Dear all, In most OFDM standards (802.11a, 802.16, DAB, DVB), there is a data scrambling stage, which involves multiplying the...

Dear all, In most OFDM standards (802.11a, 802.16, DAB, DVB), there is a data scrambling stage, which involves multiplying the frequency-domain data stream with a PRBS. My question is, what is the purpose of this? In the DAB spec (EN 300 401), it says: "The purpose is to avoid the transmission of signal patterns which might result in an unwanted regularity in the transmitted signal...

Hi, I'm new to OFDM. I read in several textbooks and papers that timing synchronization can be separated into symbol synchronization and...

Hi, I'm new to OFDM. I read in several textbooks and papers that timing synchronization can be separated into symbol synchronization and sampling clock synchronization. The latter can be further broken down into sampling phase offset and sampling frequency offset. There is also carrier frequency synchronization (i.e., carrier frequency recovery technique), which is utilized to eliminate the...

Hi, I am new to MATLAB and I have the following question regarding OFDM simulation: how do I implement a discrete three-ray multipath...

Hi, I am new to MATLAB and I have the following question regarding OFDM simulation: how do I implement a discrete three-ray multipath channel as follows: h[n] = c1delta[n] + c2delta[n - n2] + c3delta[n - n3] where c1, c2 and c3 are complex Gaussian channel parameters i.e. real and imaginary components of c1,c2 and c3 are real Gaussian. their variances and time delays n2 and n3 are given....

Hi, If a frequency bin width is determined, then the symbol time is known. How many bins are acceptable, i.e. is there a restriction on the...

Hi, If a frequency bin width is determined, then the symbol time is known. How many bins are acceptable, i.e. is there a restriction on the bandwidth of the OFDM symbol? Thanks,

I try to implement the matlab code on BER for QPSK in OFDM over rayleigh channel (with n taps). However the result is a straight line. There must...

I try to implement the matlab code on BER for QPSK in OFDM over rayleigh channel (with n taps). However the result is a straight line. There must be something wrong in my code but I cannot figure it out what is wrong. Could you please help me to check it. I have to hand the work soon. Please please please help. Thank you very much. [QUOTE]clear; clc; N=64; % FFT size Nsd = 48; % Number of ...

Hi, I understand that for OFDM, each symbol is 4us. I read some WLAN books and it says that there are 12 symbols for the preamble period...

Hi, I understand that for OFDM, each symbol is 4us. I read some WLAN books and it says that there are 12 symbols for the preamble period (short + long). However, the duration for the preamble is only 16us (10 short, 8us + 2 long, 8us). Should the preamble is 4 symbols instead? Thanks for your insight!

in OFDM systems, the LS channel estimation result should be H'=P'/P if we compensate the received data symbols with one tap scheme,...

in OFDM systems, the LS channel estimation result should be H'=P'/P if we compensate the received data symbols with one tap scheme, the equalization result should be D''=D'/H' = P*D'/P'; one the right of the above equation, D'/P' looks like the differential decoding result so the coherent demodulation with LS estimation and onetap equalization sees like the differential demodulation...

hi i am using this code for simulation of ofdm clear all; Fd=1; % symbol rate (1Hz) Fs=1*Fd; % number of sample per...

hi i am using this code for simulation of ofdm clear all; Fd=1; % symbol rate (1Hz) Fs=1*Fd; % number of sample per symbol M=4; % kind(range) of symbol (0,1,2,3) Ndata=128; % all transmitted data symbol Sdata=8; % 8 data symbol per frame to ifft Slen=16; % 16 length symbol for IFFT X=zeros(Ndata,1); Y1=zeros(Ndata,1); Y2=...

Hi, I'm simulating an OFDM system with Multipath and AWGN channels. One thing that i'm observing is that whenever I simulate the system on...

Hi, I'm simulating an OFDM system with Multipath and AWGN channels. One thing that i'm observing is that whenever I simulate the system on baseband the AWGN command adds almost the correct noise but whenever I modulate the baseband signal to a carrier and then add the noise, it adds very little noise compared to previous case. I have implemented the system as follows. ============================...

Hi here, I'm now simulation OFDM Systems in WLAN with Matlab. As to the Rician Fading Channel, 1. Since WLAN enrioment is a static...

Hi here, I'm now simulation OFDM Systems in WLAN with Matlab. As to the Rician Fading Channel, 1. Since WLAN enrioment is a static frequency-flat channel, do you think the following clauses is enough in Channel simulation? chan = rayleighchan; signal_out = filter(chan,signal_in); 2. I also see someone using such clauses to descripe the Rician channel. Kmax = ceil(10* ExpDecayTrms*...

I am working on a ISDB-T receiver implemented in software on my laptop. I am only interested in a 1-seg receiver at this point (1-seg is the...

I am working on a ISDB-T receiver implemented in software on my laptop. I am only interested in a 1-seg receiver at this point (1-seg is the single OFDM segment 422-carrier reduced BW part of the Japanese ISDB-T spec). I have an ADC connected to a Xilinx Spartan 3 FPGA and Cypress USB chip. The ADC samples the low-IF output of a tuner chip, the FPGA does the I/Q down-conversion to baseband, and al...

I was simulating an OFDM system, and used 802.11a type preamble (short and long training symbols). I found that correlation based coarse...

I was simulating an OFDM system, and used 802.11a type preamble (short and long training symbols). I found that correlation based coarse frequency synchronization with a delay of 16 samples is not very accurate. Then, even using the long training for fine frequency estimation (same correlation but with 64 samples delay) doesn't give very good results. For example, if I plot the BER vs SNR curve...

I have a problem with the definition of SNR. We are working in a project regarding to WiMAX systems and we would like to know how SNR is defined...

I have a problem with the definition of SNR. We are working in a project regarding to WiMAX systems and we would like to know how SNR is defined in a WiMAX or in an OFDM system. In the WiMAX standard they didn't defined but they use it. And we know that they didn't use the SNR=Eb/N0 equation. 1, How should we calculate SNR in our simulations? 2, We also use the charachteristics of several...

Hi, In a typical application of OFDM receiver an 8 bit -ADC is sampled at 6.4 Msamples/s. I have to take ADC output through a serial port....

Hi, In a typical application of OFDM receiver an 8 bit -ADC is sampled at 6.4 Msamples/s. I have to take ADC output through a serial port. After transfering to memory I need to perform 1024-point FFT on real time basis. What should be my optimum buffer size. Do we need to know FFT processing delay, Clock speed of the processor etc. in advance? I thought it should be 2*1024 - Is that...

OFDM is used for WiFi, HomePlug, and HD radio. How much data rate increase do you get by using the multiple carriers, as opposed to just one...

OFDM is used for WiFi, HomePlug, and HD radio. How much data rate increase do you get by using the multiple carriers, as opposed to just one carrier? For example, HomePlug 1.0 goes upto 20Mhz in carriers. How much benefit do you get by using its 84 carriers, as opposed to just using one 20Mhz carrier at the highest data rate you can make work? WiFi is 2.4Ghz. Same type of questi...

Hi All, I'm really in trouble because of this awgn. I am trying to add noise awgn to oversampled ofdm signal. my signal is oversampled 20 times...

Hi All, I'm really in trouble because of this awgn. I am trying to add noise awgn to oversampled ofdm signal. my signal is oversampled 20 times and modulated on a high frequency carrier. After applying band pass filter I have tried to do this SNR = EbNo + 10*log10(k) - 10*log10(upsamp) corrupted = awgn(usig, SNR,'measured','dB'); where upsamp is 20, and k is 2, two bits per symbol with ...

In OFDM systems, we have preamble transmitted before data for various purpose. In 802.11a preamble, we have short training sequence for...

In OFDM systems, we have preamble transmitted before data for various purpose. In 802.11a preamble, we have short training sequence for AGC, packet detection, and others; after short training sequence, we have long training sequence for channel estimation and others. In general, for the training sequence, it is a certain number of repetition of a certain sequence. For example, in 802.11a, t...

Hi folks, Can anyone give me some idea about demapping/detection algorithm for Dual carrier modulation . its used in OFDM based UWB...

Hi folks, Can anyone give me some idea about demapping/detection algorithm for Dual carrier modulation . its used in OFDM based UWB systems. DCM is like mapping same databits into different constellation points from different constellation diagrams. In OFDM UWB 4databits are mapped into 2 I/Q points in (16 QAM like constellation) from 2 different constellation digrams. http://www.wi...

Dear all, I am trying to simulate OFDM baseband in AWGN with frequency offset and look for BER vs. Eb/No in matlab. I have used the...

Dear all, I am trying to simulate OFDM baseband in AWGN with frequency offset and look for BER vs. Eb/No in matlab. I have used the form: r = s.*cfo + n; where: r = received signal with frequency offset s = transmitted signal n = noise and cfo = exp(j*2*pi*freqOffset*(0:length(s)-1)) freqOffset = normalised frequency offset. But I havent get the pro...

Hi, I am very new at this topics and I am now studying on an ofdm simulation with a blind channel estimation.I can do a basic ofdm simulation but...

Hi, I am very new at this topics and I am now studying on an ofdm simulation with a blind channel estimation.I can do a basic ofdm simulation but in fact I have a rayleigh fading channel with doppler shift and for making good blind estimation I must develop some algorithms to eliminate doppler shifts.Is there anyone that can give me some help? Thanks for your attention... ...