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yes it provides security as it will prevent a hacker from deciphering the pilot (known sequence) hence he cannot find the channel conditions and this prevents him from synchronizing to the unknown data stream..
hi,
Im uploading a pdf which explains in very simple terms what is the Difference
between DCT and DFT, how DCT is derived from DFT and many other elementary
things one needs to know about the two transforms. Im sure it would make for
a good read.
Re: CO-FDM
COFDM and OFDM are very similar to each other except for the fact that COFDM has a sort of Forward Error Correction(FEC) coding before OFDM.
This is done to make the OFDM system insensitive to Frequency selective fading. i.e. usually some carriers in a OFDM system undergo deep...
simulink ofdm synchronization
yes, you need to take the complex conjugate before correlating with the original signal.
Well, you might be thinking why should one take complex conjugate of a real signal. Think in this way: Your signal is real at the Tx end, this signal is multiplied by a...
hi gurpreet,
you might be thinking that as the CP is discarded at the receiver, the CP can be anything. yes, the cyclic prefix can be anything. But, it is more advantageous to have it as a repeated version of the starting portion of the same OFDM symbol, this will help in maintaining the...
remove zero padding in simulink
hi antonio,
with reference to pic1, you can neglect the effects of convolutional encoding and Viterbi decoding, i.e. you can match the output of Cov Enc and input of Vit Dec, in your model, this itself is not matching.
the problems seems to be at the...
hi,
To get a real signal after IFFT operation, you need to feed conjugate symmetric. This results in wastage of half the carriers.
There are no conjugate carriers. In 802.11a they use the whole 48 data carriers for sending data, this will result in complex numbers in the time domain. These...
hi thommer,
if you use the "Multipath rayleigh fading channel" , the block itself gives you a means by which one can mention the delays and gains of each tap. so, this means you dont need to use the channel transfer function "h". In addition to this you can use the AWGN noise after this...
hi,
even if you find the impulse responses for such cases (which are readily available in the net) how will you simulate the channel?. for this you can use "Multipath rayleigh fading channel" or "rician fading channel" blocks readily available in Matlab.
The effect of Equalization on BER exists...
ofdm synchronization with verilog
Frequency offset erros in OFDM occurs because of two reasons,
1) Tx - Rx oscillator mismatch
2) doppler frequency shift
doppler shift is a more predominant factor than oscillator mismatch. as this is not present in a wired system we can neglect the 1st...
channel estimation in ofdm
"ML Estimation of Timing and Frequency Offset in Multicarrier Systems"
this paper deals with OFDM symbol synch and Freq Offset estimation. power line channels dont introduce Frequency offsets , this can be neglected, but, OFDM symbol synchronization cant be...
1) zero padding of the initial zeros 2 to 12 using vertcat , the input to the vertcat block should be the data frame and a zero's frame of size 11, as specified by you. Now the output of this should go into another vertcat block which will do the later zero padding of coefficients from 49 to 64...
ifft real valued
hi,
there would not be any problems in the DSP implementation, as most of the DSP processors will not maintain such high precision (definitely not in the order of e-16),
even if its there, the other decoding processes like vitterbi decoding will take care of such small...
there are two options here, both are easy.
1) you can do zero padding two times, using the vertcat block
2) you can do zero padding of the total number of zeros and using a "selector" block you can distribute the guard carriers (zero) wherever you want specifying the output indicies.
this...
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