Quadrature Phase Shift Keying
0
votes
0answers
20 views
Soft-decision Viterbi decoder branch metrics
I understand how the hard-decision Viterbi algorithm works, it uses the Hamming distance to calculate branch metrics. But what about soft-decision? Assuming an AWGN channel, QPSK modulation and 8-bit ...
0
votes
0answers
26 views
Peculiar OFDM Constellation
Currently testing blind demodulation methods on recorded OFDM signal.
The recordings were done with coax cables.
While the estimated Frequency and Time shifts were not accurate enough for ...
0
votes
1answer
60 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
0answers
34 views
Why QPSK and 4-QAM is similar? [duplicate]
I'm facing confusion regarding similarity between QPSK and 4-QAM.
As we know that QPSK, the radius of the circle in constellation graph remains constant (as the amplitude is constant).
$$
x(t) = a_{...
0
votes
1answer
49 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
128 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 ...
0
votes
1answer
50 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
78 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
292 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
139 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 ...
0
votes
0answers
107 views
QPSK modulation validation
I tried to replicate a Matlab code in python (for testing reasons) to do a QPSK modulation. So this is the original code(source Gaussian waves website):
...
0
votes
0answers
101 views
How to implement an OFDM system in MATLAB
Hi guys,
I am trying to simulate OFDM in MATLAB. I am referring this diagram to model the system. I have used QPSK modulation. My doubts are as below. Kindly go through them and help me. Thanking you ...
0
votes
0answers
355 views
Help with OQPSK Demodulation with GNU Radio
I am working on demodulating/decoding the GOES-15 satellite EMWIN signal @1692.7MHz, BW: 50KHz Mod: OQPSK. I have minimal experience in signal processing and some experience in using GNU Radio. I have ...
0
votes
0answers
33 views
BER Graph for a PSK Modulation through a linear channel model
This is the graph that occurs when M-PSK symbols pass through a linear channel with impulse response given in a vector h. The simulation is done in Matlab and I am unsure about the result because of ...
2
votes
1answer
67 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
156 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
234 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
753 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
77 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
338 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
137 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
328 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
341 views
2
votes
2answers
1k 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 ...
0
votes
0answers
146 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
4k 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
2k 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
98 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
120 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
0answers
132 views
Eye opening calculation
I wrote a MATLAB code for RRC filtered QPSK modulated signal. The eye diagram is plotted using object commscope.eyediagram. The analysis of the eye object gives a ...
0
votes
1answer
304 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
359 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
164 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
62 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
7k 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
2answers
720 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
134 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
594 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
173 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 ...
0
votes
0answers
358 views
Compute probability of error to each QPSK symbol
I'm trying to compute the probability error function of a QPSK modulation. I have a single user, who send a determined symbol $x = \frac{1}{\sqrt 2} \left(1+1j\right)$.
Then I estimate at the ...
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
2k 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
373 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
656 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
330 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....
1
vote
2answers
2k views
High Transmission Power : BPSK or QPSK?
In BPSK,
the constellation consists of 2 points (equiprobable) spaced at distance of $\sqrt{E_b}$ each from the origin.
So the average power from the constellation can be obtained by:
For BPSK, $P = ...
3
votes
1answer
3k views
GNU Radio - PSK Mod block - unexpected constellation diagram
I am simulating a QPSK modulation in GNU radio. Here is the flowgraph:
.
The source is a binary stream coming from the Random Source block. There are 4 PSK Mod blocks configured identically (4 ...
0
votes
1answer
130 views
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 ...
1
vote
1answer
1k views
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 ...
