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### 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 ...
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 ...
369 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 ...
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 ...
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 ...
627 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 ...
121 views

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?
106 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 ...
594 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?
456 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 ...
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 ...
252 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. ...
62 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?
160 views

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 ...
46 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 ...
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 ...
187 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 ...
354 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 ...
25 views

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 ...
42 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 ...
65 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 ...
172 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 ...
71 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 ...
87 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 ...
94 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 ...
78 views

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 & ...
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 ...
40 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 ...
47 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 ...
67 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? ...
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: <...
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 ...
446 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 ...
32 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 ...
62 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 ...
49 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 ...
17 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 ...
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 ...
40 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 ...
564 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 ...
46 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 ...
57 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 ...
38 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-...
I'm trying to solve the following: $$A \cos(2\pi f t + \theta_1) + B \cos(2\pi f t + \theta_2) = D\cos(?f?\theta)$$ I just need to know the correct value of D, the value ...