802.11a PLCP training sequence question

Started by ofdm2006 in comp.dsp14 years ago 2 replies

I have a question that why in 802.11a IEEE standard, the PLCP long training sequence takes the GI2(Guard interval 2) as the prefix of two OFDM...

I have a question that why in 802.11a IEEE standard, the PLCP long training sequence takes the GI2(Guard interval 2) as the prefix of two OFDM symbols, not one GI before one OFDM and the other GI before the second OFDM symbol? What is the advantage of that?? The following includes the IEEE 802.11a 1999 version: http://standards.ieee.org/getieee802/802.11.html Thanks.


question on ofdm transceiver front end design.

Started by philgo in comp.dsp14 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...


OFDM model

Started by Anonymous in comp.dsp13 years ago 4 replies

Hi, i am learning about OFDM currently. And i am learning to implement the model in SIMULINK. Yet, i am stuck at the 'training symbols'. I...

Hi, i am learning about OFDM currently. And i am learning to implement the model in SIMULINK. Yet, i am stuck at the 'training symbols'. I dont really understand why training is needed in channel estimation and what forms those training symbols. Can recommend some nice books for OFDM or simulink? Thanks for ur patience.


ofdm in power line communication simulation

Started by junbao in comp.dsp14 years ago

Hie all, I am now doing the OFDM Simulation for Power Line Communication. I have written a very simple code for OFDM and have the impulse response...

Hie all, I am now doing the OFDM Simulation for Power Line Communication. I have written a very simple code for OFDM and have the impulse response of the power line channel. I am facing the problem that the BER of my result are high and constant along the SNR. So I would like to know whether my simulation is correct or not, and hope that someone can give me an advice on the simulations. I am using...


Question regarding Concatenated Codes on OFDM

Started by Ubaid Abdullah in comp.dsp12 years ago

I am simulating an OFDM system and want to employ concatenated codes with different modulation schemes. I have a few queries about it. 1. RS code...

I am simulating an OFDM system and want to employ concatenated codes with different modulation schemes. I have a few queries about it. 1. RS code works on frame-by-frame basis like for a shortened code RS(32,24) on byte boundary. In this case, I need a minimum of 24*8 uncoded data bits. If i work on this boundary, the resulting symbols dont map completely to the OFDM symbol. How can i make it sat...


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.


OFDM Multipath Time-Varying Channel

Started by fmtzbalt in comp.dsp14 years ago 2 replies

Hi there. I have a question regarding the wireless channel model to be used on an OFDM system simulation. I have investigated for a while and...

Hi there. I have a question regarding the wireless channel model to be used on an OFDM system simulation. I have investigated for a while and most of the people use an ARMA Filter to simulate the time variations of the wireless channel, but this approach is for modeling a multipath channel. The thing is that I don't know if this model includes the distortion on the receiver do to the echoes. OFDM...


simulation of carrier offset in OFDM

Started by sandy80 in comp.dsp15 years ago 6 replies

Hi i want to simulate small carrier offset in OFDM and see its effect on QAM constellations. How can is simulate...

Hi i want to simulate small carrier offset in OFDM and see its effect on QAM constellations. How can is simulate carrier offset in MATLAB for OFDM signal.. is iterpolation - decimation technique helpful?? i want to introduce this offset after passing the signal through channel filter. i want to simulate by noninteger factor say 0.5 i.e shift of tones by 0.5 ...


Two questions about OFDM

Started by Harry Lin in comp.dsp16 years ago 4 replies

Some articles say that an OFDM system will reduce the symbol rate through parallel data transmission. Is this really true? Let's say suppose...

Some articles say that an OFDM system will reduce the symbol rate through parallel data transmission. Is this really true? Let's say suppose there are 100 subcarriers in an OFDM system and the data rate before the IDFT is 100 symbols per second. It seems to me that, after IDFT, each subcarrier only transmits one of the 100 symbols in 1/100 second like this: 1st subcarrier: 1/100 idle ...


EVM in OFDM

Started by rbb in comp.dsp10 years ago 5 replies

Measuring the RMS EVM of the underlying modulation in an OFDM signal is straight forward. However the accuracy of the EVM appears to be...

Measuring the RMS EVM of the underlying modulation in an OFDM signal is straight forward. However the accuracy of the EVM appears to be affected by the number of null tones present in the OFDM FFT. In other words if there are no null tones, then the EVM measurement is as expected and as the number of null tones increases the EVM measurement diverges from expected. Does anybody know of any lit...


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


ofdm preamble format used in 820.16

Started by premnerella in comp.dsp14 years ago 1 reply

can any one please tell me the format of ofdm preamble used in 802.16 ofdm system and also its generation

can any one please tell me the format of ofdm preamble used in 802.16 ofdm system and also its generation


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

Started by harishm in comp.dsp6 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


Minimization of phase error fluctuation in OFDM equalizer

Started by danael in comp.dsp11 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...


why is OFDM good? How does OFDM work?

Started by kiki in comp.dsp16 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


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

Started by runinrainy in comp.dsp5 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?...


OFDM Modulator

Started by Anonymous in comp.dsp14 years ago 1 reply

hi everyone Im devloping an OFDM modulator using DSP techniques, with the following specifications: Bit rate = 16Kbs/s 16...

hi everyone Im devloping an OFDM modulator using DSP techniques, with the following specifications: Bit rate = 16Kbs/s 16 sub-carriers QPSK 8 Bit Resultion DAC can anyone help regarding how to start the matlab program for this project.. thnx best regards Omar


White Noise Level in OFDM & SNR Definition

Started by PhyLyrDude in comp.dsp11 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,...


OFDM and CFO EStimation

Started by JALEX in comp.dsp13 years ago 9 replies

Hi I am trying to generate a OFDM signal with CFO, of which i am trying to plot a BER Vs the CFO for various SNR.... I started by...

Hi I am trying to generate a OFDM signal with CFO, of which i am trying to plot a BER Vs the CFO for various SNR.... I started by transmitting a signal and receiving it over a flat fading channel, using cyclic prefix, and zero padding the data.... which I was successful But when i tried it over the CFO .....i am not getting it... The following is the section of the CFO which I use in t...