Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [spread-spectrum]

55 questions
5
votes
3 answers

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 frequencies, or is the data stream actually divided…
estolua
  • 153
  • 1
  • 3
4
votes
3 answers

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 occupies some bandwidth $B_1$ which is less than…
Jason S
  • 959
  • 9
  • 14
4
votes
1 answer

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 systems based on chirp spread spectrum (CSS) like…
sigur_ros
  • 43
  • 1
  • 4
4
votes
1 answer

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 transmitters. If I understand correctly, Gold…
Jason S
  • 959
  • 9
  • 14
3
votes
1 answer

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 stays as interference in Rake finger. With CP, no…
AlexTP
  • 5,555
  • 1
  • 18
  • 36
3
votes
2 answers

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 two linear feedback shift registers (LFSRs). This…
Dan Boschen
  • 31,238
  • 2
  • 33
  • 93
2
votes
1 answer

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 resource?
Anna Noie
  • 73
  • 4
2
votes
1 answer

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?
user46622
2
votes
3 answers

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 made difficult to jam, but additionally, the…
awelkie
  • 153
  • 4
1
vote
3 answers

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). You could imagine a clandestine scenario with…
Chris_F
  • 237
  • 1
  • 6
1
vote
1 answer

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 implemented it. Let us focus on the 125KHz wide channel…
user3141592
  • 137
  • 6
1
vote
1 answer

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 beyond the allocated radio channel". I don't know if I…
MagicMan
  • 83
  • 6
1
vote
1 answer

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 transceivers. Can the hackRF switch between…
lws803
  • 113
  • 3
1
vote
1 answer

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 clear and can be demonstrated easily. But regarding…
New_student
  • 609
  • 3
  • 14
1
vote
1 answer

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 orthogonal CDMA code (8-bit Walsh Haddamard code).…
divB
  • 415
  • 3
  • 10
1
2 3 4