Questions tagged [qpsk]
Quadrature Phase Shift Keying
105
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24 views
Which type of modulation should I use ?? QPSK or QAM? [closed]
Which type of modulation should I use ?? QPSK or QAM ?
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3answers
92 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
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1answer
65 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
32 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
31 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
40 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 ...
1
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1answer
21 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 ...
1
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2answers
76 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
30 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 ...
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2answers
61 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 ...
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1answer
80 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
49 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
32 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:
<...
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1answer
50 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 ...
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0answers
13 views
What is the QPSK Constellation Diagram used in LTE
I think the question is pretty straightforward. I have to do a class project that requires me to modulate a signal, and one of the steps is Quadrature Phase Shift Keying (QPSK). It is to be done in ...
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0answers
28 views
QPSK matlab/simulink Quantisation effects
I am trying to simulate the effects of quantization of an ADC on different waveforms (e.g. QPSK,8PSK) in Simulink.
For the case of QPSK the default BER curve would be generated with 2 bits per symbol ...
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1answer
27 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 ...
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1answer
54 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/...
0
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1answer
64 views
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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0answers
48 views
Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK
I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
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1answer
65 views
Understanding Matlab's Automatic Gain Control function
I am trying to understand the automatic gain control block provided by the communications toolbox. The documentation is here: Documentation
My questions are in regards to two of the configurable ...
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0answers
33 views
Learning PSK Modulation and Demodulation - Good Text to Read?
Title sums it up. I am curious to see what you all suggest. I'm a newbie and just need some beginner/intermediate material.
Thanks!
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0answers
138 views
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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1answer
49 views
Mapping soft symbols in DQPSK
I'm trying to soft decode DQPSK. According to this paper the bits are:
$b_1 = \mathrm{Re}\{s_n s^*_{n-1}\}, b_2 = \mathrm{Im}\{s_n s^*_{n-1}\}$
If I put 0.707 as a 100% probability of 0:
$\begin{...
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0answers
26 views
lte matlab baseband IQ recovery
I am a beginner again to signal processing, I did my degree over ten years ago, and I am relearning all my signal processing stuff.
I am a software developer by trade but now I am looking at some LTE ...
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1answer
100 views
Phase shifts of QPSK
I'm honestly lost on creating timing diagrams for bit sequences. I understand for QPSK there are symbols 00, 01, 10, 11 with phase shifts of 45,135,225 and 315.
I'm just not understanding how you ...
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1answer
231 views
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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1answer
27 views
BER performance of a space-time code over Rayleigh channel model
For a given space-time code, and in general terms, how would one proceed in the evaluation of the BER performance of this code ?
In order to be more clear, say i have 16 code matrices(who's elements ...
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2answers
375 views
BER of QPSK modulation in Rayleigh fading channel model
i am having trouble deriving a BER analytical expression for QPSK modulation system operating in a Rayleigh Fading channel model.
Could anyone direct me to a reference that would help in this matter.
...
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1answer
250 views
Relation between constellation SNR and baseband SNR
Let's say I have an I/Q modulation, ie. QPSK.
I can simulate an the effects of an AWGN channel by adding to my QPSK symbols the realizations of a complex normal.
$\mathcal{CN}(0,\frac{1}{\mathrm{SNR}...
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0answers
25 views
How to compare two 802.15.4 O-QPSK modulated digitals signals?
I am working on wireless sensors project and I am trying to simulate a transmission between two nodes.
So let's say I have two nodes which transmit the message to each other, i.e. node 1 transmits ...
3
votes
1answer
231 views
QPSK Phase Recovery : Maximum-likelihood Vs Costa's Loop
I have implemented a QPSK Costa's loop in GNU Radio and run some BER benchmarking. All is going well. Out of curiosity, I'm trying to implement the Maximum Likelihood phase recovery shown below.
For ...
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1answer
528 views
Offset QPSK detection in GNU Radio - Sample delay
An OQPSK detector is being tested in GNU Radio. The architecture was obtained from Michael Rice's Digital Communications - A discrete-time approach. The flowgraph is shown below.
The modulator ...
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2answers
2k views
Why is bit error rate = symbol error rate / number of bits per symbol in QPSK
I saw a code computing the error probability of QPSK, and I found that in this code the bit error rate is computed as symbol error rate divided by $2$.
I think that $2$ is because the QPSK symbol ...
2
votes
1answer
808 views
QPSK Data Rate vs Bandwidth at Passband: Why can it only transmit 1 bit per Hz and not 2 bits per Hz?
1) This is a follow up question to the most up-voted answer to this question.
2) The accepted answer is that "QPSK transmits 1 bit per Hz at passband".
3) The theory found in books seems to agree ...
2
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1answer
197 views
OQPSK vs QPSK envelope query
We use OQPSK because of envelope of signal but my question is
"In Phase Shift Keying(or QPSK) the amplitude of the transmitted signal is constant then how the envelope will change in OQPSK"??
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0answers
53 views
what waveform using to send qpsk signal with IQ tranceiver
I have an SDR tranceiver (AD9361 on fmcomms3) working with IQ channels, i wanted to make a c++ software that modulate and send a digital QPSK signal but i'm a beginner in digital signal processing and ...
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0answers
216 views
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, ...
0
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1answer
77 views
QPSK demodulation problem due to apparent transmitter clock frequency drift
I am using FPGA to generate 10Mbaud QPSK signal in two channels corresponding to two quadratures. Upsampling to 1GSample/s (using raised cos filter for interpolation) and complex upconversion (f_up=...
0
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1answer
199 views
“Revolving” QPSK Constellation
I am trying to code a QPSK transmitter in VHDL but first I want to create one out of Simulink blocks and translate it into VHDL code. I am using an example project for the PlutoSDR as a guide.
This ...
0
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1answer
231 views
QPSK constellation from baseband signal
My IQ sampler is measuring a QPSK carrier at a set frequency/bandwidth (40MSamp/s), but shifts the signal spectrum to baseband. My signal is 1.5Msym/s, but sampling at 1.5Msym/s gives me a ...
0
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1answer
80 views
Phase versus time graph of QPSK
In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained <...
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2answers
2k views
What is a constant envelope modulation?
The Book "Digital Modulation Techniques" by Fuqin Xiong groups digital modulation schemes into two classes: "constant envelope" and "nonconstant envelope." However, I was surprised by the inclusion ...
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1answer
1k views
The code explanation about QPSK modulation
This is the code about the QPSK modulation, and I don't understand the real part and the imaginary part code. Can anyone explain it to me if you know?
Why is ...
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1answer
355 views
Understanding the over sampling factor effects before a Matched Filter?
I am trying to design a matched filter at the receiver side to a half sine pulse shaping function sent by the transmitter of an OQPSK transceiver. I am not sure I understand the effect of varying the ...
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2answers
2k views
GNU Radio QPSK 4 Symbols
I'd like to generate a simple QPSK signal in GNU radio, but so far I haven't been able to get it to perform the way I'd like and I'm not sure if this has to do with some misunderstanding I have about ...
4
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1answer
625 views
What techniques are available for correcting constellation rotation due to phase ambiguity?
In order for a receiver to recover a baseband signal, it needs a carrier signal equivalent to that used by the transmitter for upconverting the original baseband signal. Unless pilot tones are used, a ...
2
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1answer
103 views
QPSK fundamental
I am trying to understand the QPSK fundamental and when I read that the phase shifts are 45°, 135°, 225°, and 315° in QPSK, I can not figure it out how.
In other word, I do not understand how the ...
0
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1answer
407 views
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} \...
1
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1answer
766 views
Question on the definition of one-sided PSD in AWGN channel
I am currently simulating the following in a telecommunications exercise in Python:
Consider a binary sequence $m[n]$ that is being modulated with QPSK
(Gray-mapped) that is being transmitted via ...
