# 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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### The Amplitude of the Correlation Function Peaks After Matched Filtering

I have 2 signals: $s_1(t)$ and $s_2(t)$. The autocorrelation functions are given by $R_{s_1}(\tau)$ and $R_{s_2}(\tau)$ with $|R_{s_2}(\tau)|<|R_{s_1}(\tau)|$. I would like to know if the previous ...
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### Capacity of channels with pilots?

Question is about "channel capacity". I guess it is pretty elementary for experts, however I have not seen it discussed in e.g. Proakis book or Tse "Fundamentals of Wireless Com". ...
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### Distortion-Rate function for standard Gaussian signals quantized with a uniform alphabet

Let's say $X \sim N(0, 1)$ is a standard Gaussian input signal and $Y \sim U\{y_1, y_2, \cdots, y_{16}\}$ follows a discrete uniform distribution (in fact, $\{y_1, y_2, \cdots, y_{16}\}$ is a ...
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### Block CMA algorithm

The Constant Modulus Algorithm is a common equalization method which adapts at every sample in an attempt to give a filter which produces a fixed power output. Divergence/convergence of the CMA ...
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### OFDM channel estimation using the transmitted signal multiplied with a matrix

I have OFDM system, where the modulated signal $x$ with length $N$, and $N$ is the number of subcarriers in OFDM symbol. $x$ is multiplied with a well-known unitary matrix $G \in N \times N$ before ...
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### How does matched filter output provide sufficient statistic when the channel has ISI + AWGN?

In Forney’s MLSE paper (link: https://ieeexplore.ieee.org/document/1054829), Forney mentioned that the matched filter output is still sufficient statistics even with ISI (second column on page 365). I ...
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### GMSK Transmitter Implementation based on AMP representation ( laurent decomposition)

Implementation of a linear approximated GMSK block scheme based on Laurent decomposition. My goal is the Implementation of the following block scheme: I think $v_k$ is an NRZ element ( 1 or -1). <...
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### dsss and correlation

Generally, a DSSS (Direct Sequence Spread Spectrum) communication is used to secure a communication. However, because of the repetition of the spreading sequence, a cyclostationary analysis makes it ...
361 views

### How to compute (in non adaptative way based on MMSE FIR) the feedback and feedword filter for DFE equalization?

System Model Consider the single-input single-output (SISO) communication system in the figure below: where the information bit stream is encoded and mapped such that the output of the encoder is a ...
818 views

(This is a follow up question to a previous question: link) I have implemented a flowgraph of a transceiver loopback inspired by the examples found at ...
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### Symbol timing recovery design

I am trying to design the Symbol timing recovery(#STR) block of #DVBS Receiver. These are the specifications Symbol rate ($f_s$) = $2\textrm{ MHz}$ Acquisition range = $10\%$ of Symbol rate ...
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### Chip rate and sample rate

If a sequence of +1 and -1 with chip rate ($\frac{1}{0.57 ns}$) is being used for purpose of estimating channel impulse response with delay spread of 6ns. We decide to have a new rate change to rate ...
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### Phase noise estimation and compensation schemes

Brief background There is a known problem that high order modulation schemes suffers from phase noise of reference generator. It's very important issue for e.g. line-of-sight (LOS) modems exploiting ...
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### Why does my simulation of the binary symmetric channel disagree with theory?

Could someone please answer me why the simulated performance (using matlab) of a Hamming code over a binary symmetric channel does not fit exacly with the theoretical? Here is my code: ...
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### IQ demodulation from specific rate

We have an acquisition hardware in our lab that acquires and digitizes data from a source generating band-limited signal in the MHz range. It samples the signal at a rate of 4 times the center ...
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### How to prove the mutual infomation expression in paper "Optimized Degree Distributions for Binary and Non-Binary LDPC Codes in Flash Memory"

Recently I met a question when I read the paper Optimized Degree Distributions for Binary and Non-Binary LDPC Codes in Flash Memory and Soft Information for LDPC Decoding in Flash: Mutual-Information ...
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### optimal RX beamforming

I was asked this question in an interview couple of weeks ago. I think I answered it correctly, but I think I might missing some points. Here is the problem, following by my answer. Part 1) In Figure ...
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### multi h CPM implementation

I have understood the math behind CPM. but recently I came across multi h CPM. I haven't found any good document to explain about multi h CPM. Can anybody explain the math behind it. and how it ...
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### Implementing digital controller in the time domain

I have simulated a digital control system in the Z domain using MATLAB and I have got satisfactory results. However, when I converted the plant and the digital controller to difference equations and ...
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### Generating signal in a different frequency band than another signal but transmitted at the same time

I have a signal $x(t)$ of bandwidth $W_1$ transmitted over carrier frequency $f_1$, and another signal $i(t)$ of bandwidth $W_2$ transmitted over carrier frequency $f_2$. The main lobe of both signals'...
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### Understanding the In-band Emission limit in TS 38101-1 Table 6.4.2.3-1?

I am sharing the IBE table 6.4.2.3-1 on TS 38101-1 For General emission requirement, there are three parts.The third part is (-57 dBm+10*log10(scs/15kHz))-P_RB. Where, P_RB is the average transmitted ...
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### localization based on TDOA

To locate a transmitter, I use a localization based on TDOA(Chan's method) with 3 receivers. The results obtained are not effective. What is a possible solution to improve the localization accuracy ...
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### How to implement GMSK model by Thierry Turletti

I'm kind of new to signal processing and trying to implement a GMSK modulator using GMSK in a nutshell by Thierry Turletti to modulate a bunch of binary data and send them over RF antennas. I'm very ...
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### Symbol timing recovery: Polyphase vs piecewise linear interpolation

A symbol timing recovery scheme shown below has been successfully implemented in C++. Different TEDs (Mueller & Mueller, Early-Late, Maximum Likelihood, Gardner, Zero-Crossing, etc) are included ...
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### 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 ...
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### What does the sample entropy of a digital signal mean?

What sample entropy signifies about a signal and how it used to analyse a signal?
254 views

### symbol synchronization

PLL is typically used in carrier synchronization and its diagram is well known, consisting of a multiplier, a low pass filter, and a VCO. In "Phase-locked Loop" at wiki (https://en.wikipedia.org/wiki/...
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### Sending and receiving an image

After studying digital communication courses, I wanted to implement these theories and create an application for sending and receiving a gray image via WiFi between two Raspberry Pi devices. The ...
1 vote