Questions tagged [qpsk]
Quadrature Phase Shift Keying
172
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IQ Mismatch and Image-II
I asked the question IQ Mismatch and Image about the relationship between IQ mismatch and image signals in an IQ transmitter. The accepted answer says that the in-phase component (with amplitude A in ...
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2
answers
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Why does constellation looks odd when the number of filter span is an odd number?
I use Wireless Waveform Generator app in MATLAB to simulate QPSK. When I select the filter span parameter as an even number, the constellation diagram looks normal. ...
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DIgital QPSK demodulation of I/Q Data (Costas Loop, Symbol Sync, etc.)
I am trying to implement in hardware demodulation of QPSK-modulated I/Q samples from an SDR. The data would come from the reception of satellite transmissions. My approach is based on mapping onto ...
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1
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What's wrong with 180 degree phase shift in QPSK?
I red that 180 degree phase shift causes spurious high frequency components which As a result methods such as OQPSK are invented, but I can't understand how it can happens? In fact, I can't find any ...
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50
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BPSK decoding with a non-ideal transmission medium
I'm simulating tranmission via power line communications (PLC) using BPSK. Due to the coupling circuit and slightly inductive nature of the line, the BPSK signal received is far from ideal. In the ...
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Unable to decode QPSK
I am trying to decode QPSK data and these are the constellation and timing plots, what could be the reason for the non convergence of QPSK constellation
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How to extract data from .iq file?
I am trying to extract data from .iq file recorded by radio. The modulation is QPSK. I have implemented a GRC flow graph but the costas loop is not converging. Can anyone please help in understanding ...
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How can a costas loop work when root raised cosine filter used on QPSK signal?
I just finished a costas loop for QPSK signal,I transmit the baseband signal and sent it into the costas loop, which worked well, but when I filter the baseband signal with root raised cosine filter ...
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2
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Which is the correct equation for union bounds for non-standard QPSK?
This a not a typical QPSK where $\alpha \neq \beta$
My book gives me the following
$$
P_e
\leq
Q(\frac{2\alpha} {\sqrt{2 N_0}})
+
Q(\frac{2\beta} {\sqrt{2 N_0}})
+
Q(\frac{2\sqrt{\alpha^2 + \beta^2}...
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QPSK Receiver: Blind coarse frequency offset esimation issue
In this single carrier QPSK receiver, is designed to receive QPSK data from a satellite in Low Earth Orbit. Since the satellite speed in this orbit is around 3000 m/s and our carrier frequency is 12 ...
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QPSK Channel Detection Algorithm
I send a QPSK signal over pluto sdr and receive it from rtlsdr. As you can see from the screenshot below SNR of the received signal is very high, and the signal is very distinguishable. Hence, it is ...
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I/Q scatter plot of raised cosine filter in QPSK
I am using a raised cosine filter in my QPSK receiver and I see this IQ diagram of the signal, but it seems off to me. Can someone explain why this happens?
This is the MATLAB code I used to generate ...
- 121
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51
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In wireless communication, is pulse shaping applied to each BPSK signal before OFDM is used, or not?
I have read a number of posts that seem to ask this question but have not been able to find a definitive answer. Here goes...
I understand that BPSK with NO pulse shaping would produce a signal in ...
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Removing fixed phase offset noise
This feels like a real basic question but I'm struggling to find a clear answer.
I have PSK signal that subjected to a fixed phase shift noise, introduced between the transmitter and receiver - so the ...
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2
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Transmitting data with QPSK using an SDR
My question assumes that I want to transmit some data using QPSK using and SDR.
The SDR will be fed with IQ data and this will transmitted at a sample rate Fs and be up converted to a carrier ...
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1
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What is the relationship between Symbol Duration and Sampling Frequency in a 256 MPSK radio link
I'm struggling to work out the relationship between Symbol Duration and Sampling Frequency in an MPSK link.
For instance, if the Sampling Frequency is 10MHz this means that a sample is taken every ...
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Comparing communication systems with different modulation orders and code rates
I propose an end-to-end communication method in my research. The key part of the method is not the channel coding and modulation but we use them anyway. I am using 1/3 rate Turbo codes with QPSK and ...
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90
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How to choose sample offset values in timing synchronization for a QPSK demodulator?
I am implementing a timing synchronization loop for a QPSK demodulator. I have chosen to use a Gardner timing error detector, which has often been mentioned. I am about to close my loop and I am ...
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628
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spectral bandwidth of QPSK signal
When running the MATLAB QPSK transmitter and receiver example (found here: QPSK Tx and Rx Example) you can see on the plot of the spectrum that the bandwidth is ~80kHz.
If we double click on ...
2
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1
answer
515
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QPSK demodulation carrier frequency offset compensation on python
I am new to signal processing and I am trying to demodulate the IQ data, and I am stuck on the carrier frequency offset compensation.
I has 1000 samples and it is 1MHz data.
For the general idea, I ...
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118
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QPSK implementation with 2 BPSK [duplicate]
I have a tiny problem with understanding a thing here.
for the 1st the phase shift is 0 degrees, so on its modulated wave we put 180-degree phase shift.
for the 2nd 0, the oscillator puts a 90-degree ...
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163
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Modeling an OFDM signal and comparing it with QPSK
I am trying to model an OFDM signal based on original QPSK stream and compare their baseband spectrums.
I've used this article as a reference for plotting spectrum and this as a MATLAB OFDM reference
...
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544
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Why is the symbol duration in QPSK twice the bit duration?
I saw many answers for such questions by writing down equations such that the symbol is formed of n bits so the duration of the symbol in QPSK must be n multiple of the bit duration.
I am not ...
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How to remove Phase Offset from PSK signal?
Suppose you have captured IQ data from a PSK modulated signal with intermittent blanks between signal transmission as shown in the figure below.
I want to be able to automate and run an algorithm on ...
- 65
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2
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339
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QPSK: sampling frequency versus carrier frequency
I was trying to write 4QPSK in Python for my self learning based on the book Digital Modulations Using Python.
When I have my sampling frequency set to 4 times the carrier frequency, I get exactly 4 ...
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261
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QPSK InPhase and Quadrature [duplicate]
I am new to DSP. Please bear with my question. In QPSK why are we multiplying InPhase (Odd Bit) with Cosine and Quadrature (Even Bit) with Sine wave in this QPSK formulae
$$ s \left( t \right) = I \...
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2
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396
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Effect of Passband Slope on QPSK Constellation
What is the effect of a passband slope on a QPSK (or any QAM) constellation? Specifically given a linear slope (in magnitude, not dB), and no phase distortion (linear phase or even zero-phase) how ...
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The difference about QPSK, BPSK and 16-QAM in spectrum
What is the difference about QPSK, BPSK and 16-QAM in spectrum? I just simulated all three, but I can't see the difference clearly.
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Demodulate qpsk with gnu radio
I'm trying to demodulate a qpsk signal with gnu radio. The signal is from the meteor satellite on 137MHz https://www.sigidwiki.com/wiki/Low_Rate_Picture_Transmission_(LRPT).
I recorded the signal with ...
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Signal filtering with rrcos filter doesn't seem to work
I'm trying to learn some signal processing and recorded some iq data from the meteor satellite which transmits data with qpsk. I read the file with python and tried applying a rrcos filter on the ...
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469
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Why should costas loop be done after clock recovery, as opposed to before?
In GNURadio's PSK tutorial they place the costas loop after clock sync and linear equalizer. This seems odd to me.
I'm thinking that it's easier to lock onto a carrier frequency at the higher RF ...
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GNURadio 3.8 QPSK : Hard time to recover the right symbols/data
Cheers, I am demodulating a QPSK signal on GNURadio, the data transmitted is a known HEX file with the "1ACFFC1D" foreword every 124 bytes, to check if the demodulation is a success, it ...
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1
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121
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How to decode a MIMO stream using V-BLAST?
I am attempting to implement the V-BLAST algorithm for MIMO streams as described by Wolniansky et al. in the following paper: https://ieeexplore.ieee.org/document/738086 (I am not commenting on its ...
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2
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Symbol Timing Recovery with Fractional Sample per Second
I'm trying to write symbol timing recovery loop and taking help from "Digital Communications A Discrete-Time Approach" by Miachel Rice. MATLAB communication toolbox has also implemented the ...
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Do PSK/QAM modulators (e.g. 4G/5G) fundamentally use more energy per packet than CSS modulators (e.g. LoRa)?
Not sure if this is the right place or even the right question to ask, but googling did not get me much further, so here goes:
I'm trying to assess whether the power consumed by an IoT device, based ...
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subquestion 2 : original Q "Difference between MSK and GMSK?"
if we talk about a modulation, we mention a linear and nonlinear modulation.
GMSK is nonlinear modulation, but it can be derived from a linear modulation as MSK, PAM and we talk about a linear ...
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subquestion: original Q "Difference between MSK and GMSK?"
I am studying GMSK modulation for an understanding its realisation in practice.
I have the question posted in 2021: "Difference between MSK and GMSK?"
And Mr Boschen explained how the ...
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129
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How do I set GNU Radio Es/No?
I am trying to create a random signal in GNU Radio (using DVB-S2 specs for the physical layer) and transmit this signal using a USRP X310. This is shown below:
Problem: I would like to be able to ...
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3
answers
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Do BPSK vs QPSK have the same performance?
I'm trying to re-learn digital communication theory again and am creating a bit error probability simulation for various modulations. So far I've added BPSK, QPSK, and 8PSK and below is a plot that ...
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1
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Exact formula for 8-PSK BER
Is there an exact formula for the probability of bit error (or bit error rate, BER) for 8-PSK (in the literature, course slides, etc.)? I am not referring to SEP (Symbol Error Probability) but BER.
...
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Modulation in laser satellite communication
In small satellite communication technique we can use optical spectrum (optical (laser) communication system). The common and simplest modulation techniques used are On and Off
keying (OOK), Q-ary PPM ...
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In practice, why is there any overlap in frequency-division multiplexing?
Okay, so I am aware of the math behind perfect reconstruction in filterbank and wavelet theory when there is half-band symmetry. But I don't understand, when we have the computational power to do ...
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oQPSK/QPSK conversion with fractional interpolation
I once used a GNU Radio QPSK receiver for oQPSK demodulation. All I did was to "forcefully" delay the Q channel by half the symbol time. At the time, I was using a discrete number of samples ...
-1
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1
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How to find the bandwidth of the transmitted M-FSK signal?
I'm tried to find the solution, but I failed.
my question in the figure below, and the correct answer it's shown at the end of Figure.
I'm using this formula but the answer is not correct!
Is there ...
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612
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Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?
From the peak to average power ratio point of view OQPSK is better than pi/4-DQPSK. What is the advantage of pi/4-DQPSK compare to OQPSK? Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?
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RRC filter in receiver side well applied?
I would like to ask question bout the rrc filter that I applied as an matched filter for receiver side in communication. My aim after RRC filter is to draw the eye diagram, and so far the eye opening ...
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Matlab: Could anyone suggest why Iam getting a different geometry for QPSK constellation diagram
I'm developing a Multi-user MIMO communication model in MATLAB where a base station communicates with 2 users. The model uses OFDM (QPSK) modulation. Channel model, precoding and covolutional encoder ...
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Why do I see a frequency shift from center when transmitting a QPSK via USRP with GNU Radio?
I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
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understanding FIR SRRC filter with memory implementation in C
I translated the Matlab QPSK receiver/transmitter into real-time C code that I have running on a PlutoSDR platform. QPSK receiver/transmitter
I wrote the square root raised cosine filter for the TX ...
0
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1
answer
316
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QPSK sync sequence detection problem
I have IQ data collected
This is the beginning of the packet that includes preamble and sync sequence. Red is real part, blue is imaginary.
Also constellation diagram for this data
I don't have ...
