Active interference cancellation (AIC) is a multicarrier spectrum sculpting technique which reduces the power of undesired out-of-band emissions by adequately modulating a subset of reserved cancellation subcarriers. In most schemes online complexity is a concern, and thus cancellation subcarriers have traditionally been constrained to linear combinations of the data subcarriers. Recent AIC designs truly minimizing out-of-band emission shift complexity to the offline design stage, motivating the consideration of more general mappings to improve performance. We show that there is no loss in optimality incurred by constraining these mappings to the set of linear functions.

%B IEEE Communications Letters %V 18 %P 1543-1546 %8 09/2014 %G eng %N 9 %& 1543 %R 10.1109/LCOMM.2014.2338316 %0 Conference Paper %B IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) %D 2014 %T Antenna competition to boost Active Interference Cancellation in cognitive MIMO-OFDM %A Schmidt, J.F. %A R. López-Valcarce %K cognitive radio %K dynacs %K spectrum shaping %X Active Interference Cancellation (AIC) techniques for OFDM spectrum sculpting have gained interest over the last years, and several extensions to the MIMO case have been recently proposed. However, these designs do not fully exploit the spatial diversity provided by the multiple transmit antennas, as canceler allocation is fixed. This paper proposes a more general mechanism for the allocation of the cancellation subcarriers across antennas in order to better exploit spatial diversity. In particular, we present a novel AIC design for cognitive MIMOOFDM systems, in which transmit antennas compete against each other for a fixed number of cancellation subcarriers. We show that this more general allocation approach results in significant performance improvements with respect to previous designs. %B IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) %C A Coruña, Spain %G eng %R 10.1109/SAM.2014.6882392 %0 Conference Paper %B IEEE Workshop on Information Forensics and Security (WIFS) %D 2014 %T Detecting Misreporting Attacks to the Proportional Fair Scheduler %A Schmidt, J.F. %A R. López-Valcarce %K adversarial signal processing %K compass %X

The Proportional Fair Scheduler (PFS) has become

a popular channel-aware resource allocation method in wireless

networks, as it effectively exploits multiuser diversity while

providing fairness to users. PFS decisions on which mobile station

(MS) to schedule next are based on Channel Quality Indicator

(CQI) values. Since CQI values are reported by the MSs to the

scheduler, network performance can be severely degraded if some

malicious MSs report forged information. Previous approaches to

this security issue are based either on modifying PFS, which may

be undesirable in some contexts, or authenticating CQI reports

by periodic transmission of challenges, which increases overhead.

Instead, we propose to detect misreporting attackers, based on the

time correlation features of the wireless channel. Our approach

does not require scheduler modification, and it does not increase

overhead. Simulation results under realistic settings are provided

to show the effectiveness of the proposed test.

%B IEEE Workshop on Information Forensics and Security (WIFS)
%C Atlanta, USA
%8 12/2014
%G eng
%R 10.1109/WIFS.2014.7084310
%0 Conference Paper
%B European Signal Processing Conference (EUSIPCO)
%D 2014
%T Low-Power Active Interference Cancellation for OFDM Spectrum Sculpting
%A Schmidt, J.F.
%A Daniel Romero
%A R. López-Valcarce
%X We present a low-power design for Active Interference

Cancellation (AIC) sculpting of the OFDM spectrum, based

on sparse design concepts. Optimal AIC designs compute

cancellation weights based on contributions from all data subcarriers.

Thus, as the number of subcarriers grows, power

consumption becomes a concern, and suboptimal solutions

that avoid involving all subcarriers are of interest. In this context,

we present novel sparse AIC designs based on a zeronorm

minimization of the matrix defining the cancellation

weights. These designs drastically reduce the number of operations

per symbol, and thus the power consumption, while allowing

to tune the loss with respect the optimal design. They

can be efficiently obtained and significantly outperform usual

thresholding or sparsity-inducing l_1-norm minimization approaches.

%B European Signal Processing Conference (EUSIPCO)
%8 09/2014
%G eng
%U http://www.eurasip.org/Proceedings/Eusipco/Eusipco2014/HTML/papers/1569912103.pdf
%0 Conference Paper
%B IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
%D 2014
%T OFDM spectrum sculpting with active interference cancellation: Keeping spectral spurs at bay
%A Schmidt, J.F.
%A R. López-Valcarce
%K cognitive radio
%K dynacs
%K spectrum shaping
%B IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
%I IEEE
%C Florence, Italy
%P 1-5
%8 05/2014
%G eng
%R 10.1109/ICASSP.2014.6855169
%0 Journal Article
%J IEEE Journal on Emerging and Selected Topics in Circuits and Systems
%D 2013
%T Choose Your Subcarriers Wisely: Active Interference Cancellation for Cognitive OFDM
%A Schmidt, J.F.
%A Costas-Sanz, S.
%A R. López-Valcarce
%K cognitive radio
%K dynacs
%K spectrum shaping
%B IEEE Journal on Emerging and Selected Topics in Circuits and Systems
%V 3
%P 615-625
%8 12/2013
%G eng
%N 4
%& 615
%R 10.1109/JETCAS.2013.2280808
%0 Conference Paper
%B European Signal Processing Conf. (EUSIPCO), Marrakech (Morocco)
%D 2013
%T Low Complexity Primary User Protection for Cognitive OFDM
%A Schmidt, J.F.
%A R. López-Valcarce
%K cognitive radio
%K dynacs
%K spectrum shaping
%B European Signal Processing Conf. (EUSIPCO), Marrakech (Morocco)
%8 09/2013
%G eng
%0 Journal Article
%J Vehicular Technology, IEEE Transactions on
%D 2011
%T Bit Loading Using Imperfect CSIT for Prediction-Based Resource Allocation in Mobile OFDMA
%A Schmidt, J.F.
%A Cousseau, J.E.
%A Wichman, R.
%A Werner, S.
%K bit loading
%K channel state information in the transmitter
%K CSIT
%K frequency division multiple access
%K imperfect channel prediction information
%K mobile OFDMA
%K mobile radio
%K mobile stations
%K OFDM modulation
%K orthogonal frequency division multiple access
%K prediction error
%K prediction-based resource allocation
%K radio transmitters
%K time-varying channels
%K wireless channel
%B Vehicular Technology, IEEE Transactions on
%V 60
%P 4082 -4088
%8 oct.
%G eng
%R 10.1109/TVT.2011.2165305
%0 Journal Article
%J Circuits and Systems I: Regular Papers, IEEE Transactions on
%D 2011
%T Low-Complexity Channel Prediction Using Approximated Recursive DCT
%A Schmidt, J.F.
%A Cousseau, J.E.
%A Wichman, R.
%A Werner, S.
%K autoregressive modeling
%K autoregressive processes
%K basis expansion model
%K channel estimator
%K computational complexity
%K DCT
%K discrete cosine transform
%K discrete cosine transforms
%K Doppler frequencies
%K filter bank
%K Kalman filters
%K low-complexity channel prediction
%K OFDM modulation
%K OFDM systems
%K recursive formulation
%K steady-state Kalman filter
%K sum-of-sinusoids channel predictors
%K time-varying channels
%B Circuits and Systems I: Regular Papers, IEEE Transactions on
%V 58
%P 2520 -2530
%8 oct.
%G eng
%R 10.1109/TCSI.2011.2158139
%0 Conference Paper
%B Information Sciences and Systems (CISS), 2011 45th Annual Conference on
%D 2011
%T Prediction based resource allocation in OFDMA
%A Schmidt, J.F.
%A Cousseau, J.E.
%A Wichman, R.
%A Werner, S.
%K empirical characterization
%K frequency division multiple access
%K low-complexity channel predictor
%K mobile radio
%K mobile stations
%K mobile wireless channels
%K OFDM modulation
%K OFDMA downlink
%K orthogonal frequency division multiple access downlink
%K perfect channel state information
%K prediction error characterization
%K prediction-based RA strategies
%K prediction-based resource allocation algorithm
%K wireless channels
%B Information Sciences and Systems (CISS), 2011 45th Annual Conference on
%P 1 -4
%8 march
%G eng
%R 10.1109/CISS.2011.5766224
%0 Conference Paper
%B Signal Processing Advances in Wireless Communications, 2007. SPAWC 2007. IEEE 8th Workshop on
%D 2007
%T Fast-fading channel estimator using DCT and simplified kalman filter
%A Schmidt, J.F.
%A Cousseau, J.E.
%A Wichman, R.
%A Gregorio, F.H.
%K band-pass filters
%K basis function approximations
%K channel coefficient
%K channel Doppler spectrum
%K channel estimation
%K channel estimator
%K channel variations
%K decoupled parameters
%K discrete cosine transform
%K discrete cosine transforms
%K Doppler effect
%K fading channels
%K fast-fading channel
%K Kalman filter
%K Kalman filters
%K low complexity estimator
%K narrow-band filters
%K passband filters
%K training symbols
%B Signal Processing Advances in Wireless Communications, 2007. SPAWC 2007. IEEE 8th Workshop on
%P 1 -5
%8 june
%G eng
%R 10.1109/SPAWC.2007.4401355