This document compares and contrasts three mobile communication technologies: GSM, TDMA, and CDMA. GSM is a digital cellular standard that uses TDMA and operates in the 900/1800MHz bands. TDMA allows multiple users to share the same frequency channel by dividing transmissions into time slots. CDMA differs in that it allows all users to transmit over the whole spectrum simultaneously by assigning each user a unique spreading code.

1. Compare with
GSM,TDMA & CDMA

2. Outline
 GSM
 TDMA
 CDMA
 Compare

3. What is GSM?
Definition: GSM stands for Global System for Mobile
Communication and is an open, digital cellular technology used for
transmitting mobile voice and data services.
Characteristics:
 Fully digital system using 900,1800 MHz frequency band.
 TDMA over radio carriers(200 KHz carrier spacing).
 User/terminal authentication for fraud control.
 Encryption of speech and data transmission over the radio path.
 Full international roaming capability.
 Compatibility with ISDN.
 Support of Short Message Service (SMS).

4. Architecture:

5. What is TDMA?
Time division multiple access
is a channel access method
which allows several users to
share the same frequency
channel by dividing the signal
into different time slots .
TDMA is used in the digital 2G
cellular systems such as GSM ,
Personal Digital Cellular (PDC)
and in the Digital Enhanced
Cordless Telecommunications
(DECT) standard for portable
phones.

6. Characteristics of TDMA
 Shares single carrier frequency with multiple users
 Non-continuous transmission makes handoff simpler
 Slots can be assigned on demand in dynamic TDMA
 Less stringent power control than CDMA due to reduced intra cell
interference
 Higher synchronization overhead than CDMA
 Advanced equalization may be necessary for high data rates if the
channel is "frequency selective" and creates Inter symbol
interference
 Cell breathing (borrowing resources from adjacent cells) is more
complicated than in CDMA
 Frequency/slot allocation complexity
 Pulsating power envelop: Interference with other devices

7. What is CDMA?
Definition:
 CDMA is a technology that allows multiple users to share the whole
spectrum at all the time unlike TDMA and FDMA.
 CDMA has wider bandwidth compared to TDMA & FDMA.
 Requires digital transmission

8. CDMA: basic principles
 In CDMA each user is assigned a unique code sequence (spreading
 code), which it uses to encode its data signal.
 The receiver, knowing the code sequence of the user, decodes the
 received signal and recovers the original data.
 The bandwidth of the coded data signal is chosen to be much largerthan the
bandwidth of the original data signal, that is, the encoding
 process enlarges (spreads) the spectrum of the data signal.
CDMA is based on spread-spectrum modulation.
 If multiple users transmit a spread-spectrum signal at the same time,the
receiver will still be able to distinguish between users, provided that each
user has a unique code that has a sufficiently low crosscorrelation with the
other codes.