PRESENTATION ON 2ND-GENERATION

TELECOMMUNICATION SYSTEM

SECOND GENERATION2G (or 2-G) is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard.

Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages.

While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

GSM Overview:

GSM (global system for mobile communication) is a common second generation cell phone standard.

.GSM is a digital standard that was adopted over the original analog system.

.THE GSM network operates at 850MHZOr 1900MHZ bands in the US.

GSM (Global System for Mobile communication) is a digital mobile telephone system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephone technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot.

.GSM uses GMSK or Gaussian minimum shift keying for modulation .GMSK is a kind of continous frequency shift keying

.The on-off binary signal is first transformed to a polar binary signal.

.The polar binary signal is filtered such that a Gaussian-shaped signal is produced.

.Frequency modulation is then applied to signal.

.The weaker digital signal may not be able to reach cell tower.

.Digital signal will drop out faster then an analog signal.

.Users separated by code

.Require digital transmission

.Wider bandwidth compared to TDMA

.Introduced in 1980

.Used in cellular communication system

HOW IT WORKS?.Generating a CDMA signal

1. Analog to digital conversion2. Vocoding3. Encoding and

interleaving4. Channelizing the signal5. Conversion of digital to

radio frequency signal

∑

USER#N

Cn

User#2

Rate=R2

User#1

Rate=R1

Rate=Rn

C1

C2

User#1,2,3….#n

FDMA vs TDMA vs CDMA: What's the difference?Three of the more common transmission schemes include FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), and CDMA (Code Division Multiple Access).

FDMA divides the given spectrum into channels by the frequency domain. Each phone call is allocated one channel for the entire duration of the call.

Frequency Division Multiple Access

TDMA enhances FDMA by further dividing the spectrum into channels by the time domain as well. A channel in the frequency domain is divided among multiple users. Each phone call is allocated a spot in the channel for a small amount of time, and "takes turns" being transmitted

Unlike FDMA and TDMA, CDMA transmission does not work by allocating channels for each phone call. Instead, CDMA utilizes the entire spectrum for transmisson of each call. Each phone call is uniquely encoded and transmitted across the entire spectrum, in a manner known as spread spectrum transmission.

Code Division Multiple Access