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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Inter-Symbol Interference (ISI) channels
Is there any open and free data-set for digital ISI channels? I want to have a variety of ISI channels' taps, such as $h[k]$ here. Especially looking for BPSK channels.
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OQPSK constellation question
The following block diagram shows an OQPSK modulator/demodulator.What I fail to understand is that the peaks at the output of the Rx matched filter give a nice QPSK constellation after compensating ...
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1answer
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Quality of experience engineer
I have noticed certain overlap between digital signal processing and quality assurance for jobs that require expertise in evaluating the quality of the transmitted signals on telecommunication systems ...
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1answer
23 views
Correlating a sequence or a code with itself at QPSK symbol rate
I am sending a QPSK signal that represents a certain sequence or code and that needs to be correlated with itself on the receiver (there are other sequences/codes in the system, and they are all ...
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1answer
32 views
Phase synchronization between 2 PLLs
If 2 PLLs as the one shown are driven from the same reference/crystal and the ratio between divider N and R is an integer (note that divider R is outside the loop), does one need a sync pulse for ...
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Plot Bit-Error-rate (BER) vs Eb_N0 of a discrete BPSK signal passed through integrator in MATLAB [closed]
I am a novice to communication systems but I am in need to solve this question. I would appreciate inputs in this regard. Apologies if you my question lengthy.
I have a BPSK signal such that the ...
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28 views
how to set Equalizer's coefficient using generalized eigenvector.
In that paper https://jwcn-eurasipjournals.springeropen.com/articles/10.1186/1687-1499-2012-72 .. Equation 3,
$J(w) = w^HBw/w^HCw$ ..
$B$ and $C$ are matrices, $w$ the filter coefficients vector ...
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Shaping filter for a multi-user communication
In a CDMA system, should we multiply by the PN code before the shaping filter or after?Is the order of the steps important?
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2answers
34 views
Averaging out noise and SNR improvement
Suppose I have a sequence of identical symbols carrying the same information at a sample rate equal to the symbol rate, why do we always talk about averaging them to average out noise, why not just ...
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1answer
20 views
Calculating the energy of trapezoid wave
Here is the trapezoid wave,although i know we can use $\int^{4}_0 |x(t)|^2dt$ to calculate its power,but i want to divide this trapezoid to right triangle$(t=0$~$2)$,and a square ($(t=2$~$4)$).
I ...
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1answer
69 views
Noisy and Noiseless Channels
I am trying to understated the the achievable bit rate in noiseless and noisy channels. Particularly, I would like to solve the following problem:
Let a real symbol $0\leq x_i < 1$ be ...
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1answer
26 views
External frequency divider in a PLL
Does a frequency divider external to the loop BW of a PLL cause any phase ambiguity ? and why? and is the result of dividing by an odd number different than dividing by an even number?
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3answers
57 views
“Complex Matched Filter”
What does a complex matched filter mean? . A complex bandpass filter can be formed by multiplying a low pass filter by exp(jwt) getting an analytic filter (one sided in the frequency domain) which is ...
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18 views
Basis Expansion Model (BEM)
As you know, Basis Expansion Model (BEM) is a time-varying channel model.
I try to understand that model from the beginning, but when searching in Google, I get many many things. Could you please ...
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13 views
Microphone array steering pattern visualization
Steering patter for a linear Microphone arrays (ex 2 microphones at d distant) would look like an oval-shaped steering pattern connecting two microphones.
Single microphone appear to be a spherical ...
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1answer
29 views
How does a telephone change your voice? [closed]
Is it due to vocal length normalization during MFCC? Please be kind enough to explain.
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1answer
89 views
Symbol timing synchronization using a high sampling rate
Symbol timing synchronization usually relies on a digital PLL procedure, an iterative process that relies on detecting a timing error signal that is used to control an interpolation filter that in its ...
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1answer
21 views
What does it mean that the normalized power of a received equals one?
I have read in that lecture, page 2, here that, the symbols are independent, and normalized to have power 1, which means $E(x x^H) = I$ .. what does that mean? could you please explain that for me?
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Dynamic loop bandwidth for a Costas loop
I'm using a Costas loop for carrier recovery. The BER vs SNR (from GNU Radio Simulation) curve for different loop bandwidths (0.03,0.05 and 0.07) is shown in the graph below. It can be seen that the ...
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Symbol timing synchronization of non pulse shaped signals
Asynchronous symbol timing synchronization is based on the concept of interpolation, i.e. finding between the available samples an interpolant that would be at the position of the maximum of the eye ...
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2answers
72 views
Carrier Frequency Offset, Rotating Constellation and Correlator
I have been further reading up on carrier recovery methods and something is not clear to me:
It's written that a carrier frequency offset results in a rotating constellation diagram but if you are ...
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1answer
14 views
What does SDMA's space actually mean?
What does SDMA's space mean?
I mean,T for TDMA is time,and unity of time is second. F for FDMA is frequency,and unity of frequency is Hz.Now i know the S for SDMA is space or spatial,but i don't ...
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1answer
45 views
Phase versus time graph of QPSK
In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained <...
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How to transmit beamform without explicit phase shifting at RF frequency
I would like to perform beamforming from an array of antennas when transmitting.
I know the difference between analog and digital beamforming when receiving a signal from an array (there is a lot of ...
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1answer
33 views
What is the difference between Antenna port and Physical Antenna in LTE?
I have just started working on the 5G NR physical layer and I have difficulty understanding the concept of Antenna Port at the downlink.
In release 10 there supposedly 15-22 antenna ports for CSIRS (...
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28 views
What is the unit of distance used to calculate spatial diversity?
Spatial diversity gain depends on the power angular spread of the incident rays on the antenna(s) of a receiver and also on the distance between say 2 antennas, is what meant by distance a physical ...
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1answer
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Frame acquisition vs symbol timing synchronization
For a known length of frames and using a known sequence in a preamble that is also of known length can auto correlation at the receiver be enough to acquire timing or is timing synchronization at ...
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calculating average received SNR and outage probability
Consider a SIMO channel with three receive antennas
$y_i[m]=h_i[m]x[m]+w_i[m],i=1,2,3$
Where $E[|x[m]|^2]=E_s,w_i[m]$ is AWGN with variance $N_0$.The channel coefficients {$h_i[m]$} are iid and have ...
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1answer
71 views
Generate Complex White Gaussian Noise in MATLAB
n_3=sqrt(0.1)*randn(1,K);
n_4=sqrt(0.1)*randn(1,K);
beta_NLoS=(n_3+1i*n_4); % CN(0,0.1)
I want to create a $CN(0,0.1)$,does my code have any problem?
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2answers
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Timing error detector used for symbol timing synchronization
The Gardner timing error detector is independent of carrier phase and frequency error, and is also quite immune to self noise (to my understanding, I may wrong about that). Can one assume that it is a ...
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2answers
57 views
BPSK signal that has not been pulse shaped by any filter
Can one consider that a BPSK signal that has not gone through any pulse shaping filter to be equivalent to a signal that has gone through a rectangular filter of which the pass BW is equal to the ...
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How to decode the received sequence by using convolutional code with generator matrix and Viterbi algorithm?
Consider the discrete memoryless channel with input alphabet $𝐴_𝑋 = ${$0,1$},
output alphabet $𝐴_Y=${$0,𝛼,𝛽,1$}, and transition probabilities:
\begin{array}{}
& 0 & \...
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2answers
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Intersymbol interference due to limited channel bandwidth
What is the difference between limited-bandwidth induced intersymbol interference (ISI) and ISI due to multipath propagation.
I noticed that the delay spread in indoor environment is in the range of ...
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1answer
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Maximum Likelihood Detection of Signal Vectors in Gaussian Noise
Consider a binary-input additive white Gaussian noise channel.
Let $\mathbf{x}_0 = (\sqrt{Es},\sqrt{E_s},⋯,\sqrt{E_s})$ and $\mathbf{x}_1 = (-\sqrt{E_s},-\sqrt{E_s},⋯,-\sqrt{E_s})$, be two codewords ...
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2answers
42 views
Signal bandwidth of an 802.15.4 signal at 2.4 GHz
This signal uses Offset QPSK with a half sine pulse shaping filter for the purpose of getting a constant signal envelop. Does anyone know the exact bandwidth of this signal after being pulse shaped, ...
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4answers
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Bandlimiting and OFDM spectrum - what is considered “bandlimited”?
I have been reading about OFDM modulation, it's not clear to me how you can have band-limited OFDM but given its prevalence in wireless communication there must be some designation of approximately ...
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2answers
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What is a constant envelope modulation?
The Book "Digital Modulation Techniques" by Fuqin Xiong groups digital modulation schemes into two classes: "constant envelope" and "nonconstant envelope." However, I was surprised by the inclusion ...
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Implementing Fractionally Spaced Equalizer
I have been searching for robust algorithm that can be implemented for avoiding the ISI (Inter-Symbol interference), I came across two types of channel equalizations are there. One is data Aided (...
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1answer
42 views
Recursive Least Square Adaptive Linear Equalizer
For the adaptive filter to work properly, a desired signal d(n) needs to be provided. The output from the equalizer y(n) is subtracted from d(n) to produce an error signal, which is used to adjust the ...
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2answers
69 views
Software PLL tracking of carrier frequency in bandlimited transmission
My understanding is that a PLL(either in hardware or software) can recover the carrier frequency(or be used to correct the frequency offset) of a system. My question is how does this work when the ...
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multi-user communications techniques
I am working on multi-user communications. But I saw several differences in communication with one user.
For example, there are several techniques to compensate for Doppler in a communication with ...
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26 views
Noncoherent Burst Detection
I am interested in developing a noncoherent receiver for a burst signal in an SDR. One of the first problems is developing a signal-detection method. I am wondering what is the standard way to go ...
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1answer
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Is there just a carrier in each frequency band in FDMA?
The figure is the FDMA,and i know that FDMA is that dividing the bandwidth into many blocks(frequency band),i want to ask Is there just a carrier in each frequency band in FDMA?i mean one carrier for ...
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1answer
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Inter Symbol Interference (ISI) / Equalization in Digital Signal Processing
I am studying the OFDM system and before to start I have decided to study the main concepts of modulation. And I have spent yet a lot of time to understand the concept of an equalization to reduce ISI....
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Blind equalization with constant modulus algorithm in GNU Radio
I'm currently simulating the effect of multitap channel on BPSK as well as its remedy i.e. equalization.
The modem is expected to work with satellite TT&C transponder.
The communication channel ...
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1answer
29 views
IQ generation separation
To generate I & Q samples from data samples S
I = S(1:2:length(S)-1) * cos(2*pi*f*t) ;
Q = S(2:2:length(S) ) * sin(2*pi*f*t) ;
I & Q to integer ...
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Preamble Detection and Frequency Offset Estimation in radio packets
I have generated a radio packet of data with a preamble header of 0x55555555 and crc32 for the data only.
The entire packet was separated in even and odd streams for I and Q. The I and Q were ...
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Doppler compensation method for cdma
Do you know of effective and simple methods to compensate for Doppler due to movement for the CDMA protocol?
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The relation of sub-carrier and FDMA
In Mengyu Liu, Yuan Liu, "Charge-then-Forward: Wireless Powered Communication for Multiuser Relay Networks", it is said that
while information signals are conveyed by using FDMA over $N$
sub-...
