Questions tagged [spread-spectrum]
The spread-spectrum tag has no usage guidance.
37
questions
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10 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
votes
1answer
31 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 ...
1
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1answer
53 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. ...
0
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1answer
33 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
14 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
vote
2answers
51 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?
1
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2answers
143 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
votes
1answer
110 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?
0
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2answers
46 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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0answers
34 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 ...
-1
votes
1answer
34 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
vote
1answer
39 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
vote
1answer
60 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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459 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
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1answer
43 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
85 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
31 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
77 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
$$H = \begin{pmatrix}
1 & 1 & 1 & ...
1
vote
2answers
50 views
What is the duration of the spreading sequence
I have a question regarding the spreading sequence duration using Walsh matrix. I've read a paper related to that, they consider the signal $S = R(S) + I(S)$, where $R(S), I(S)$ are the real and ...
-1
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1answer
75 views
How to solve signal MFSK or FHSS question (received signal+ noise+jamming)
I'm trying to solve the following:
\begin{equation}
A \cos(2\pi f t + \theta_1) + B \cos(2\pi f t + \theta_2) = D\cos(?f?\theta)
\end{equation}
I just need to know the correct value of D, the value ...
1
vote
1answer
144 views
Frequency Hopping Spread Spectrum Synchronization Methods
Frequency-hopping spread spectrum waveforms change the carrier frequency at some interval.
I can see if the frequency is constant for the duration of an entire packet, the pilot symbols could be used ...
0
votes
2answers
37 views
Rate in CDMA setup
I am working on a CDMA system with only 4 chips/symbol. I want to use $R=\frac{1}{2}log_2(1+SNR)$ chips/channel use to calculate what $SNR$ I require to successfully receive a given transmission. In ...
4
votes
3answers
319 views
How to reconcile “bandwidth” in the Shannon-Hartley Theorem with a spread-spectrum principle
I'm trying to understand something about channel "bandwidth" $B$ in the Shannon-Hartley Theorem: $$C = B \log_2 \left( 1 + \dfrac{S}{N} \right) $$
Suppose I have a bitstream encoded as a signal that ...
1
vote
2answers
94 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
votes
1answer
3k 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
271 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
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 ...
1
vote
0answers
149 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
101 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
418 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
votes
1answer
91 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
336 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
432 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
573 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
56 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
501 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 ...
