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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How to find frequency and phase shift in the recorded wave( .wav file )

I am working on BPSK at frequecies near 20 kHz with a sample rate of 44100 Hz. We can't afford sample rates above than this due to computational complexities. Have found that the frequency of ...
97 views

Proving DFT equation

How can I prove the equation $(3)$? I can't understand why there is a $2/N$ in $(3)$. Why he just get the second term in DFT? Consider a sinusoidal input signal of frequency $\omega$ given by ...
232 views

Loop Filter Coefficients in Timing Recovery loop in Baseband Receiver

I am trying to design the Symbol timing recovery(#STR) block of #DVBS Receiver. For reference, I am using the following matlab simulink design (NDA timing recovery part within Digital Baseband ...
649 views

Generating LDPC codes of arbitrary sizes in MATLAB

I am having problems generating LDPC codes of arbitrary sizes in MATLAB primarily because MATLAB insists on the parity check matrix that is input into its ldpcenc ...
160 views

How often do a LTE eNodeB scheduler schedule?

Scheduler schedules the resource for each UE. How often do a LTE eNodeB scheduler schedule? Is the time between each scheduling fixed? any idea/reference will be great help on this regard. Thanks.
3k views

Minimum bandwidth condition in FSK

I know that FSK occupies a larger bandwidth compared other keying schemes, $$BW= f_1 -f_2 +2R_b$$ where $f_1$ and $f_2$ are carrier frequencies and $R_b$ is the bit rate. For achieving a ...
343 views

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 ...
2k views

spectral mask and power spectral density

I have been reading a paper that specifies the spectral mask for certain communication devices attempting transmit over a channel Can someone explain 1) importance if this spectral mask, is it a ...
147 views

Basic “filtering” in digital communications

I am completely stuck on solving some problems for my digital communications class. Junior level undergrad class, so fairly basic. I have been searching around all day for related articles etc but can'...
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Does anyone know , how the spread spectrum sequences are used in airports. I've attended a presentation this morning regarding spread spectrum in my college, the author mentioned that the sequences ...
199 views

PPM Variant - Analytic symbol error probability

I'm trying to calculate symbol error probability of variant of pulse position modulation considering only AWGN channel. The decoder is maximum likelihood so the implementation of the detector is by ...
78 views

Modulating ofdm in audio spectrum

Trying to modulate audio with OFDM data. My fs = 44.1khz, i'm using 64 sub-carriers, but i'm only using 5 sub-carriers for data, so my bandwidth is about 3.445khz. I'm not sure how to properly write ...
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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?
30 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 ...
30 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 ...
18 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 ...
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(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? ...
32 views

I am working on satellite receiver burst mode I am trying to build receiver. My data rate is typically 10kpbs. As the data rate is low and carrier frequency offset may also be around 10kbps so i have ...
25 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
47 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 ...
48 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,...
44 views

matched filter position

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