why center tone is null in input of IFFT in OFDM systems

Started by harishm in comp.dsp7 years ago 12 replies

why center tone is null in input of IFFT in OFDM systems ? is it for reducing PAPR ...? or to reduce complexity in OFDM receiver ? ...

why center tone is null in input of IFFT in OFDM systems ? is it for reducing PAPR ...? or to reduce complexity in OFDM receiver ? _____________________________ Posted through www.DSPRelated.com


oversampling in OFDM

Started by mishal81 in comp.dsp10 years ago 1 reply

Hi All,, Plz help me for ofdm simulation. I have tried to simulate ofdm signal with 64 subcarriers, with an oversampling of factor 4 in...

Hi All,, Plz help me for ofdm simulation. I have tried to simulate ofdm signal with 64 subcarriers, with an oversampling of factor 4 in frequency domain. Now I've got 256 QPSK symbols with zero paddings.I'm doing IFFT of 256 points. But I need to modulate my data on 64 subcarriers. then how would it be possible if i'm doing IFFT/FFT of 256 points. plz clarify me this thing, if i have zeronpadde...


why is OFDM good? How does OFDM work?

Started by kiki in comp.dsp17 years ago 1 reply

Hi all, Can anybody enlighten me a little bit using concept of eigenvalues of the channel matrix? I vaguely heard about that the...

Hi all, Can anybody enlighten me a little bit using concept of eigenvalues of the channel matrix? I vaguely heard about that the eigenvalues correspond to the impulse response of the channel matrix and then it somehow did blah blah blah, so the OFDM idea is good... blah blah blah, I am not sure I understood it... anybody provides some intuition and thoughts? Thanks a lot! ...


mmse in ofdm

Started by charanchar in comp.dsp12 years ago

how to design MMSE equqlizer for ofdm? fft length=64, number of pilot tones=4

how to design MMSE equqlizer for ofdm? fft length=64, number of pilot tones=4


question on ofdm transceiver front end design.

Started by philgo in comp.dsp15 years ago 1 reply

Hi all, I am interested in writing a baseband simulator for OFDM, including the OFDM transceiver front end design, and particularly in the...

Hi all, I am interested in writing a baseband simulator for OFDM, including the OFDM transceiver front end design, and particularly in the following items: upsampling, downsampling, Power amplifier predistortion non-linear amplifier frequency synthesizer with phase noise I/Q (de-)modulator with amplitude and phase mismatches AGC could any one kindly give some reference or link that...


Minimization of phase error fluctuation in OFDM equalizer

Started by danael in comp.dsp12 years ago 2 replies

I am designing ofdm equalizer.Ofdm frame contains: -19 symbols -24 subcarriers per channel -pilot symbols that are comb type arranged -BPSK...

I am designing ofdm equalizer.Ofdm frame contains: -19 symbols -24 subcarriers per channel -pilot symbols that are comb type arranged -BPSK modulation The period of one frame (19symbols) is 625us,pilots are inserted every four symbol in time direction and every four subcarrier in frequency direction. I made real measurements to determine the channel nature between base station and rece...


DC Subcarrier in OFDM

Started by karthikbalaguru in comp.dsp13 years ago

Hi, I find that there are Null Subcarriers that are frequency guard bands (there is no transmission). But, What is the use of DC (Direct...

Hi, I find that there are Null Subcarriers that are frequency guard bands (there is no transmission). But, What is the use of DC (Direct Current) subcarrier in OFDM ? Thx in advans, Karthik Balaguru


How many samples are there in one period of a subcarrier which is produced after IFFT in OFDM systems?

Started by runinrainy in comp.dsp6 years ago 4 replies

Hello, In an OFDM system, by using N subcarriers we get one OFDM symbol. But before that the data is first mapped into frequency domain by...

Hello, In an OFDM system, by using N subcarriers we get one OFDM symbol. But before that the data is first mapped into frequency domain by the constellation mapper and we get N-parallel streams as an input to the IFFT process. The IFFT takes these N-parallel streams and produces N-parallel subcarriers in time domain, all these subcarriers are in digital form and has different frequencies. Let?...


SNR to EbNo in OFDM scheme

Started by Anonymous in comp.dsp13 years ago 1 reply

hey all, I made an ofdm simulation in matlab, I want it to output Ber/EbNo plot, and I use the awgn function in order to add white noise in...

hey all, I made an ofdm simulation in matlab, I want it to output Ber/EbNo plot, and I use the awgn function in order to add white noise in the channel, and as u know the awgn function requires SNR as input, so I need to convert from Eb/No to SNR. I know this: Es/No(dB)=10log10(Tsymb*Fs)+SNR(dB) now I need to convert the Es/No of the ofdm signal to Eb/No: Es/No(dB)=Eb/No(dB)+10log10(...


Sampling Clock Problem in OFDM

Started by Anonymous in comp.dsp12 years ago 1 reply

I have made a simulation of ofdm on baseband and it works fine. to simulate the sampling clock synchronization problem, i have resampled the...

I have made a simulation of ofdm on baseband and it works fine. to simulate the sampling clock synchronization problem, i have resampled the baseband waveform using resample function in MATLAB. yt = resample(yt, 1601, 1600); Now, even with such a small offset, my receiver does not work (yt contains 1600 samples comprising 20 ofdm symbols each of 64 point + 16 cyclic prefix = 80 samples). M...


question of ICI in OFDM system

Started by totohaha in comp.dsp13 years ago 2 replies

Could anyone tell me if my understanding for the acronym of ICI is right or not? There are 2 types of ICI, one is Inter Carrier Interference...

Could anyone tell me if my understanding for the acronym of ICI is right or not? There are 2 types of ICI, one is Inter Carrier Interference which is caused by the frequency offset between transmitter and receiver in OFDM system, and another is Inter Code Interference which is caused by the Code Divison Multiplexing in OFDM-CDM system.


Digiatal Sampling correction Interpolation/Decimation in e OFDM Modem

Started by nqh in comp.dsp14 years ago

Hi all, My project is Digiatal Sampling correction Interpolation/Decimation for application in flexible OFDM Modem. I'm implementing in Matlab...

Hi all, My project is Digiatal Sampling correction Interpolation/Decimation for application in flexible OFDM Modem. I'm implementing in Matlab the 5_taps optimized interpolator which will improve the performance for long data OFDM bursts. I used control parameters basepoint index (m(k)) and fractional interval (mu(k)) (reference to FM Gardners article "Interpolation In Digital Modems---PART1: ...


OFDM and channel modeling

Started by cpshah99 in comp.dsp12 years ago 4 replies

Hi All. I have never worked on OFDM but still I have a doubt. I know how to model time varying frequency selective channel for...

Hi All. I have never worked on OFDM but still I have a doubt. I know how to model time varying frequency selective channel for single carrier system in *time domain*. I am pretty sure that exactly the same way you can model the time varying frequency selective channel for OFDM. But is it something like you can model the time varying frequency selective channel for OFDM in *frequency domai...


FFT in OFDM

Started by srikoll in comp.dsp18 years ago 3 replies

hi all, I have a question regarding FFT in OFDM. why do we use FFT in OFDM systems? thanx.

hi all, I have a question regarding FFT in OFDM. why do we use FFT in OFDM systems? thanx.


LTE, FFT, OFDM

Started by Sharan123 in comp.dsp5 years ago 55 replies

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth of 1.4/3/5/10/15/20 MHz. I don't know how these N point FFT are selected for OFDM implementation. Let us take 1.4 MHz and 128 point FFT for example. 128 point FFT has N value of (2^N = 128) of 7. With a sub-carrier spacing of 15 KHz, this covers = 7*15 KH...


OFDM systems

Started by patrick12 in comp.dsp14 years ago 2 replies

Hallo, In an OFDM systems, if the users are not orthogonal, how does the multiuser interference affects the mapping of SNR to BER (BLER).I do...

Hallo, In an OFDM systems, if the users are not orthogonal, how does the multiuser interference affects the mapping of SNR to BER (BLER).I do have only a vague idea about this. Could anyone help me in the right path/ any literatures. Thanks a lot in advance Cheers, Patrick


Looking for books on OFDM

Started by Nikos Annitsakis in comp.dsp17 years ago 1 reply

Hi all: I am looking for books to read about OFDM. Could you offer some suggestions? Thanks, Nikos

Hi all: I am looking for books to read about OFDM. Could you offer some suggestions? Thanks, Nikos


implementation of OFDM-MFSK

Started by shamma in comp.dsp12 years ago 7 replies

hi can anyone have the idea how to implement OFDM-MFSK in matlab . Regards

hi can anyone have the idea how to implement OFDM-MFSK in matlab . Regards


Computing per stream SNR in a full CSI MIMO-OFDM system for fast link adaptation

Started by Dani Camps in comp.dsp13 years ago 1 reply

Dear all, I have a MIMO-OFDM system, like 802.11n. I assume full CSI in both TX and RX and my goal is to obtain in the receiver a per spatial...

Dear all, I have a MIMO-OFDM system, like 802.11n. I assume full CSI in both TX and RX and my goal is to obtain in the receiver a per spatial stream and per OFDM subcarrier SNR estimation in order to perform a fast link adaptation algorithm, i.e. I want to compute SNR[i][k] where i=1..Nss (Nss: number of spatial streams) and j=1..Nsc (Nsc: number of OFDM subcarriers). Since I assume ful...


White Noise Level in OFDM & SNR Definition

Started by PhyLyrDude in comp.dsp12 years ago

Hi All, I have this problem on the level of white noise to be added into an OFDM system. Firstly, I have series of symbols mapped to a series...

Hi All, I have this problem on the level of white noise to be added into an OFDM system. Firstly, I have series of symbols mapped to a series of subcarriers and then go through an IFFT (size 2048). For simplicity, I assumed that it goes through a 1 path channel (i.e. no change to the OFDM signal). I then added some white guassian noise. Now here is the problem, if say I want a SNR of 10 dB,...