# Questions tagged [constellation-diagram]

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### Plotting Constellation Diagrams

I'm working with some IQ data from the paper A Wideband Signal Recognition Dataset. Specifcally I've been trying to plot the constellation diagram for some the modulations within the dataset, however, ...
524 views

### How to do QAM modulation and plot the constellation diagram for a complex signal (I+jQ)?

I want to plot the constellation diagram of 64-QAM for a complex signal, x = cos(2*pi*n/N) + 1i*sin(2*pi*n/N) where ...
161 views

### A vanilla BPSK set up, but constellation disgram is a line

I set up a vanilla BPSK modulation in GNU-radio, but the constellation is showing me a line. I am using: ...
1 vote
60 views

### Decision region when bit/symbol mapped to multiple points on the constellation

Let $x$ be 0, +1 or -1 with probability $1/2$, $1/4$, $1/4$, $\cdots$ What is the decision region? I was asked this question during an interview. Can someone please give me a hint or source (from a ...
1 vote
202 views

### Why is 16 APSK arrangement 4 + 12?

Why does constellation arrangement affect the BER ? For example 4 + 12 vs 6 + 10 ? Is it because the correlation coefficient ?
149 views

### Complex Filter (Modelling a Channel ) convolved with complex baseband modulation gives error *Plots inside -Updated*

I have a complex filter that is modelling the channel response, its not symmetrical on 0. The complex filter is convolved with a complex baseband modulation of QPSK. Plot 1 Zoom in on impulse response ...
525 views

### Frequency Error/CFO effect on Constellation for OFDM

Very often in literature we see that effect of carrier frequency offset is seen as rotating of a constellation points. And explanation is generally that after down converting and sampling the time ...
394 views

### Software implementation of Gardner Loop

My objective is to create a Gardner loop to remove the timing offset present in my signal. To achieve best timing SNR, I downsample my signal to 2 samples per symbol. It is depicted below: where blue ...
125 views

### The timing offset remains after Gardner loop

I would like to use Gardner loop to remove the timing offset in order to demodulate the signal. My signal contains the frequency offset, however I know that the Gardner loop can handle substantial ...
1k views

### Clock recovery using Mueller and Muller adds noise affecting EVM or SNR (Two cases - GNU Radio & Python code)

The implementation of the Mueller and Muller clock recovery that I am seeing adds a large amount of 'noise' or degradation to the Error Vector Magnitude (EVM) to the symbols on the constellation. This ...
1 vote
60 views

### Matlab: Could anyone suggest why Iam getting a different geometry for QPSK constellation diagram

I'm developing a Multi-user MIMO communication model in MATLAB where a base station communicates with 2 users. The model uses OFDM (QPSK) modulation. Channel model, precoding and covolutional encoder ...
5k views

### How exactly do I plot a constellation diagram?

I am relatively new to signal processing and I would like to correctly draw a constellation diagram to check the results of a study. I need my signal processing to be close as them to make sure I am ...
1 vote
135 views

### Why does carrier frequency offset (CFO) cause carrier phase error (CPE)?

I've already asked 2 questions on this but there is one discrepancy I cannot reconcile and is the crux of the problem: \begin{align} \newcommand{\prefix}{\frac1N\sum\limits_{n=0}^{N-1}} R_l &= \...
357 views

### Why does fine CFO cause rotation of the constellation?

Just thinking about it, why does fine CFO cause rotation only? I only see diagrams that show rotation of the constellation. We assume this is a complex magnitude frequency domain plot In order for ...
523 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 ...
1 vote
39 views

How can you distinguish between two quadratures in QAM when the phase is not known at the receiver? For example, if the quadratures are sin and cos, how can the receiver tell which one is which, since ...
219 views

### Matlab Plotting custom constellation along with decision regions

How do I create a custom constellation along with decision regions in Matlab, any help is greatly appreciated
303 views

### Having trouble transmitting/receiving a BPSK signal using two USRPs

I am relatively new to working with SDRs and GNURadio and I am attempting to generate a BPSK signal and transmit it through one USRP and receive and demodulate it on another USRP. I am using GNURadio ...
5k views

332 views

### Zeros inserted in QAM Constellation

I need to ask about insertion of Zero Symbols after QAM modulation in a OFDM system. Such that the 4 QAM has a constellation with 4 corner and 1 center symbol indicating zero. What advantages or ...
931 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). ...
4k views

### Matlab : How to plot the constellation diagram for this method?

I am trying to generate symbols +1,-1 using a function by partitioning the interval of the function into two levels. The function is the Tent Map. This in a way achieves bpsk modulation. I want to ...
266 views

### P2 symbol constellation in DVB-T2

DVB-T2, 32K SISO, not extended. I've acquired P2 symbol, PRBS bits have matched with bits recovered from pilots. Then equalization was applied to all subcarriers. The constellation I've got looks ...
1 vote
2k views

### Generating QPSK Constellation Diagram

I was wondering how a diagram like this is generated. I am generating a QPSK signal using MATLAB by taking a cos and sin wave, multiplying each one by either 1 or -1 and adding them together to form ...
3k views

### OFDM symbol acquisition block in GNU Radio gives rotating constellation even if there is no carrier offset. How is this possible?

Why does the constellation rotate when using OFDM Symbol Acquisition block in this flow graph below ? The only explanation I could think of would be carrier frequency offset but in this flowgraph ...
1k views

### How does carrier frequency offset effect the constellation diagram in OFDM?

In the case of OFDM modulation, if the carrier frequency is slightly off then how does that effect the constellation diagram ? Is there some general rule how it will change (such as rotate) ? Or ...