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Nonlinear 1-Bit Precoding for Massive MU-MIMO with Higher-Order Modulation
(2016)2016 50th Asilomar Conference on Signals, Systems and ComputersMassive multi-user (MU) multiple-input multiple-output (MIMO) is widely believed to be a core technology for the upcoming fifth-generation (5G) wireless communication standards. The use of low-precision digital-to-analog converters (DACs) in MU-MIMO base stations is of interest because it reduces the power consumption, system costs, and raw baseband data rates. In this paper, we develop novel algorithms for downlink precoding in massive ...Conference Paper -
Time-varying Learning and Content Analytics via Sparse Factor Analysis
(2014)Proceedings of the 20th ACM SIGKDD international conference on Knowledge discovery and data miningWe propose SPARFA-Trace, a new machine learning-based framework for time-varying learning and content analytics for educational applications. We develop a novel message passing-based, blind, approximate Kalman filter for sparse factor analysis (SPARFA) that jointly traces learner concept knowledge over time, analyzes learner concept knowledge state transitions (induced by interacting with learning resources, such as textbook sections, ...Conference Paper -
Recovery Guarantees for Restoration and Separation of Approximately Sparse Signals
(2011)2011 49th Annual Allerton Conference on Communication, Control, and Computing (Allerton)In this paper, we present performance guarantees for the recovery and separation of signals that are approximately sparse in some general (i.e., basis, frame, over-complete, or incomplete) dictionary but corrupted by a combination of measurement noise and interference that is sparse in a second general dictionary. Applications covered by this framework include the restoration of signals impaired by impulse noise, narrowband interference, ...Conference Paper -
One-Bit Massive MIMO: Channel Estimation and High-Order Modulations
(2015)2015 IEEE International Conference on Communication Workshop (ICCW)We investigate the information-theoretic throughout achievable on a fading communication link when the receiver is equipped with one-bit analog-to-digital converters (ADCs). The analysis is conducted for the setting where neither the transmitter nor the receiver have a priori information on the realization of the fading channels. This means that channel-state information needs to be acquired at the receiver on the basis of the one-bit ...Conference Paper -
HSPA+/LTE-A Turbo Decoder on GPU and Multicore CPU
(2013)2013 Asilomar Conference on Signals, Systems and ComputersThis paper compares two implementations of reconfigurable and high-throughput turbo decoders. The first implementation is optimized for an NVIDIA Kepler graphics processing unit (GPU), whereas the second implementation is for an Intel Ivy Bridge processor. Both implementations support max-log-MAP and log-MAP turbo decoding algorithms, various code rates, different interleaver types, and all block-lengths, as specified by HSPA; and ...Conference Paper -
Iterative detection and decoding in 3GPP LTE-based massive MIMO systems
(2014)2014 22nd European Signal Processing Conference (EUSIPCO)Massive multiple-input multiple-output (MIMO) is expected to be a key technology in next-generation multi-user cellular systems for achieving higher throughput and better link reliability than existing (small-scale) MIMO systems. In this work, we develop a novel, low-complexity iterative detection and decoding algorithm for single carrier frequency division multiple access (SC-FDMA)-based massive MIMO systems, such as future 3GPP LTE-based ...Conference Paper -
Accelerating Massive MIMO Uplink Detection on GPU for SDR Systems
(2015)2015 IEEE Dallas Circuits and Systems Conference (DCAS)We present a reconfigurable GPU-based uplink detector for massive MIMO software-defined radio (SDR) systems. To enable high throughput, we implement a configurable linear minimum mean square error (MMSE) soft-output detector and reduce the complexity without sacrificing its error-rate performance. To take full advantage of the GPU computing resources, we exploit the algorithm's inherent parallelism and make use of efficient CUDA libraries ...Conference Paper -
Conjugate Gradient-based Soft-Output Detection and Precoding in Massive MIMO Systems
(2014)2014 IEEE Global Communications ConferenceMassive multiple-input multiple-output (MIMO) promises improved spectral efficiency, coverage, and range, compared to conventional (small-scale) MIMO wireless systems. Unfortunately, these benefits come at the cost of significantly increased computational complexity, especially for systems with realistic antenna configurations. To reduce the complexity of data detection (in the uplink) and precoding (in the downlink) in massive MIMO ...Conference Paper -
Tag-aware ordinal sparse factor analysis for learning and content analytics
(2013)Proceedings of the 6th International Conference on Educational Data Mining (EDM 2013)Conference Paper -
An Estimation and Analysis Framework for the Rasch Model
(2018)Proceedings of the 35th International Conference on Machine LearningThe Rasch model is widely used for item response analysis in applications ranging from recommender systems to psychology, education, and finance. While a number of estimators have been proposed for the Rasch model over the last decades, the associated analytical performance guarantees are mostly asymptotic. This paper provides a framework that relies on a novel linear minimum mean-squared error (L-MMSE) estimator which enables an exact, ...Conference Paper