This freescale appnote: http://www.freescale.com/files/dsp/doc/app_note/AN3059.pdf talks about all the different kinds of channel estimation...

This freescale appnote: http://www.freescale.com/files/dsp/doc/app_note/AN3059.pdf talks about all the different kinds of channel estimation schemes for OFDM reception. They discount differential modulation, but how does it compare with the simplest channel estimation techniques: Least Square (LS)? Alan

For 802.11a there are 64 point ifft @ 20MHz transmit signal OFDM. The carriers are spaced 312500 Hz apart [20e6/64]. Demodulated baseband...

For 802.11a there are 64 point ifft @ 20MHz transmit signal OFDM. The carriers are spaced 312500 Hz apart [20e6/64]. Demodulated baseband signal is from -10MHz to +10MHz.[48 data carriers + 4 pilot carriers + some zero channels at the highest frequencies to make up the number to 64 carriers. Now at the receiver, if we have a 80MHz oversampling ADC sampling the 20MHz wide signal, followed b...

I have read a lot about the cyclic prefix used in OFDM, to combat ISI due to multipath. I think I somewhat understand this. You make your...

I have read a lot about the cyclic prefix used in OFDM, to combat ISI due to multipath. I think I somewhat understand this. You make your guard interval longer that the delay spread, so 1 symbol leaks energy into the next only within that guard interval. However, doesnt intra-symbol interference still exist, that is the same symbol interefering with itself due to being received within that delay s...

Hi all, I'm trying to perform the OFDM modulation of a DVB-T system. So far, I have the complex valued carriers ck, 1705 altogether (for the...

Hi all, I'm trying to perform the OFDM modulation of a DVB-T system. So far, I have the complex valued carriers ck, 1705 altogether (for the 2k mode). To perform the 2048 point IFFT, somehow I have to map this 1705 carriers into 2048 values, xq. My question is, how should I perform this mapping? It seems to me that the solution would be symply padding with 2048-1705 zeros at the end of th...

Hi, I am a student of IIT Madras (chennai),India and working for the compensation of IQ Imbalance in OFDM system. I followed ieee paper...

Hi, I am a student of IIT Madras (chennai),India and working for the compensation of IQ Imbalance in OFDM system. I followed ieee paper "compensation of IQ imbalance in OFDM system" by Jan Tubbax et al and found it very interesting and implementable. I wrote Matlab code for this method but alpha and beta (parameter as defined in the paper--functions of gain and phase imbalance)) estimati...

Hello, I'm developing a project of a DAB signal generator in C but I have some doubts about the OFDM modulation. Let's suppose to have a vector...

Hello, I'm developing a project of a DAB signal generator in C but I have some doubts about the OFDM modulation. Let's suppose to have a vector of 1536 elements (=number of carriers), they are ordered in such way that the first element (index 0) is the simbol that has to modulate the carrier -768 and the last element (index 1535) is the simbol that has to modulate the carrier 768. The DC has no...

Hi, What is the difference between the coarse symbol timing and the fine symbol timing in ieee 802.11a ofdm signal synchronization? Thank u...

Hi, What is the difference between the coarse symbol timing and the fine symbol timing in ieee 802.11a ofdm signal synchronization? Thank u in advance

Hi guys, I am building a synchroniser for OFDM. I read in a paper that the FFT window can start anywhere in the Cyclic prefix, & that this only...

Hi guys, I am building a synchroniser for OFDM. I read in a paper that the FFT window can start anywhere in the Cyclic prefix, & that this only results in Phase rotation at the output of FFT. 1st, is this right? 2nd, how do we fix these phase rotation? In some papers I read, I think I am supposed to calculate the angle of the 1st symbol, & rotate all the other symbols by same degree. But thi...

The frequency scheduling improves the total throughput in the OFDM(A) system. This scheduling enables to select the best user in each frequency...

The frequency scheduling improves the total throughput in the OFDM(A) system. This scheduling enables to select the best user in each frequency band so that all the frequency band are used for the best transmission in terms of downlink throughput. In FDD systems, especially the CSI (Channel State Information) feedback through the uplink channel is required to do this scheduling since chann...

Hi all, I've been developing an OFDM receiver for some time. I wrote demodulation routines in the complex baseband, where I can access a...

Hi all, I've been developing an OFDM receiver for some time. I wrote demodulation routines in the complex baseband, where I can access a digital baseband signal resulting from a general purpose RF digitizer or a vector analyser. As the bandwidth of my digitizer is much larger than my signal bandwidth and there is no IF bandpass filter I decided to implement an FIR lowpass filter in baseband. Bu...

Hi All So far I have worked on time domain equalizers such as LE and DFE. Recently I have started to work on OFDM systems. And I am trying to...

Hi All So far I have worked on time domain equalizers such as LE and DFE. Recently I have started to work on OFDM systems. And I am trying to compare the performance for Proakis channel B which is three tap channel. First system: map the info bits to BPSK, pass the symbols through channel, add noise. The channel output I write it as y=conv(h,x)+noise, where h=[0.407 0.815 0.407] and x= +/-...

Hello group We know that the use of cyclic prefix (CP) in an OFDM turns the linear convolution (between the channel and the transmitted...

Hello group We know that the use of cyclic prefix (CP) in an OFDM turns the linear convolution (between the channel and the transmitted signal) into a circular convolution. This is efficient to do because then we can easily equalize the channel. In most books it is referred that CP combats ISI and ICI. With ISI i am fine. I know that a circular conv between the channel (L points ) and...

I am currently testing OFDM using BPSK modulation using the FEC (convolutional coding), since my bits are random 0s and 1s and without using a...

I am currently testing OFDM using BPSK modulation using the FEC (convolutional coding), since my bits are random 0s and 1s and without using a quantiser or interleaver, the channel that is used for testing is AWGN channel (non-frequency selective), I am not sure what BER I am suppose to expect. The convolutional parameters used:constraint length = 7 rate =1/2 the trackback length = 12 Decisio...

Hi, I am working on a uncode 16-QAM OFDM simulation. The simulation works fine when used in AWGN channel. I have a couple of questions now...

Hi, I am working on a uncode 16-QAM OFDM simulation. The simulation works fine when used in AWGN channel. I have a couple of questions now when i am simulating performance in multipath channels. 1) What I want to understand through simulation is the effect of cyclic prefix length on performance in a multipath channel. For example consider that the channel impulse response is [0.7071 0 ...

Hello On trying to demodulate an OFDM signal based on the DVB-T standard, I immediately encountered difficulties in doing so. The problem lies...

Hello On trying to demodulate an OFDM signal based on the DVB-T standard, I immediately encountered difficulties in doing so. The problem lies in: 1. Frequency offset estimation. 2. Symbol timing estimation (symbol timing ambiguity occurs during the sampling process at the receiver A/D converter. 3. Channel coefficient estimation. Problem 1 is addressed in a straightforward manner usi...

Hi I am looking for robust timing and frequency synchronization algorithm based on preamble detection for a single carrier non...

Hi I am looking for robust timing and frequency synchronization algorithm based on preamble detection for a single carrier non ofdm(orthogonal frequency division multiplexing) system.most of the papers on synchronization deal with ofdm system, which is based on auto-correlation of identical short training symbols proceeded by cyclic prefix.currently I am trying to perform timing synchronization o...

Hi, I need a help please and an answer for this: I'm trying to do a BER simulation for QPSK in OFDM system over a Multipath Channel in Matlab...

Hi, I need a help please and an answer for this: I'm trying to do a BER simulation for QPSK in OFDM system over a Multipath Channel in Matlab and I'm using the function (ht=rayleighchan()) for model the multipath channel with the following parameters: tau=[0 1e-4 2e-4] second %Path Delay Ts=1e-5 sec or 1e-3 sec(for another simulation) %Sample Period Fd=0; %...

Hi all, In preamble based frequency offset estimation for OFDM, the literature says about 'identical parts'. More clearly, let the...

Hi all, In preamble based frequency offset estimation for OFDM, the literature says about 'identical parts'. More clearly, let the preamble consists of 2 OFDM symbols S1 and S2. It is given that S1 has L1 identical parts and S2 has L2 identical parts. Does this mean, out of 256 symbols in S1, L1 symbols should be same???? If so, what should be the value of L1 and at what position in S...

Openings for DSP (wireless) professionals Skills required · Extensive knowledge of OFDM algorithms (channel es,timation, Mobile...

Openings for DSP (wireless) professionals Skills required · Extensive knowledge of OFDM algorithms (channel es,timation, Mobile Synchronization, ranging, advanced antenna system, MIMO, Frequency Estimation) · DSP -FPGA based architectures for OFDM,CDMA systems · Hands-on with step-by-step baseband-to-RF integration Location: Bangalore. Exp: 8- 15Yrs. Client P...

Openings for DSP (wireless) professionals Skills required · Extensive knowledge of OFDM algorithms (channel es,timation, Mobile...

Openings for DSP (wireless) professionals Skills required · Extensive knowledge of OFDM algorithms (channel es,timation, Mobile Synchronization, ranging, advanced antenna system, MIMO, Frequency Estimation) · DSP -FPGA based architectures for OFDM,CDMA systems · Hands-on with step-by-step baseband-to-RF integration Location: Bangalore. Exp: 8- 15Yrs. Client P...