## Forums Search for: Modulation

## Definition of modulation index for shaped FSK

inI have a pretty elementary question. For an unshaped, 2-FSK signal, the modulation index h is defined as the ratio of the difference between...

I have a pretty elementary question. For an unshaped, 2-FSK signal, the modulation index h is defined as the ratio of the difference between the two tone frequencies to the symbol rate. For shaped 2-FSK, how is h usually defined? I can think of a few possibilities: (1) Base it on the peak frequency excursion exhibited by one isolated symbol, ignoring ISI from other nearby symbols. ...

## AD TxDAC - quadrature digital modulation purpose ?

Hi! While learning about QAM modulation (in context of DVB-C transmission) I came to Analog Devices AD9773 TxDAC datasheet. I'm slighlty...

Hi! While learning about QAM modulation (in context of DVB-C transmission) I came to Analog Devices AD9773 TxDAC datasheet. I'm slighlty confused with its digital complex modulator. Could someone read below and check my understanding ? If I understand correctly, one mode of operation is to output plain I/Q signals and mix them using external analog quadrature modulator (e.g. AD8345). In...

## OFDM LS Channel Estimation or Differential Modulation

inThis freescale appnote: http://www.freescale.com/files/dsp/doc/app_note/AN3059.pdf talks about all the different kinds of channel estimation...

This freescale appnote: http://www.freescale.com/files/dsp/doc/app_note/AN3059.pdf talks about all the different kinds of channel estimation schemes for OFDM reception. They discount differential modulation, but how does it compare with the simplest channel estimation techniques: Least Square (LS)? Alan

## 4Hz modulation energy from MFCC coefficients

Hi, with respect to your community, I'm just starting my journey with signal processing topic. I'm currently working on small voice activity...

Hi, with respect to your community, I'm just starting my journey with signal processing topic. I'm currently working on small voice activity detection (VAD) C++ code snippet. After reading .wav file, passing it trough FFT and feeding with obtained data MFCC algorithm I got my MFCC coefficients. Now I'm little confused. How should I calculate modulation energy in 4Hz frequency (and in bandwith...

## satellite transponder nonlinearity effect on QAM

inHi i am trying to implement 16QAM modulation with effect of transponder nonlinearity i got transponder power input and output values and i have...

Hi i am trying to implement 16QAM modulation with effect of transponder nonlinearity i got transponder power input and output values and i have to pass my modulated signal through this nonlinear channel but am not getting how to perform this function . so if anyone here has done such sort of work i.e. implemented a satellite nonlinear channel with any modulation scheme please let me know how to do...

## OFDM system

inHi, It is clear that OFDM systems may have different SNR values for each subcarrier due to frequency selectivity of the channel. If an OFDM...

Hi, It is clear that OFDM systems may have different SNR values for each subcarrier due to frequency selectivity of the channel. If an OFDM packet consists of n number of FEC blocks and in case of adaptive modulation and coding systems, a single FEC block may have different modulation scheme. However, is it possible for OFDM (e.g.IEEE 802.11a/n) systems that the block error probability of FEC b...

## Pilot Symbol Assisted QAM

inHi, How the pilot symbol assisted QAM works ? What are the symbol information sent on this Pilot ? It's in the same frequency band than...

Hi, How the pilot symbol assisted QAM works ? What are the symbol information sent on this Pilot ? It's in the same frequency band than the QAM modulation ? I think we send a BPSK pilot over the QAM modulation in time duplex ? Do you have good paper on that, I found nothing over google... Thanks

## Coding Gain

inHello all, I have a question about coding gain for a convolutional code. In the books that I have, the coding gain is presented in the form of...

Hello all, I have a question about coding gain for a convolutional code. In the books that I have, the coding gain is presented in the form of graph of BER vs Eb/No for a given modulation format, typically BPSK. The coding gain is the horizontal distance between the uncoded and coded curves on the graph. My question is, what if I change the modulation format to FSK instead? I understand...

## Calculating BER for optical communications

inHi! I would like to calculate the BER of an optical communications system. The only known value is the total collected intensity as a...

Hi! I would like to calculate the BER of an optical communications system. The only known value is the total collected intensity as a function of time (I thus can calculate mean intensity, variance,...). The modulation format doesn't matter. The simplest is the best; so we can take OOK modulation. I think that BER is also function of the SNR. How can I calculated the BER if I take a O...

## Coding/Modulation Question

inDoes a modulation with q different symbol states absolutely require a code over X^n, where X = {a_1, a_2, ..., a_q}? Or can you use a symbol...

Does a modulation with q different symbol states absolutely require a code over X^n, where X = {a_1, a_2, ..., a_q}? Or can you use a symbol set (X) with a different order (count)? A slightly different question: is this *typically* done (q symbol states ==> order q symbol set)? I.e., although it's not required, is it typically done this way? As a simple example, could a binary (7,4) Ham

## I/Q modulation and phase noise sensitivity

inHi, I am observing something that is very counter-intuitive to me: I/Q modulation is very susceptible to phase noise? In an experiment I...

Hi, I am observing something that is very counter-intuitive to me: I/Q modulation is very susceptible to phase noise? In an experiment I plot "phase noise" vs. "SNR" and see a constant slope of ~20dB/dec. I use a real baseband signal, multiply it by cos(2*pi*fc*t) and then multiply it again by cos(2*pi*fc*t + phi(t)) where phi represents the phase noise. Finally, a simple image filter. I...

## Analytic signal

inHello Forum, in AM modulation, a carrier (pure monochromatic signal) is multiplied by the message signal m(t). In angle modulation, the phase...

Hello Forum, in AM modulation, a carrier (pure monochromatic signal) is multiplied by the message signal m(t). In angle modulation, the phase or derivative of the phase is modulated according to m(t). In both case we have a real signal. What is the advantage of associating the analytic signal to the real modulated signal? The analytic signal has its imaginary part equal to the Hilbert tra...

## QAM Shannon Limit?

inHi all, I am told that there are Shannon Limit (Eb/No) with every code-rate BPSK modulation. Are there Shannon Limit (Eb/No) with every...

Hi all, I am told that there are Shannon Limit (Eb/No) with every code-rate BPSK modulation. Are there Shannon Limit (Eb/No) with every code-rate QAM(like 16QAM and 64QAM) modulation? Any suggestions will be appreciated! Best regards, Davy

## BER performance for BPSK and QPSK

inHi, I read this statement from a book "The bit error probability for QPSK modulation is the same as for BPSK, and hence, the results for BPSK...

Hi, I read this statement from a book "The bit error probability for QPSK modulation is the same as for BPSK, and hence, the results for BPSK can be used also for the QPSK case". The author of the book simulated the BER performance for BPSK modulation in multipath and AWGN channel. May I know how true is this statement? Under what scenario can I make such an approximation? Where can I find t...

## DSSS modulation DQPSK

inHi, I made a complete DSSS demodulator with DBPSK and DQPSK demodulation. In the case of DQPSK demodulation I've got the same PN_code on I...

Hi, I made a complete DSSS demodulator with DBPSK and DQPSK demodulation. In the case of DQPSK demodulation I've got the same PN_code on I and Q branchs. What is the advandatage to put different PN_code on I and Q ? And what is the advantage to make a complex spreading like this : At spreading (modulation) : (I+jQ).(PN_I+jPN_Q) So I signal becomes : I.PN_I-Q.PN_Q and Q signal become...

## WiMax data rate

inHi all, I am new in WiMax and I intend to construct the table of modulation, SNR and BER.. does anybody know how can I do it and by which...

Hi all, I am new in WiMax and I intend to construct the table of modulation, SNR and BER.. does anybody know how can I do it and by which equation ? I mean the table can be like the following: SNR modulation type data rate BER --- --------------- -------- ---- thanks for any help, Ashlie

## Simulation of digital communication system under various fading channels

inAs part of my final year project, i have to design a digital communication system in simulink using any modulation scheme. the modulation scheme...

As part of my final year project, i have to design a digital communication system in simulink using any modulation scheme. the modulation scheme that i chose is BPSK.... i have to plot the BER of the system against SNR and compare the acheived results to the theoretical results in order to proove that my system is correct. i also have to use the AWGN channel, the multipath rayleih fading cha...

## Question about coding for high order modulation

inHi, I have a question about channel coding. As I know, coding is used for improving system performance. At the same time, coding will result...

Hi, I have a question about channel coding. As I know, coding is used for improving system performance. At the same time, coding will result in lower spectral efficiency, except TCM. For higher modulation, the coding gain is useful only when its performance is better than that of lower order modultion without coding. Except TCM, other coding schemes are general of bandwidth expansion type....

## Detection of Bessel components of a received PM signal

inHi My current work involves estimation of modulation index for a PM signal with or without subcarriers. I have found articles to do the same...

Hi My current work involves estimation of modulation index for a PM signal with or without subcarriers. I have found articles to do the same without subcarriers, but I am yet to find something which might work when subcarriers are included. An important method to estimate the modulation index (which I believe can be extended for subcarriers later) is to detect the Bessel components and find cor...

## Coding Gain for TCM (Trellis-Coded Modulation)

inHi! I want to make sure that what I've learned so far about Trellis-Coded Modulation is correct which is why I'm asking for...

Hi! I want to make sure that what I've learned so far about Trellis-Coded Modulation is correct which is why I'm asking for confirmation. d_free^2 is minimal the sum of squared Euclidean distances between two symbol sequences that can be generated by the TCM, right? The coding gain is 10*log10(d_free^2/d_min^2) where d_min is the minimum Euclidean distance for a pair of "uncoded" symbo...