Hello all, I am trying to simulate an algorithm for voice + data in order to send throuhg a Rayleigh Fading channel, by using lpc-10 (2.4...

Hello all, I am trying to simulate an algorithm for voice + data in order to send throuhg a Rayleigh Fading channel, by using lpc-10 (2.4 kbps) vocoder and an ofdm channel (with 36 subcarriers) and I realized some troubles related to SNR and BER which are not good (i.e I expect 10e-6 for 14 db or more) and the output is bad. I was wondering if there is a trouble related to synchro. due to of...

Hello all, What kind of modulation scheme that will suit high speed transmission (at least to 1 Gbps)? And obvious choice will be those...

Hello all, What kind of modulation scheme that will suit high speed transmission (at least to 1 Gbps)? And obvious choice will be those highly spectral efficient modulation scheme like OFDM. However, if the linearity requirement and the sensitivity to phase noise are very high, then OFDM could be out of question especially for system that operate at very high frequency such as 40-70GHz . ...

I have finished a basic OFDM simulation with BPSK modulation on it. Now I want to use the convolutional code in transmitter and a...

I have finished a basic OFDM simulation with BPSK modulation on it. Now I want to use the convolutional code in transmitter and a multipath channel with AWGN. At receiver , a viterbi decoder would be used. But I have some question in it.First,when the data have done FFT at the receiver.There would be still imaginary part in signal,should I discard the imaginary part or not? Second,because ...

OFDM is touted as a multipath-resistant modulation, but I have a simple scenario that seems to challenge that assertion. Consider the...

OFDM is touted as a multipath-resistant modulation, but I have a simple scenario that seems to challenge that assertion. Consider the situation in which the received signal consists of the direct path plus a reflected path that is exactly 180 degrees out of phase at the center frequency and at (or near) the same signal strength as the direct path. This is going to cause a deep null. Howe...

I have pilots which are either +1 or -1, (bpsk modulated). I am using OFDM . After passing through rayleigh channel (used the function...

I have pilots which are either +1 or -1, (bpsk modulated). I am using OFDM . After passing through rayleigh channel (used the function rayleighchan) and than adding noise, i am trying to estimate the channel. Simplest way is the least squared approach , do (Y/X) to get H_ls (least squared impulse response in freq domain). note : this is done after doing fft in ofdm. The problem is how do i kno...

Hi, I am currently making a OFDM receiver in @ltera DSP builder...using 10 short preambles and 2 LP...so here is my question 1. when we...

Hi, I am currently making a OFDM receiver in @ltera DSP builder...using 10 short preambles and 2 LP...so here is my question 1. when we detect the start of the packet using the short preamble....how do we know as to whether its SP1 , sp2 ...or SPi. 2.because based on this, we have to start with the long preamble detection. i know the algorithm for sp packet detection and lp symbol sync...

Hi all, In many OFDM system(like 802.11a and DVB-T), they always padding zeros to data before go to the IFFT module. Why use padding...

Hi all, In many OFDM system(like 802.11a and DVB-T), they always padding zeros to data before go to the IFFT module. Why use padding zeros? Best regards, Davy

Hello, I am testing different OFDM Channel estimation (CE) approaches by modelation in Simulink, and I am having a problem, that might be...

Hello, I am testing different OFDM Channel estimation (CE) approaches by modelation in Simulink, and I am having a problem, that might be stupid but is taking to much of my time without finding a solution. My problem comes when I want to compare several methods to ideal LMMSE CE. I know the channel from measurements, so I have the attenuation coefficients for each subcarrier, i.e. the column...

hi all, i'm trying to plot ofdm normalized (dBr) psd after ifft function. i.e: carriers=NFFT.*ifft(tx); %plot normalized PSD i've tried...

hi all, i'm trying to plot ofdm normalized (dBr) psd after ifft function. i.e: carriers=NFFT.*ifft(tx); %plot normalized PSD i've tried pwelch(), psd() and their varients but my results do not match the theory. i'll appreciate some help on the subject. thanks.

I have made an OFDM transmitter and receiver in MATLAB and it works fine as far as baseband simulations are concerned. Now, I have play backed...

I have made an OFDM transmitter and receiver in MATLAB and it works fine as far as baseband simulations are concerned. Now, I have play backed this signal from a vector signal generator at a carrier frequency and then sampled it. When, I down sample it using decimate filter to the sampling rate at which it was play backed, the receiver is unable to demodulate it. My questions is 1. at the tr...

Hi all, I am trying to simulate a data flow according to the wimax standard. Could someone please help to understand how to manage the...

Hi all, I am trying to simulate a data flow according to the wimax standard. Could someone please help to understand how to manage the data flow dimensions after encoding before mapping to ofdm symbols? More precisely: I generate, for example, a message of 72 words having in mind a 16 QAM modulation, with an overall coding rate 3/4. This, after rs and cc coding, interleaving and puncturi...

I am trying to understand and visualize the usage of covariance in channel estimation in OFDM systems. For example in MMSE estimator, we...

I am trying to understand and visualize the usage of covariance in channel estimation in OFDM systems. For example in MMSE estimator, we use covariance in formulating the estimated h channel. I have a couple of questions below and I would appreciate if you could please help me in understanding covariance and correlation here. 1-As far as I know, covariance tells us how two variables are movin...

I have a question concering Homeplug and OFDM.What if had to be able to talk to Homeplug chips, BUT I needed very very low data rates like...

I have a question concering Homeplug and OFDM.What if had to be able to talk to Homeplug chips, BUT I needed very very low data rates like nothing more than 800 bps. So since I have such low data rate needs, and would need to work within the Homeplug standard but not use high MIPS and increase my costs.If the standard allows me to null sub-carriers which it does, would feeding those zeros to the...

In an OFDM signal, if the symbol window (of N samples) is misaligned at the input to the FFT, the constellation points on each tone are rotated...

In an OFDM signal, if the symbol window (of N samples) is misaligned at the input to the FFT, the constellation points on each tone are rotated by a certain amount. To undo this effect we use the Fourier shift theorem which allows us multiply by a complex exponential on each tone. I am using a Wavelet Packet Transform instead of an FFT. My question is, is there an equivalent time/scale shi...

Hi! Can someone explains to me what is the difference between using OFDM and frequency hopping technique for UWB? Thanks. L

Hi! Can someone explains to me what is the difference between using OFDM and frequency hopping technique for UWB? Thanks. L

Could someone please explain me in details how we select the FFT window size at the receiver of the OFDM system? Does it include both the size...

Could someone please explain me in details how we select the FFT window size at the receiver of the OFDM system? Does it include both the size of N parallel sub carriers and the Cyclic Prefix length? Thanks! _____________________________ Posted through www.DSPRelated.com

hi all, Generally i have coded my OFDM system, but i have some problem in understanding about the one tap equalizer. Actually i know how to...

hi all, Generally i have coded my OFDM system, but i have some problem in understanding about the one tap equalizer. Actually i know how to generate a ZF equalizer , but i would like to know how to generate MMSE equalizer, even i have the algorithm , but i dont understand the symbol stand for,hence i cant code in matlab Г=E[||X||]^2 G= [Г^0.5 * conj(H)] / Г||H||^2+ &

Hi all, I am doing frequency domain channel estimation in OFDM. In the most basic way, we receive k samples in the frequency domain y1,...

Hi all, I am doing frequency domain channel estimation in OFDM. In the most basic way, we receive k samples in the frequency domain y1, ....,yk, and divide them by the corresponding preamble symbols p1, ..., pk (that are known in advance to the receiver) to estimate the frequency response H1, ..., Hk Hk=yk/pk, k=1, ...N In this way, I find that the resulting BER performance (based...

Dear my friends. I have some problems with OFDM simulation on AWGN channel.I have 260 bits lenght data After ifft block of OFDM...

Dear my friends. I have some problems with OFDM simulation on AWGN channel.I have 260 bits lenght data After ifft block of OFDM transmitter. I add cyclic prefix and I have 300 bits lenght data. I want to add AWGN noisy signal (sigma*randn(1,300)) on to my signal (y_ps) ynoisy = y_ps+sigma*randn(1,300) my noisy signal became like this but my AWGN noisy signal is bigger than my y_p...

Hello. In OFDM systems, there are CINR(carrier to interference and noise ratio) and SINR( signal to interference and noise ratio). Of course,...

Hello. In OFDM systems, there are CINR(carrier to interference and noise ratio) and SINR( signal to interference and noise ratio). Of course, the acronyms and its meanings are evident. But, in OFDM, why is CINR important? For example, is it a metric directly related with some specific performance criterion? I'd highly appreciate your comments. Thank you very much.