sent.

HOW IT WORKS: 

       The message is sent to a paging subscriber via paging system access number . The message sent in this case is called a "page".

As we can observe in below fig . Initially the message or page is sent to paging control center through public switched telephone network ( PSTN) . Now the paging control center will transmit the message through landline link to other paging terminals , Then here onwards it will be sent to corresponding base stations .

With the help of base stations message will be broad casted on "radio carrier" reaching finally the destination.

The range of paging system varies depending on the need . It can created only to cover o building or it can be made to cover large area .

But as coverage area increases the complexity of system increases.

SIMULCASTING:

                              " Wide area paging systems consists of number of base station transmitters, and large radio towers that simultaneously broadcast a page from each base station".

Simulcast transmitters may be located within the same service area or in different cities or countries.

DIFFICULTIES: 

                  Paging system comes with some difficulties ,

1) The messages are very short.

2) As the service area increases the      data rate reduces .

3)  The system requires large               number of base stations to cover     large area i e : To cover two   countries we need to use   simulcasting .

MODIFICATION:

                              In the small areas as well as large coverage areas the distortion will be more so in order to overcome this problem at receiving end .Small RF( Radio frequency) bandwidths are used to maximize the "signal-to-noise" ratio .