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PSD in ZP-OFDM and CP-OFDM

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 throug...

OFDM with Pilots

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 ...

ofdm frame

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 ...

OFDM Implementation (DVB_T)

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 t...

IFFT in OFDM

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 ...

OFDM sychronization implementation?

Hi all, How to achieve synchronization(carrier phase timing) in ofdm? did ofdm need a pilot? ...

OFDM vs DMT

Hi, What is the difference between DMT and OFDM. Why isn't OFDM used in the xDSL technologies? If I have to guess the difference, I think that OFDM has several carrier frequencies that are orthogonal. DMT I think uses carriers seperated by some space on the frequency spectrum. Kind Rega...

Q) OFDM and BER verification

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 channe...

OFDM Simulation & understanding

Hi, I would like to understand more and more about OFDM and its applications for my work. I need to simulate it with Matlab. If possible, could you supply me matlab code which will be enable me to simulate OFDM ( that will be very helpful for understanding OFDM and its concept). Thx in a...

some good papers on OFDM/MIMO-OFDM

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 ...

Channel tracking in an OFDM system

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 o...

Measuring PAPR of OFDM signals

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 Spec...

OFDM Spectrum

Hi, I'm trying to visualize the sub-carriers in my ofdm model. What I do is I generate a BPSK OFDM symbol and after IFFT I plot the FFT of transmitter output. I only get one Sinc graph not the overlapping sub-channels. Could you please correct me to get a proper view o...

TDoA in OFDM

Does anyone know about or can refer to me any work/papers related to TDoA (Time Differential of Arrival) of OFDM signals?. I would like to learn more about current and new algorithms for TDoA estimation that take advantage of the multi-carrier structure of OFDM. Thanks in advance... ...

OFDM-coherent

Im a little confused about how you employ coherent demod in OFDM. After the FFT at the receiver, how do I perform a coherent demodulation-dont I need a carrier for phase estimation in case of BPSK, QPSK etc. Also this is what coherent OFDM is, right? ...

MB-OFDM-UWB

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 nee...

Cylic prefix and postfix

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: ...

IFFT & DAC in IFFT

Hi, I am doing project in OFDM .I have doubts regarding the functionality of IFFT & DAC in OFDM TX. In OFDM block Where the carrier comes into picture?. After IFFT what is exactly done in DAC block?. There we are using any carrier suppliers?. IF possible anybody can explain the flow of data...

OFDM Block-type Pilot, channel estimation

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 i...

Need help in understanding OFDM

Hello Everyone, My name is Rohith and I recently started working on OFDM. I am trying to simulate 4 carrier OFDM system using QPSK modulation. I am not sure if my current test model is correct or not. Could you please review this and let me know if I am doing anything wrong? Here is the...

OFDM in SystemC

Does anyone has experience of using SystemC for OFDM based design. Please share your experience. I'm new in SystemC so not sure how to start. If you know any good books/websites for OFDM in C/C++ please post here. kind regards, Rezwan ...

Simulation of symbol synchronization in a OFDM receiver

Dear all I am doing a block for a OFDM receiver that receives as input the ofdm received signal and gives as output a rectangular signal (for synchronization) in which each pulse represents a peak in the autocorrelation function realised over the ofdm received signal. How can i define a thresh...

OFDM Transmit diversity

Hello, Assume you have 2 OFDM transmitters that are simultanously transmitting different data and the data is somehow coded (ie CDMA). After IFFT the ofdm symbol of each transmitter , X1 and X2, passes a freq. selective fading channel: Y = X1.G1 + X2.G2 + N My question is at the ...

Q) MIMO-OFDM and freq-domain equalization

Hello, everyone. In SISO-OFDM, we usually employ a frequency domain equalization after the receiver FFT module, as a way to compensate for the channel distortion along frequency bins. We depend on OFDM channel estimation and simple inversion for this purpose. In MIMO-OFDM, either multiplexed s...

a mini question about the "sample sheme" of OFDM

Hi all, I have a mini question and need yr help pls. It is simply about the understanding of sample scheme of OFDM. For convenience, the parameters of a OFDM system are presented as follows. .the sample period: T .FFT/IFFT point: N .the OFDM symbol period: N=B7T Then we ...

Re: synchronization in OFDM and others...

On Nov 27, 3:47 am, "rifo" wrote: > Hello, > > I am wondering there is so much literature about carrier and timing > recovery in communications*. However as far as I understand, OFDM uses > a different approach in synchronization. My question is since OFDM is > becoming more and more ...

ofdm preamble format used in 820.16

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

waterfilling for single user ofdm

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...

SNR to EbNo in OFDM scheme

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)+S...

MIMO-OFDM systems

Hi all, I've been looking at MIMO-OFDM based systems for about the last week (802.11n and 802.16) and have a couple of questions that I was hoping someone out there could answer. Here goes: 1) I want to look (in detail) at one of the more computationally demanding blocks of a typical MIMO-O...

OFDM average power

Hi, I understand the problem of high Peak to Average Power Ratio in OFDM. However, I am not sure how the average power of an OFDM signal is calculated. Suppose you have an N-carrier transmitter where the average power per carrier is p, what would the average power of the OFDM signal be? Tha...

OFDM simulation

Dear all, I am new to this group.I am bit confise about orthogonality in OFDM. I want to know what is orthogonal. Any help regarding this is greatly appreciate. Regards Lau ...

OFDM uses null DC. Why?

Hi~ everybody~ I have one thing about OFDM to want to know. In general OFDM system, DC sub-carrier is not used, that is, null is inserted there. Suddenly I come to curious about the reason. According to the some documents that I found in the web, the reason is due to direct conversion whic...

MIMO - OFDM

Hi guys, my question is: What is the minimum frame length for SF-OFDM schemes(2x1 or 4x1)??Any help is really appreciated. Thanks ...

Re: Data rate of 8psk

It's also not clear whether single or multi-carrier (e.g., OFDM) modulation will be used. If you use OFDM, sure, you don't have such a complex equalizer to implement. ...

OFDM

hi I really need some help to simulate an ofdm system. i need to show that graph of magnitude (amplitude) against frequency... Can somebody assist me in solving this problem. thanks all sheen ...

Is low latency important in CFR of OFDM?

Hi, all: I am interested in CFR of OFDM. I find some relavant paper mentioned low latency feature in the crest factor reduction (CFR) topic of OFDM. I don't understand the reason. It seems to me that several hundreds of microseconds delay is not a big issue. I don't know the specification of Wi...

Help with OFDM transmitted over multipath channel

Hi I want to simulate the transmission of a set of OFDM symbols over a multipath channel. The steps I intend to implement are 1) Generate a 64 subcarrier OFDM system as follows. Take binary data and modulate it using a standard modulation scheme, say 64 QAM. Pass these modulated symbols throug...

I am new to OFDM, I need help.. Thanks...

Recently, I am doing a project related to DAB receiver. And I knew very little about OFDM,and my question is very simple. In the DAB standard it said that there are some NULL symbols receiver can use to detect the begin of the OFDM Signal, after that there is the Phase reference symbol. I am...

MIMO-OFDM

I want to modify my OFDM program into a MIMO-OFDM one. But I dont know where I should modify? channel matrix? Can anybody share a simple MIMO matlab program and tell me how I can do it? ...