Questions tagged [qpsk]
Quadrature Phase Shift Keying
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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 ...
0
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1answer
34 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
17 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 ...
0
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1answer
37 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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33 views
Channel state information from non-HT packets: is that possible?
I read several papers about CSI data, but one thing is not clear.
I would like to extract csi from legacy rate packets. I read some forums related to existing CSI tools and they only state that CSI ...
0
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1answer
66 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 ...
0
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1answer
20 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
130 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
148 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
24 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 ...
2
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1answer
125 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
223 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 ...
0
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2answers
137 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
237 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
92 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
35 views
QPSK signal 'passthrough' - not working as expected
as a fun project I am trying to build Quadrature Phase Shift Keying (QPSK) modulator & demodulator for a Digital Video Broadcasting (DVB) application. I am using the LimeSDR mini as my hardware ...
0
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0answers
26 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
106 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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0answers
55 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=...
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1answer
95 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 ...
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1answer
169 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 ...
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1answer
66 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
1k 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
895 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
243 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
1k 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 ...
3
votes
1answer
428 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
votes
1answer
88 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
353 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
vote
1answer
586 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 ...
0
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1answer
2k views
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 ...
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2answers
135 views
mpsk demodulation using digital sample
I am trying to receive and demodulate a 8PSK modulated sinusoidal waveform (real not complex) which is constant envelop and changing only in phase of the continuous sinusoid carrier every Symbol ...
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3answers
766 views
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 ...
0
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1answer
251 views
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\;...
0
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1answer
684 views
Calculating bit-error-rate of QPSK data
I am working on a simulation of QPSK data using the code below (Matlab):
...
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1answer
609 views
2
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2answers
2k views
Creating an Eye Diagram for QPSK Simulation
I am trying to implement an eye diagram for an application, where the input signal is QPSK. However, I feel that there is some fundamental concept
concerning these plots that I am missing. Several ...
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0answers
291 views
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 ...
3
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2answers
6k views
Envelope behavior dIfference between QPSK, OQPSK and $\pi/4$-QPSK
I am trying to analyze whats the major difference between these three variants of 4PSK.
I know that
QPSK - signal points are at 0,90,180,270
OQPSK - The bit period of Quadrature component is ...
0
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1answer
3k views
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:
...
0
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1answer
123 views
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 ...
0
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1answer
184 views
Frequency-ratio at baseband IQ-mixing
I was wondering by what logic or mathematics the frequency-ration $$ \frac{f_{lo}}{f_s} $$ in the sine-functions comes into existence?
Source
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1answer
385 views
Eye Diagram of QPSK Modulated Signal
I need to plot eye diagram for RRC filtered QPSK modulated signal. The specifications are given as follows
Sampling frequency : $1.024$ MHz
Symbol Rate : $256$ Kbps (Hence, Upsampling rate = $4$)
...
0
votes
2answers
613 views
How to scale measured QPSK points to determine magnitude error?
I am trying to determine the magnitude error between demodulated I,Q values and reference values on a constellation plot for a QPSK signal. The reference points are at (1,0),(0,1),(0,-1), and (-1,0). ...
2
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1answer
202 views
Recommendation for good ressources on digital processing and D-QPSK
I've been a C++ developer for 10 years. Quite high level. And I am completely new to Digital Signal Processing.
I am trying to implement a Software Defined Radio. Specifically I am trying to receive ...
0
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2answers
66 views
Sphere decoding for non-binary modulation
I have a simple question on how to implement SD for non-binary modulation, let say QPSK. Assume we transmit a complex symbol $\overline{a}$ drawn from a QPSK constellation. On a vector form, we can ...
2
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1answer
12k views
what is the difference between QPSK and 4QAM? [duplicate]
i need to know the main difference between QPSK and 4QAM, i have searched over the internet and still i have not found a good explenation.
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1answer
1k views
QPSK using Root Raised Cosine Filter
The implementation of QPSK requires 2 orthogonal basis.
So when using root raise cosine filter to implement QPSK, what is the 2 orthogonal signals?
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0answers
209 views
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 -
<...
3
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1answer
1k views
The difference between MSK as CPFSK and OQPSK
I am working on MSK simulation. I have read the Chapter 5 of book entitled Digital Modulation Techniques by Fuqin Xiong. It is said that MSK can be viewed as a Sinusoidal Weighted OQPSK or CPFSK. If ...
