28 August 2011

Mobile Telephone


                Mobile Phone System is a wide area cordless telephone system. High power transmitters and elevated antennas are used in this system.Thus, nearly 20 to 30 miles radius of the link between the base station antenna

Two basic parts are in mobile telephone. They are 

1. A base station (or) base unit 
 
2. A mobile telephone unit (or) Mobile unit

1. Base Unit :

            The base station with the power of several hundred watts is enough to cover the average city. The actual work of the base stations is to transmit and receive some frequency signals. A typical base station can transmit the output power of 200 to 250 watts. The base stations consist of several transmitters and receivers which simultaneously handle full duplex communications and generally have towers which support several transmitting and receiving antenna. 

            The base station serves as a bridge between all mobile users in the cell and connects the simultaneous mobile calls via telephone lines or microwave links to the MSC. The MSC (Mobile Switching Center) coordinates the activities of all of the base stations and connects the entire cellular system to the PSTN (public switched telephone network). A typical MSC handles 100,000 cellular subscribers and 5,000 simultaneous conversations at a time, and accommodates all billing and system maintenance functions, as well. In large cities, several MSC’s are used by a single carrier.

2. Mobile Unit :

            Mobile stations is the technical name of the mobile or the cellular phone. In early days mobile phones were a little bulky and were sometimes installed in cars like other equipments. Even the handheld terminals were quite big. Though the phones have been smaller and lighter, they are still called Mobile stations. 

MS consists of two main elements :

            * The mobile equipment or the mobile device. In other words, this is the phone without the SIM card.

            * The Subscriber Identity Module (SIM)