Questions tagged [qpsk]
Quadrature Phase Shift Keying
171
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I/Q Sampling and Demodulation
A bit stream is mapped to symbols during baseband modulation, each symbol (say for QPSK) represents two bits. Each symbol has a corresponding I & Q value, which in QPSK, are used as the amplitude ...
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QPSK and OQPSK Modulation
In QPSK, after splitting the odd and even bits into the I and Q channels, and then multiplying them with the sine and cosine function, what next am I suppose to do?
Do I rearrange them back into ...
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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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What is the theoretical bit error rate for QPSK Matlab simulation when constellation points are transmitted (no symbol duration)?
I'm simulating a QPSK system in Matlab and I'm trying to calculate the theoretical bit error rate to compare it with the simulated ber. The formula that I'm aware of involves the term Eb/N0, but how ...
- 21
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1
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Spectral properties of QPSK modulation
From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well ...
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1
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Phase Noise in Constellation Plot
I have the following phase noise plot (-100dBc/Hz @ 1MHz offset and -130dBc/Hz noise floor):
The integrated phase jitter for this phase noise is around $4.6^\circ$. According to my understanding the ...
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IQ Mismatch and Image
I was reading the following paper about direct conversion receivers from TI: link.
In this paper they compare the performance of direct conversion and heterodyne receiver with IQ mismatch.
The ...
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1
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How to correct the phase offset for QPSK I-Q data
I have an I-Q data of QPSK modulation, the data is is smeared and I have to correct the phase offset that causes the smearing problem, how can I apply the Phased-locked loop or the Costas loop on this ...
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1
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Practical Gardner timing error implementation
I'm trying to demodulate a QPSK communication.
For the moment I do:
Signal detection by computing the ratio between the power of the carrier wave compared to the signal power.
Initial clock ...
- 223
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Why is a precoder necessary for DQPSK and what does it accomplish?
I've implemented a soft-decoder for DQPSK using the wonderful answers I received here:
How to soft decode DQPSK?
To get the soft-decoder working properly I needed to precode the data I was sending ...
- 805
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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 ...
- 125
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1
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361
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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 ...
- 377
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1
answer
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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
answer
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Error probability for 8-PSK
How can I calculate bit error rate for 8-PSK modulation when I have $E_b/N_0$ given? I know that for QPSK/BPSK the matter is quite simple, but I cannot cope with 8-PSK.
Let's say that my $E_b/N_0$ = ...
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QPSK demodulator on GNURadio continuously loses phase lock
I am designing a QPSK demodulator to be used for receiving Meteor M2 (LEO satellite) signals (QPSK at 72Kbaud). However, I am finding a lot of problems in my way.
First of all, this is the flowchart I ...
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Differential Encoding for M-PSK
Confused about a few topics w.r.t. differential encoding/decoding. First, consider the below BER curve taken from wikipedia ( https://en.wikipedia.org/wiki/Phase-shift_keying ) comparing BPSK/QPSK and ...
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1
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545
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How to plot BER Vs SNR of a received signal
I am using USRP to transmit and received MIMO frames similar to Wi-Fi standard that I created on my own. After receiving the signal, it is processed as described in the standard.
While I plot the ...
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1
answer
59
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Modulation classification via demodulation confidence?
I'm not sure if this is the right place to post this question, but will try anyway :-)
I recently started reading up on the field of automated modulation classification (AMC) where an algorithm ...
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1
answer
350
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ADC sampling rate implications Matlab/Simulink M-PSK modulation
I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink.
The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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1
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Burst QPSK demodulator
I am working in burst QPSK demodulator. I just want to double check if what I am doing is right.
Large frequency feedforward recovery by FFT
Carrier recovery Costas with 4 samples/symbol
Timing ...
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1
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3k
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Sampling frequency and oversampling factor
A quite naïve question. I need some clarification regarding choosing the sampling frequency and oversampling factor. The scenario is as follows:
I have an OQPSK modulated sequence with symbol rate 2 ...
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DFE for QPSK in MATLAB
I need to do a DFE for QPSK simulation in MATLAB.
The system consists of a QPSK signal transmitted with power = 1 which is then pulse shaped with a square raised-cosine filter. Add AWGN and a filter ...
1
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2
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3k
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Why do you get instantaneous phase by calculating correlation with a carrier signal?
I am somewhat new to DSP. I'm trying to implement BPSK by following this Python QAM tutorial.
My code seems to work, but I really just ported the tutorial's Python code to C++, and do not understand ...
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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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1
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90
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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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1
answer
134
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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 ...
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0
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242
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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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0
answers
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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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0
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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 ...
1
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0
answers
170
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Trade-off in sample-rate & FFT-size & Doppler
I've got a stream of digital IQ samples let's say at $F_s = 1 MSPS$ that consist of a narrowband signal, in awgn. Let's say the signal BW is ~ 100Hz. The narrowband signal's center (or base) frequency ...
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GNU Radio - Bandwidth and Band Reject Filter
I am currently trying to generate a psk modulated carrier with gnu radio.
Attach is an image of my flow graph.
As can be seen I am generating a bit stream using the Random Source module and ...
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1
answer
991
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SOQPSK-TG pulse shaping
I'm trying to build an SOQPSK-TG signal in MATLAB/Octave. I am following this paper for formulas.
I'm trying to generate a waveform for the phase, equation 2.4:
Where q(t) is the phase pulse, ...
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How to calculate the doppler shift?
I am writing a QPSK receiver in MATLAB. In the transmitter part, I have generated random data using randi, QPSK modulated and pulse shaped using a RRC filter.
The ...
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0
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Unable to stabilize 8-PSK signal with self designed costas loop
I am trying to make a signal processing block which implements the costas loop to stabilize an 8-PSK signal. Here is the flowgraph with "costas_loop" being my block.
My workflow is the following -
<...
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Processing OBPSK as OQPSK
I'm trying to create and process an OBPSK signal, which, as I understand it, transmits even bits on one axis and the odd bits on the opposite axis, resulting in a constellation with 4 unique points. ...
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3
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How can I generate offset QPSK symbols from QPSK symbols
I am trying to generate Offset-QPSK modulated symbols. But I am facing some difficulties. I know how to make QPSK symbols but I am unable to figure out at what stage I have to bring in changes to make ...
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Noise variance calculation for 16APSK Demodulator
I need to use approximate LLR algorithm for 16APSK demodulation. For that, I need to calculate noise variance which is given as
$Noise\;variance = \frac {Signal\;power\;\times\;Symbol\;time}{Sample\;...
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Barker Sequence for QPSK
I'm trying to implement a QPSK burst modulation and demodulation through a channel and I'm now considering the synchronization part.
I've read that Barker sequence were excellent option for this as ...
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1
answer
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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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Constellation diagram for QPSK modulation
I need to plot (in MATLAB R2011a) constellation diagram of a QPSK modulated signal after AWGN was added to the signal. My current MATLAB code looks like this:
...
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Why does DPSK constellation shrink when noise is added?
I am generating a DQPSK waveform at complex base band with constellation points on the unit circle and when I add AWG noise the constellation shrinks. The noisy constellation "blob" migrate inside ...
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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 ...
0
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1
answer
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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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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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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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Signal Timing Recovery, Loop Bandwidth and SNR
As explained in the answer here, for the symbol timing recovery loop we need to keep loop bandwidth sufficiently below the modulation bandwidth of the signal so as to avoid the filtering of the signal ...
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MATLAB: Generating a random bit stream in a frequency Band for PSK Modulation
I want to generate a pseudo-random bit stream in MATLAB in a given frequency band for PSK Modulation. I am using the idinput function to generate the bit stream:
<...
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What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?
Consider we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take samples from the received signal. So what is the minimum ...
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QPSK on baseband question
Given a signal you are asked to perform baseband QPSK (not on a
carrier).
Does this mean the following?
In baseband QPSK the (possible) constellation points are $$\sqrt {E_s} e^{jn \pi / 2} \...
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Which window function to use for QPSK signal?
I am trying to Receive a QPSK signal and for Sampling I need to recover clock. Now QPSK Signal is generated at 2.4GBaud. It is than sampled at 80GHz.Than further it is downsampled to 10GS/s (Symbols ...