Presentation on CDMA

There is a whole overview of CDMA.

1. CDMACDMA
Submitted By
Shuvangkar Dhar (Id No: WUB09/12/51/2002)
Dept: EEE Batch: 51-B
World University of Bangladesh
Submitted To
Rajib Mondal
Senior Lecturer, Dept. of EEE

2. Introduction to CDMA
•CDMA – Code Division Multiple Access
•Fully digital wireless data transmission system
•Uses special random numbers to encode bits
of information.
•Allows multiple access by assigning different
users different random numbers on the same
channel.
•Users have control of a very wide channel
bandwidth 1.5 to 5 MHz
•Built-in interference minimization.

3. Background
•1993, the first CDMA standard IS-95 was issued;1993, the first CDMA standard IS-95 was issued;
•In 1995, CDMA technology was put into In 1995, CDMA technology was put into
commercialization in Hong Kong and America on commercialization in Hong Kong and America on
large scale.large scale.
•In April, 2001, China Unicom began to construct In April, 2001, China Unicom began to construct
CDMA networks—the largest in the world (about CDMA networks—the largest in the world (about
70Million line now).70Million line now).
•At present, CDMA commercial networks are At present, CDMA commercial networks are
established in about 40 countries or area, almost established in about 40 countries or area, almost
20% of all users in the world20% of all users in the world..

4. Executive Summary
•CDMA stands for Code Division Multiple Access.
•It provides a new dimension which represent the
Code.
•It works in two method which are Direct
sequence and Frequency Hopping.
•It has a huge application in cellular network.
•There are three evolution for CDMA:
1.IS-95
2.CDMA2000
3.WCDMA
•Soft handoff increases reliability of handovers.

5. Objective
•Introduce to CDMA Networks
•What is CDMA?
•How it works?
•To know about types of CDMA.
•To find the Advantages and
Disadvantages of CDMA.
•To know about application

6. Methodology
•Collection of information from books as
well as different websites such as
Wikipedia, Slideshare.com.
•Got help from the communication theory
classes taken by Rajib Mondal sir.

7. Basic diagram of CDMA
•There exist a new
dimension with time
and frequency.
•The new dimension
represent the code
which provided by
the operator for the
user.

8. Working Principle of CDMA
CDMA transmitter:
•The voice has to be digitalize (Pulse Code
Modulation (PCM) then compressed)
•Each user is given a unique PN code.
•The Codes must have low cross-correlation
•The transmitter multiplies the code by the data
to get the coded massage (bit)

9. Working Principle of CDMA
CDMA Transmitter:

10. Working Principle of CDMA
-5000-4000-3000-2000-1000010002000300040005000
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
noise
massege
After SpredingChip Duration is 0.4
ms.
Bit Duration is 6.4 ms.
Processing Gain is 16

Spectrum of the CDMA:

11. Working Principle of CDMA
CDMA Receiver:
•The received signal is multiplied again by the same
code that used in the transmitter.
•Integrate over bit duration and, then using a hard
decision to get the transmitted massage (bit)

12. Working Principle of CDMA
CDMA Receiver:

13. Working Principle of CDMA

14. Types of CDMA
1. Frequency Hopping
•Fixed sequence of frequency values & Time is
divided into slots .
•In the first time slot, a given user transmit to the
base station using the first frequency in its
frequency hopping sequence.
•In the next time interval, it transmits using the
second frequency value in its frequency hopping
sequence, and so on.
•This way, the transmit frequency keeps changing in
time.

15. Types of CDMA
2. Direct Sequence
•Each user transmits its message to the base station
using the same frequency, at the same time.
•Here signals from different users interfere with each
other.
•But the user distinguishes its message by using a
special, unique code. This code serves as a special
language that only the transmitter and receiver
understand.

16. CDMA Application in Mobile Network
•IS-95
•Mainly used in U.S.A
•Standard was finished in 1993 and first
commercially launched in 1996
•Basic data rate is 9.6 kbps
•Chip rate of 1.2288 Mchip/s
•Allocated bandwidth is 1.25 MHz
•Fixed spreading code of length 64

17. CDMA Application in Mobile Network
•CDMA2000
•CDMA2000 1x
•Use same 1.25 MHz as IS-95
•CDMA2000 1xEV-DO
•CDMA2000 1xEV-DO delivers peak data speeds of 2.4Mbps
and supports
•Applications such as MP3 transfers and video conferencing
•CDMA2000 1xEV-DV
•CDMA2000 1xEV-DV provides integrated voice and
simultaneous high speed
•Packet data multimedia services at speeds of up to 3.09
Mbps.

18. CDMA Application in Mobile Network
•WCDMA
•The faster chip rate of 3,84 Mchips/s
•5 MHz bandwidth
•Wider bandwidth implies greater frequency
diversity Rake Receiver
•Data rates
•Up to 2 Mbps for packet switched data

19. Advantages of CDMA
•Capacity is CDMA's biggest asset. It can
accommodate more users per MHz of bandwidth
than any other technology.
•3 to 5 times more than GSM
•CDMA consumes less power and covers large areas
so cell size in CDMA is larger.
•CDMA is able to produce a reasonable call with lower
signal (cell phone reception) levels.
•CDMA uses Soft Handoff, reducing the likelihood of
dropped calls.
•Has a well-defined path to higher data rates.

20. Disadvantages of CDMA
•Most technologies are patented and must be
licensed from Qualcomm.
•Breathing of base stations, where coverage area
shrinks under load. As the number of subscribers
using a particular site goes up, the range of that
site goes down.
•Currently CDMA covers a smaller portion of the
world as compared to GSM which has more
subscribers and is in more countries overall
worldwide.

21. Conclusion
•The CDMA will allow many signals to be
transmitted at the same channel at the same
time. This done by giving each user a Pseudo-
Noise code which is a binary sequence. This code
should have low cross-correlation between each
other.
•Multiple access interference has bad effect on
the CDMA system so the multiple user detection
is used to reduce the MAI.

22. Recommendation
•To produce of the application of optical CDMA,
adhoc networks, dense wireless LANs.
•Now a days CDMA has lost its popularity in our
country though it has much better
communication system from the other
technologies. So if it provides the 4G network it
will be a masterpiece of mobile communication.