Search Engine

Doppler Ofdm

Add Question

30 Threads found on Doppler Ofdm
in ofdm sytems carrier frequency offset can occur due to doppler shift and local oscillator mismatch. you have understood the first part. When the baseband signal is converted to RF signal at the Tx, there will be a oscillator used to generate the RF carrier wave. Now, at the Rx end, there will be a similar oscillator used, it may so happen that
i have question if the mobile channel cause a frequency modulation of the subacarriers in an ofdm based syste? And i want to know what is the physical explanation of the doppler shift from the communications point of view?
So that means.....ofdm is used in frequency selective fading channel.....but...actually.....each symbol from the subcarrier suffers flat I right? Therefore, to model it during simulation......received signal for each subcarrier is equivalent to: Let say this is the 1st subcarrier: received_signal=rayleigh_flat_fading_variable*trans
Othogonality is preserved if the frequency of all subcarriers are matched. So only doppler shift, phase noise or inaccurate frequency estimates could distort the orthogonality of the subcarriers. The orthogonality is more important for ofdmA where different subscribers send interleaved subcarriers. So maintain in a system that all subscibers to
Hi,QMA From the Rx side, assume perfect operation (1) is the position of time index start for DFT window process of N point (only useful data length) mean as find the first edge of each symbol or some point between channel length
hi udit .. my MS thesis was in channel estimation for ofdm transmission in fast fading doppler channels so that would be phy layer. righ now I am inclined towards getting to know WiMax so want to focus more on mac layer, though interesting ideas in phy are still welcome
dear friends.. did anybody used the function by name : rayleighchan in matlab.. actually when i use this function for simulating my ofdm system by making dopler frequency = 0 working well..but when i make dopler frequncy Fd is varying the code is not giving any performance variations.. could u pls suggest me whether i have
Some one have code about ofdm Pilot based channel estiamtion in time domain? Could you send the to me?I need them urgently. :cry: My Email: Thanks. Added after 5 hours 8 minutes: help me! how to add doppler shift to channel?
Actually if you look at the frequency domain plot, the peak of one carrier is on the point where the the two carriers; one on its right and one on its left have their zero crossing. And you know at zero crossing they would contribute to zero energy to the center carrier, And this is how, even after 'overlapping' they dont mix. In fact if you loo
Hi , I am working on ofdm systems. I have come across a paper on channel estimation methods for ofdm systems . In this paper it was mentioned that , BPSK modulation doesn't require the traking even in a time varying channel . would any one please explain the reason behind this .. Thanks in advance . Regards Prem
Hi all I want a sample source code in matlab for simple ofdm modulation that shows the doppler shift effect I have some source codes for ofdm but none of them has the doppler effect I'm wondering if anybody can help thanks :|
How can I use doppler signal in my M_File in MATLAB?Is there a function or command for it? I'm not good in MATLAB!please help me.
Hi all, I'm performing ofdm equalizer for a pilot assisted system. The system parameters are: Signal BW = 6 MHz Carrier = 700 MHz chip rate = 5.55 MHz doppler shift corresponds to max 200 km/s receiver speed Fading channel is a Rayleigh fading channel, the problem is that when I apply the channel to signal, the channel has a very ra
hi , frequency offsets are due to channel delay spread (coz of channel impairments ) and doppler spread ( movin vehicles) suppose ur upconvertin RF frquency is @ 2 Ghz and IF :100 MHZ , ur transmitting frequency will be 2100 MHZ so if ur channel delay spread is say 10 HZ ur recieved signal at RX will be 2100. 000 010 hz , ur receiver d
hi, i'm doing a comprfassion between ofdm and cdma. doppler spread destroy the orthogonality between the sub carriers in ofdm and cause ICI. but i cant figure if and how doppler spread effects CDMA (not MC CDMA but DS CDMA) i mean, every user spread its information with PN code on all the BW can somone explein how and (...)
frequency offset (FO) occurred by the mismatch between the oscillators in the transmitter and receiver or doppler frequency and it can cause performance degradation or we can say it can increase BER
Hi All, I would like to include doppler shift to a 2x2 multipath MIMO-ofdm channel because i am considering fastfading channel instead of block fading channel. How do I implement this? Do I have to "cut" my ofdm symbol into several parts and at each part apply a different channel/? If so, those channels need some kind of link whjat (...)
hi everybody i have a bad problem with my code .... First of all i write a matlab code for ofdm-CDMA system. the following picture shows the structure of the system : 70365 but unfortunally the results for BER not stable . for doppler frequency = 0.0001 [ATTACH=
AA The following code gives higher BER than the theoretical. Can anyone help me why? and give me the way to modify the code. code of BPSK- ofdm =============== clc; clear all nFFT = 4; % fft size nDSC = 4; % number of data subcarriers nBitPerSym = 4; % number of bits per ofdm symbol (same as the number of subcarriers for BPSK) nSym =
hi i am working on MC-CDMA channel estimation cdma + ofdm(802.11a) i try two types of channel estimation : Block type and Comb type i am using MATLAB built in function (rayleighchan) more specificlly (stdchan) as follow: bitrate = 20000000; % Bit Rate ts
I used an matlab example " syncCarrierFreqMSKSignalRecovery" to construct my model and apply it for QPSK system,it works . but when i applied it to ofdm-QPSK , it doesn't work. Kindly advice Matlab Code ============ %Initilization %%%%%%%%%%%%%%%%%%%% nBitPerSym = 64; % number of bits per ofdm symbol nSym = 10^3; % number of symbol
Please anyone help me for correcting the program given below. its very urgent.:cry:.....thanks in advance. clear; ch_no=6; fc=2e9; fs_Hz=1e7; M=1024; N=10000; Nfosf=4; =SUI_parameters(ch_no); =SUI_fading(Power_dB,K_factor,doppler_shift_Hz, Fnorm_dB, N, M, Nfo
Hello, I am looking for a MATLAB code for ofdm that introduces doppler effect due to relative motion of Tx/Rx. Thanks in advance
I have simulated a certain wireless communication system in doppler fading channels. However the simulation results (BER vs. SNR) are different from the other books and papers, even the channel parameters and demodulation techniques are the same. Is this a serious problem, or this kind of difference is popular when channel model( just model, no
hi all I will want to study ofdm with time varying channel. I have a question. As Rayleigh makes it possible to simulate time varying channel, why in the articles I find models defined by authors (pdf of doppler and delay spread)?. and how to use these functions in simulations? that really blocks me; Thank you.
Could someone help me on this, please I am studying about the newly developed non-linear phase Generalized DFT proposed by Akansu. (It's not that long, if you have time, please help) The system is basica
I am working on the evaluation of the effects of interference on DVB-T using matlab/simulink, and need help on analyzing the effects. The only area i could reference to is the variation in the SNR using the AWGN and the doppler shift using rayleigh. I will appreciate anyone who can help in this area. ---------- Post added a
Hi all, I am using MATLAB's Rayleighchan function to simulate a fading channel. My ofdm system chip rate/Sampling rate = 5.55 MHz, but giving this rate to the function will cause an 'Out of Memory' error, so I enter a sampling rate of 4096 Hz and normalize path delays to this by multiplying path delays by 5.55 MHz / 4096 Hz. My Question is:
Hi everyone, I do have problems implementing a 2x1D Wiener-Filter as channel estimator for an ofdm-System. I use the concept introduced in the following
Hi all I know this thread isn't very concern with digital communication, but my main goal is to simulate an ofdm system. So if anyone familiar with parallel computing this is my problem and. I think it is simple. In one of my functions I am using parfor loop and it working well ,improving by 50%. I defined NumOfWorkers = 8 And launched "matl