# 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

### synchronization with 2 users

I have $2$ users with different distance from the receiver and each user's message is spread with a different waveform. The $2$ waveforms are orthogonals. With a perfect synchronization, I don't have ...
29 views

### FSK carrier frequency estimation in non equiprobable data

We know that in equiprobable data,change in phase over a time interval, this result will be directly proportional to frequency: f∝Im(s(n)s(n−1)∗) Where s(n) is the normalized complex FSK time domain ...
22 views

### receiver for a multi-user communication

I have an asynchronous multi-user communication with $10$ users. With a matched filter, I see the average BER by user is small ($<0.08$). Do you know any methods that can reduce the BER by user on ...
79 views

### should implementing the MMSE equalizer in time domain and frequency domain give same results?

Assume we have a received signal $r$ explained as below: $r = h * x + n$ where $h, x ,*, n$ denote to the multi-path channel, transmitted signal, convolution operation and AWGN, respectively. ...
26 views

### IID noise assumption at Matched Filter sample time

I read that at the correct sample times of a matched filter output the noise is independent assuming a Nyquist pulse. Can someone provide a proof of this or explain it more? Assuming your matched ...
26 views

### Calculating average power of a discrete random signal with complex values

I have a Rayleigh channel that transmits discrete values according to the following: $$y(n) = h(n) * s_n + \omega_n$$ Where $y$ is the received message, $s_n$ is the symbol sent (constellation 2-PSM), ...
23 views

### What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)?

What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)? I think they are essentially the same phenomenon?
106 views

### How to generate rayleigh fading coefficients in matlab

I want to calculate received SNR for each cellular user CUs, so i want the corresponding transmission power P of base station BS to each user, the noise, and the channel gain coefficient of the ...
38 views

### Deep Learning based NDA Channel Estimation

I was wondering if it is possible to use Deep Learning to estimate the Channel Impulse Response for NDA synchronization? I understand Deep Learning is not normally used for regression problems but I ...
33 views

### LTE system. How to compute precoder for resourse block

guys! I am studying a massive Mimo system and 3gpp LTE system and have questions about precoding in the LTE system. In LTE RB (resource block) is used to group consecutive subcarriers. To compute ...
56 views

### (Frequency Offset): Relationship between Normalized Carrier Frequency Offset (normalized CFO) & ppm in OFDM system

How can I change a normalized carrier frequency offset (CFO) to ppm? And If the DAC sampling rate is 30GS/s, and the clock frequency is 15GHz, then should I use 30G or 15G when I calculate ppm? ...
30 views

### Resampler and PLL reference document

can anybody suggest good documents on resampler for TED and PLL by which i can understand basics because there is lot of confusion for resampler and PLL
62 views

### burst qpsk demodulator

i am working in burst qpsk demodulator i just want to double check if what i am doing is right large frequency feedforward recovery by fft carrier recovery costas with 4 samples/symbol timing ...
63 views

### Carrier and timing offset

Assume my reference is 1 ppm so if my transmit frequency is 400 MHz and symbolrate is 100 kHz. Then, my carrier will have +/- 400 Hz offset and then my symbol will have +/-0.001 Hz offset. Similarly,...
62 views

### matched filter position

I have seen that matched filter should be used in TED (gardner loop) after resampler ...
11 views

### Is the SWIPT technology not the good method to increase the life of using battery?

Is the SWIPT( simultaneous wireless information and power transfer ) technology not the good method to increase the life of using battery? Because I design the Full duplex system with three device,...
23 views

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### If the beamforming of these signal,$x_B$ and $x_A$, are orthogonal to each other,can the SINR increase?

Here is my thinking ,two device transmit $x_A$ and $x_B$ at the same time and with same frequency,meanwhile,device $C$ transmits $x_C$ to the other devices,and as we know,because the device $C$ is a ...
25 views

### Is there any technology or method that let user $Z$ knowS which message is $x_B$ and which is $x_C$

There is a device $Z$ which transmits the signal $x_A$ and receives the informations $x_B$ and $x_C$ simultaneously. I think when this device receive the signal,it won't know which is $x_B$ and ...
41 views

### How to recover 2*Zc systematic bits punctured in LDPC?

In 5G NR LDPC encoder 2Zc systematic bits are punctured at the transmitter end. At the receiver end, it is able to recover all bits excluding the punctured bits at the transmitter end. As the ...
22 views

### Hardware that Mixes Two Digital Audio Source into One

Is there any off-the-shelf hardware that extracts two digital audio streaming source from two digital audio stream(like USB+SPDIF), mixes, and transmits in single digital stream real-time(if the ...
41 views

### How to detect missing bit position in a bit-stream?

I'm trying to establish a one-way communication and facing problem in the receiver end because of some missing bits. For example, if the sender sends 100 bits the receiver received 95/96 bit. Now the ...
19 views

### If i use some method to decrease the self interference,how should i rewrite the constraint?

In the MIMO full duplex energy harvest optimization,we can find the similar constraint like this: $SINR > \gamma$,this $\gamma$ is some of SINR value,it means that my SINR want to be higher ...
35 views

### Convolutional Code: choosing a trellis and puncture pattern for code 2/3

I'm working on convolutional coding in which I'm using generator polynomials as {13, 15} with puncture pattern of {1 1 0 1} for code rate 2/3. I don't get expected BER trend. If I use puncture ...
38 views

### RRC filter or rectangular pulse shaping filter in LFM chirp signal

I am working with a LFM up chirp signal, and I wanted to embed some data on it using a BPSK constellation. My doubt was, ¿should I use a RRC filter, like in usual communications schemes, or should I ...
12 views

### Which channel is the suitable channel for the short distance?AWGN?rayleigh or rician channel?

What is the unsuitable channel for the short distance?The short distance i mentioned is 1m or 2m.Unsuitable channel I mean is that if i assume this channel in my system,it will be very strange. In my ...