Sharan Basappa (@Sharan123)
with respect to puncturing associated with channel coding, I have a question.So, when a code word is punctured at the transmitted how does the receiver know the...
Thanks.On memory less coding method:if a coding method does not involve delays of some sort. It means that output is a function of current inputs and not previous...
Hi All,I would like to know if my understand as given below is correct,Error correcting codes can be classified into1) Block codesBlock codes are memory less2) convolution...
Hi,Can anyone explain how to change the phase of a signal.For example, if I have a sine signal, how can I modify its phase?
I have a question related to 5G NR numerology and bandwidth part.I would like to refer to the following article as a reference.http://www.techplayon.com/5g-nr-bandwidth-part-bwp/Please...
Hello Rick,
I think I am focusing with the term and hence the actual issue is not being discussed.
I am copying part of your response below so that we can discuss...
Hello Rick,In digital domain, where data to be transmitted is available then I have to readout or sample the data before doing final RF processing to transmit. Probably,...
Hi Rick,I would like to reverse the process and ask my follow-up questions ...Assume, you have sampled an analog signal to produce time domain sequence x(n). Now...
Hello dgshaw,Regarding point 1 above.let me take an example so that I am not confused again.Let us take an array of data = [1,2,3,4,5,4,3,2,1,-1,-2,-3,-4,-5,-4,-3,-2,-1...
Hello Rick,I often get confused with the concept of bandwidth of a signal.Further, I also get confused when it comes to data transmission as the data exists as digital...
Hi Greg,Is it because you eventually transmit 8 bits in the former case vs 16 bits in the latter. The latter has 8 additional 0s even though both of them are equal...
Thanks, Greg.so, instead of having 1,2,3,4 if I have 2,4,6,8 numbers, you mean to say the bandwidth occupied by such a signal will change. I thought, only the power...
I am trying to understand the concept of bandwidth from a point of view of bandwidth occupied by a signal.Let me take an example to state my question.Let us assume...
I am computing FFT of a sine wave signal. Since this is a signal with a single frequency, I was expecting FFT to give one spike indicating the presence of a single...
Thanks a lot. A few follow-up questions ...On question 1, so the LTE standard defines exactly which sub-carriers to be used then?On the NB-IoT, in case of a 2048...
I have a few general questions pertaining to OFDM ...Let us assume an 1048 point IFFT and number of number of sub-carriers as 600.1) in this case, does it matter...
Hello Mike,So, irrespective of what method I use to do source encoding or modulation method, the above equation stands?Also, a follow-up question.Since SNR is related...
The max data rate for a given channel and SNR is given as,rate = available BW * log2(1+SNR)In the above equation, in using th term log2(1+SNR), is there a fundamental...
Hi All,Are there example octave code that shows different modulation schemes including quadrature modulation?Thanks,
20MHz bandwidth means the signal occupies 20MHz of bandwidthHow can I ensure that the signal occupies 20 MHz bandwidth.I am sure it does not happen automatically. Is...
2) The modulation type is Orthogonal Frequency Division Multiplexing (OFDM), and the mixing you are describing sounds like "direct conversion"As I understand, first...
Hello,I have a few questions related to wireless and I will use LTE standard to put these questions.1) if we look at the sub-carriers frequency plot, we see sub-carriers...
jbrower,Thanks. I have seen multiple references. They explain pretty well how Intra and Inter prediction work in case of H.264 and H.265. However, I don't find description...
I understand the process of quantization but I am unable to understand inverse quantization process.Can someone please provide some background into this?Thanks,
Thanks. Do you know why half pel or quarter pels are needed?Eventually, display is always in terms of pixels.
Hello all,Thanks for the replies. The snippet is from an HEVC tutorial.Anyway, I do understand what interpolation is in image processing context.But what I am not...
Hi everyone,
I am new to the world of image and video processing and have been going through some documents to understand some basics. At multiple places, I see...
I am often confused between PHY, L1 and Baseband processing.Are they same? if not, can anyone help with some explanation please.Thanks,
I am trying to understand Energy and Power concepts as applied to discrete electrical signals.Is the concept of power needed because periodic signals will have infinite...
The following is from Wikipedia - https://en.wikipedia.org/wiki/Euler%27s_formulabelow is what I get when I try for 0 and 30 deg>> sqrt(cos(0)+sin(0))ans = ...
Thanks to everyone for helping me on this topic.I have refined my earlier Matlab to include 3 different examples, as follows:1) example 1 - signal is a single tone;...
I've never heard the term "observation window" applied to the frequency domain. It may be correct in some philosophical way, but it'll confuse people.I think my...
You should be careful about what you mean by "fully described". Mathematically that may be fine. You state fs=4*f0. And, 4 samples only covers a time span...
Thanks a lot. Some follow-up questions below.I did not understand what you mean by "I can compute DFT of 4 points and my N points in frequency domain cannot go...
Thanks, Dgshaw6.1) You are correct. If you have 4 time domain points, then you will have 4 frequency domain points. The frequency domain points will be complex...
I would like to get some concepts cleared on DFT. I will use a single tone signal (say of frequency f0) in time domain to explain my questions.DFT equation for reference...
Kaz,This is DFT computation. I am not able to understand where the term (exp(-j*2*pi*k*n/N)) is computed in the DFT expression is computed. Obviously, something...
Dear Rick,You are right about computing DTFT at 401 discrete points.The idea is to evaluate X(e^j*omega) and examine its periodicity. That's the reason why it is...
I have re-created a Matlab code to compute DTFT of a signal. The example is from a text book.The following is the code:n = 1:10;x = (0.9*exp(j*pi/3)).^n;k = -200:200;w...
ok. Thanks. One follow-up question. Why is that we don't usually see plots of complex value directly. For example, if the following is the complex array:3+2j, 2+3j,...
I agree but my question is, what inference I can draw by looking at a re/im plot? I have looked at a few plots and I cant make much sense out of it. Magnitude/Phase...
In DFT plots, multiple plots are shown. One if magnitude/phase and second one being, real/imaginary.One can look at magnitude part of the plot and get an idea about...
Ok. So, typically windowing is applied to incoming samples before they are passed to filer? Though in practical designs, I have not seen anyone implementing window...
I would like to know if there is any difference between the two purely from a DFT computation:a) DFT of a signalb) DFT of an impulse response of a LTI systemI assume...
Hello Rick,Actually, I have taken screenshot for the plots. So, some portion of my windows background is appearing. I will update the code for modified L value...
This the code listing with updated frequencies:Fs = 100; % Sampling frequencyT = 1/Fs; % Sampling periodL1 = 100; ...
I would like to know the consequence of adding 2 sinusoids of different frequencies. I assume that the result is not a pure sinusoid. I have tried a octave example...
high PAPR results in higher power consumption. Is this the only issue? I have read that high PAPR will also result in sub-carrier interference. Is this correct?
I would like to know the relevance of peak to average power ratio and what is the ideal (or preferred) value? #OFDM
We know that in #LTE downlink transmit uses #OFDM but in case of uplink transmit, OFDM scheme is not used. Can someone explain the reason behind this?
thanks. Can you throw some light on the application of Hermitian matrix. I have seen this in the context of receive diversity in a wireless system where multiple...
I would like to clarify about Hermitian matrix. I am referring to the following URL to understand this:http://mathworld.wolfram.com/HermitianMatrix.htmlIt is defined...
fzzy,I assume that code rate is a simple function that can be part of any FEC block (Turbo, LDPC) and just needs FEC to select subset of FEC encoded bits. Probably,...
slartibartfast,I am trying to understand the concept better. So, useing any standard (e.g. LTE) is fine. Is puncturing a part of rate matching scheme? I assume decisions...
I am getting a little confused between rate matching vs code rate as applied at FEC/Channel coding.How and when what code rate and rate matching is applied?Are these...
Dear dgshaw6,The waveforms shown are the RF or antenna input. You have assumed that these signals are what they look like when baseband data is transformed into...
to explain my question further, please refer to the figure below. Both the signals are same except for the amplitude/power at the receiver. In this case, what difference...
Q: Does the power at the receiver matter at the RF or the baseband stage?A: The receiver adds noise to the receive signal - so more signal power means more signal-to-noise-ratio...
In the context of wireless communication, I would like to know the relevance of power at the receiver side. In literature it is mentioned that received power should...
Thanks, Oliviert. I think it is clear now.Occupied BW = 15000*1200Total BW = 15000*2048Sample rate = 1//total BW
oliviert,sorry, I am opening an old topic. referring to the equation: 30.72*1200/2048 = 18Though the value is 18 MHz, I am still not sure what the N point FFT has...
Kaz,in reality, such signals would cancel each other anyway even before they appear at the filter input. If I just compute power of 2 sine waves individually then...
Kaz, Rick,I have used the approach given by Fernandoorg to measure power of various signals and it looks as below:1 power of input signal 1.994952 power of output...
All,Thanks a lot for your inputs.Dear Rick,Thanks. Probably, this is what I am looking for.I would like to come back to my main intention of computing the power.Input...
I have implemented a filter and passing composite signal with multiple frequencies.I would like to measure the power of signal before and after filtering. This is...
Multipath propagation on primitive level makes two things: previous symbol can step on current one; current symbol can step on the next oneTo clarify, with multipath...
thanks, gmsk1. So, cyclic prefix itself does not eliminate interference effects but helps the receiver in equalization ...
I am trying to understand cyclic prefix concept that is used in LTE. Referring to the figure above, there are 3 copies of the symbol received by the receiver. So,...
Sigh! Why I did not think about this earlier. Yes, I was referring to sampling an analog signal when I referred to Fs.
Dear Rick,Sorry about that. To summarize, keeping f1 and f2 constant, we are varying Fs and deriving value of N for 2 cases of Fs. Is this correct understanding?If...
Dear Rick,Thanks. I want to clarify on your explanation.So, in the above example, f1 and f2 remain same.Fs is either Fs = 19200 or 384000 KHz.N is either 115 or...
Hi Kaz,I don't understand what you mean by f1 and f2 change with Fs. Typically, these are independent parameters I start with irrespective of Fs. Can you please...
Dear Rick,I am still trying to wrap my head around the equation and what you mention about the transition bandwidth being ratio of (f2-f1)/FsN = dB*Fs/(22*delta_f);So,...
Dear Rick,Case 1: f1 = 10000; f2 = 15000; Fs = 192000Case 2: f1 = 10000; f2 = 15000; Fs = 384000My design parameter remain the same in case 1 and case 2. In case...
Dear Rick,Keep design parameters same in the above equation, can I not Fs independently? This is the case I was referring to when I said increasing Fs
Dear Rick, Michael, Fred, Kaz,Thanks. I really appreciate your inputs. I think I am clear on the original question. At least, I have lot of input for consumption.One...
Pardon me if my question is very basic.I would like to know why in the design of an Filter in Matlab, one has to specify sampling frequency.It looks like the cut-off...
The MIMO naming convention seems confusing to me.SISO – Single Input Single Output system – 1 1
Tx antenna , 1 1
Rx antennaSIMO – Single Input Multiple...
Hello All,The concept of TTI in #LTE has always confused me. I am giving a brief understanding from a base station perspective.So, assuming BW is fixed (e.g. 20...
Hello All,In case of #LTE, it is mentioned (http://www.sharetechnote.com/html/Handbook_LTE_Dow...) that control channels are made strong wrt to other channels. This...
Makes perfect sense. I forget that entities like Basestations are just conduits for ends users data.
Sorry, rrlagic. I am asking about source coding and not channel coding. In digital communication, Huffman or RLC are examples of source coding ...I have been working...
Hi,I am interested to know what source coding method is used in case of #WiFi or #LTE. I assume Turbo coding or LDPC are used for channel coding.Thanks,
Dear Rick,Currently, this is more of an hands-on to get better understanding. I assume your reference to low pass filter is due to 2 frequency bands that result...
Dear Tarik,Thanks a lot such detailed explanation.you can create RRC filtered waveform which represents your information in digital domain, up sample it, convert...
Hello Rick,Thanks for answering. I just implemented a small Matlab code for DUC and then I got this doubt. I used a pure sine tone to do this. My next exercise would...
Hi Ahmed,Thanks a lot for the detailed explanation. One more question - what is the practical application of DDC or DUC?Thanks,
I am a bit confused between digital down conversion and de-modulation (or up conversion and modulation). Let us assume I receive a modulated signal where a base...
Dear Fred and others,I think my incorrect terminology might have created confusion. I am sorry about that. So, let me re-phrase my question without using fancy/formal...
I have a question regarding FFT and representing a discrete periodic signal using DTFS.From the equation of DTFS, it appears that it is same as inverse Fourier transform.DTFS...
I would like to know if there an intuitive way, without going through rigorous maths, to check if a given system is LTI system or not.I have the following examples...
I am interested to conceptually understand the layer mapping stage in #LTE downlink processing.While all the literature clearly describe how the layer mapping is...
All,Thanks a lot. YOu are right. I should probably spend a little more time on this topic. I have got access to MIT lecture notes. I will have a look ...thanks...
Dear @drmike, @motilito, @Tim Wescott,Thanks a lot for spending your valuable time and providing inputs.Few additional questions based on the inputs:If there are...
Hello,This question is to get concepts clear than nitty-gritties.In case of convolution coding, I am confused how puncturing where bits are removed at encoder and...
Hello Tim,Thanks for the response. Actually, Nyquist in the above case confuses me a lot. They say occupied bandwidth of a 20 MHz system is 18 MHz. In that case,...
Just a follow-up question: 1 Symbol of baseband data has to be transmitted in ~66 us. Irrespective of the sampling rate, 1 symbol of baseband digital data has...
I would like to know importance of sampling frequency in the baseband. I am using #LTE as an example.If we take a 20 MHz system, the sampling frequency is specified...
Hello rrlagic,(OFDM symbol period) = 1 / (subcarrier spacing * IFFT size)Thanks. OFDM symbol period is constant across system bandwidth.Did you mean, sampling time...
Hello Prashant,
This zero padding is done towards both positive and negative frequency bands(424 on each positive and negative end of the 2048 point IFFT) to ensure...
Hello Napier,Thanks. So, one question. Before the OFDM stage, the inputs are first mapped onto constellation points and then I/Q data go into OFDM stage. So, when...
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