Questions tagged [qpsk]
Quadrature Phase Shift Keying
0
votes
2answers
30 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.
...
0
votes
0answers
72 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}...
0
votes
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
votes
1answer
50 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 ...
1
vote
1answer
43 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
votes
2answers
46 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
61 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
votes
1answer
48 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"??
0
votes
0answers
23 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
votes
0answers
15 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 ...
1
vote
0answers
65 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
votes
0answers
41 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
votes
1answer
66 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
votes
1answer
118 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
votes
1answer
60 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 <...
1
vote
2answers
765 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 ...
-1
votes
1answer
574 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 ...
1
vote
1answer
182 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 ...
0
votes
2answers
714 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
327 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
79 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
votes
1answer
292 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
428 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 ...
-1
votes
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 ...
0
votes
2answers
116 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 ...
0
votes
3answers
586 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
votes
1answer
208 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
votes
1answer
561 views
Calculating bit-error-rate of QPSK data
I am working on a simulation of QPSK data using the code below (Matlab):
...
0
votes
1answer
506 views
2
votes
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 ...
1
vote
0answers
252 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
votes
2answers
5k 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
votes
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
votes
1answer
120 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
votes
1answer
158 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
0
votes
1answer
354 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
548 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). ...
3
votes
1answer
181 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
votes
2answers
65 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
votes
1answer
10k 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.
0
votes
1answer
920 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?
1
vote
0answers
171 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
votes
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 ...
1
vote
1answer
920 views
Adding AWGN noise with a correct noise power to the signal
I would like to add AWGN noise to my BPSK and QPSK signal. So assume the BPSK signal is x1 and QPSK signal is x2. The ...
3
votes
1answer
195 views
How should I isolate a single QPSK signal from a noisy band?
I've worked through a number of PSK demodulation tutorials, but they all start with a single PSK signal that fills the entire sample rate.
But what if the signal is in the real world? What kind of ...
2
votes
1answer
1k views
Gardner Timing Recovery for Repeated Symbols
I am implementing the Gardner Timing Error Detection algorithm for a QPSK signal. I understand the concepts behind it but I am curious as to what effect repeated signals can have on the phase lock.
...
1
vote
1answer
3k views
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 ...
0
votes
0answers
462 views
Sampling rate versus number of sample of I and Q
I am acquiring data of an O-QPSK signal (chip rate : 2Mchip/s) with a SDR. I am undersampling the signal at 20 Mhz (carrier is at 2.8 GHz) so I respect the Shannon-Nyquist criterion that you need to ...
3
votes
1answer
775 views
O-QPSK constellation interpretation - GNU Radio
I am currently trying to recover the I&Q of a O-QPSK signal generate from the standard XBEE arduino module using a B200. I can get somehow get a "look-like" of a constellation. Here an screenshoot:...
2
votes
0answers
402 views
Problem in constellation diagram
In a waveform designing i am getting this type of constellation(image_attached).
Can anyone please tell me why i am getting this type of constellation?
this constellation is after frequency correction....
