This document compares the bit error rate (BER) performances of 64-PSK and 64-QAM modulation schemes in additive white Gaussian noise (AWGN) channels. It first provides background on digital communication, modulation, binary modulation, and M-ary modulation. It then describes M-PSK and M-QAM modulation specifically. The document discusses how AWGN noise affects signals and how BER is calculated. It presents theoretical BER graphs for 64-PSK and 64-QAM and compares their bandwidth and power efficiencies. The document concludes by thanking the reader.

1. COMPARISON OF BER PERFORMANCES
OF
64-PSK AND 64-QAM
IN AWGN CHANNELS
EE451 Communication Systems II
Berk SOYSAL
Yiğitcan AYDOĞMUŞ

2. OUTLINE
1 INTRODUCTION
2 BINARY MODULATION
3 M-ARY MODULATION
4 M-PSK MODULATION
5 M-QAM MODULATION
6 AWGN CHANNEL EFFECT
7 BIT ERROR RATE
8 RESULTS
9 CONCLUSION

3. INTRODUCTION
• What is digital communication ?
• Digital communication is the transmission of
information that has been encoded digitally,
and passed through digital devices such as
computers.

4. INTRODUCTION
• What is modulation ?
• Modulation is the process of varying one or more
properties of a periodic waveform, called the carrier
signal with an information bearing signal.
• Why do we need modulation ?
• Low frequency signals are more immune to noise.
• Prevent interference.
• Reduce the antenna size in designed transceivers.

5. BINARY MODULATION

6. M-ARY MODULATION
• In general, M-ary communication is used when one
needs to design a communication system that is
bandwidth efficient.
• However, the gain in bandwidth is accomplished at
the expense of error performance.

7. M-ARY MODULATION
• To use M-ary modulation, the bit stream is blocked
into groups of λ bits.
• The number of bit patterns is M = 2λ
• The symbol transmission rate is;
Rs = 1/Ts = 1/(λTb) = Rb/λ symbols/sec
There is a bandwidth saving of 1/λ compared to binary
modulation.

8. M-PSK MODULATION
• In this modulation type, the information is encoded in
the phase of the transmitted signal.

9. M-PSK MODULATION
• The signals lie on a circle of radius √Es, and are
spaced every 2π/M radians around the circle.
Constellation Diagram of 64-PSK;
Decision Regions for M-PSK receiver;

10. M-QAM MODULATION
• In this modulation type, the information is encoded in
both the amplitude and the phase of the transmitted
signal.
• In QAM the transmitted signal has the form:• This signal is demodulated by multiplying with a cosine signal;• Or equivalently;
• Applying LPF removes the sine and cosine terms
and leaves only the message term.

11. 64-QAM MODULATION
• In 64 QAM there are 64 signal points in the constellation
that are equally divided into four quadrants.
• Since the constellation is divided equally into four
quadrants, normalizing the energy in a single quadrant
will simplify things.
Constellation
Diagram of
64-QAM;
Calculating the total energy in any one of the quadrant;
The average energy is
and the normalization factor will be .

12. AWGN CHANNEL EFFECT
Additive white Gaussian noise (AWGN) is a channel model
in which the only impairment to communication is a linear
addition of wideband or white noise with a constant spectral
density and a Gaussian distribution of amplitude.
Noisy Constellation Diagrams;

13. BIT ERROR RATE
• The bit error rate or bit error ratio (BER) is the
number of bit errors divided by the total number of
transferred bits during a studied time interval.
• Bit error rate (BER) is a parameter which gives an
excellent indication of the performance of a data link.

14. THEORETHICAL BER OF
M-QAM & M-PSK
k=log2M

15. THEORETHICAL BER GRAPH OF M-
PSK

16. THEORETHICAL BER GRAPH OF M-
QAM

17. RESULTS

18. M-PSK VERSUS M-QAM
Bandwidth and Power Efficiency of M-PSK Signals
Bandwidth and Power Efficiency of M-QAM Signals

19. SHANNON’S LIMIT

20. THANK YOU FOR
LISTENING !