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 complex conjugate it? 2.There's this block called 'moving average', what is that? I apologise if i sound confused, coz i've read so many papers and there's like a million ways for ofdm sync that i duno which is which. But i've more or less decided on the coarse and fine sync method. Please advise. Thx!
Preamble detection in ofdm synchronization
Started by ●December 8, 2005
Reply by ●December 9, 20052005-12-09
On 8 Dec 2005 18:56:59 -0800, "Ant_Magma" <vcteo1@gmail.com> wrote:>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 complex >conjugate it?Do you mean correlating the cyclic prefix against the delayed signal or a specific preamble? In either case, though, the processing is done at baseband so the signal is complex.>2.There's this block called 'moving average', what is that?Presumably a moving average or FIR filter.>I apologise if i sound confused, coz i've read so many papers and >there's like a million ways for ofdm sync that i duno which is which. >But i've more or less decided on the coarse and fine sync method.Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●December 9, 20052005-12-09
On 8 Dec 2005 18:56:59 -0800, "Ant_Magma" <vcteo1@gmail.com> wrote:>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 complex >conjugate it?Do you mean correlating the cyclic prefix against the delayed signal or a specific preamble? In either case, though, the processing is done at baseband so the signal is complex.>2.There's this block called 'moving average', what is that?Presumably a moving average or FIR filter.>I apologise if i sound confused, coz i've read so many papers and >there's like a million ways for ofdm sync that i duno which is which. >But i've more or less decided on the coarse and fine sync method.Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●December 9, 20052005-12-09
On 8 Dec 2005 18:56:59 -0800, "Ant_Magma" <vcteo1@gmail.com> wrote:>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 complex >conjugate it?Do you mean correlating the cyclic prefix against the delayed signal or a specific preamble? In either case, though, the processing is done at baseband so the signal is complex.>2.There's this block called 'moving average', what is that?Presumably a moving average or FIR filter.>I apologise if i sound confused, coz i've read so many papers and >there's like a million ways for ofdm sync that i duno which is which. >But i've more or less decided on the coarse and fine sync method.Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. Yes, it's sync with cyclic prefix
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. What am i missing here? Should i perform the sync operation after FFT? Shouldn't i synchronize first and get the correct start of the frame before FFTing it? And if so, how could i perform complex conjugate on the receiving signal which is real? I'm transmitting in BPSK...please explain..thx... Yes, it's sync with cyclic prefix
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. What am i missing here? Should i perform the sync operation after FFT? Shouldn't i synchronize first and get the correct start of the frame before FFTing it? And if so, how could i perform complex conjugate on the receiving signal which is real? I'm transmitting in BPSK...please explain..thx... Yes, it's sync with cyclic prefix
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. What am i missing here? Should i perform the sync operation after FFT? Shouldn't i synchronize first and get the correct start of the frame before FFTing it? And if so, how could i perform complex conjugate on the receiving signal which is real? I'm transmitting in BPSK...please explain..thx... Yes, it's sync with cyclic prefix
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. What am i missing here? Should i perform the sync operation after FFT? Shouldn't i synchronize first and get the correct start of the frame before FFTing it? And if so, how could i perform complex conjugate on the receiving signal which is real? I'm transmitting in BPSK...please explain..thx... Yes, it's sync with cyclic prefix
Reply by ●December 11, 20052005-12-11
> Do you mean correlating the cyclic prefix against the delayed signal > or a specific preamble? In either case, though, the processing is > done at baseband so the signal is complex.U mentioned processing is done at baseband, meaning the correlation is done after FFT at the receiver? but most blocks i c have their estimation and synchronization blocks before FFT. The ones after FFT are only the estimation and equalization blocks. What am i missing here? Should i perform the sync operation after FFT? Shouldn't i synchronize first and get the correct start of the frame before FFTing it? And if so, how could i perform complex conjugate on the receiving signal which is real? I'm transmitting in BPSK...please explain..thx... Yes, it's sync with cyclic prefix
