Questions tagged [spread-spectrum]
The spread-spectrum tag has no usage guidance.
47
questions
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Is Bluetooth Low Energy jamming possible with an SDR like the HackRF on GNURadio?
It seems like BLE jamming is technically possible by just jamming the 3 advertising channels 37, 38 and 39 https://github.com/lws803/BLE-jammer and it has been proven to work on an STM32 + 3x NRF24l01 ...
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0answers
25 views
what are resources you recommend to learn GPS signal processing?
I want to learn about GPS and other GNSS signal processing algorithms.
I have solid background in signal processing and some experience in OFDM.
Could you please recommend some books or online ...
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35 views
How to implement Walsh demodulation in matlab?
1 1 1 1 ==> 0
1 -1 1 -1 ==> 1
1 1 -1 -1
1 -1 -1 1
I have this sequence of walsh spreading ...
0
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1answer
69 views
Cant find Doppler shift with LFM signal
Im stuck on this one. I hope someone helps me!
Problem: I need to find Dopler shift with array of reflected chirps.
I have bursts of chirps which then i sampled, and calculated fft.
Im suposed to ...
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1answer
25 views
About the orthogonality of columns in Zadoff-Chu matrix
As we know that Zadoff-Chu matrix is similar to Walsh-Hadamard matrix where every columns in those matrices is orthogonal with the any other column.
For Walsh-Hadmard matrix, the orthogonality is ...
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1answer
46 views
How to correct for delays in a PAM-X signal with orthogonal CDMA?
I have a receiver which receives data bits at a rate of 5kbit/s. The number of data bits per burst is low (say, 16 bits). These databits are obtained after despreading the incoming signal using an ...
0
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2answers
41 views
difference in spectrum
First I defined 5 signals with same length (40 samples) with different frequency and sampling frequencies, then I've put them together like [X1 X2...] and took it's fourier transform and the result is ...
0
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1answer
62 views
Help in designing filter for DUC (Digital Up-Converter) and DDC (Digital Down-Converter) using the built-in DUC and DDC blocks in MATLAB Simulink
Can anyone please help me in simulating a simple BPSK transceiver system that correctly receives a signal through a DUC and DDC? I have attached the screenshot of my Simulink system along with ...
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2answers
76 views
Jamming resistance in spread spectrum systems
In direct sequence spread spectrum, which is the basis of CDMA systems, the baseband signal is multiplied with a pseudo noise (PN) sequence which has a high chip rate, thus the resulting modulated ...
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0answers
20 views
Path delay influence in BER performance using Rayleigh channel
I am simulating a DSSS modulation in a Rayleigh channel to get the BER performance. For these purpose I am using the comm.RayleighChannel object.
My problem comes when I change the Paths delays of the ...
0
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1answer
125 views
What's the difference between spreading and scrambling
I have a question regarding the scrambling code, What's the difference between spreading and scrambling? As I know, following the below figure, the scrambling doesn't affect the signal bandwidth:
As ...
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1answer
312 views
What are the advantages and disadvantages of PN sequence over Walsh code
I would like to ask what are the disadvantages and advantages of PN sequence over Walsh code? and also Gold code over Walsh code.
I have checked online, but I didn't get clear explanation for that. ...
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1answer
58 views
Detect low power DSSS-BPSK signal
I have heard that it is possible to detect a low power (ie not visible on a spectrum analyzer) DSSS-BPSK (direct sequence spread spectrum) signal even when you don't know the spreading code by ...
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0answers
17 views
How to estimate the channel in DS CDMA system
I am working with DS-CDMA system based on multi-path Rayleigh channel,My question, how can I estimate the channel from the received signal to cancel the effect of channel?
for example in OFDM system ...
1
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2answers
67 views
Early - late gate spread spectrum
For situation that received signal is complex, how Early and late are calculated in spread spectrum tracking?
How I can consider both real and imaginary in error calculation?
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2answers
181 views
Spread spectrum receiver
I want to design a receiver for a spread spectrum system. I know that two Pseudo sequence with two different length must be used in the receiver, but I can' t manage this with common receivers(such as ...
2
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1answer
123 views
DSSS spread method
How do you implement Direct Sequence Spread Spectrum (DSSS) to synchronize the spreading rate with the symbol rate when there is a non-integer but rational relationship between the two?
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2answers
72 views
How are CDMA codes distributed?
I think this question is so trivial that it's nowhere explained (I would not find it) and the answer is probably trivial too. But I still wonder how codes in a typical CDMA system are distributed? ...
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41 views
Spread Spectrum (CDMA) signal phase noise measurement
A CDMA signal is considered for this application.
I would like to have an information on the generated signal oscillator's quality using a phase noise measure. If the signal was a pure carrier, it ...
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1answer
42 views
What's the effect of spread spectrum on frequency- selective channel
In brief, we consider the channel as frequency-selective channel if the frequency of the signal is larger than then frequency of channel.
So, does using the spreading spectrum change the frequency-...
1
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1answer
47 views
Is it possible to spread signal using sum of more than one orthogonal code
I was wondering if we can spread the signal using more than one spreading code. Assume we have the Walsh code used to spread the transmitted signal, the Walsh code is, for example, gotten based on ...
1
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1answer
67 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 ...
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597 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 ...
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1answer
47 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
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1answer
96 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 ...
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2answers
45 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
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2answers
78 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
$$H = \begin{pmatrix}
1 & 1 & 1 & ...
1
vote
2answers
51 views
What is the duration of the spreading sequence
I have a question regarding the spreading sequence duration using Walsh matrix. I've read a paper related to that, they consider the signal $S = R(S) + I(S)$, where $R(S), I(S)$ are the real and ...
-1
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1answer
81 views
How to solve signal MFSK or FHSS question (received signal+ noise+jamming)
I'm trying to solve the following:
\begin{equation}
A \cos(2\pi f t + \theta_1) + B \cos(2\pi f t + \theta_2) = D\cos(?f?\theta)
\end{equation}
I just need to know the correct value of D, the value ...
1
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1answer
201 views
Frequency Hopping Spread Spectrum Synchronization Methods
Frequency-hopping spread spectrum waveforms change the carrier frequency at some interval.
I can see if the frequency is constant for the duration of an entire packet, the pilot symbols could be used ...
0
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2answers
42 views
Rate in CDMA setup
I am working on a CDMA system with only 4 chips/symbol. I want to use $R=\frac{1}{2}log_2(1+SNR)$ chips/channel use to calculate what $SNR$ I require to successfully receive a given transmission. In ...
4
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3answers
382 views
How to reconcile “bandwidth” in the Shannon-Hartley Theorem with a spread-spectrum principle
I'm trying to understand something about channel "bandwidth" $B$ in the Shannon-Hartley Theorem: $$C = B \log_2 \left( 1 + \dfrac{S}{N} \right) $$
Suppose I have a bitstream encoded as a signal that ...
1
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2answers
107 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 ...
4
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1answer
4k 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
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1answer
311 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
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1answer
2k 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 ...
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0answers
177 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 ...
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3answers
108 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
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1answer
459 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 ...
3
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1answer
109 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 ...
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2answers
358 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 ...
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2answers
197 views
How can I insert message bits into the frequency spectrum of an audio signal using Matlab?
I have been trying to use the DSSS spread spectrum technique for audio steganography in MATLAB. I multiplied the PN sequence with the message bits. Now I want to insert this spread message into a ...
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1answer
465 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 ...
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2answers
600 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
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1answer
61 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
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2answers
662 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 ...
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3answers
3k 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 ...
