Questions tagged [spread-spectrum]
The spread-spectrum tag has no usage guidance.
1
vote
1answer
45 views
Is it possible to use MRC with DS-CDMA-MIMO [closed]
I'm wondering how to use the Maximum Ratio Combining with MIMO-DS-CDMA, I have used the MIMO with DS-CDMA using Walsh code, then at receiver I couldn't recover the transmit signal using the MRC. here ...
0
votes
0answers
58 views
Simulate capture effect in Matlab with LoRa modulation
I have a Matlab code to generate a LoRa signal modulation and demodulation. Now I would like to simulate a capture effect with 2 signals of slighly different powers. I need some help on how to proceed ...
0
votes
0answers
71 views
How to Extract frequency bands from Short-time Fourier Transform?
I am reproducing the results reported by the author in a research paper. In which he takes the STFT of EEG signals. The input data has a shape of (1 X500) and I used Scipy library built-in function to ...
0
votes
1answer
39 views
Using Spreading spectral with Maximal likelihood
As asked here, HERE if we have the signal
x =
[0.7 + 0.7i;
0.7 - 0.7i;
-0.7 + 0.7i;
-0.7 -0.7i];
Which was spread over code ...
0
votes
1answer
72 views
Using MIMO with DS-CDMA and spread spectrum
I have a question about using MIMO with DS-CDMA. suppose we are using 4 TX antennas, and 4 RX antennas, then the Reyleigh ...
0
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1answer
28 views
How can I spread a modulated signal over walsh code
I need to confirm if spreading signal by using walsh code in MATLAB is right or no,
Suppose I'm using QAM modulation, so I need to spread the signal over walsh code, is the below step is right:
<...
0
votes
2answers
62 views
About using Walsh matrix as spreading sequence
I'm asking about some details about using the Walsh matrix as spreading sequence code. For example, suppose I'm using a $4\times 4$ Walsh matrix given by
$$H = \begin{pmatrix}
1 & 1 & 1 & ...
1
vote
2answers
44 views
What is the duration of the spreading sequence
I have a question regarding the spreading sequence duration using Walsh matrix. I've read a paper related to that, they consider the signal $S = R(S) + I(S)$, where $R(S), I(S)$ are the real and ...
-1
votes
1answer
34 views
How to solve signal MFSK or FHSS question (received signal+ noise+jamming)
I'm trying to solve the following:
\begin{equation}
A \cos(2\pi f t + \theta_1) + B \cos(2\pi f t + \theta_2) = D\cos(?f?\theta)
\end{equation}
I just need to know the correct value of D, the value ...
1
vote
1answer
67 views
Frequency Hopping Spread Spectrum Synchronization Methods
Frequency-hopping spread spectrum waveforms change the carrier frequency at some interval.
I can see if the frequency is constant for the duration of an entire packet, the pilot symbols could be used ...
0
votes
2answers
35 views
Rate in CDMA setup
I am working on a CDMA system with only 4 chips/symbol. I want to use $R=\frac{1}{2}log_2(1+SNR)$ chips/channel use to calculate what $SNR$ I require to successfully receive a given transmission. In ...
5
votes
3answers
210 views
How to reconcile “bandwidth” in the Shannon-Hartley Theorem with a spread-spectrum principle
I'm trying to understand something about channel "bandwidth" $B$ in the Shannon-Hartley Theorem: $$C = B \log_2 \left( 1 + \dfrac{S}{N} \right) $$
Suppose I have a bitstream encoded as a signal that ...
1
vote
2answers
67 views
Use of pseudo-random binary sequence (Gold, Kasami, etc.) in frequency hopped code-division multiple access (FH/CDMA)
I have a clear idea of how a PN-sequence is used in a Direct Sequence Code-Division Multiple Access(DS-CDMA) system with BPSK. In such a system, a different pn-sequence is assigned to each user and ...
5
votes
1answer
2k views
Conversion between Eb/N0 and SNR in spread-spectrum modulation like LoRa CSS?
This question is somewhat related to the one asked here: How is multiplexing achieved in spread-spectrum modulations like CSS?
I am looking at the bit error rate (BER) performance of communication ...
-1
votes
1answer
176 views
Recovering DSSS signal from below noise Floor
I want to understand what actually happens in the direct sequence spread spectrum demodulator ? Why is it said that the signal is recovered from below the noise floor ? Can someone please explain the ...
4
votes
1answer
1k views
Why are Gold codes and Kasami codes used instead of pure m-sequences?
I'm trying to understand why Gold codes and Kasami codes are used instead of pure m-sequences, in direct-sequence spread-spectrum (DSSS) communication systems, to prevent interference between multiple ...
1
vote
0answers
124 views
What kind of signal modulation is more resistant to jamming?
I've understood that spread-spectrum type of modulations are more resistant to narrow band jamming, for obvious reasons. What is less obvious is why someone would try to jam for example a cellular ...
2
votes
3answers
91 views
Is there an asymmetric crypto analog to direct sequence spread spectrum?
In section 12.1.1.2 of Digital Communications: Fundamentals and Applications, Bernard Sklar makes this claim about spread spectrum signals:
Therefore, not only can the spread-spectrum signal be ...
0
votes
1answer
329 views
How does the PSK demodulator differentiates one carrier from the other in CDMA
I'm trying to understand the way in which CDMA works. Once the transmitter bit sequence is spread it is modulated for instance using a PSK modulator. Lets assume BPSK is used. I'm particularly ...
4
votes
1answer
71 views
Is there any Spread Spectrum system that uses Rake with cyclic Prefix?
My question is that could the use of cyclic prefix can enhance the performance of Rake receiver ?
I find this proposal here CP for DSSS Rake Receiver that seems correct.
Without CP, ISI emerges and ...
0
votes
1answer
291 views
Time and frequency domain spreading in CDMA and MC-CDMA?
For time domain CDMA transmitter, how the spreading sequences should look like? Is it necessary to be from $\{ -1,+1\}$ like PN sequences ? How will the codes be in frequency domain?
I am confused in ...
1
vote
1answer
354 views
Can i use frequency hopping spread spectrum technique for audio steganography?
I have been trying to use spread spectrum technique for audio steganography. I read a lot about it.But i didn't find any information about the steganography scheme using FHSS(frequency hopping spread ...
1
vote
2answers
486 views
How is multiplexing achieved in spread-spectrum modulations like CSS?
I understand why it doesn't interfere with narrowband communication systems but how do different clients communicate in a system like LoRa. Is it time orthogonality like TDM?
0
votes
1answer
52 views
Spreading sequence and equalization based on a paper
I am having difficulty in understanding how the Authors in this paper, An EM based method for semi blind identification of linear systems driven by Chaotic signals
have used the expressions derived ...
2
votes
1answer
335 views
Minimum Output Samples needed to crack a “Gold Code” Generator (Dual LFSR)
Please preface your answer with spoiler notation by typing the following two characters first ">!"
Below is an implementation of a "Gold Code" Generator formed by adding (in $GF(2)$) the outputs from ...
5
votes
3answers
2k views
What exactly happens with Spread Spectrum Modulation
With regard to DSSS and CDMA(DS), what does it mean to spread a signal over a spectrum of frequencies in terms of individual frequencies? Is it about sending the same signal redundantly on multiple ...
