6
votes
OFDM use a pulse shaping filter or not?
The purpose of pulse shaping filters is not to overcome ISI as is implied in the OP's question. The only reason for using a pulse shaping filter is spectral efficiency, and in the process ISI can be ...
- 48.2k
5
votes
Accepted
How to remove the modulation before doing frequency offset estimation?
For lower-cardinality PSKs like the QPSK, the "classical" way is to
take the signal to the $M$th power, $M$ being the number of constellation points.
From the shape of an $M$-PSK modulation, ...
- 29k
3
votes
Why SRS signalling is used in 5g?
Because DMRS is only sent if there is data to transmit and, therefore, narrowband while SRS, as the term sounding suggests, is not associated to any data transmission and also wideband.
For example, ...
- 6,020
3
votes
What is the physical meaning of coherence bandwidth in mmWave massive MIMO channel?
You are right, coherence bandwidth is the frequency domain counterpart of delay spread.
However, to achieve diversity across antennas the spacing between the antennas is important "relative to the ...
- 2,592
3
votes
Accepted
Why multi-path channel has linear phase within the coherence bandwidth?
For the classical baseband channel model for multipath, $h(t)=\sum_ka_k\delta(t-\tau_k)$, the frequency response $H(f)=\sum_k a_ke^{-j2\pi f\tau_k}$. If $K=1$, single tap the phase would have been ...
- 2,213
3
votes
Accepted
Simulating Es/N0 by adding noise to analog signal
$E_s$ would be the energy of the channel symbols at the output of the matched filter as scaled by the path loss between transmitter and receiver as long as all timing and carrier offsets have been ...
- 48.2k
3
votes
Undestanding antenna gain applicability
The answer has to do with the definitions of antenna gain and space loss. Antenna "gain" is essentially defined relative to space loss, which is due to isotropic (uniform spherical) ...
- 1,248
3
votes
Accepted
Undestanding antenna gain applicability
Of course, the gain of an antenna is not like that of an op-amp. It is just a measure of how sharply it focuses the beam in a specific direction with regards to a reference antenna, e.g., an isotropic ...
- 563
2
votes
Why does altering path length in radio transmission alter the phase of the received signal?
Yes indeed it will be (although we could argue that it may not be necessarily for all distances since the phase is cyclical!).
In free space the signal propagates at the speed of light, therefore ...
- 48.2k
2
votes
Relationship between Nyquist and Shannon channel capacity
They become the same if $M = \sqrt{1+SNR}$
Nyquist simply says: you can send 2B symbols per second. Shannon extends that to: AND the number of bits per symbol is limited by the SNR. Shannon builds on ...
- 41.4k
2
votes
Relationship between Nyquist and Shannon channel capacity
Well, I think both are unrelated unless you have some constraints.
The Nyquist channel capacity says you can transmit $2B\log_2(M)$ bits per second for given channel bandwidth $B$. It does not say ...
- 2,213
2
votes
Why multi-path channel has linear phase within the coherence bandwidth?
When we talk about linear phase in an LTI system we are talking about the phase of the FFT of the time domain system response. Thus the linearity is with respect to the frequency of the signal and not ...
- 2,592
2
votes
Accepted
awgn function in MATLAB
Does that mean awgn function behavior depends on the zero padding (length of the signal)?
Yes, it does depend on the length of the signal.
How does the 'awgn(input_signal,snr_db,'measured')' ...
- 2,854
2
votes
Accepted
How is the Tx/Rx Gain calculated in USRP?
The term "gain" is pretty appropriate. It's a number describing the output power relative to some arbitrary base power.
So I would like to know how this transmitter channel gain process is ...
- 29k
2
votes
Accepted
Can Oversampling help to mitigate the effect of additive white gaussian noise?
Oversampling will not do anything to change the existing noise in the waveform other than the quantization noise that is added. Sampling does not change the waveform but the quantization process of ...
- 48.2k
2
votes
Accepted
Shannon formula for channel capacity
This formula is for baseband with real symbols in an AWGN channel.
However, it is trivially easy to adjust it for quadrature modulation or complex symbols: just double the capacity.
OFDM and other ...
- 14.6k
2
votes
Accepted
Difference between sampling rate and baud rate and their relation to channel capacity
First let's estabish the context.
Let's say you want to transmit a sequence of numbers $\lbrace a_k \rbrace_{k=1}^{N} = a_1, a_2, \ldots$ Using PAM, this sequence is transmitted with the signal $$s(t) ...
- 14.6k
2
votes
Accepted
What does $\mathcal{ E}(|h|^2)$, where $|h|^2$ is power of the channel gain $h$ represent?
As Marcus says, it's the expectation:
$$ \mathcal{E}(|h|^2) = \int |h|^2 p_{|h|^2}(|h|^2) d|h|^2$$
where $p_{|h|^2}(|h|^2)$ is the probability density function of $|h|^2$.
This assumes that there's ...
- 25k
2
votes
Accepted
How to code Rician fading channel gains from k-factor?
To Q1: Yes you can use a complex Gaussian distribution with mean to simulate a Ricean distribution. In Matlab, you can use something like
...
- 477
2
votes
Distance between Transceiver and Receiver and AWGN
Although AWGN is modeled as being added by the AWGN channel (which by definition does nothing to the signal traversing the channel except add the white Gaussian noise), the truth of the matter is that ...
- 20.1k
2
votes
Joint channel model for space-air-ground link
These bands are going to be separate, not a single channel shared by both. You can already find satellite cellular frequencies in current 3GPP releases. (Every other assignment will be, at this point, ...
- 29k
1
vote
How does higher received signal power enable higher data rates?
The answer is Shannon's limit, which is given by:.
$C = B log_2 (1 + γ)$
where $C$ is the “capacity,” or maximum error-free data rate, $B$ is the bandwidth of the
channel, and $γ$ is the SNR (or SINR)....
- 95
1
vote
Optimal FEC option for extremely low SNR situation
Very shortly: as you approach the ultimate Shannon limit (-1.59 dB = Eb/N0) with a finite-length code, then you're better off not coding at all. Intuitively, you have very little energy to spend, and ...
- 29k
1
vote
Accepted
Centre channel derivation using correlation
Here's a simplified overview:
Start with L and R signals. Run an fft on each to extract Mag and Phase at every frequency bin.
Compare the Mag and Phase values of the L and R signals. If they're &...
- 55
1
vote
Centre channel derivation using correlation
Audio up-mixers are fairly complicated and the "better" ones are either protected IP or trade secrets.
To extract a center channel you would look at the correlation between the left and ...
- 41.4k
1
vote
Accepted
Channel estimation using bit reversed order of FFT matrix
So, according to your text,
$$ H := F^bh,$$
i.e. what you call the bit-reversed order FFT of the channel impulse response.
Since "bit-reversed order" just implies you're permuting outputs of ...
- 29k
1
vote
Accepted
What is impulse response in simple AWGN channel?
A linear system cannot add anything new to its input signal, so additive noise is modeled separately from any linear distortion of the signal. In your case with just scaling and delay, the channel ...
- 87.2k
1
vote
BER and distance relation
In short, increasing the distance results in a decrease in $E_b$.
Consider two antennas in an otherwise empty universe (this is known as "free space"). The transmitter antenna radiates $P_t$ ...
- 14.6k
1
vote
White noise generation for different bandwidth signals in MATLAB
Regarding the bandwidth, this should be the channel bandwidth from the channel symbol rate $R_{ch}$. The preamble and stuff like ASMs (attached synch markers) are used for synchronization purposes and ...
- 3,356
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