Mobile and Mobile Technology

Belcha and Paul

DEFINATION

GSM now stands for Global System for Mobile Communications, but

you might think that in that case it should really be GSMC.

In fact, GSM was originally an acronym for the name of the committee

that was doing the standardization work – called Groups Special

Mobile.

As GSM was about to be launched, it was decided that such an

obscure acronym was not appropriate, so someone managed to find a

different meaning for the existing acronym.

GSM MILESTONESThe rapid growth of cellular telecommunications has led to the need of designing a universal cellular radio system.

1982 the Nordic PTT made a proposal to CEPT and a standardization group called GSM was established to specify the new pan-European mobile cellular radio system.

After discussions it was decided in 1985 to design a digital system.

1986, a field test in Paris led one year after to a narrow band TDMA solution.

1988 A MoU (Memorandum of Understanding) was signed by operators in 13 countries to follow the specifications and deliver a GSM system by July 1991.GSM finally evolved in phases (steps), since the entire amount of services was too big to be finalized by 1991.

Advantages of GSM

• It provides better quality and spectrum usage, increasing the number of subscribers.

• A GSM subscriber may move with his phone and use it within all countries covered by GSM.

• It can provide many new user services, such as data and Fax, SMS etc.

• It introduces lower cost equipment such as powerful handheld mobile phones.

Why is it called a cellular system?

Two reasons

• Composed of a number of cells, each with radius of a few kilometers, spread across the country.

• The second reason has to do with the availability of something called radio spectrum.

Simply, radio spectrum is what radio signals use to travel through space.

The public switched telephone network (PSTN)

• By picking up the phone on your desk, you can make a call to any other phone in the world due tomassive network of wires and telephones spanning the world. This network is referred to as the public switched telephone network (PSTN): “public” to differentiate it from a private network (such as the internal telephone system in your office, which only employees can use); and “switched” because whenever you make a call, it passes through a switch, linking you to the person at theother end to whom you want to speak.

Mobile phone call

• Similarly, if you try to call someone who is a subscriber the network from your office phone, then

the call will pass to your local switch, which will recognize that the prefix means the call is routed to

a particular switch.

MAIN COMPONENTS OF THE GSM SYSTEM

1. The Switching part:

This ensures that when you dial a number you are connected to the right person.

2. The Base Station Sub system part:

This makes sure that the radio communications part takes place correctly

3. The Mobile Station: Allows the user to make and receive a call.

Base Station Controller

THE BASE STATION SUBSYSTEM

Base Transceiver Station (BTS)

The BSS mostly consists of a collection of transmitters, known in GSM terminology as Base Transceiver Stations (BTSs) where “transceiver” is a shorter version of “transmitter/receiver.”Each BTS sits in the center of a cell and radiates radio signals so that mobile users can Have conversation. Transmitters also have a fair amount of computing power, correcting errors in the received signals and encrypting the conversations so that they cannot be overheard.

Base Station Controller (BSC)The Base Station Controllers (BSC) within the BSS that are concentrating points to which a number of transmitters are connected before being connected back along a single line to the switch. This hierarchy simply serves the function of reducing the number of connections into the switch and thus simplifying the role of the switch.