Questions tagged [qpsk]
Quadrature Phase Shift Keying
120
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21 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
51 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
36 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
5 views
Simulating Rayleigh channel - Problem with adding channel coefficents
I am currently trying to simulate a Rayleigh channel using python (numpy).
Full Jupyter Notebook on GitHub: Jupyter Notebook
I assume that the channel changes with each new symbol. So I create myself ...
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0answers
42 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
37 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
32 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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48 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 ...
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33 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
55 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 :
$$
\boxed{\text{Binary Data signal}}{\...
2
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3answers
250 views
Use of pulse shaping in digital modulation
Sorry, I am a little bit confused here cause I thought when we say QPSK, the signal looks like the following.
I thought the bits to send/receive depends on the phase shift of the carrier, or is the ...
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1answer
81 views
When I double bit rate I do not see a difference in I_spectrum and Q_spectrum, but why?
I wanted to compare two different I-Q spectrum plots of a basic transmitter, one in which I doubled the bit rate. I expected a different result, that of possibly a higher/faster graph. It looks sort ...
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1answer
51 views
Modulation upsampling method
I try to implement a qpsk modulator in Octave.
The chain is the state of the art I guess:
$$\text{Symbol mapper} \rightarrow \text{Upsample 4} \rightarrow \text{Root raised cosine filter} $$
My main ...
1
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1answer
102 views
Differential Encoding for M-PSK
Confused about a few topics w.r.t. differential encoding/decoding. First, consider the below BER curve taken from wikipedia ( https://en.wikipedia.org/wiki/Phase-shift_keying ) comparing BPSK/QPSK and ...
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1answer
32 views
How to deal with modulator jitter?
I have a question regarding an implementation of a modulator.
I guess some people here have an FPGA background.
I would like to implement a QPSK modulator ofĀ 31 Mbit bitrate using a 125 MHz clock.
I ...
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3answers
135 views
What causes this type of distortion in a constellation I/Q plot?
I'm transmitting QPSK through a digital pulse shaping filter (RRC, 35% excess BW, 2 samples per symbol, 64 taps) at a rate of 56Msym/sec.
Receiving it on standard lab equipment (Vector signal ...
3
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1answer
229 views
Sample rates, Samples per Symbol, and Digital Pulse Shaping
Having some confusion about digital pulse shaping for complex baseband (passband) signals. The complex baseband linear modulation equation is
$$s(t)=\sum_{m=-\infty}^{\infty}\text{Re}\{a_m\}h(t-mT)+j\...
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1answer
43 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
801 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 ...
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1answer
33 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
113 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:
...
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1answer
42 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
112 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
115 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
73 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
66 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
65 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
19 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
30 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
63 views
Digital Tanlock carrier recovery loop
Iām 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/...
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1answer
92 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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1answer
83 views
Burst QPSK demodulator
I am working in burst QPSK demodulator. I just want to double check if what I am doing is right.
Large frequency feedforward recovery by FFT
Carrier recovery Costas with 4 samples/symbol
Timing ...
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0answers
70 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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2answers
166 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
221 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
55 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
36 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
123 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
383 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
29 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
446 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
289 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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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 ...
4
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1answer
279 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
818 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
3k 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
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1answer
1k 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 ...
