TY - JOUR T1 - FER Estimation in a Memoryless BSC with Variable Frame Length and Unreliable ACK/NAK Feedback JF - IEEE Transactions on Wireless Communications Y1 - 2017 A1 - Alberto Rico-Alvariño A1 - R. López-Valcarce A1 - Carlos Mosquera A1 - Robert W. Heath Jr. KW - adaptive signal processing KW - compass KW - Cramér-Rao bound (CRB) KW - frame error rate KW - myrada KW - winter AB -
We consider the problem of estimating the frame error rate (FER) of a given memoryless binary symmetric channel by observing the success or failure of transmitted packets. Whereas FER estimation is relatively straightforward if all observations correspond to packets with equal length, the problem becomes considerably more complex when this is not the case. We develop FER estimators when
transmissions of different lengths are observed, together with the Cramer-Rao Lower Bound (CRLB). Although the main focus is on Maximum Likelihood (ML) estimation, we also obtain low complexity schemes performing close to optimal in some scenarios. In a second stage, we consider the case in which FER estimation is performed at a node different from the receiver, and incorporate the impairment of unreliable observations by considering noisy ACK/NAK feedback links. The impact of unreliable feedback is analyzed by means of the corresponding CRLB. In this setting, the ML estimator is obtained by applying the Expectation-Maximization algorithm to jointly estimate the error probabilities of the data and feedback links. Simulation results illustrate the benefits of the proposed estimators.
VL - 16 IS - 6 ER - TY - CONF T1 - Time-domain channel estimation for wideband millimeter wave systems with hybrid architecture T2 - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) Y1 - 2017 A1 - Kiran Venugopal A1 - Ahmed Alkhateeb A1 - Robert W. Heath Jr. A1 - Nuria González-Prelcic KW - compass KW - mmWave KW - myrada AB -

Millimeter wave (mm Wave) systems will likely employ large antennas at both the transmitter and receiver for directional beamforming. Hybrid analog/digital MIMO architectures have been proposed previously for leveraging both array gain and multiplexing gain, while reducing the power consumption in analog-to-digital converters. Channel knowledge is needed to design the hybrid precoders/combiners, which is difficult to obtain due to the large antenna arrays and the frequency selective nature of the channel. In this paper, we propose a sparse recovery based time-domain channel estimation technique for hybrid architecture based frequency selective mmWave systems. The proposed compressed sensing channel estimation algorithm is shown to provide good estimation error performance, while requiring small training overhead. The simulation results show that using multiple RF chains at the receiver and the transmitter further reduces the training overhead.

JF - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) ER - TY - CONF T1 - Frequency selective multiuser hybrid precoding for mmWave systems with imperfect channel knowledge T2 - Asilomar Conf. on Signals, Systems and Computers Y1 - 2016 A1 - Jose P. Gonzalez-Coma A1 - Nuria González-Prelcic A1 - Luis Castedo A1 - Robert W. Heath Jr. KW - compass KW - mmWave JF - Asilomar Conf. on Signals, Systems and Computers ER - TY - JOUR T1 - Low complexity hybrid precoding strategies for millimeter wave communication systems JF - IEEE Trans. Wireless Communications Y1 - 2016 A1 - Cristian Rusu A1 - Roi Méndez-Rial A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - compass KW - mmWave AB -

Millimeter communication systems use large antenna arrays to provide good average received power and to take advantage of multi-stream MIMO communication. Unfortunately, due to power consumption in the analog front-end, it is impractical to perform beamforming and fully digital precoding at baseband. Hybrid precoding/combining architectures have been proposed to overcome this limitation. The hybrid structure splits the MIMO processing between the digital and analog domains, while keeping the performance close to that of the fully digital solution. In this paper, we introduce and analyze several algorithms that efficiently design hybrid precoders and combiners starting from the known optimum digital precoder/combiner, which can be computed when perfect channel state information is available. We propose several low complexity solutions which provide different trade-offs between performance and complexity. We show that the proposed iterative solutions perform better in terms of spectral efficiency and/or are faster than previous methods in the literature. All of them provide designs which perform close to the known optimal digital solution. Finally, we study the effects of quantizing the analog component of the hybrid design and show that even with coarse quantization, the average rate performance is good.

VL - 15 IS - 12 ER - TY - JOUR T1 - An overview of signal processing techniques for millimeter wave MIMO systems JF - IEEE J. Selected Topics in Signal Processing. Special issue on Signal Processing for Millimeter Wave Wireless Communications Y1 - 2016 A1 - Robert W. Heath Jr. A1 - Nuria González-Prelcic A1 - Sundeep Rangan A1 - Wonil Roh A1 - Akbar M. Sayeed KW - compass KW - mmWave AB -

Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

VL - 10 IS - 3 ER - TY - JOUR T1 - Properties of real and complex ETFs and their application to the design of low coherence frames JF - Linear Algebra and its Applications Y1 - 2016 A1 - Cristian Rusu A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. VL - 508 UR - http://www.sciencedirect.com/science/article/pii/S0024379516302555 ER - TY - JOUR T1 - Robust analog precoding designs for millimeter wave MIMO transceivers with frequency and time division duplexing JF - IEEE Trans. Communications Y1 - 2016 A1 - Pengfei Xia A1 - Robert W. Heath Jr. A1 - Nuria González-Prelcic KW - compass KW - mmWave AB -

Millimeter wave (mmWave) communication provides high data rates thanks to large arrays at the transmitter and receiver, coupled with large bandwidth channels. Exploiting the arrays is challenging due to the need to configure precoding at the transmitter based on the large frequency selective channel. In this paper, we exploit the power iteration principle and propose a robust analog precoding training algorithm that can be applied in both frequency division duplex transmission systems and time division duplex transmission systems with or without RF calibration. We further analyze the convergence of the proposed algorithm and show how it converges to the singular value decomposition optimality exponentially. We propose null space projection on top of the power iteration to form multiple orthogonal beams at the transmitter and receiver. Strongest tap selection with proper energy pruning is used to collect as much precoding gain as possible from a frequency selective fading channel. The exponential effective SINR mapping performance is evaluated and demonstrates that the overall approach works smoothly. Numerical simulation results demonstrate algorithm robustness and the algorithm works not only for the simplified mmWave directional channels, but also for more general rich scattering channels.

VL - 64 IS - 11 ER - TY - CONF T1 - An attack on antenna subset modulation for millimeter-wave communication T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) Y1 - 2015 A1 - Cristian Rusu A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - adversarial signal processing KW - compass KW - mmWave AB -

Antenna subset modulation (ASM) is a physical layer security technique that is well suited for millimeter wave communication systems. The key idea is to vary the radiation pattern at the symbol rate by selecting one from a subset of patterns with a similar main lobe and different side lobes. This paper shows that ASM is not robust to an eavesdropper that makes multiple simultaneous measurements at multiple angles. The measurements are combined and used to formulate an estimation problem to undo the effects of the side lobe randomization. Simulations show the performance of the estimation algorithms and how the eavesdropper can effectively recover the information if the signal-to-noise ratio exceeds a certain threshold. Using fewer active radio frequency chains makes it harder for the attacker to recover the transmit symbol, at the expense of more grating lobes.

JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) PB - IEEE CY - Brisbane, Australia ER - TY - CONF T1 - Augmented covariance estimation with a cyclic approach in DOA T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) Y1 - 2015 A1 - Roi Méndez-Rial A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - DOA estimation KW - Non-uniformly spaced arrays AB -

High resolution direction-of-arrival (DOA) estimation is an important problem in many array signal processing applications. This paper proposes an augmented covariance estimator for DOA estimation. The new method exploits the periodicity of the covariance lags when the DOAs are assumed on a discrete grid with a certain resolution. Then, it achieves twice the resolution of typical methods such as the direct augmentable approach or forward backward spatial smoothing. When the sources are not on the discrete grid, an interpolated array manifold technique is proposed to mitigate the grid mismatch error.

JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) PB - IEEE CY - Brisbane, Australia ER - TY - CONF T1 - Dictionary-free Hybrid Precoders and Combiners for mmWave MIMO Systems T2 - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC) Y1 - 2015 A1 - Roi Méndez-Rial A1 - Cristian Rusu A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - compass KW - mmWave JF - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC) PB - IEEE CY - Stockholm, Sweden ER - TY - CONF T1 - Low Complexity Hybrid Sparse Precoding and Combining in Millimeter Wave MIMO Systems T2 - IEEE Int. Conference on Communications (ICC) Y1 - 2015 A1 - Cristian Rusu A1 - Roi Méndez-Rial A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - compass KW - mmWave JF - IEEE Int. Conference on Communications (ICC) PB - IEEE CY - London, UK ER - TY - CONF T1 - Channel estimation in millimeter wave MIMO systems with one-bit quantization T2 - Asilomar Conf. on Signals, Systems and Computers Y1 - 2014 A1 - Jianhua Mo A1 - Phil Schniter A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - adaptive signal processing KW - compass KW - mmWave JF - Asilomar Conf. on Signals, Systems and Computers ER - TY - CONF T1 - FER prediction with variable codeword length T2 - ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM) Y1 - 2014 A1 - Alberto Rico-Alvariño A1 - Robert W. Heath Jr. A1 - Carlos Mosquera KW - adaptive signal processing KW - compass KW - dynacs KW - Effective SNR KW - FER prediction KW - PHY abstraction AB -

Frame error rate (FER) prediction in wireless communication systems is an important tool with applications to system level simulations and link adaptation, among others. Although in realistic communication scenarios it is expected to have codewords of different lengths, previous work on FER prediction marginally treated the dependency of the FER on the codeword length. In this paper, we present a method to estimate the FER using codewords of different length. We derive a low complexity FER estimator for frames of different length transmitted over a binary symmetric channel of unknown error probability. We extend this technique to coded systems by the use of effective SNR FER predictors. The proposed estimation scheme is shown to outperform other simpler estimation methods.

JF - ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM) CY - Florence, Italy ER - TY - JOUR T1 - Learning-Based Adaptive Transmission for Limited Feedback Multiuser MIMO-OFDM JF - IEEE Transactions on Wireless Communications Y1 - 2014 A1 - Alberto Rico-Alvariño A1 - Robert W. Heath Jr. KW - adaptive signal processing KW - dynacs ER - TY - JOUR T1 - MIMO precoding and combining solutions for millimeter wave systems JF - IEEE Communications Magazine Y1 - 2014 A1 - Ahmed Alkhateeb A1 - Jianhua Mo A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. KW - adaptive signal processing KW - compass KW - mmWave AB -

Millimeter-wave communication is one way to alleviate the spectrum gridlock at lower frequencies while simultaneously providing high-bandwidth communication channels. MmWave makes use of MIMO through large antenna arrays at both the base station and the mobile station to provide sufficient received signal power. This article explains how beamforming and precoding are different in MIMO mmWave systems than in their lower-frequency counterparts, due to different hardware constraints and channel characteristics. Two potential architectures are reviewed: hybrid analog/digital precoding/combining and combining with low-resolution analog- to-digital converters. The potential gains and design challenges for these strategies are discussed, and future research directions are highlighted.

VL - 52 IS - 12 ER - TY - CONF T1 - Learning Based Link Adaptation in Multiuser MIMO-OFDM T2 - 21st European Signal Processing Conference 2013 (EUSIPCO 2013) Y1 - 2013 A1 - Alberto Rico-Alvariño A1 - Robert W. Heath Jr. KW - dynacs KW - link adaptation KW - Machine Learning KW - Multiuser MIMO-OFDM AB -

Link adaptation in multiple user multiple-input multiple-output orthogonal frequency division multiplexing communication systems is challenging because of the coupling between user selection, mode selection, precoding, and equalization. In this paper, we present a methodology to perform link adaptation under this multiuser setting, focusing on the capabilities of IEEE 802.11ac. We propose to use a machine learning classifier to solve the problem of selecting a proper modulation and coding scheme, combined with a greedy algorithm that performs user and spatial mode selection. We observe that our solution offers good performance in the case of perfect channel state information or high feedback rate, while those scenarios with less feedback suffer some degradation due to inter-user interference.

JF - 21st European Signal Processing Conference 2013 (EUSIPCO 2013) CY - Marrakech, Morocco ER - TY - CONF T1 - Link Adaptation in MIMO-OFDM with Practical Impairments T2 - Asilomar Conference on Signals Systems and Computers Y1 - 2013 A1 - Alberto Rico-Alvariño A1 - Robert W. Heath Jr. KW - dynacs KW - link adaptation KW - MIMO-OFDM JF - Asilomar Conference on Signals Systems and Computers ER -