### Sumit Kumar (@cogwsn)

This one is good. https://onlinelibrary.wiley.com/doi/book/10.1002/9...And the MATLAB code is also available.

Hi, so it is a proper OFDM signal with preambles (gold sequence). I use preambles for frame sync and channel estimation. No matter what I am doing at the transmitter,...

I am sorry. Here is a picture of the SDR I am using. https://www.ettus.com/wp-content/uploads/2019/01/USRP_B2x0_Enclosure_Rear_Diagonal_View.jpgI have two of them...

I am trying to implement a very basic pre-coder using SDR (USRP B210). Both Tx and Rx have single antenna and the transmit and receive SDRs are frequency synced...

Hi Kaz, :D Well the second part of the sentence I understood but the first part was not obvious: "Why low number of subcarriers is needed for high path loss...

In one of the papers related to 5G numerology, I read this statement: "Low number of subcarriers is needed for
high path loss scenarios
because higher number of...

Ok, thanks, this one I understood. And what should be the implementation for an active divider. So that I make sure power_out_1 + power_out_2 = power_in; I mean...

Hi Neil, Thanks much for reply. I tried much to search. Upto 6 GHz should be OK for me. I would like to check both options, passive as well as active. If you can...

Hi, Can anyone please suggest any tunable power divider available in market. I tried searching a lot, but found only research articles or patents. For a project...

I have made a C code to generate sine wave. I generate two sine waves of frequency 100 and 500 Hz respectively. The sampling rate is 2000 Hz.But when I see the dumped...

Thanks, the idea is more clear to me than before. I know the topic is very old, but can you share any reference (if you remember) about "LLR is just one way to...

Hi,My question may be very basic but I always get confused over this. What is the difference between bit-metrics and LLR. For example, in the attached paper, the...

Hi all, New year wishes :) I am going through the specs of AD9364 which has direct conversion receiver architecture. https://www.analog.com/media/en/technical-document...When...

But first 16 samples, i.e., CP may get corrupted due to ISI (right ?). Why do we use them to append :-/

I am going thru wlanOFDMDemodulate.m (script used by MATLAB to demodulate 802.11g OFDM symbols)wlanOFDMDemodulate(x, cfgOFDM, ofdmSymOffset)x is the array of received...

Indeed! I also replicated and this happens without zero-padding. I was in the impression that taking 2048 point FFT of the LTE+WiFi will introduce some ICI in the...

Hi, Suppose I have time domain LTE signal L and time domain WiFi signal W. L is generated by taking 2048 point IFFT and W is generated by taking 64 point FFT. Power...

Suppose I am operating in an environment where Tx and Rx are static and channel does not change between them. In this case if I have channel estimate between Tx...

I am working on hardware implementation of Maximal Ratio Combiner for OFDM based system. Consider a two antenna receiver performing MRC over received signals y1...

My apologies, I should have used standard notations. So, 30.72 MHz is the sampling rate of LTE and 20 MHz is sampling rate of 802.11a.ADC performs sampling at 30.72...

No, provided that I can upsample/downsample it finally to 30.72 and 20 MHz. 30.72 MHz signal is coming from LTE and 20 MHz signal is coming from WiFi. Center freq...

Hi, I have two signals. Signal A, sampling rate 30.72 MHz and signal B, sampling rate 20 MHz. Their center frequency is same though. Now assuming a simultaneous...

Hi, I have a followup question. Using STS we perform coarse frequency offset estimation and then using LTS , we refine the frequency offset estimation. When performing...

Hi,Is this correct that when we implement MRC in 802.11a/g (say with 2 antennas), the preamble based sync needs to be performed on both the antennas ? If yes, then...

And here is the reason! http://www.lifeaspire.com/7342/the-cause-of-square...Very interesting indeed.

Yes indeed. I found the mistake. I was supposed to transpose the carrier array by using ' operator but since carrier is complex, so ' operator was doing a conjugate...

So that the length of time array is equal to the length of interference. Apology these was a confusion in naming. load('zigbee_baseband.mat') % Baseband loads...

Interference is zigbee. Yes when I plot it without multiplying with carrier, it lands on 0 MHz. The very first plot in the subplot.

As the baseband is it 0 MHz, either is applicable i.e. shifting to -7 MHz or shifting by -7 MHz.I have attached the picture now for downloading. untitled.pngLink...

Hi, It might be a very silly question. I have a baseband zigbee dump (zigbee._baseband.mat attached). I wish to shift it to -7 MHz, -2 MHz to the left and also...

Well in that case : Suppose your signal chunks are X1, X2, X3, ....Xn and your SNR requirement is SNR_dB1, SNR_dB2, SNR_dB3, .... SNR_dBnYou do as : Y1 =...

New year Wishes to you too :) To be honest I couldn't understand your answer at all ... could you please share some link for details.

Well I found this reference where it says that soft Viterbi could be used with additional channel state information. http://ieeexplore.ieee.org/document/793537/I...

I am using the WLAN Tool Box of #Matlab V2107b. A term named CSI for each data subcarrier is defined as CSI(i) = H(i) X conj(H(i)) + N(i)H(i) = channel estimate...

RF data i.e. passband data is never complex, it is real. It becomes complex only when you down convert it to baseband(using 2 ADC i.e. two channels). In MATLAB...

Ohh I see! So let me know if my understanding is correct (thanks much for your time :))Considering the case of 802.11g system where long training sequence(LTS) is...

As you said "If you do the combining first, you will get the SNR improvement of the combiner and will be equalizing on the combined channels."So for the equalization...

My basic question is that in SIMO OFDM system with Maximal Ratio Combining : Do we need to do equalization after MRC or just send the combined signal for further...

Hi, I have to generate AWGN noise whose power is -100 dBm I do the following calculation in MATLAB. np_dBm = -100; % desired noise power in dBm
np_watts =...

It sounds like maybe the advantage of complex sampling is that you trade off one fast ADC for two ADCs operating at half the speed. Is this correct?YESAre there...

Normally we do complex sampling where the incoming data is splitted in two channels, each channel is multiplied with 2 sinusoids(which are 90 degree out of phase)...

Hi, If my understanding is correct, most of the 802.15.4 receiver implementations perform frame synchronization i.e. find the start of the frame using the preambles...

What I have read so far, indicates that commercial multi-antenna wifi access points use selection combining i.e. uses only one antenna at a time (even if there are...

Thanks napierm for your reply :)However I was looking for suggestions on Fixed Point DSP books :) I am used to do floating point DSP, hence with fixed point DSP...

Hello, I am working with C and assembly code for DSP for some real time SDR applications and frequently get stuck in the basics. Can anyone suggest some reference...

Hi Tarik, In the receiver side what is the Error threshold used chip errors. I mean when a symbol is decoded from 32 bit sequence, how many chip error could be...

Hi Tim, Now I am trying to come out of theory-land :)I have another related question. I am using an SDR USRP B210 which shows me approx -100 dBm noise floor on...

Yes I am counting the PER for WiFi already, So with your suggestion, I think I have no option but to mark all the bits as error in the dropped packet !

Hi,I am performing some tests with WiFi and ZigBee. There are some situations when the header of the frame is lost and hence the receiver discards the packet. In...

So that means, a total of 256 bits for the preamble part. And since zigbee uses oqpsk, there will be total 256/2 = 128 complex symbols in the front of a zigbee frame....

Visual interpretation and understanding in time domain is difficult, but if you plot the fft, you will start seeing peaks at different frequencies.

I would append to motilito's reply by saying that : if you want to go with AD9361 , USRP B210 from Ettus Research is the best option you can have. It will not only...

Okk.. I just got it ..so awgn(a) = a + noise awgn(b) = b + noise awgn(a) + awgn(b) = a + b + noise + noise = a + b + 2 * noise :) Thanks !

Not sure about sub carrier interference but due to PAPR there is also inter modulation(IP3) which will distort the transmitted constellation.

For uplink, lte uses sc-fdma which has relatively low PAPR compared to OFDM. A low PAPR is required in order to avoid high power consumption in
the mobile terminal,...

I could not understand this properly. Can you explain it again please "For Eb/N0 you should normalize the values according to signal bandwidth"

Hi, I have to mix two signals WiFi and ZigBee. What should be the correct method to add AWGN after chanel effects A . awgn(WiFi + ZigBee) OR B. awgn(WiFi) +...

Hi, In the commercial cell phones mostly we have WiFi, ZigBee and Bluetooth working. I was wondering if they use the same RF front end for sampling the signals...

Hello, How does ZigBee copes up with multipath. I don't see any inherent support for channel estimation ? TIASumit

Hello, In ZigBee (802.15.4), is there a preamble like WiFi (STS, LTS). I have not studied much details, but from first view it looks like there are sequence of...

As of now my WiFi and ZigBee Rx are working in real time independently. Yes I will try your suggestion also, to make them working independently in vicinity of each...

Hahaha, I agree with you Tim. But this is more than that :D (Devil is in the details :D)Following to this, I have to generalize it for other standards where there...

No actually I have to decode both WiFi and ZigBee at the same time. So during interference, assuming most of the time WiFi will be strong, I can detect the WiFi...

Yes, I am trying to do ZigBee and WiFi simultaneously in real-time. So far I found successive interference cancellation the most suitable one.

Hello, thanks for your reply. Yes, I have a confusion because for Successive Interference Cancellation, I have to recreate the entire OFDM symbol. ZigBee signal (4...

Hello,I am planning the following.First sample the 20 MHz WiFi channel (WiFi channel-1 in figure).Put band pass filters (5 MHz wide) around each of the ZigBee center...

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