The document discusses various digital modulation formats including BPSK, QPSK, OQPSK, and π/4 QPSK. BPSK carries only 1 bit per symbol and has low bandwidth efficiency. QPSK carries 2 bits per symbol but has issues with zero crossing during transitions of 2 bits. OQPSK addresses this with a delay between in-phase and quadrature components to avoid 180 degree phase shifts. π/4 QPSK provides further improvements with phase shifts of up to 135 degrees, allowing for non-coherent detection and better performance in noisy environments. DQPSK first performs differential encoding before QPSK modulation to minimize transitions.
This presentation covers:
Some basic definitions & concepts of digital communication
What is Phase Shift Keying(PSK) ?
Binary Phase Shift Keying – BPSK
BPSK transmitter & receiver
Advantages & Disadvantages of BPSK
Pi/4 – QPSK
Pi/4 – QPSK transmitter & receiver
Advantages of Pi/4- QPSK
In digital modulation, minimum-shift keying(MSK) is a type of continuous-phase frequency-shift keying that was developed in the late 1950s and 1960s.
Similar to OQPSK(Offset quadrature phase-shift keying),
This presentation covers:
Some basic definitions & concepts of digital communication
What is Phase Shift Keying(PSK) ?
Binary Phase Shift Keying – BPSK
BPSK transmitter & receiver
Advantages & Disadvantages of BPSK
Pi/4 – QPSK
Pi/4 – QPSK transmitter & receiver
Advantages of Pi/4- QPSK
In digital modulation, minimum-shift keying(MSK) is a type of continuous-phase frequency-shift keying that was developed in the late 1950s and 1960s.
Similar to OQPSK(Offset quadrature phase-shift keying),
The Quadrature Phase Shift Keying QPSK is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier DSBSC modulation scheme, which sends two bits of digital information at a time, called as bigits.
Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs. This decreases the data bit rate to half, which allows space for the other users.
QPSK (Quadrature Phase Shift Keying) is type of phase shift keying. Unlike BPSK which is a DSBCS modulation scheme with digital information for the message, QPSK is also a DSBCS modulation scheme but it sends two bits of digital information a time (without the use of another carrier frequency).
The amount of radio frequency spectrum required to transmit QPSK reliably is half that required for BPSK signals, which in turn makes room for more users on the channel.
LEDs are of interest for fibre optics because of five inherent characteristics..
How it works?
Spectrum of an LED
Modulation of LED
LED Vs. Laser diode
disadvantages of LED
In this chapter we examine the capacity of a single-user wireless channel where transmitter and/or receiver have a single antenna. We will discuss capacity for channels that are both time invariant and time varying. We first look at the well-known formula for capacity of a time-invariant additive white Gaussian noise (AWGN) channel and then consider capacity of time-varying flat fading channels. We will first consider flat fading channel capacity where only the fading distribution is known at the transmitter and receiver. We will also treat capacity of frequency-selective fading channels. For time -invariant frequency-selective channels the capacity is known and is achieved with an optimal power allocation that water-fills over frequency instead of time. We will consider only discrete-time systems in this chapter.
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
This slide describe the techniques of digital modulation and Bandwidth Efficiency:
The first null bandwidth of M-ary PSK signals decrease as M increases while Rb is held constant.
Therefore, as the value of M increases, the bandwidth efficiency also increases.
The Quadrature Phase Shift Keying QPSK is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier DSBSC modulation scheme, which sends two bits of digital information at a time, called as bigits.
Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs. This decreases the data bit rate to half, which allows space for the other users.
QPSK (Quadrature Phase Shift Keying) is type of phase shift keying. Unlike BPSK which is a DSBCS modulation scheme with digital information for the message, QPSK is also a DSBCS modulation scheme but it sends two bits of digital information a time (without the use of another carrier frequency).
The amount of radio frequency spectrum required to transmit QPSK reliably is half that required for BPSK signals, which in turn makes room for more users on the channel.
LEDs are of interest for fibre optics because of five inherent characteristics..
How it works?
Spectrum of an LED
Modulation of LED
LED Vs. Laser diode
disadvantages of LED
In this chapter we examine the capacity of a single-user wireless channel where transmitter and/or receiver have a single antenna. We will discuss capacity for channels that are both time invariant and time varying. We first look at the well-known formula for capacity of a time-invariant additive white Gaussian noise (AWGN) channel and then consider capacity of time-varying flat fading channels. We will first consider flat fading channel capacity where only the fading distribution is known at the transmitter and receiver. We will also treat capacity of frequency-selective fading channels. For time -invariant frequency-selective channels the capacity is known and is achieved with an optimal power allocation that water-fills over frequency instead of time. We will consider only discrete-time systems in this chapter.
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
This slide describe the techniques of digital modulation and Bandwidth Efficiency:
The first null bandwidth of M-ary PSK signals decrease as M increases while Rb is held constant.
Therefore, as the value of M increases, the bandwidth efficiency also increases.
The paper discuses about the performance of digital modulation schemes – BPSK, QPSK and QAM using
MATLAB. The performance of these schemes is evaluated by finding the bit error rate (BER) on AWGN and
Rayleigh channels. Initially a MATLAB code is generated and the performance of these modulation schemes
BPSK,QPSK and QAM is evaluated by finding BER and signal to noise ratio over AWGN and Rayleigh fading
channels. Later a simulation model is created using Simulink for these modulation schemes and its performance is
evaluated on AWGN channel.
Digital Communication System
Communication Channels
AWGN: Universal channel model
Band Limited Channel: Channel BW <Signal BW, ISI
Fading Channel: multipath waves
Basic Modulation Methods
Criteria for choosing Modulation Schemes
Power Efficiency: Required Eb/N for certain error probability over AWGN channel
Bandwidth Efficiency: no. of bits per second that can be transmitted on system bandwidth.
System Complexity: Amount of circuit involved and complexity
System Performance Parameters
Average SNR
Outage Probability: instantaneous prob. Exceed certain limit
Average BEP
Amount of Fading/severity of fading
Average Outage duration: O/P SNR fall below certain SNR
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The typical three path propagation and anti jamming capability associated with DSSS were carried out
through the combination of Lab VIEW and MATLAB 7.8. At the transmitter, the NRZ data stream is first mapped
into BPSK symbols and then spread-out using different PN code like Hadamard code, Gold or Kasami sequences.
And we see that single user is not total utilization band. Direct Sequence Spread Spectrum (DSSS) techniques are
used same bandwidth Number of user to increase, and we see that better performance. That we can say Direct
Sequence Spread Spectrum techniques is reused to bandwidth. And we can say that in this techniques power loss is
low, anti jamming capability is less and system is more reliable. Furthermore, BPSK-Spreading transceiver should be
analyzed for their performance, multipath scenario and interference whether under AWGN channel which show that
these has been overcome effectively and attain more robust performance, when using direct sequence spread
spectrum.
Comparative Study and Performance Analysis of different Modulation Techniques...Souvik Das
A comparative study and performance analysis of different modulation
techniques which shows graphically and comparative results Channel Noise
with Bit Error Rate of ASK, FSK, PSK and QPSK.
Similar to 3.2 modulation formats bpsk, qpsk, oqpsk, (20)
2.3b access control random access methods - part 3 - csma caJAIGANESH SEKAR
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Hello People.. Welcome to GURUKULA!!!
Have you ever thought that how the protocols that are required for the effective delivery of the messages from one place to anpther place take place in a real time internet..... This video explains about the concept called PROTOCOL LAYERING, where you can learn the way how the protocols are layered in such a way..
Simple examples are also used to make the concepts clean nd clear.
This video will help you to learn:
What is protocol layering in networks, OSI Model in Computer Networks, Layers of OSI Model, OSI Model, OSI Internet Module, OSI Layers and their Functions, Examples of OSI Models, 7 layers of OSI Models, Principles of Protocol Layering, Why layering the Protocols,
Thanks for Watching, Keep Supporting and Keep Sharing...
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A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
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Final project report on grocery store management system..pdfKamal Acharya
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Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
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3. Modulation:
Modulation is the process of encoding information from a message source in a manner suitable for transmission.
Qualities of Modulation Formats:
Spectral Efficiency:
This must be as HIGH as possible
This is achieved by using Higher order modulation formats.
This allows higher data bits to be transmitted with each symbol.
Adjacent Channel Interference:
This must be as LOW as possible.
This entails that the power spectrum of the signal should not roll outside the desired band.
This is achieved by proper filtering mechanisms.
Sensitivity with respect to noise:
This must be as LOW as Possible.
This is achieved by using lower order Modulation formats.
Robustness with respect to delay and Doppler dispersion:
This must be as LARGE as Possible.
To achieve this Filtering must be as minimum as possible.
Waveform must be easy to generate
To use class C Amplifiers , then modulation formats with constant envelop must be used
To use class A or B amplifiers, then modulation formats with envelop distortions can be used.
4. Choice of Digital Modulation
• Several factors that influence the choice of a digital modulation scheme. A desired
modulation scheme provides,
Low bit error rates at low received signal to noise ratios
Performs well in multipath and fading conditions
Occupies a minimum of bandwidth
Easy and cost effective to implement
• Existing modulation formats do not simultaneously satisfy all of these requirements.
Hence trade-offs were made when selecting a digital modulation schemes.
• The performance of the modulation formats are decided by
Power efficiency:
This parameter describes the ability of modulation format to preserve the
fidelity of digital messages at low power levels.
Bandwidth efficiency:
This parameter describes the ability of modulation format to accommodate
data within a limited bandwidth.
5. Binary Phase Shift Keying (BPSK)
In Binary Phase Shift Keying (BPSK), the phase of the carrier signal is varied between two possible states m1 and m2
corresponding to binary 1 and binary 0. These two waveforms will have 180o phase shift.
Considering the Energy per bit Eb,
𝐸 𝑏 =
1
2
𝐴 𝑐
2
𝑇𝑏
The Most Generalised Eqn. is Given by:
Then, Amplitude Ac is given by
𝐴 𝑐 =
2 𝐸 𝑏
𝑇𝑏
6. Power Spectral Density of BPSK
Power Spectral Density of BPSK:
PSD of any band pass signal is given by,
g(t) for BPSK is given by
The power spectral density of BPSK is given by
The PSD frp the BPSK signal at RF can be evaluated by translating the
baseband spectrum to the carrier frequency using the relation shown
above, Hence the PSD of a BPSK signal at RF is given by
Null to Null Bandwidth:
The simpler and most widely accepted measure
of bandwidth is equal to the width of the main
spectral lobe.
BW = (f+Rb) – (f-Rb) = 2Rb
Where Rb = Bit Rate
7. Quadrature Phase Shift Keying (QPSK)
There are certain drawbacks with BPSK, it can carry only 1 bit in a symbol.
This makes the BPSK not suitable for High data rates. Also BPSK is not spectrum Efficient.
Quadrature Phase Shift Keying has twice the bandwidth efficiency of BPSK, since 2 bits are transmitted in a single
modulation symbol.
The phase of the carrier takes 1 of 4 equally spaced values, such as 0,Pi/2, pi, and 3Pi/2 where each value carries
unique message bits.
The equations for QPSK is given by
9. Comparison of BPSK and QPSK
Constellation Diagram:
No. of Points in constellation diagram is inversely proportional to the spectrum occupancy. i.e., More
the number of points lesser the bandwidth occupancy (Spectrum Efficient)
Distance between the points on constellation diagram directly replicates the Error Probability of the
modulation format.
BW = (f+Rb) – (f-Rb) = 2Rb
BW = (fc + Rb /2) - (fc - Rb /2)
= Rb
10. OQPSK – Offset QPSK or Staggered QPSK
Drawbacks of QPSK are:
Where there is a 2 bit change in the input sequence, the transition in the state crosses
the origin of the constellation diagram for a particular period of time.
This causes NON LINEARITY effects in the systems.
Because of this effect the systems attracts the Side Lobes.
Also the Linear Amplifiers that are used in the system cannot amplify the signals
to optimal levels.
These drawback of QPSK is mainly because of the 180o transition. This can be eliminated by introducing an Offset
between the in phase and quadrature components will eliminate the 180o phase shift. Instead it will be 90o phase
shift.
Other than the offset all others things are as similar to the
QPSK
The phase shifts are delayed to half a symbol period that
ensures 180o phase shift never occurs in the input sequence.
This avoids the problem of zero crossing there by effective
amplification is achieved.
However, this is not spectrum efficient as compared to the
QPSK.
But, OQPSK is proved to perform better than QPSK in the
presence of phase jitter due to noisy reference signals at the
receiver.
11. π/4 QPSK
• π/4 QPSK is a compromise of QPSK and OQPSK.
• This modulation format allows a maximum phase shift to +/- 135o .
Which further improves the performance of the modulation scheme.
• The most important feature of Pi/4 QPSK is that it offers non coherent
method of detection.
• This technique performs better in the presence of Multipath spread and
Fading.
12. Differential QPSK
• DPSK → Differential Phase Shift Keying
• Non-coherent Rx can be used
• easy & cheap to build
• no need for coherent reference signal from Tx
• Bit information determined by transition between two phase states
• incoming bit = 1 → signal phase stays the same as previous bit
• incoming bit = 0 → phase switches state
13. Summary
• Binary Phase Shift Keying
Carries only 1 bit at a time
Not bandwidth efficient
• Quadrature Phase Shift Keying
Problem of zero crossing when 2 bit change is detected
Non linearity effects due to 180o phase shift
Offset QPSK
Inserting a offset reduces the phase shift to 90o there by improving the effective amplification
of signals with linear amplifiers
• Pi/4 QPSK
Compromise between the QPSK and OQPSK
More points on Constellation Diagram thereby better spectrum efficient
Since more points on constellation diagram distance between the points is also less there for
performs better in noisy environments also. Better Error probability
• DQPSK
Further improvements in modulation qualities
First Differential encoding is performed and then QPSK is performed.
Minimizes the amount of transition during modulation.
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