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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16 views

Related to successive interference cancellation?

I am trying to understand the following query: " Is it necessary to do channel estimation to perform successive interference cancellation at the receiver operating over fading channel" Any ...
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Frame synchronization for single carrier burst applications in fading channels

I recently started to implement communication systems with software-defined radios in GNU Radio. In my system design, I am planning to transmit data in burst mode, the frames will be not sequentially ...
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23 views

How to recover modulation symbols?

I am using GNURadio to send and receive a limited number of modulation symbols. I have constructed the following flow chart:random source(no repeat)->chuncks to symbols(file sink1)->polyphase ...
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19 views

maximum faithful coverage distance of signal

For a microwave terrestrial-based line-of-sight communication operating at 10 GHz, what is the maximum faithful coverage distance that the signal could make before requiring a repeater? The following ...
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410 views

Signal to Quantization Noise ratio concept

I was reading Simon S. Haykin's Digital Communications in order to understand the concept of quantization. However, on SQNR, I got stuck over the point where the author mentioned: With the input $M$ ...
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1answer
78 views

What is the maximum rate of a coherent demodulator implemented in a PC?

I would like to implement my own xPSK coherent demodulator on a traditional PC connected to an acquisition board. I am wondering what kind of bitrate it is possible to reach processing only with the ...
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17 views

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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1answer
26 views

Cross-correlation for delay estimation in acoustic signals

iam doing BPSK transmission and receiving with acoustic signals, in order to get my actual signal from my received signal I am using xcorr in matlab to find peak point of alignment and getting my ...
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1answer
64 views

What is Homodyne BPSK? [duplicate]

Could someone explain what Homodyne BPSK is? What is a difference between BPSK and Homodyne BPSK? I have read about this type of modulation in researches in optic communication. I surprised how phase ...
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22 views

Why do adjacent cells use different channels?

In chapter 15 of the book Wireless Communications by Andrea Goldsmith, Goldsmith gives a formula for an estimate of the signal-to-interference-ratio for the node on the edge of a cell in a cellular ...
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1answer
44 views

Receiver and transmitter in RF/optic satelite communciation: distance vs datarate

I am doing research in laser satellite communication and am trying to understand a difference between RF and optical/laser communication systems. With an increase in distance between a transmitter and ...
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3answers
60 views

Difference Mb/s and mbps as a measure of data rate

"... Ka-band radio system flown to the moon (100 Mb/s)..." Mb/s is megabit pro second or megabyte pro second? Can I write 100 mbps? Mb/s and mbps, are different units?
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58 views

Modulation in laser satellite communication

In small satellite communication technique we can use optical spectrum (optical (laser) communication system). The common and simplest modulation techniques used are On and Off keying (OOK), Q-ary PPM ...
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59 views

Optical or laser communication?

I am reading about satellite communication and have found a very interesting topic for me: optical communication in satellite communication. It is not a new concept but a lot of researches are made. ...
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550 views

What is the definition of a "Symbol"

I’m looking for the simplest, precise definition of a Symbol e.g. The symbols found within a signal The signal has a N symbols per second I'm following this tutorial. The fellow defines the term ...
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1answer
28 views

Eliminate different microphones textures from their recordings

In my setting, I have different microphones recording a same speech signal. For each microphone recording, I can feel a slight difference in the playing sound. I am calling this property of a ...
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41 views

How to convert SNR to Eb/N0 in Chirp Spread Spectrum modulations

This question is related to Conversion between Eb/N0 and SNR in spread-spectrum modulation like LoRa CSS?. However I couldn't solve my issue. I'm simulating a Binary Orthognal Chirp Keying ...
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1answer
35 views

Related to channel power gain

I am having a doubt that why channel power gain is denoted by $|h|^2$. For example, if the signal received is $$y(n) = hx(n)+w(n)$$ where $x(n)$ is transmitted signal with power $P$ , $w(n)$ is AWGN ...
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31 views

derivative matched filter

I am reading a reseach paper "Joint Synchronization of Carrier Frequency, Symbol Timing and Sampling Rate in Digital Satellite Receivers" written by Suesser-Rechberger B and Gappmair W and ...
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71 views

Choice of loop filter for carrier recovery

I'm currently trying to build a PLL system to perform the fine frequency correction on a complex baseband signal, for the sake of simplicity I've adapted a Costas loop by replacing the sin/cos mixing ...
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52 views

Voice glitch while selecting signal to play from a series incoming recorded signals

In my setting, I have multiple microphones recording the same speech signal in real-time. The speaker is moving while speaking. I am selecting one of the recorded signal to play based on their RMS ...
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1answer
61 views

weird Demodulated BPSK waveform

I am using an acoustic wave of 3khz(audio BPSK) as my carrier frequency with a sampling rate of 10k samples per bit. at the receiver end, I play the audio from my phone to my computer, record it ...
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49 views

Frequency offset estimation accuracy

To improve frequency offset estimation, we could: Use the second order interpolation / equation in the frequency domain based on the coarse estimation fc, e.g. BPSK frequency offset estimation; Zero ...
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1answer
57 views

Difference between FFSK and FSK modulation schemes

Can somebody explain to me what is the difference between FFSK (Fast Frequency Shift Keying) and FSK (Frequency Shift Keying) modulation schemes?
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3answers
71 views

Why does the term "discrete" usually appear near the term "digital?"

Are these terms just parallel words? If not, why is it that when one reads about the first then one is very likely to come across the second? In such case, what would be a nice example to explain the ...
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43 views

How is the distribution of the received signal affected if the transmitted signal is changed from complex Gaussian to PSK

Suppose the received signal is $y(n) = h_0s(n)+w(n)$----(1) Where $h_0, s(n), w(n)$ all are distributed as zero mean complex Gaussian. Thus I know that $y(n)$ will also have the same distribution. If $...
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23 views

understanding the distribution of received signal

In one of the research paper following equations are given : $y(n) = h_0s(n)+w(n),d = 0$ $y(n) = h_1s(n)+w(n),d = 1$ where $n$ ranges from $1$ to $N$ and $h_0,h_1$ are wireless channel assumed as $\...
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35 views

Related to wireless channel fading

I am reading some papers wherein a wireless channel is assumed as zero mean circularly symmetric complex Gaussian (ZMCSCG) with unit variance and it is also mentioned that the channel undergoes ...
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1answer
46 views

related to random nature of wireless channel

I am reading An Approximate BER Analysis for Ambient Backscatter Communication Systems With Tag Selection wherein it is mentioned that "when the distance between two nodes is very small and line ...
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1answer
63 views

Subspace decomposition

While reading the paper "Perturbation analysis for subspace decomposition with applications in subspace-based algorithms" by Zhengyuan Xu, I came across the decomposition technique called ...
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62 views

How to calculate the data rate of OFDM system

I have OFDM system with following parameters, Bandwidth $B = 5$ KHz, Number of sub-carriers $N = 64$, guard interval $N_g = 8$; Sampling frequency $F_s = 10000$ and Modulation order $M$ is QPSK. Is it ...
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17 views

PAPR used in PAM constellations

Can anybody explain me how to derive analytically the PAPR (Peak-to-Average Power Ratio ) for PAM constellations. E.g. 2-ASK (unipolar/bipolar), 8-ASK (unipolar/bipolar), 16-QAM, and 8-PSK? Thank you ...
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36 views

How to calculate received signal power for a Multi-User MIMO OFDM system?

I have a Multi-User MIMO system where there are 2 users served by a base station. The base station consists of 64 transmit elements and the users are equipped with linear antenna array consisting of 3 ...
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40 views

Do the effects of OFDM pilot tones spacing appear in time or in frequency domain?

As known, the pilot tones are transmitted via subcarriers predefined and known in the transmitter and the receiver. The pilot spacing is repeated with a certain rate that depends on how fast the ...
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39 views

How does higher received signal power enable higher data rates?

On page 30, of the book Fundamentals of LTE by Arunabha Ghosh et al. it is written: This allows broadcast signals from different cells to combine over the air to significantly enhance the received ...
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59 views

In practice, why is there any overlap in frequency-division multiplexing?

Okay, so I am aware of the math behind perfect reconstruction in filterbank and wavelet theory when there is half-band symmetry. But I don't understand, when we have the computational power to do ...
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5answers
176 views

Setting the duration of subcarriers in OFDM system

If have an ofdm system with $N$ subcarriers, and sampling frequency $F_s$, that means that duration of each subcarrier is $T_s = \ {1/F_s}$ and the duration of whole symbol (which includes $N$ ...
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46 views

Phase offset analysis in real trsnsmitted signal

Assume we are transmitting a real signal $x(t)$ through a channel $h$ in passband as : $y(t) = x(t)cos(2πf_c t + ∅) * h(t)$ = $Re(x(t)e^{j2πf_c t})*h(t)$ where $f_c$ is the carrier frequency and $t$...
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40 views

What is the meaning of the channel gain is normalized

Transmitting the signal $x$ over the channel $h$ and affected by noise $n$ can be expressed: $y = hx + n$ $h$ is the channel gain, that is known for me. I sometimes see phrases saying "when the ...
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2answers
74 views

CDMA generating the sequence for gold codes

Is this the correct way to generate a set of Gold codes: Take a preferred pair of M sequence polynomials and load each one of them into a separate LFSR. The serial bit streams that are generated from ...
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52 views

Difference in methods: coarse and fine frequency correction algorithm [closed]

I am currently studying frequency and phase correction methods. Most probably my question very basic but i am having difficulties to understand it. Could you please explain what is a difference ...
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2answers
79 views

Convolution between a channel with real signal vs. channel with complex signal

The real transmitted signal $x(t)$ is convolved with channel $h$ in passband as : $y(t) = x(t)cos(j2πf_c t) * h(t)$ = $Re(x(t)e^{j2πf_c t})*h(t)$ where $f_c$ is the carrier frequency and $t$ is the ...
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20 views

Generating a 2D delay-Doppler channel matrix

I was wondering if anyone here has any idea on 2D delay-Doppler channel and how to generate the channel matrix? Even a hint or a resource would be helpful. I just want to understand and visualize the ...
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73 views

Modulation order in real signal and complex signal modulation

In real signal modulation, e.g. ofdm based on DCT transform, the modulation order $m$ should be $\sqrt{M}$ where $M$ is the modulation order of the complex signal. for example, if we are using QPSK ...
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45 views

How to choose frequency of local oscillator for heterodyne principal

I am trying to implement the heterodyne principle in order to make an AM signal demodulator that can demodulate signals on a set bandwidth(550 - 1720kHz). Is there a formula or some other method of ...
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2answers
53 views

Difference between single tone and dual tone signals?

Editted Single tone signal has 1 frequency: $$ y = \sin(2\cdot \pi \cdot f_1 \cdot t)$$ Dual tone was created by using 2 frequencies: $$\sin(2\cdot \pi \cdot f_1 \cdot t) + \sin(2\cdot \pi \cdot f_2 ...
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104 views

Can we use Gardner timing error detector for multi level QAM or OFDM systems? [duplicate]

Sampling frequency offset (SFO) between the transmitter and the receiver in any system causes a gradually increasing timing error which is seen as an increasing phase rotation (function of time). In ...
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42 views

How to find the bandwidth of the transmitted M-FSK signal?

I'm tried to find the solution, but I failed. my question in the figure below, and the correct answer it's shown at the end of Figure. I'm using this formula but the answer is not correct! Is there ...
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45 views

Optimal Combination of received signals from two antenna

I really appreciate an answer or any hint how to approach this problem: Problem: A receiver has two antennas. The first antenna receives $Y_1=hx+n_1$, where $x\in\{-A,+A\}$, $h$ estimated channel, and ...
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1answer
77 views

Downsampling( decimation) theory: additional frequency

I work on a simulation decimation filter: downsampling + filter. My test environment: low data rate receiver, BPSK, square root raised cosine filter with cutoff frequency =0.5, transition bandwidth = ...

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