Computer Science Engineering (CSE) Exam  >  Computer Science Engineering (CSE) Notes  >  Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE) PDF Download

 Introduction

 

The slides cover the following topics:

 

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

EE104: Lecture 25 Outline

 

•Announcements
 
•Review of Last Lecture
 
•Probability of Bit Error in ASK/PSK
 
•Course Summary
 
•Hot Topics in Communications
 
•Next-Generation Systems
 

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Announcements

 

•HW 7 due Monday at 9 pm (no late HWs)
 
•Solutions will be posted then.
 
•Final Exam is Th., 3/20, 8:30am in Gates B03 (basement)
 
•Exam is open book/notes, covers through today’s lecture.
 
•Emphasis is on material after midterm, similar to practice finals
 
•SCPD student must make remote arrangements w/me by this Friday
 
•Practice finals posted on class website
 
•10 bonus points if turned in by 3/20 at 8:30am (Joice has solutions)
 
•Final Review: Monday 7-8pm (room 380-380Y)
 
•Extra Office Hours
 
•My extra hours: M 4:30-6:30, TW 12-2, and by appointment
 
•Jaron: W 4-6 (Bytes), Nikola: after review and T 5-7pm (110 Packard)
 
•τβπ will be done at end of class (10 bonus points)
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Review of Last Lecture
 
•Passband Digital Modulation
 
  • ASK/PSK special cases of DSBSC
 
  • FSK special case of FM
 
 
•ASK/PSK Demodulator:
 
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)  Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Noise in ASK/PSK

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Eb is average energy per bit

 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Course Summary
 
•Communication System Block Diagram
 
•Fourier Series and Transforms
 
•Sampling
 
•Power Spectral Density and Autocorrelation
 
•Random Signals and White Noise
 
•AM Modulation
 
•FM Modulation
 
•Digital Modulation
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Communication System Block Diagram
 
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
 
Source encoder converts message into a message signal or bits. Source decoder converts back to original format.
 
Transmitter converts message signal or bits into a transmitted signal at some carrier frequency.
 
Modulation, may also include SS, OFDM, precoding.
 
Channel introduces distortion, noise, and interference.
 
Receiver converts back to message signal or bits.
 
Demodulation (for SS and OFDM too), may also include equalization.
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Main Focus of This Class
 
 
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
Modulation encodes message or bits into the amplitude, phase, or frequency of carrier signal.
 
Channel filters signal and introduces noise
 
 
Demodulator recovers information from carrier

Need tools for manipulating and filtering signals and noise

 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Fourier Series
 
Exponentials are basis functions for periodic signals
 
Can represent periodic signal in terms of FS coefficients
 
Complex coefficients are frequency components of signal
 
 
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Fourier Transform

 
Represents spectral components of a signal
 
Signal uniquely represented in time or frequency domain
 
These coefficients are frequency components of signal

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Timelimited signals have infinite frequency content Bandlimited signals are infinite duration

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Key Properties of FTs

 

Frequency shifting (modulation)
  • Multiplying signal by cosine shifts it by fc in frequency.
 
 
Multiplication in time ⇔ Convolution in Frequency
 
 
Convolution in time Multiplication in Frequency                
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Filtering
 
Convolution defines output of LTI filters
 
Convolution (time) Multiplication (freq.)
 
Easier to analyze filters in frequency domain
 
Filters characterized by time or freq. response
 
Exponentials are eigenfunctions of LTI filters
 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)              

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Sampling

 

Sampling (Time):

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Sampling (Frequency)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Nyquist Sampling Theorem

 

A bandlimited signal [-B,B] is completely described by samples every .5/B secs.

  • Nyquist rate is 2B samples/sec
 
Recreate signal from its samples by using a low pass filter in the frequency domain
  • Sinc interpolation in time domain
  • Undersampling creates aliasing

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Power Spectral Density

 

Distribution of signal power over frequency

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

PSD/autocorrelation FT pairs: Rx(t) Sx(f)
 
Useful for filter and modulation analysis

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Random Signals

 

Not deterministic (no Fourier transform)
 
Signal contained in some set of possible realizations
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
 
Characterize by average PSD Sn(f)
 
Autocorrelation Rn(t) Sn(f) is the correlation of the random signal after time τ.
 
Measures how fast random signal changes
 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Filtering and Modulation

 

Same PSD effect as for deterministic signals
 
Filtering

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Modulation (no bandwidth constraint on Sn)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

White Noise

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 
Signal changes very fast
 
Uncorrelated after infinitesimally small delay
 
Good approximation in practice
 
Filtering white noise: introduces correlation

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Amplitude Modulation

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 
Constant added to signal m(t)
 
  • Simplifies demodulation if 1>|kam(t)|
  • Constant is wasteful of power
 
Modulated signal has twice the BW of m(t)
 
Simple modulators use nonlinear devices
 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
 
Double Sideband Suppressed Carrier (DSBSC)
 
Modulated signal is s(t)=Accos(2πfct)m(t)
 
Generated by a product or ring modulator
 
Requires coherent detection (φ2»φ1)
  • Costas Loop
 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

Noise in DSBSC Receivers

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Single Sideband
 
Transmits upper or lower sideband of DSBSC

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Reduces bandwidth by factor of 2
 
Uses same demodulator as DSBSC
 
Coherent detection required.
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
FM Modulation
 
 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
FM Bandwidth and Carson’s Rule

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

 
 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Generating FM Signals
 
NBFM
  • Circuit based on product modulator
WBFM
  • Direct Method: Modulate a VCO with m(t)
  • Indirect Method: Use a NBFM modulator, followed by a nonlinear device and BPF
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
FM Generation and Detection
 
Differentiator/Discriminator and Env. Detector

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

Zero Crossing Detector
  • Uses rate of zero crossings to estimate fi
Phase Lock Loop (PLL)
  • Uses VCO and feedback to extract m(t)
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
ASK, PSK, and FSK
 
Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

ASK/PSK Demodulation

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Probability of Bit Error in ASK/PSK------------------------------------------Next slide

 

FSK Demodulation (HW 7)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

 
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
 
Megathemes in EE104
 
Fourier analysis simplifies the study of communication systems
 
Modulation encodes information in phase, frequency, or amplitude of carrier
 
Noise and distortion introduced by the channel makes it difficult to recover signal
 
The communication system designer must design clever techniques to compensate for channel impairments or make signal robust to these impairments.
 
Ultimate goal is to get high data rates with good quality and low cost.
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 
Hot Topics in Communications
 
All-optical networks
 
Components (routers, switches) hard to build
 
Need very good lasers
 
Communication schemes very basic
 
Evolving to more sophisticated techniques
 
Advanced Radios
 
Adaptive techniques for multimedia
 
Direct conversion radios
 
Software radios
 
Low Power (last years on a battery)
 
Ultra wideband
 
Wireless Communications
 
Probability of Bit Error in ASK/PSK------------------------------------------Next slide
 

 

Future Wireless Systems

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)
 

Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

  

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FAQs on Chapter - Probability of Bit Error in ASK/PSK, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE)

1. What is the probability of bit error in ASK/PSK modulation schemes?
Ans. The probability of bit error in ASK/PSK modulation schemes is influenced by various factors such as noise, interference, and the modulation scheme itself. It is typically calculated using the bit error rate (BER) formula, which takes into account the signal-to-noise ratio (SNR) and the modulation scheme. A higher SNR results in a lower probability of bit error.
2. How does the probability of bit error in ASK/PSK relate to the signal-to-noise ratio (SNR)?
Ans. The probability of bit error in ASK/PSK is inversely related to the signal-to-noise ratio (SNR). As the SNR increases, the probability of bit error decreases. This is because a higher SNR means that the signal is stronger compared to the background noise and interference, making it easier to detect and decode the transmitted bits accurately.
3. How does the probability of bit error in ASK/PSK affect the data transmission reliability?
Ans. The probability of bit error in ASK/PSK directly affects the data transmission reliability. A higher probability of bit error implies a higher chance of incorrect bit decoding, leading to data corruption. Therefore, in order to ensure reliable data transmission, it is important to minimize the probability of bit error by optimizing the signal quality, reducing noise, and employing error correction techniques.
4. What is the role of analog-to-digital converters (ADCs) in data transmission?
Ans. Analog-to-digital converters (ADCs) play a crucial role in data transmission by converting analog signals into digital form. In the context of ASK/PSK modulation, ADCs are used at the receiver end to convert the received analog signal, which may be distorted by noise and interference, into a digital representation. This allows for further processing and decoding of the received signal, enabling accurate recovery of the transmitted data.
5. How does the semester influence the study of computer science engineering?
Ans. The semester system in computer science engineering provides a structured approach to learning and progressing through the curriculum. Each semester focuses on specific subjects and topics, building upon the knowledge gained in previous semesters. It allows students to have a well-rounded understanding of computer science engineering concepts and skills over the course of their studies. The semester system also facilitates the evaluation and assessment of students' progress through regular examinations and assignments.
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