# 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.

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### orthogonal family and pulse shaping filter

I am a beginner in digital communications and I have a question on the pulse shaping filter. For example, I have an orthogonal family $\{s_1,...,s_N \}$. Can we preserve the orthogonality with a ...
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### QAM constellation coder - transmitting a file

The file with size 6 MB is transmitted in 100 seconds using a constellation coder QAM with a constellation of 6 bit/symbol ${ M = 10^6, B = 8}$ Tasks: 1. What is the signal bandwidth if the band ...
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### Converting a non-stationary random process into a WSS process by adding a random phase

Here is an example where this method has been implemented. We were trying to calculate the spectrum of a transmitted signal(Random signal/weighted pulse) The auto correlation function of the pulse ...
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### upsampling for a signal

We have a signal $s(t)$. If we do an upsampling, does the signal duration increase? What is the point of upsampling if the signal time increases? Can we do an upsampling if we don't use a shaping ...
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### Questions about reproducing results of a paper on Communication Systems and Wireless Communication

I'm trying to reproduce the results of a paper on Device-to-Device Communication, channel assignment and mode selection (G. Yu, L. Xu, D. Feng, R. Yin, G. Y. Li and Y. Jiang, "Joint Mode Selection and ...
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### differential phase tracking loop for the receiver

For a DBPSK modulation, how can we track the differential phase? I thought about using a phase tracking loop but I did not find articles for this.
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### Representing data in combination of QAM and BPSK

I have a question regarding the data representation in different modulations. Assuming we are using MIMO system whith $4$ $T_x$ x $4$ $R_x$ which means four transmission antennas by four receiving ...
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### Modulating ofdm in audio spectrum

Trying to modulate audio with OFDM data. My fs = 44.1khz, i'm using 64 sub-carriers, but i'm only using 5 sub-carriers for data, so my bandwidth is about 3.445khz. I'm not sure how to properly write ...
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### phase tracking loop for dbpsk

I have a communication with a DBPSK modulation. The communication is disrupted by a Doppler shift (due to movement) and Doppler spread (due to channel). At the reception, after Doppler shift ...
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### How to get sensor covariance matrix from CSI values?

I try to use musicdoa() function in Matlab to estimate the direction of arrival of the paths of signals received by the receiver in a wireless link. The function ...
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### About combination between QAM and PAM

I have confused question regarding the possibility of combination between QAM modulation and PAM in order to improve the spectral efficiency. Is that possible? As you see in the below Figure, it's ...
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If we have data we need to transmit which is $i$, so we should multiply is using XOR function with spreading code $y$. How many bits (Maximum and Minimum) should $i$ and $y$ can have ?
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### The notion of white and colored noise

The autocorrelation function of AWGN is an impulse response at t=0, and its fourier transform or its spectral power density has a flat infinite BW Now any receiver will have bandpass or low pass ...
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### Is CMA equalization applicable for OFDM

I have a question regarding the constant modulus algorithm (CMA), as you know it's one of the known algorithms used for blind equalization. The cost function of the CMA is build blindly, it means ...
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### How to calculate $p_c$ (binomial probability)

In the given image I don't understand how to calculate $p_c$, can anyone please explain?
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### How to calculate $E_b/N_0$ for a 8-PSK?

How to calculate $E_b/N_0$ for a 8PSK? My BER is given. But I don't understand how to calculate $E_b/N_0$ as it is inside a Q function.