Hi all.... I just simulated the Zero-Padding OFDM and Cyclic-Prefix OFDM system... I found some difference between their power spectrum...

Hi all.... I just simulated the Zero-Padding OFDM and Cyclic-Prefix OFDM system... I found some difference between their power spectrum density... In CP-OFDM, the in-band ripple is larger than ZP-OFDM... But in out-of-band, the ZP-OFDM is larger than CP-OFDM.... I just got the conclusion through simulation... How could i explain the phenomenon in physical or math. sense.... Anyone can tel...

Hi friends I have doubt in mind. I always read about OFDM frame where in each OFDM frame consist of 2 or 1000 or ...... OFDM symbols. Why...

Hi friends I have doubt in mind. I always read about OFDM frame where in each OFDM frame consist of 2 or 1000 or ...... OFDM symbols. Why OFDM signal is transmitted in frame format ? Why OFDM does not transmitted in each OFDM symbol ? Many thanks in advances. Regards, Wiwi

On May 12, 10:55 pm, "dvo" wrote: > > what is a typical bits/Hz for CE-OFDM compared to conventional OFDM? > what about the channel? it...

On May 12, 10:55 pm, "dvo" wrote: > > what is a typical bits/Hz for CE-OFDM compared to conventional OFDM? > what about the channel? it seems to me that the ofdm modem now sees result > of the transform of the real channel with FM demodulator. I doubt whether > ofdm is optimal for such environment. Also would FM demod introduce any > orthogonality problem for ofdm demod

Hi there! I am working on PAPR measurement of OFDM signals connected to a RF amplifier.I created the OFDM signal from a signal studio. Then the...

Hi there! I am working on PAPR measurement of OFDM signals connected to a RF amplifier.I created the OFDM signal from a signal studio. Then the signal is connected to RF amplifier and with the spectrum generators to see the input OFDM spectrum and output OFDM spectrum. The generated OFDM Spectrum from the Spectrum generator is stationary or it is changing for a particular input power of RF ...

Hello All I am looking to implement an OFDM system in VHDL on a DVB-T system. I have designed a 16-QAM block with outputs of a 3 bit binary bus...

Hello All I am looking to implement an OFDM system in VHDL on a DVB-T system. I have designed a 16-QAM block with outputs of a 3 bit binary bus for I and Q. I know want to build the OFDM block. I am looking as how to convert I and Q into a complex number I+jQ so I can buffer that up to push through the IFFT. This willl then output an OFDM value for I(OFDM) and Q(OFDM). Can anyone offer ...

Hi I am new to OFDM and wideband communication in general. I went through the tutorial on OFDM at www.complextoreal.com. I have understood the...

Hi I am new to OFDM and wideband communication in general. I went through the tutorial on OFDM at www.complextoreal.com. I have understood the concept of orthogonality and how it works in OFDM, however I am not so clear about the use of pilots in OFDM. Can anyone guide me to some resources which explicitly explain what a OFDM pilot symbol is, with examples, and how it helps in frequency estimat...

Dear sir / Madam, I am doing M.E in Communication system, i have gone through the concept and fundamentals of OFDM first time , but i could...

Dear sir / Madam, I am doing M.E in Communication system, i have gone through the concept and fundamentals of OFDM first time , but i could not understand the process of IFFT in OFDM modulation, why FFT is not taken at the first stage? if any kind personality explains the concepts behind the IIFT in OFDM, which will helpful for me to understand better. How can i get e-version of any OFDM text...

Hi, I am working on channel estimation in OFDM systems, and have a question related to block-type pilot arrangement. Block-type pilot...

Hi, I am working on channel estimation in OFDM systems, and have a question related to block-type pilot arrangement. Block-type pilot arrangement is one where all subcarriers in an OFDM symbol carry pilots. Does this mean that this OFDM symbol contains no null subcarriers, even at DC? Or is it assumed that these 'pilot' carrying OFDM symbols contain some minimum number of null-subcarriers a...

Let's say my transmittid frame is like this: || Preamble || GI1 | OFDM symbol 1 || GI2 | OFDM symbol 2 || Removing GI1 would remove any...

Let's say my transmittid frame is like this: || Preamble || GI1 | OFDM symbol 1 || GI2 | OFDM symbol 2 || Removing GI1 would remove any interference effects caused by the preamble. But what if the last few samples of OFDM symbol 1 is interfered by GI2? Wouldn't a structure like this: || Preamble || GI1 | OFDM symbol 1 | GI1' || GI2 | OFDM symbol 2 | GI2' || With GI1' and GI2' p...

Hello. Could I have some help & discussion please? I built an OFDM simulator with IEEE 802.20 channel model. But, I'm not sure if my BER...

Hello. Could I have some help & discussion please? I built an OFDM simulator with IEEE 802.20 channel model. But, I'm not sure if my BER results are correct or not. Thus, I checked BER of OFDM in AWGN first. Then, I checked BER of OFDM in very very low bit rate. For example when a channel shows rms delay spread of 0.37usec, I tested with Rb = 1E4 bps. Then, I checked BER of OFDM with ...

Hi, i'm trying to simulate waterfilling for single user ofdm in matlab. i can't seem to find any reference on this topic as most papers deal...

Hi, i'm trying to simulate waterfilling for single user ofdm in matlab. i can't seem to find any reference on this topic as most papers deal with multiuser or multiple access ofdm system. Papers which mentioned watefilling for single user ofdm stopped short at providing simply the formula and not the implementation. im new to waterfilling and ofdm and thus need some help. I understand that f...

I want to simulate a MB-OFDM-UWB system in Matlab. I did pure OFDM system before which consist of convolution code block, modulation block,...

I want to simulate a MB-OFDM-UWB system in Matlab. I did pure OFDM system before which consist of convolution code block, modulation block, FFT block, Cyclic Prefix block, multipath block and corresponding receiver blocks. However, how to modify them to a MB-OFDM-UWB system, what kind of block I need to add into? thank!

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...

Hi, I have problem concerning process of generating OFDM signal. From what I know, the real part of IFFT is sampled OFDM signal. So why after...

Hi, I have problem concerning process of generating OFDM signal. From what I know, the real part of IFFT is sampled OFDM signal. So why after IFFT block is IQ modulator that uses real and imaginalis part of IFFT? Why we do not take the real part of IFFT and then convert it to analog signal and then upconvert to the IF frequency? And what about real part of OFDM signal at the output of IQ modula...

Hello, I am trying to design an adaptive equalizer for an OFDM system which has an extremely low symbol rate. I have a question regarding...

Hello, I am trying to design an adaptive equalizer for an OFDM system which has an extremely low symbol rate. I have a question regarding this. The transmitter and the receiver are moving wrt each other. For what amount of relative motion between them in one OFDM symbol period (as a fraction of the carrier wavelength) can I assume that the channel is reasonably correlated across OFDM symbols...

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...

Hi, It is clear that OFDM systems may have different SNR values for each subcarrier due to frequency selectivity of the channel. If an OFDM...

Hi, It is clear that OFDM systems may have different SNR values for each subcarrier due to frequency selectivity of the channel. If an OFDM packet consists of n number of FEC blocks and in case of adaptive modulation and coding systems, a single FEC block may have different modulation scheme. However, is it possible for OFDM (e.g.IEEE 802.11a/n) systems that the block error probability of FEC b...

Hi All Can anyone please suggest me some good papers/books on OFDM and MIMO-OFDM. Of course, I did google it but the problem is that so...

Hi All Can anyone please suggest me some good papers/books on OFDM and MIMO-OFDM. Of course, I did google it but the problem is that so much of stuff is out there that it is difficult to pick the right one. Thanks. Chintan

Hello, I am pretty confused with some DFT/Sampling techniques and how these apply to OFDM. Fundamentally, if a (baseband) signal has a...

Hello, I am pretty confused with some DFT/Sampling techniques and how these apply to OFDM. Fundamentally, if a (baseband) signal has a highest frequency component of f Hz, that signal needs to be sampled at 2f Hz for aliasing-free data reconstruction. My confusion begins with OFDM, which does the process in reverse. That is IDFT is performed first. So, in OFDM, the output of the IDFT blo...

Hi All, I'm having trouble making an analog conversion of OFDM signal using DAC 904E from Burr Brown. The DAC works fine, I have set up a...

Hi All, I'm having trouble making an analog conversion of OFDM signal using DAC 904E from Burr Brown. The DAC works fine, I have set up a digital sine signal and when I looked at the osciloscope and spectrum analyzer it has 600mVpp and 0dBm power with good spurious performance in the baseband bandwidth that I want to use for OFDM (0-4MHz -- OFDM bandwith is 7MHz) with adequate sampling rate in ...