Wireless multimedia systems: equalization techniques ... fine terzo anno... · canceller for DVB-T/H”, GTTI 2009, Parma, Italia, Jun 2009 L. Toni, A. Conti, F. Zabini and O. Andrisano,

Wireless Communication Laboratory (WiLAB) Tutor: Chiar.mo Prof. Ing. Oreste Andrisano Co-Tutor: Prof. Ing Andrea Conti

Consiglio Nazionaledelle RicercheIEIIT

DEIS - Doctorate in Electronics, Computer Science and Telecommunications – XXII Cyclefinal presentation

Bologna, 13th January 2010

Wireless multimedia systems: equalization techniques, nonlinearities

on OFDM signals and echo suppressionFlavio Zabini

[email protected]

WiLAB - IEIIT CNRUniversity of Bologna

Items Partial equalization techniques in the

down-link of MC-CDMA systems (in collaboration with: School of Electronics and Computer Science -University of Southampton, UK)

Reduction of out of band radiation in OFDM systems with nonlinearities (developed at: DoCoMo Eurolabs, Munich, Germany)

Echo canceller for DVB-T repeaters (“DVB 2006” project: Metasystem S.p.A.)

x


Outline Scenario description

Coupling channel effects

Low-complexity repeater and echo-canceller architecture

Coupling channel estimation based on Pulse Sounding

Echo-canceller performance: MRR, ES, ESNP

Results from theory and measurements

Conclusions


Scenario descriptionSingle Frequency Network (SFN) constituted by:

a DVB-T/H broadcasting station an on-channel relay station or repeater (OCR) many stationary and mobile users


Coupling channel effects Coupling effects between the transmitting and the

receiving antennas (positive feedback) instability risk performance degradation at the final user

Limited amplifier gains

reduced areas covered by the service

Possible countermeasures exploitation of the environment exploitation of the antenna directional characteristics insertion of a digital echo-canceller unit (negative feedback)


Basic scheme of the OCR

Receivingfilter

Transmittingfilter

Amplifier

Coupling channel

Equivalent low-pass representation of signals and processing blocks.

Freq. fs=1/Ts

AWGN

DVBsignal


Coupling channel estimation

Start-up mode

Ti : time sample Tp=RTs, with R integer : time interval between two consecutive

pulses (of amplitude A) N : Lenght of the estimation pulse train G : Power Amplifier

D/A HC(f) HRA/DHT G +

n[nR+k]

d[nR+k]

p(t) pr[nR+k]pm = p[mR]


Coupling channel estimation Transmitted pulse train:

Equivalent channel transfer function:

where

Received pulse train at the instant nTp+kTs:


Coupling channel estimation Averaging the normalized received pulses:

where:


D stages

P taps

Cancelling filter structure

Transfer function:


Search and cancelling window Condition for a perfect echo cancellation:

for

Set the filter taps to mimic the behaviour of the equivalent channel


Echo-canceller performance

We define the Rejection Ratio (RR) as

where is the PSD of the DVB signal to repeat at the output of the D/A.

The Mean Rejection Ratio (MRR) is defined as

W(f)--++

+

Heq (f))( fPS

(*)


Mean Rejection Ratio After some computations, we obtain:

autocorrelation function of h(t)

MRR =


Echo Suppresion The value of MRR in the absence of the canceller is:

The Echo Suppression can be defined as:

It quantifies the reduction of the echo power due to the echo canceller


Echo Suppresion at Nominal Position Let be s0(t) the signal returning in the repeater in the absence of the

canceller and s1(t) the returning signal in the presence of the canceller, and being t* the instant in which the power of the echo pulse response is maximum

The Echo Suppression at Nominal Position is defined as:

It is an over-estimation of the actual Echo Suppression


Theoretical Results


FPGA design and implementation FPGA Stratix II Altera EP2S180F1020C3Analog I/O:

•Two-channel, 12-bit, 125-million samples per second (MSPS) analog-to digital (A/D) •Two-channel, 14-bit, 165-MSPS digital-to-analog (D/A)

Digital I/O • Connector for the Texas Instruments (TI) Evaluation Module (TI-EVM) • Two 40-pin connectors for Analog Devices' A/D converter evaluation boards • Mictor connector for Agilent and Tektronix logic analyzers • RS-232 serial port • 10/100 Ethernet physical layer/media access control (PHY/MAC) and RJ-45 jack

Memory • 32-Mbyte SDR SDRAM • 16-Mbyte flash • 1-Mbyte SRAM • 16-Mbyte compact flash


Test-bed

Repeater with Echo Canceller

DVB-T Modulator

Anritsu


Measured impulse response of the channel between the modulator and the demodulator.


Echo suppression when the echo level is 10dB lower than the inputDVB-T signal.


Echo suppression when the echo level is 0.2dB lower than the inputDVB-T signal


Comparison between ESNP theoretical values and measurements


Conclusions A low-complexity digital echo-canceller based Pulse Sounding has been

presented

The problem of cancelling window position and dimension has been discussed

Analytical expressions for MRR, ES and ESNP has been obtained

The performance of the canceller in the term of echo suppression have been analytically quantified

The measurement done with the test-bed on-board have shown a perfect agreement with the theoretical results


Pubblications (1)Journal papers

A. Conti, B. M. Masini, F. Zabini and O. Andrisano, “On the down-link performance of multi-carrier CDMA systems with partial equalization” , Wireless Communications, IEEE Transactions on, Vol.6, n°1, Jan 2007, pp.230-239

F. Zabini, B.M. Masini, A. Conti, and L. Hanzo, “Partial Equalization for MC-CDMA Systems in Non-Ideally Estimated Correlated Fading”, submitted to IEEE Transactions on Vehicular Technology

M. Mazzotti, F. Zabini, D. Dardari, and O. Andrisano, “Echo Cancellers based on Pseudo-Noise Training Sequences and on Pulse method: Performance and Stability” to be submitted to IEEE Transactions Journals

International conferences F. Zabini, A. Conti, B. M. Masini and O. Andrisano, “Impact of Partial Equalization on the Downlink Performance of Multi-Carrier CDMA Systems”, Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61°, Stockholm, Sweden, May 2005

F. Zabini, B. M. Masini, A. Conti, “ON THE PERFORMANCE OF MC-CDMA SYSTEMS WITH PARTIAL EQUALIZATION IN THE PRESENCE OF CHANNEL ESTIMATION ERRORS”, 6th International Workshop on Multi-Carrier Spread Spectrum MC-SS, MC-CDMA, OFDM, and related topics, Herrsching, Germany, May 2007

F. Zabini, B. M. Masini, A. Conti, “Slow and Fast Adaptation of Partial Equalization for MC-CDMA Systems”, Wireless Communication Systems, 2007. ISWCS 2007. 4th International Symposium on, Trondheim, Norway, Oct 2007


Pubblications (2) F. Zabini, B. M. Masini, A. Conti, “On the Performance of MC-CDMA Systems with Partial Combining and Multiple Antennas in Fading Channels“, Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE, Marina Bay, Singapore, May 2008

M. Mazzotti, F. Zabini, D. Dardari, O. Andrisano, “Performance of an Echo Canceller based on Pseudo-Noise Training Sequences”, BTS 2008 Alexandria, Usa, Oct 2008

B. M. Masini, F. Zabini, “On the Effect of Combined Equalization for MC-CDMA Systems in Correlated Fading Channels”, Wireless Communications and Networking Conference, 2009. WCNC 2009. IEEE, Budapest, Hungary, Apr 2009

F. Zabini, G. Chiurco, M. Mazzotti, R. Soloperto, “FPGA design and performance evaluation of a pulse-based echo canceller for DVB-T/H”, GTTI 2009, Parma, Italia, Jun 2009

L. Toni, A. Conti, F. Zabini and O. Andrisano, “Effective Spectral Efficiency for Adaptive QAM with Diversity and Pilot Assisted Channel Estimation”, ISWCS 2009The Sixth International Symposium on Wireless Communication Systems 2009 (ISWCS’09), Siena, Italia, Sept 2009

Documents

Wireless multimedia systems: equalization techniques ... fine terzo anno... · canceller for DVB-T/H”, GTTI 2009, Parma, Italia, Jun 2009 L. Toni, A. Conti, F. Zabini and O. Andrisano,