# 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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49 views

### Basic in “Precoding and Equalization Schemes”

I have found the interesting following paper for me: SVD-based MIMO Precoding and Equalization Schemesfor Realistic Channel Knowledge: Design Criteria and Performance Evaluation The paper is old, ...
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### What ICA should be applied?

I am using ICA from EEGLAB toolbox (not sure if I can use MATLAB's RICA() function as well). I am trying to use Infomax or JADER ICA to seperate two sources which transmitting at a carrier froquency ...
26 views

### How to add multiple sub bands of frequency into on wide band

Context: I am doing a project where I have to sample a video signal from a monitor with an SDR. The data is coming in for each pixel left to right top to bottom. Since my receiver doesn't have a very ...
18 views

### What is the function of RF chain in this system model?

Here is the system model from this paper :　 https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7008332 What is the function of RF chain in this system model ? Because i can't understand that what ...
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### Discrete Frequency Equation and Relation

I think I am looking at conflicting equations from a few sources, or maybe I just dont understand it. $\Omega$ is Discrete frequency $N$ is Discrete Period in number of samples $\omega$ is ...
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### How to measure a signal's initial phase given a buffer of received samples of the signal?

For CPM and FSK, how to measure a received signal's INITIAL phase based on its I and Q components given a buffer of received samples of the signal?
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### frequency/phase offset estimation in satellite DOA beamforming applications

In satellite QPSK demodulation, we first estimate and remove the phase offset introduced by the channel. Then, we demodulate the baseband information bits (I & Q channels). In satellite DOA ...
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### IT++ and Alternatives DSP Libraries

I want to implement some signal processing blocks in C++ so I did a bit of search on the available libraries for signal processing in C++ and I found that IT++ provides comprehensive set of functions, ...
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### Binary vs 4-PAM PSD

I'm struggling to understand how you would form an expression for the PSD of a 4-PAM signal which is using rectangular pulse shaping. I understand for binary the likelihood of +/1 is equal so the ...
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### data rate cdma chirp

I combined a chirp with a CDMA and I would like to know how to find the data rate. To begin, I spread the datas with the chirp and after I spread the previous signal with the PN code. My bandwidth is ...
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I can see, from my apartment, a cell tower. From what I have learned, in a time division duplex system the uplink and downlink communication are kept separate in time. Uplink from some time, then ...
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### Average number of time slots until successful transmission in adaptive tree walking protocol

i was searching everywhere and couldn't find in any paper or book the average number of time slots until a successful transmission. for simplicity sake, in a simple network as given in the picture, ...
175 views

### How is DJI OcuSync wireless link physical layer implemented?

I'm looking for documentation on the wireless command link of the DJI OcuSync. I found this website (in Chinese). It seems like an OFDM link that uses Alamouti codes? I'm specifically interested in ...
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### The theoretical formula of error probability and the data rate in MIMO,and the relation between $G^T$ and $G^R$ and $M$

I want to use Matlab to plot these two figures,fig(a) is the error probability,and as we can see,the higher M is,the lower error probability it has in the same SNR . The fig(b) is data rate,the higher ...
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### waveform and multiuser communication

Sorry for my very simple question but I am a beginner in digital communication. Why in a multiuser communication, we have to have the same waveforms for each user? Is this an important rule for ...
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### bandwidth and multiuser communication

I assume $3$ users. In the CDMA, the signals after the spreading for the $3$ users have the same bandwidth $B$. Is it possible to have $3$ spreading signals of the same band $B'$ such that $3B'=B$? ...
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### Parity Check matrix from degree and check nodes polynoms, LDPC codes

I'm trying to simulate LDPC codes which were optimized for the BEC channel. I generated the degree and check nodes polynomials according to chapter 3.15 in "Modern Coding Theory" by Richardson and ...
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### Symmetric Capacity of a Binary Discrete Memoryless Channel

While reading this paper https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5075875, I found that the the symmetric capacity of BDMC $W$ is given by I(W) = \sum_{y\in Y}\sum_{x\in X}\...