ADSL Equalization Van Herck Hans Verheyden Jonas

Inhoud Wireless ADSL communicatie OFDM MCM Orthogonale subcarriers Bestand tegen slechte kanaalkarakteristieken Implementatie en optimalisatie

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

Cyclic Prefix Laatste v samples vooraan toevoegen Beschermt tegen ISI o.w.v. kanaaluitsmering en bij multipath Kanaalimpulsresponsie < v+1 Verlies van efficiëntie N samplesv samples CP s y m b o l i s y m b o l i+1 copy

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

Time Domain Equalizer Kanaalimpulsresponsie verkleinen → CP kleiner → grotere efficiëntie FIR filter, optimale coëfficiënten via algoritmes (zie verder)

QAM demod decoder invert channel = FEQ S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D Bits channel P/S

TEQ Coëfficiënten Algoritmes: Minimum Mean Squared Error (MMSE) Methodes van steilste gradiënt voor foutsignaal e k Maximum Shortening SNR (MSSNR): SNR binnen verkorte kanaalimpulsresponsie maximaliseren … z-z- h + w b - xkxk ykyk ekek zkzk rkrk nknk + TIR TEQCIR

Vragen?

Referenties sl/TEQdesign.ppt Wikipedia ftp://ftp.esat.kuleuven.be/pub/sista/jvangorp/DSP 2/FSequalization.pdf ftp://ftp.esat.kuleuven.be/pub/sista/jvangorp/DSP 2/LMFequalization.pdf ftp://ftp.esat.kuleuven.be/pub/sista/jvangorp/DSP 2/bingham.pdf