Adaptive modulation techniques can improve the capacity and bit error rate (BER) of WCDMA networks. Evaluating the BER of QAM and QPSK modulation under different noise levels allows adaptive modulation to select the optimal scheme based on signal to noise ratio. While 16-QAM has higher spectral efficiency, it performs poorly under noise. Improved trellis coded modulation for QAM can gain 3-6dB over uncoded schemes, bringing performance closer to QPSK with less power. Adaptive modulation tailored to channel conditions offers flexibility and efficiency gains for WCDMA.

1. ADAPTIVE MODULATION
TECHNIQUES FOR CAPACITY
IMPROVEMENT OF BER IN
WCDMA
Presented By:
Mirza Asif Haider
ID No. 1308023
Department of
Electronics And Telecommunication Engineering
Chittagong University of Engineering And Technology

2. Contents:
1. Introduction
2. WCDMA
3. Adaptive Modulation
4. BER in QPSK and QAM
5. Improvement ofTraditional QAM

3. INTRODUCTION:

4. The specific objectives of the research are:
(1) To evaluate the effects of noise on the bit error rate and throughputs on a W- CDMA network.
(2) Evaluation of Bit Error rate of QAM and QPSK system versus signal to noise ratio (SNR) are used to
evaluate system for adaptive modulation for capacity improvement.
OBJECTIVES OF THIS PRESENTATION:

5. Introduction :
W-CDMA (Wide- band Code Division MultipleAccess )
that allows a large number of users
to share access to a single communication channel
by encoding their data
with a special pseudo noise (PN) code for each channel
spread spectrum technique

6. Introduction :
W-CDMA (Wide- band Code Division MultipleAccess )
W- CDMA offers many advantages which includes :
W- CDMA
jam resistance
privacy
flexibility
a greater
cellular spectral
efficiency than
2G systems
3,84 Mcps
chipping rate
5 MHz
bandwidth for
one user
CDMA has been considered and recognized as
a viable alternative to both FDMA andTDMA
WCDMA used by Universal Mobile
Telecommunication System (UMTS) as
platform of the 3rd generation cellular
communication system.
W-CDMA uses noise-like
broadband frequency spectrum where it has high
resistance to multipath fading where as this was
not present in conventional narrowband signal of
2nd generation (2G) communication system.

7. Adaptive Modulation
an Adaptive modulation in cognitive radio as:
―an intelligent wireless communication system that is aware of its environment
― uses the understanding-by-building methodology to learn from the environment
and adapt to statistical variations in the input stimuli.
Adapting Modulation provides many parameters that can be adjusted relative to the :
• Channel Fading
• Including data rate
• Transfer Power
• Instantaneous BER

8. -spectral efficiency
-probability of bit error
USE of Adaptive Modulation :

9. transmit simultaneously at equal powers
the receiver will receive more power from the nearest transmitter
One‘s transmitted signal is the other‘s noise, the signal-to-noise
ratio (SNR) for the farther transmitter is much lower
the nearest transmitter transmits a signal of magnitude higher
the SNR for the Further may be below detect ability
higher
magnitude
lower
Magnitude
and
SNR
Below
detect
ability
the nearest transmitter
---uses less power
---higher order modulation techniques
so that the SNR for all transmitters at the receiver is roughly the same.
Why We Use Adapting Modulation in WCDMA:

10. Source
Modulation
selector
Modulator Power
Fading
Demodulator
Channel
State
And
Quality
Estimator
Sink
Feedback
Fig::Block Diagram of Link Adaption Mechanism
Block Diagram of Adapting Modulation inWCDMA:

11. The received SNR and path loss exponent is used as the channel metric to decide on the
modulation type .
Channel State And Quality Estimator
path loss exponent is small choose QPSK and when it is large Choose QAM.
There also exists a SNR target for satisfying the target BER

12. Performance of WCDMA system using 16-QAM:

13. Performance of WCDMA System using QPSK:
Curve is more striper than !6-QAM

14. . Comparison between QPSK and 16-QAM modulation schemes shows that
--the new simple 4-state trellis-coded adaptive MQAM achieves 3-dB effective
coding gain relative to un-coded adaptive M-QAM
--3.6 dB for 8-state trellis. Compared with traditional trellis codes and fixed-rate
modulation, the new scheme showed more than 20 dB power savings.
16-QAM performs very poorly in both AWGN and AWGN with multipath fading channel
IMPROVEMENT of M-QAM:

15. Conclusions:
• WCDMA technique
• Adaptive Modulation
• BER of QPSK and MQAM
• Improvement of MQAM
THANKYOU

16. QUESTIONS:
1. W- CDMA cellular systems
2. BASIC difference between WCDMA and CDMA
3. jam resistance:
4. Mcps
5. Throughputs
6. Trellis Coded Modulation
7. Quadrature Phase Shift Keying (QPSK)
8. M-ARY QUADRATURE AMPLITUDE MODULATION (QAM)

17. W-CDMA (Wide- band Code Division MultipleAccess )
W- CDMA cellular systems use a form of direct sequence CDMA (DS- CDMA).
Third generation systems useW-CDMA as the carrier modulation scheme ;
this is because of the many advantages that it offers.

18. jam resistance:
Anti-jamming is the process of applying certain techniques to a signal to make effective
jamming impractical.Techniques for anti-jamming involve spreading the frequency spectrum
to be very wide band or hopping the frequency unpredictably to avoid any basic blocking.
The basic difference between the CDMA and WCDMA is bandwidth ,CDMA uses 1.25 MHz frequency
bandwidth whileWCDMA uses 5 MHz bandwidth.
Again CDMA is 2g telecommunication standard and provide very less data rates compared toWCDMA which is
third generation technology.
CDMA being 2g standard provide mainly circuit switched services whileWCDMA being used in UMTS system is
used in both circuit switched and packet switched networks.
BASIC difference between WCDMA and CDMA

19. Megachips per second (Mcps) is a measure of the speed with chips are generated in Direct Sequence Spread
Spectrum (DSSS) signals.This speed is also known as the chipping rate.
A speed of 1 Mcps is equivalent to 1,000,000, or 106, chips per second
The chip rate of a code is the number of pulses per second (chips per second) at which the code is transmitted
(or received).
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwijqv_E2NnPAhXBso8KHZt5BQcQFgg2MAQ&url=https%3A%2F%2Fwww.clear.rice.edu%2Felec301%2FProjects01%2Fcdma%2Fcompare.html&usg=AFQjCNGSU
1Cf4Zwi9Pj2COtUx6t4491FDA

20. Trellis Coded Modulation
In simplest terms it is a combination of coding and modulation
where the word trellis Stand for the use of trellis (also called convolutional) codes.
Whereas we normally talk about coding and modulation as two independent
Aspects of the communications link, inTCM they are combined.
The throughputs defined as the number of bits per second correctly received

21. 4-state trellis-coded adaptive MQAM achieves 3-dB effective
coding gain relative to un-coded adaptive M-QAM
8-state trellis-coded adaptive MQAM achieves
3.6-dB effective coding gain relative to un-coded
adaptive M-QAM

22. V. MODULATION SCHEMES IN WIRELESS SYSTEMS
Quadrature Phase Shift Keying (QPSK) is a digital modulation
technique. Quadrature Phase Shift Keying (QPSK) is a form of
Phase Shift Keying in which two bits are modulated at once,
selecting one of four possible carrier phase shifts (0, Π/2, Π, and
3Π/2).
QPSK perform by changing the phase of the In-phase (I) carrier
from 0° to 180° and the Quadrature-phase (Q) carrier between
90° and 270°.
Which indicate the four states of a 2-bit binary code.
Each state of these carriers is referred to as a Symbol [4]
Quadrature Phase-shift Keying (QPSK) is a widely used method of transferring digital data by changing or
modulating the phase of a carrier signal.

23. In PSK all points lie on a circle so the I and Q values are related to each other.
PSK signals are constant envelops because of this; all points have the same amplitude.
If we allow the phase and amplitude to change from symbol to symbol, then we get a modulation called quadrature
amplitude modulation (QAM).
VI. M-ARY QUADRATURE AMPLITUDE
MODULATION (QAM)
It can be considered a linear combination of two DSB-
SC.so it is an AM and a PM modulation at same time.
used to create an hybrid type of modulation that varies both in
amplitude and the phase. When M=16,we have 16 symbols,
each representing a four bit word. We can lay these out in a
circle but they would be too close an error rate is likely to be
high.