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Questions tagged [spread-spectrum]

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Are there modulation schemes that use more bandwith than they need to, but don't require a spread-spectrum code to decode? (besides AM)

In this answer to Have deep-space spacecraft always used some form of spread-spectrum for data downlink? space scientist Mark Adler explains that while spread-spectrum proper (using specific codes in ...
uhoh's user avatar
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Does MSK modulation maintain continous phase after spectrum spread?

I need to check if MSK modulation keeps the phase continuous after DS spectrum spread. My thinking is that since we're expanding the bandwidth, it likely involves abrupt frequency changes so it won't ...
Ketterle's user avatar
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1 answer
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Adding Narrowband Interference to Spread Spectrum Signal in MATLAB (Baseband Model)

I am interested in adding a narrowband interfering signal to my spread spectrum signal. In the waveform model, it's straightforward to generate a narrowband signal within the frequency range of the ...
Digi1's user avatar
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DAC sampling rate when using DSSS/CDMA

I'm currently not sure if I understood DSSS correctly. Following example: We have a shared RF network with around a thousand of users and we want to use CDMA. The RF link should allow the streaming of ...
Stefan Maier's user avatar
2 votes
2 answers
185 views

DSSS spectrum not flat

Why is the PSD of the simulated BPSK/DSSS in AWGN not flat? Here are the simulation parameters: BPSK symbols are randomly generated and are {+1,-1} Spreading factor = 128 Spreading code is a randomly ...
BigBrownBear00's user avatar
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1 answer
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DS-CDMA Spreading Code Length Selection

I'm trying to wrap my head around the process of selecting DS-CDMA spreading codes, and I'm having trouble understanding the tradeoffs of longer codes. For all scenarios described below, I'm using a ...
Jordan's user avatar
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1 answer
120 views

Dsss in digital communication, acquisition, tracking

I have some questions of direct sequence spread spectrum. Does dsss need a pulse shaped filter before it is transmitted? And is there any reference how to realize a dsss system in digital ...
Xiang Li's user avatar
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151 views

How is seen the BER of a BPSK DSSS?

I am trying to understand the DSSS (spread spectrum) performance improvments. Let's consider that we are in BPSK and on a AWGN channel without any interferences or adjacent signals. Is the theoretical ...
dsp_curious's user avatar
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255 views

BER formula for chirp spread spectrum BPSK modulation scheme

May I know how to derive the BER formula for chirp spread spectrum BPSK modulation scheme ?
kevin's user avatar
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128 views

Can an OFDM waveform be spread (DSSS)?

Is it valid to spread an OFDM waveform using direct sequence spread spectrum (DSSS)? Both operations are linear so it seems like this should work.
BigBrownBear00's user avatar
2 votes
1 answer
381 views

Do PSK/QAM modulators (e.g. 4G/5G) fundamentally use more energy per packet than CSS modulators (e.g. LoRa)?

Not sure if this is the right place or even the right question to ask, but googling did not get me much further, so here goes: I'm trying to assess whether the power consumed by an IoT device, based ...
mvds's user avatar
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GNSS : Code Phase and Carrier Phase Relation

What is the relation between code phase and carrier phase in a GNSS system (GPS L1CA, GPS L5 etc)? Any document or section of any book explaining the same will also do.
DSP Rookie's user avatar
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Bandwidth for a binary chirp spread spectrum system

Let's say data rate requirement for some application is 36Kbps. For a binary Chirp spread spectrum system, SF=6 is taken so that M=64. Time * bandwidth = 64. If binary 1 is represented as Upchirp and ...
SinC's user avatar
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1 answer
608 views

Undersampling in GNU Radio

I'd like to implement a FHSS receiver in GNU Radio, using a USRP B210. The total bandwidth of the signal is about 30 MHz, with each message having a bandwidth of about 200kHz. When I attempt to ...
George Willis's user avatar
1 vote
3 answers
679 views

How plausible is undetectable (covert) radio communication?

Ever since I found out that coding gain allows you to receive a signal that is well below the noise floor I have been fascinated with the idea of covert radio signals (low probability of detection). ...
Chris_F's user avatar
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HackRF setup for capturing GNSS signals

I have a MATLAB script which process IF signals to acquire GPS satellites. I decided to capture IF signals containing GPS L1 C/A (1575.42 MHz) myself. What I have: HackRF TCXO for HackRF Active GPS ...
Faruk UNAL's user avatar
1 vote
1 answer
122 views

Increasing Spreading Factor vs reducing FEC rate

This time, I have been reading a lot about how LoRa works and how it is able to achieve such long ranges in non-LOS propagation channels. However, a simple doubt arises regarding the way they ...
user3141592's user avatar
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2 answers
165 views

GPS | Retain Signal Tracking after Noise Bound

I have an IF data, 2 seconds signal sample from only one GPS satellite, I know the PRN number of the satellite. ...
Faruk UNAL's user avatar
0 votes
1 answer
168 views

CDMA and Pulse Shapping

I am a little confused on CDMA and its interaction with the typical pulse shaping filter ex, raised root cosine. Is the RRC filter bandwidth selected to be consistent with the CDMA spreading/update ...
FourierFlux's user avatar
1 vote
1 answer
1k views

Spectral properties of QPSK modulation

From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well ...
MagicMan's user avatar
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1 answer
181 views

How to recover data/information from real complex baseband signal?

I have recorded real complex baseband signal. I want to recover data from the same. The complex baseband signal is basically a composite CDMA signal. How can i recover that information ? Original Tx ...
Jay Patel's user avatar
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1 answer
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Multi-bit gold code

Is the multi-bit gold code resulted from a xor of two different multi-bit m-sequences will still maintain its statistical property (bounded correlation, distribution of 1 and 0) ?
Eagle Shou's user avatar
2 votes
1 answer
3k views

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 ...
lws803's user avatar
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2 votes
1 answer
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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 ...
Anna Noie's user avatar
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1 answer
355 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 ...
techno's user avatar
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2 votes
1 answer
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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 ...
New_student's user avatar
1 vote
1 answer
96 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 ...
divB's user avatar
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0 votes
2 answers
48 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 ...
Mohamad Gholizadeh's user avatar
-1 votes
1 answer
382 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 ...
Amit Sravan's user avatar
0 votes
2 answers
604 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 ...
Noha's user avatar
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1 answer
691 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 ...
Fatima_Ali's user avatar
1 vote
1 answer
2k 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. ...
Fatima_Ali's user avatar
1 vote
1 answer
748 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 ...
random_dsp_guy's user avatar
1 vote
2 answers
306 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?
Velma Benedict's user avatar
1 vote
2 answers
303 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 ...
Velma Benedict's user avatar
2 votes
1 answer
472 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?
user avatar
0 votes
2 answers
285 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? ...
divB's user avatar
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0 votes
0 answers
117 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 ...
M.FAKHFAKH's user avatar
-1 votes
1 answer
108 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-...
Gze's user avatar
  • 640
2 votes
1 answer
68 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 ...
Gze's user avatar
  • 640
1 vote
1 answer
90 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 ...
New_student's user avatar
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0 answers
1k 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 ...
Ali Raza's user avatar
0 votes
1 answer
57 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 ...
New_student's user avatar
0 votes
1 answer
141 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 ...
New_student's user avatar
0 votes
2 answers
95 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: <...
Gze's user avatar
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0 votes
2 answers
162 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 & ...
Gze's user avatar
  • 640
1 vote
2 answers
75 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 ...
New_student's user avatar
-1 votes
1 answer
89 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 ...
Shuang's user avatar
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1 vote
1 answer
756 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 ...
random_dsp_guy's user avatar
0 votes
2 answers
82 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 ...
Engineer's user avatar
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