Questions tagged [digital-communications]
Digital Communication is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel.
1,621 questions
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Auto/Cross-correlation of a sinusoidal signal
If we do auto-correlation or even cross-correlation of a sinusoidal signal, I can see multiple peaks, but they decay as the lag index increases, it looks like the output is divided by the lag index?. ...
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Doppler shift in a time varying channel
For the OFDM modulation scheme, will the Doppler shift ($f_d$) introduced by the high mobility channel make the subcarrier wider? Or will it just shift the whole set of OFDM symbol subcarriers by $f_d$...
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Fll doesnt seems to work on LEO navigation receiver code i have made. Need Help!
just a fellow researcher here.I have successfully implemented costas + gardner with loop filter and Nco but it fails to lock on frequency when i try to pass that filtered frequency error by adding it ...
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Can Bayesian methods explain probabilistic and geometric shaping for the multinomial channel?
Simpler case
In a binomial channel, inputs $X= \left [ x_{1}, x_{2} \right ]$ represent probabilities of $\left [ {\rm failure}, {\rm success} \right ]$ in $n$ trials, with output $Y\in\left\{ 0, 1, \...
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mpsk demodulation in gnu radio
I am trying to demodulate the mpsk modulated signal(generated using VSG60A) using the gnu radio.
I was doing the standards steps for demodulation: Coarse Freq correction (FLL Band-Edge), Time sync (...
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How to oversample the received OFDM signal to produce the same output of that when oversampling it at the transmitting end
In OFDM systems, several works (e.g., [1,2], and others) adopt the following approach to oversample the received signal at the receiver side, aiming to reproduce the same output that would result from ...
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How to oversample the OFDM signal at the receiving end
Assume that we have the time-domain OFDM transmitted signal $\mathbf{x} \in \mathbb{C}^{(N+\text{CP}) \times 1}$ , where $N$ is the number of subcarriers and CP is the length of the added cyclic ...
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Decision-Directed phase carrier recovery for MSK-Type modulations
I am following the book by U. Mengali: "Synchronization Techniques for Digital Receivers" and I am trying to implement decision-directed phase carrier recovery for MSK-type modulations. That ...
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How to perform the Maximum likelihood receiver for QAM in MATLAB
In the M-PSK, it's just a correlator, but it's not hold in the QAM system.
Can anyone teach me how to implement the ML for QAM ?
Here's my code, it's modified from successful M-PSK version ML detecotr,...
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How to solve the convolution of two signals when one of them isn't explicitly given and also reconstruct it?
I'm given the following:
Where in the last box it says "reconstruct".
As you can see $x(t)$ is multiplied by the impulse train $p(t)$ and then passed through this LPF and then to the ...
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Introductory Wireless Communications Text
I'm teaching an RF Comms course over the summer and have been struggling to find a beginner book.
The students have a good background in linear systems, control, and some signal processing... but most ...
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Demodulation after downconversion and resampling
I have implemented a gmsk receiver using liquiddsp library https://github.com/jgaeddert/liquid-dsp. I have used a variable for shift frequency to allow use of nco when the receiver is not exactly ...
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How is Polyphase IQ Frequency Modulation done?
The starting point is a polyphase 1 implementation where:
msg[1] is multiplied with the deviation (phase increment units) to output ∆[1].
∆[1] is used to drive the phase input ports of a DDS[1]
FM[1] ...
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How USRP B210/B200 works with external or internal clock?
I am working on wireless research on LTE 4G and trying to understand its sniffing packets. I came across LTESniffer.
The requirement says
Currently, LTESniffer only supports 2 USRP B-series (B200/B210)...
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fsk vs gfsk modulation
I am trying to generate the MFSK signal, for simple MFSK also there are two variants - with phase continuity(CP FSK - Continuous Phase FSK) or without phase continuity.
In the case general FSK - each ...
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