New answers tagged digital-communications
3
votes
Basics of interpolation: is filter or upsample first?
To add to Gillespie's correct answer, it's worth knowing that in the literature of DSP the terminology used to describe "sample rate change" is often confusing. Here's some of the ...
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2
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Spreading sequence in DSSS
the spreading sequence is known only to the receiver and the transmitter.
is only necessarily known to the receiver and the transmitter. There's nothing that says it needs to be a secret. In fact, it'...
- 26.3k
3
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Basics of interpolation: is filter or upsample first?
You wrote: Which one is correct? Filter + upsample or upsample + filter?
The answer is actually neither. Lowpass filtering is part of upsampling, not an extra step. ...
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0
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Power of noise signal through a matched filter (Digital Receiver)
Can anyone explain why that is? Which is the starting thought, or formula that yields to different times $t_1$ and $t_2$?
The noise power $P_N(t)$ at any given time $t$ at the output of any filter (...
- 18.9k
1
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Order statistics: always applicable tool in wireless communication?
Ok, first, we'll need to acknowledge that the channels you're looking at are very specifically about such a channel. It's no coincidence! In all these papers it's about considering the order ...
- 26.3k
2
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Accepted
Understanding Pathloss and latency
There are many possible ways to model path loss to include both attenuation and delay (latency). For example, this page from Molisch gives a way to include both: the Power Delay Profile approach.
- 22.5k
0
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Accepted
convert from binary to hexadecimal according to the algorithm "keeloq"
As per @tonys in the comments.
\begin{matrix}
1101 \ 1111 \ 1101 \ 1101 & \rightarrow& \mbox{inverted, bit reversed} & \rightarrow& \tt 0x04 \ 0x44\\
0001 \ 0111 \ 0001 \ 0111 & \...
- 22.5k
2
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Why should costas loop be done after clock recovery, as opposed to before?
The job of the costas loop is to "derotate" the constellation points.
But for that you first need to look at the constellation points at the symbol instants. If you look at the signal ...
- 26.3k
1
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High error when adding small value of SFO into the OFDM signal
The sampling frequency offset will induce a time offset on every symbol that is increasing from symbol to symbol. This results in the rotation as observed.
Frequency is the derivative of phase with ...
- 37.1k
1
vote
Accepted
Sampling frequency offset vs carrier frequency offset effects
If $x[n]$ is your OFDM signal in the time domain, and you compute $x[n] e^{j 2\pi \frac{\Delta f_s}{f_s} n}$ then you are simulating a carrier frequency offset of magnitude $\Delta f_s$ given a ...
- 1,372
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Designing a PI filter for a Costas Loop
The low pass filters used must have cutoff frequencies at least 10x higher than the PLL loop bandwidth and of minimum delay so as to not affect loop stability. I recommend using minimum phase filters ...
- 37.1k
3
votes
Accepted
How to choose correctly oversampling ratio?
The referenced post does not imply that 8 samples per symbol are required, that is only what was used in order to show the extended spectrum as copied below:
What I have also included in this copy of ...
- 37.1k
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Question on Signal to noise ratio (SNR)
Assuming the path losses are all equal and direct with no subsequent reflections (an unlikely but simplifying assumption), the signals if correlated (phase aligned, which beam-steering would provide) ...
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