I have been given a OFDM signal of crest factor of 12dB. The crest factor is the ratio of peak power to the average power of the signal. Does...

I have been given a OFDM signal of crest factor of 12dB. The crest factor is the ratio of peak power to the average power of the signal. Does anyone have any idea how crest factor of 12dB is derived for an OFDM signal?(assumptions on peak power,average or RMS power etc). I would highly appreciate any input on this. --------------------------------------- Posted through http://www.DSPRelated.co...

Dear all, Hi, I am trying to simulate the performance (block error rate) of ofdm over raylegih. My question is, how do I calculate SNR for...

Dear all, Hi, I am trying to simulate the performance (block error rate) of ofdm over raylegih. My question is, how do I calculate SNR for OFDM Rayleigh channel and map it to equivalent AWGN SNR so that I can calculate the block error rate ? I like to mention that I have already simulate AWGN block error rate (BLER) for different modulation and coding (MCS) combination. Difficulty arise...

Hi, I am implementing an equalization algorithm for OFDM system. For this, after calculating the channel taps, we need to divide the...

Hi, I am implementing an equalization algorithm for OFDM system. For this, after calculating the channel taps, we need to divide the complex sub-carrier symbols with complex tap values. I was wondering this division takes too many cycles for the DSP implementations. So is there any way of doing equalization in a better way or we have to live with this expensive division operation.

Hi I am trying to simulate a mimo-ofdm wireless system. I have most of the blocks ready but I could not figure out how to implement...

Hi I am trying to simulate a mimo-ofdm wireless system. I have most of the blocks ready but I could not figure out how to implement channel estimation in the mimo enviroment. If anyone could point out a way to do it or know of a paper that describes this I would appreciate the help. Thank you. Elan. This message was sent using the Comp.DSP web interface on www.DSPRelated.com

Hello, I am trying to simulate a OFDM signal I would to do the following before Generate a signal and see its charachetrics with delay...

Hello, I am trying to simulate a OFDM signal I would to do the following before Generate a signal and see its charachetrics with delay spread. I have generated a signal and then divided it into parallel signal for multipath, but now I have difficulty generating a delay spread. I would appreciate if some one could help me in this regard. Zigbee Jack

Hallo everybody, I've got a little question about the way I'm modelling a multipath-channel with AWGN using MATLAB for my...

Hallo everybody, I've got a little question about the way I'm modelling a multipath-channel with AWGN using MATLAB for my OFDM-Simulation. Can anybody tell me whether the way I'm doing it is correct or not? I've implemented to following code: %-------------------------------------------------------------------- % tx is the transmitted discrete OFDM-basebandsignal % which is normalize...

Hello all: I want to know more about how Maximal ratio combining is done in an OFDM based system. I have some IEEE references but cannot get...

Hello all: I want to know more about how Maximal ratio combining is done in an OFDM based system. I have some IEEE references but cannot get an insight as to how this is to be implemented. I am particularly interested as to how to cophase the signals on the two channels and then combine them. What sort of circuitry can be used to do this, say in a 802.11a WLAN system. Here are some of...

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am...

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am using is a Gaussian window, with factor gamma (exp(-gamma*t^2)) I have already implemented it, but I do not know if the results obtained are so satisfactory as they should be. My concern is on the proper choice of the value gamma: I make it inversely prop...

Hi ! I would like to know the utility of null subcarriers at the edge of an OFDM spectrum. For example in Hiperlan2 or 802.11g, there are 5 null...

Hi ! I would like to know the utility of null subcarriers at the edge of an OFDM spectrum. For example in Hiperlan2 or 802.11g, there are 5 null sub carriers at both edges of the spectrum. Is it useful for the receiver, in the case of multi user, in order to choose as well as possible the sub-band and so to relax the constraint on the analog filter ? Thanks a lot Sylvain

Hi i am simulating a baseband OFDM system Digital down converter. I have a problem regarding decimation and interpolation. In the last stage of...

Hi i am simulating a baseband OFDM system Digital down converter. I have a problem regarding decimation and interpolation. In the last stage of the DDC, i am doing low pass filtering of the data. My problem is when i make a sharp transition filter i.e. ( Fpass = 250e3; % Passband Frequency Fstop = 300e3; % Stopband Frequency the OFDM constellation is scattered. But...

As was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is...

As was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is at baseband, and I'm using a sound card as a DAC, this means my signals are audible. When modulating a random bitstream, the resulting audio is full of popping noises. I have taken steps to ensure that no clipping is occurring, so these pops are really...

In OFDM Transmitter, when you do the IFFT of input samples x(0),x(1),x(2)....x(N-1), then at the output of the IFFT block you get a sequence...

In OFDM Transmitter, when you do the IFFT of input samples x(0),x(1),x(2)....x(N-1), then at the output of the IFFT block you get a sequence X[0],X[1],....X[N-1]. My question is, that do we then transmit X[0],X[1],....X[N-1] one by one over the channel (and hence the need for parallel to serial blockafter IFF block)? If that is so, don't you think we only need to transmit only one element fr...

Could anyone please explain how Cyclic Prefix in OFDM system converts linear convolution to the circular convolution? Thanks in advance! ...

Could anyone please explain how Cyclic Prefix in OFDM system converts linear convolution to the circular convolution? Thanks in advance! _____________________________ Posted through www.DSPRelated.com

Hi, I am trying to design an OFDM trasmitter. My current structure is as follows: IFFT -> Cyclic Prefix insertion on I and Q -> x4...

Hi, I am trying to design an OFDM trasmitter. My current structure is as follows: IFFT -> Cyclic Prefix insertion on I and Q -> x4 interpolation filter on I and Q -> I/Q quadrature modulator -> output to DAC. My question is related to the interpolation filters. The convolution between the input to the filter and the filter impulse response smudges the symbol. For example, if the FFT

Hi I'm developing a custom OFDM modem. I use 52 carriers each encoding one nibble, so 26 bytes at a time. In order to avoid large peaks...

Hi I'm developing a custom OFDM modem. I use 52 carriers each encoding one nibble, so 26 bytes at a time. In order to avoid large peaks on transmit, I Xor the 26 bytes with 'randomly selected' 26 bytes before FFT and do the reverse on receive. These bytes were simply made using VB to make 26 'random' numbers. This works well, but it's not very scientific. How would I go about ch...

Hello, I am simulating the performance of an OFDM based communication system, where I convolve OFDM symbols with the Channel Impulse Response...

Hello, I am simulating the performance of an OFDM based communication system, where I convolve OFDM symbols with the Channel Impulse Response (7-Tap Rayleigh distributed) The problem is that Matlab function conv( ) takes a lot of processing time. I tried to declare the output variable as a vector of zeros. This did help, but only slightly. Under Monte Carlo's method, it gets really annoyi...

Hi, I'm doing simulation in frame synchronization of OFDM by using Cocentric System Studio. My task is to generate preamble and do sync in...

Hi, I'm doing simulation in frame synchronization of OFDM by using Cocentric System Studio. My task is to generate preamble and do sync in both time and frequency domain. Channel model is not necessary. Does anyone have any idea or any sources related to my task ? I'm a newbie in communication. So it would be best if you give me some fundamental sources about synch in OFDM and some si...

Hi Everybody... Good Afternoon. My name is Vanessa. I?m an engineer and I?m developing a prototype of an OFDM Modulator. The configuration I...

Hi Everybody... Good Afternoon. My name is Vanessa. I?m an engineer and I?m developing a prototype of an OFDM Modulator. The configuration I choosed was: 2K IFFT, 64QAM and 1/16 for the cyclic prefix.The sampling frequency used in the IFFT was 12.5MHz. When I did the cyclic extention, the output spectrum became filled with running spurious tones, overlaping the correct base band signal. My q...

Hi I'm trying to implement an OFDM system. I decided to use the lowest frequency carrier as a constant tone with a cyclic prefix so that I...

Hi I'm trying to implement an OFDM system. I decided to use the lowest frequency carrier as a constant tone with a cyclic prefix so that I could lock the receiver to this by adjusting RX frequency to achieve zero real signal on this channel, IOW a single sine cycle with a cyclic prefix before it starts. It locks and tests very well on the bench wired straight through, and when I c...

I'm currently studying the preamble synchronization of ofdm symbols in power line comunication (in Simulink). I haven't finished reading yet...

I'm currently studying the preamble synchronization of ofdm symbols in power line comunication (in Simulink). I haven't finished reading yet but there's a few things i dont understand. 1. In the auto-correlation of the preamble (coarse timing sync), the Rx preamble is delayed and complex conjugate and correlated with Rx (itself). However, Rx is received as a real signal, how can you comp...