about multiple access communication

1. MULTIPLE ACCESS COMMUNICATION

2. CONTENTS TO DISCUSSED
• INTRODUCTION
• HISTORY
• MULTIPLE ACCESS TECHNIQUES
• FDMA
• TDMA
• CDMA
• SDMA
• COMPARISON OF MULTIPLE ACCESS COMMUNICATION

3. INTRODUCTION
Multiple access schemes allow many users to share a finite amount of radio
spectrum in efficient manner
As the spectrum is limited, so the sharing
is required to increase the capacity of cell
or over a geographical area by allowing the
available bandwidth to be used at the same
time by different users.
Multiple Access communication

4. HISTORY
WIRELESS COMMUNICATION :
Wireless communications is a type of
data communication that is performed and
delivered wirelessly
In 1894 Guglielmo Marconi began developing
a wireless telegraph (first transatlantic
wireless messages) system using radio waves
Later wireless applications, including broadcasting
(both audio and video), radar, and mobile telephony
came into existence
Alexander Graham Bell Made a first Wireless
Phone That Ran on Sunshine
Marconi wireless telegraph

5. MULTIPLE ACCESS TECHNIQUES
KINDS OF MULTIPLE ACCESS
TECHNIQUES

6. FREQUENDY DIVISON MULTIPLE ACCESS
This was the initial multiple-access technique for cellular systems in
which each individual user is assigned a pair of frequencies while
making or receiving a call
Applications of FDMA
FDMA is used variety of applications such as telephone systems,
radio systems, TV
Advantages of FDMA
1.Simple to implement
2.Efficient with small base population
Disadvantages of FDMA
1.Network and spectrum planning are time consuming
2.Channels are dedicated to single user

7. TIME DIVISON MULTIPLE ACCESS
In digital systems, continuous transmission is not required because users do not use the allotted
bandwidth all the time. In such cases, TDMA is a complimentary access technique to FDMA.
Global Systems for Mobile communications (GSM) uses the TDMA technique. In TDMA, the
entire bandwidth is available to the user but only for a finite period of time. In most cases the
available bandwidth is divided into fewer channels compared to FDMA and the users are allotted
time slots during which they have the entire channel bandwidth at their disposal
Applications of TDMA
TDMA is used variety of applications such as 2G cellular
system,GSM
Advantages of TDMA
1. TDMA can easily adapt to transmission of data as well as
voice communication
2.Ability to carry 64 kbps to 120 Mbps of data rates
3.Most cost effective technology to convert an analog
system to digital.
Disadvantages of TDMA
1.Dropped calls are possible
2.Higher costs due greater equipment

8. CODE DIVISON MULTIPLE ACCESS
CDMA is a form of multiplexing, which allows numerous signals to occupy a single
transmission channel, optimizing the use of available bandwidth. The technology is
used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and
1.9-GHz bands.
Applications of CDMA
CDMA is used variety of applications such as 3G cellular
system,LTE,Satellite communication, Data security, GPS
Advantages of CDMA
1.Better signal quality
2.High data rates
3.Impossible for hackers to decipher the code sent.
Disadvantages of CDMA
1. Self-jamming(if sync not done b/w users)
2. As the number of users increases, the overall quality of
service decreases

9. SPACE/BEAM DIVISON MULTIPLE ACCESS
SDMA serves different users by using spot beam (A spot
beam, in telecommunications parlance, is a satellite
signal that is specially concentrated in power (i.e. sent by
a high-gain antenna) so that it will cover only a limited
geographic area on Earth) antenna,sectorized antennas
can be thought as SDMA
Applications of SDMA
OPTOELECTRONICS, Satellite communication
Advantages of SDMA
1.Increses channel capacity and transmission quality
2.High data rates Tb/sec throughput
3.Purely optical signal path
Disadvantages of SDMA
1. Interfacing problem

11. REFERENCES
1. T. S. Rappaport, Wireless Communications: Principles and Practice, 2nd ed. Singapore:
Pearson Education, Inc., 2002.
2. K. Feher, Wireless Digital Communications: Modulation and Spread Spectrum
Applications. Upper Saddle River, NJ: Prentice Hall, 1995.
3. J. G. Proakis, Digital Communications, 4th ed. NY: McGraw Hill, 2000.
4. G. R. Cooper and C. D. McGillem, Modern Communications and Spread Spectrum, NY:
McGraw Hill, 1986

12. Presented by
MADUGULA SAIKUMAR
3rd year, ECE-’B’ Sec.
15A51A0495