Basic of Mobile Communication

Cellular Mobile Communication

Previous mobile communication:

1. 1n 1946, first public mobile service was introduced.
2. Each system used a single high power transmitter and large antenna tower in order to cover distances over 50km.
3. Each system used 120khz of RF bandwidth. Channels were in half duplex mode and were based on FM.  

Limitations of previous mobile system

Operational limitations of previous mobile systems are as follows:

1. Limited service capability
2. Inefficient frequency spectrum utilization.
3. Blocking probability was as high as 65%.
4. Possibility of call drop was high enough.
5. Overall poor service performance

Cellular concept:

1. The new model was proposed by Bell system in late 1940s
2. The new model proposed for many low power transmitters, each specifically designed to serve only a small area called a cell. 

Key terms related to cellular mobile:

1. Full duplex system:

 Communication system which allows   simultaneous two-way communication. Transmission and reception is typically over two different channels. 

  2.  Half duplex system:

Communication system where users can either transmit or receive information at any given time. Same channel is used for both transmitting and receiving.

1. Forward channel:

    It is the radio channel used for transmission of information from base station to mobile station. 

    2. Reverse channel:

    It is the radio channel used for transmission of information form the mobile set to base station.

1. Uplink and downlink :

    A duplex channel such as that used during a mobile call, uses two frequencies: one to the MS and one from the MS.

1. The direction from the MS to network is referred to as uplink.
2. The direction from the network to the MS is referred to as downlink.

1. Duplex distance:

 The uplink and downlink transmissions must be separated in frequency by a minimum distance. This is known as duplex distance. Without it, uplink and downlink frequencies would interfere with each other.

1. Carrier separation:

 Every mobile system includes a carrier separation. This the distance on the frequency band between channels being transmitted in the same direction.

1. Transceiver unit:

It is a device capable of simultaneously transmitting and receiving radio signals.

1. Mobile station:

It is a node or terminal in a cellular radio service intended for use while in motion at unspecified location. (Hand Set)

Basics of cellular mobile:

1. ISDN➔  Integrated Services Digital Network
2. PLMN➔Public Land Mobile Network
3. PSTN➔ Public Switched Telephone Network
4. PSDN➔Packet Switched Data Network
5. CCCH ➔Common Control CHannel
6. DCCH ➔Dedicated Control Channels
7. BCH   ➔ Broadcast channels