Questions tagged [qpsk]
Quadrature Phase Shift Keying
138
questions
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55 views
Calculating complex AWGN in BPAM and QPSK
I was trying to add complex awgn in a bpam and a qpsk signal, manually. However i started using formulas as it is shown below (e.g. in BPAM) but the result was not the expected (also using as a ...
4
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3answers
127 views
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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1answer
73 views
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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84 views
GNURadio Guided Tutorial PSK Demodulation Example
I have been reading and doing the steps on this webpage of GNUradio : https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation
In the middle of the page, there is a section: "Using ...
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0answers
66 views
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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0answers
67 views
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 ...
1
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1answer
63 views
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 ...
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1answer
53 views
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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1answer
77 views
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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37 views
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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37 views
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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19 views
How to solve this question on communication lines?
The Question asked is as follows:
A communication link operates at a bitrate of 20 Mbps. The receiver is expected to perform at a $BER$ of $10^{-6}$ or better using $QPSK$ modulation scheme.
[Note: $...
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1answer
99 views
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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0answers
70 views
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 ...
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1answer
101 views
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 ...
1
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1answer
291 views
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 $E_b/N_0$ = ...
1
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1answer
405 views
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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39 views
Correcting large frequency offsets at very low data rates
Consider a typical BPSK system running at a baud rate of 1 kbaud/sec - the receiver needs to deal with severe frequency offsets, let's say up to +/- 1 MHz offset and that the frequency offset can ...
2
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1answer
544 views
Block diagram of M-PSK modulation and demodulation
I have come across this quadrature modulator block diagram in many books and websites:
I've read that the quadrature modulator allows to realize many different digital modulations, including ...
1
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1answer
133 views
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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0answers
51 views
What does this mean? The elliptical constellation in the QPSK constellation diagram?
Can you explain what kind of signal is this or what can you characterize when you see QPSK constellation like this? to get a better signal it needs to be near 1 and be a round circular constellation. ...
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56 views
Questionable Eb/N0 results for different modulations - measurements for 8-PSK do not match the theory
I would like to warn you that this post will be long, so thank you in advance to everyone who reads it and is able to help.
I am running a certain simulation. I created a measurement environment (...
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2answers
131 views
Why is the bandwidth for this QPSK system larger than expected?
Below is my gnuradio-companion graph.
As you can see the sample rate is 100k, I am modulating with QPSK, and am filtering the waveform (RRC) with the "Excess BW" parameter, at 0.35. The ...
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1answer
332 views
Why 8-PSK modulation has higher Eb/N0 than QPSK or BPSK?
I run a transmitter/receiver simulation using QPSK, BPSK, and 8-PSK modulations. As far as I have noticed, the best SNR per bit results are obtained when simulating with 8-PSK modulation (and also at ...
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0answers
363 views
Offset QPSK Demodulation using GnuRadio
I am currently trying to demodulate an Offset QPSK signal coming from a satellite using GNURadio.
If I understood correctly, an OQPSK is a QPSK with one of the two bits per symbol delayed by half a ...
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0answers
72 views
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 ...
0
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1answer
231 views
Transferring data over sound with QAM / QPSK
Been working on a FSK Modem in the last few weeks and have gotten it to work with 400bps, very reliable, atleast over a virtual audio cable, but it also works when playing a sound directly into a ...
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0answers
124 views
QPSK transmission simulation
I am trying to simulate a QPSK transmission using GNU Radio following mpsk_stage6.grc example in Gnuradio tutorials.
Currently I have no idea where is the problem and everytime I execute the flow ...
0
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1answer
167 views
Packet Encoder GNU QPSK Transmission
Hello everyone!.
This is a template to QPSK transmission but Packet Encoder block is no longer available in new GNURadio versions, what do I need to replace this block in order to do a QPSK ...
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1answer
200 views
How to separate Even and odd part (in-phase bit streams I and quadrature-bit streams Q) of the signal?
I am working on communication system in simulink and wondering, how can i separate the Even and odd part of the signal.
In my Transmitter block, I have :
$$
\boxed{\text{Binary Data signal}}{\...
2
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3answers
933 views
Use of pulse shaping in digital modulation
Sorry, I am a little bit confused here cause I thought when we say QPSK, the signal looks like the following.
I thought the bits to send/receive depends on the phase shift of the carrier, or is the ...
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1answer
101 views
When I double bit rate I do not see a difference in I_spectrum and Q_spectrum, but why?
I wanted to compare two different I-Q spectrum plots of a basic transmitter, one in which I doubled the bit rate. I expected a different result, that of possibly a higher/faster graph. It looks sort ...
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1answer
108 views
Modulation upsampling method
I try to implement a qpsk modulator in Octave.
The chain is the state of the art I guess:
$$\text{Symbol mapper} \rightarrow \text{Upsample 4} \rightarrow \text{Root raised cosine filter} $$
My main ...
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1answer
255 views
Differential Encoding for M-PSK
Confused about a few topics w.r.t. differential encoding/decoding. First, consider the below BER curve taken from wikipedia ( https://en.wikipedia.org/wiki/Phase-shift_keying ) comparing BPSK/QPSK and ...
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1answer
36 views
How to deal with modulator jitter?
I have a question regarding an implementation of a modulator.
I guess some people here have an FPGA background.
I would like to implement a QPSK modulator of 31 Mbit bitrate using a 125 MHz clock.
I ...
4
votes
3answers
213 views
What causes this type of distortion in a constellation I/Q plot?
I'm transmitting QPSK through a digital pulse shaping filter (RRC, 35% excess BW, 2 samples per symbol, 64 taps) at a rate of 56Msym/sec.
Receiving it on standard lab equipment (Vector signal ...
3
votes
1answer
840 views
Sample rates, Samples per Symbol, and Digital Pulse Shaping
Having some confusion about digital pulse shaping for complex baseband (passband) signals. The complex baseband linear modulation equation is
$$s(t)=\sum_{m=-\infty}^{\infty}\text{Re}\{a_m\}h(t-mT)+j\...
0
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1answer
53 views
How to Tx CDMA signal physically using an existing point-to-point modem? [closed]
I am working in acoustic communication, I want to test CDMA network capabilities in acoustic environment. I had an acoustic modem that has serial interface, a WHOI micromodem.
How can i serialized ...
0
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1answer
3k views
Python code for QPSK modulator [closed]
Have any of you done anything like QPSK Modulation in python? I am in the middle of it and having problems in setting up bits? like odd and even bits.
Have you got any idea?
Regards,
Sam
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2answers
50 views
How are pulse trains generated in a radio transmitter?
When simulating a PSK signal in MATLAB or Python, I often create an impulse train where each impulse is modulated with a symbol. This modulated impulse train then passes through a pulse shape filter ...
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1answer
221 views
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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2answers
254 views
MATLAB: Issue with passing data through AWGN Channel [closed]
I am trying to send QAM data through AWGN channel and I have 256 samples/symbol, I have the following code:
...
0
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1answer
156 views
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 ...
0
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2answers
691 views
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 ...
2
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1answer
266 views
Carrier Tracking Loop: Tracking noise vs Phase Noise Trade-off
I would like to compare two different implementations of carrier tracking loop which differ in the way phase detection happens in the PLL. I am using PSK modulation for the data.
In the first ...
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1answer
182 views
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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1answer
149 views
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:
<...
0
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1answer
104 views
Loop Bandwidth for Carrier Demodulation loop
I am trying to implement a simple MATLAB model for the demodulators for phase modulated signals (PSK) used in communication systems.
For the detection of the phase modulated output (PM out in the ...
1
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1answer
42 views
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 ...
0
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1answer
114 views
Digital Tanlock carrier recovery loop
I’m currently trying to understand a digital tanlock carrier recovery loop for QPSK (for example)
I cannot understand how it works.
For example we an ideal QPSK constellation.
phi = atan2(Q/I) = pi/...
