About

I am an Assistant Professor at UCLA working on wireless communication and sensing. My research focuses on upgrading next-generation wireless systems, like 5G and future 6G cellular systems, with full-duplex capability, which allows simultaneous transmission and reception over the same frequency spectrum. I combine theory and experimentation to develop and validate my research, aiming to impact real-world wireless systems.

Research topics

• Computer science
• Electronic engineering
• Telecommunications
• Computer network
• Remote sensing

Selected publications

• Site-Specific Beamforming for Full-Duplex Massive MIMO Systems via Implicit Channel Estimation

  arXiv (Cornell University) · 2026-05-20

  preprintOpen accessSenior author

  Beamforming has proven to be valuable in enabling full-duplex massive MIMO base stations, but doing so effectively often requires knowledge of the self-interference channel matrix H. Estimating this high-dimensional channel is costly in practice, however, since it requires a prohibitive number of measurements, especially in fast-fading conditions. In this work, we overcome this dilemma by designing full-duplex beams using implicit channel knowledge gathered from a relatively small number of measurements across H. These measurements are collected by the base station using a sequence of beams tailored to both the deployment environment and the particular users being served. This is accomplished through site-specific training of a transformer-based deep learning model that learns to efficiently probe portions of H most relevant to the particular users being served by exploiting the underlying structure of the surrounding environment. The deep learning model then uses these probing measurements to design transmit and receive beams that couple low self-interference while delivering high gain to a pair of downlink and uplink users. For favorable multi-user scaling, a single set of probing measurements can be used by the model to serve several users throughout the coherence time of H by leveraging correlations across those users' channels. Simulation results using ray-tracing demonstrate that our proposed approach exceeds the best possible performance with explicit channel estimation across a wide range of scenarios, especially with large antenna arrays.

  PublisherDOI

• Beyond Beam Sweeping: One-Shot Satellite Acquisition With Doppler-Aware Rainbow Beamforming

  IEEE Transactions on Vehicular Technology · 2026-01-01

  articleOpen access

  High-gain beamforming (BF) is essential for low Earth orbit (LEO) satellite communications to overcome severe path loss, but this requires acquiring precise satellite positions. Conventional satellite acquisition typically relies on time-domain beam sweeping, which incurs substantial overhead and latency. In this correspondence, we propose an efficient one-shot satellite acquisition framework that capitalizes on two phenomena traditionally regarded as impairments: i) Doppler effects and ii) beam-squint effects. Specifically, we derive a closed-form <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rainbow beamformer</i> that leverages beam-squint effects to align frequency-dependent beam directions with satellite positions inferred from their Doppler shifts. This approach enables reception from multiple satellites at once without requiring beam sweeping. To extract satellite position information, we develop three Doppler-aware angle estimation algorithms based on received signals. Simulation results demonstrate that the proposed method significantly outperforms conventional beam sweeping approaches in both acquisition accuracy and required time slots. These gains stem from the ability of the proposed rainbow BF to exploit the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">angle-dependent nature of Doppler shifts</i>, enabling full angular-domain coverage with a single pilot transmission and reception.

  PublisherDOI

• Space-Time Beamforming for LEO Satellite Communications: Enabling Extremely Narrow Beams

  IEEE Transactions on Wireless Communications · 2026-01-01

  article

  Inter-beam interference is a core challenge in low Earth orbit (LEO) satellite communications, driven by dense constellations, aggressive frequency reuse, and overlapping beam footprints. To address this, we propose space–time beamforming, a novel approach that jointly exploits spatial and temporal channel characteristics—specifically the angle of arrival (AoA) and relative Doppler shift—to optimize transmission between moving satellites and ground users. By synthesizing a virtual array-of-subarrays across repeated transmissions, this method effectively expands the aperture and forms ultra-narrow beams, sharply suppressing interference leakage to neighboring users. We develop two strategies within this framework: space-time zero-forcing (ST-ZF) and space-time signal-to-leakage-plus-noise ratio (ST-SLNR) beamforming. In partially connected networks, ST-ZF provides a 3 dB SNR gain over conventional maximum ratio transmission (MRT). In more general interference scenarios, ST-SLNR delivers significant improvements in sum spectral efficiency. While temporal repetition introduces a rate trade-off, it also enables finer spatial discrimination through Doppler-induced temporal signatures. Our analysis and simulations demonstrate that space-time beamforming offers a powerful and adaptable solution for interference mitigation in next-generation LEO satellite systems, unlocking better spectral efficiency and more reliable connectivity in densely served orbital environments.

  PublisherDOI

• Can TDD Be Employed in LEO SatCom Systems? Challenges and Potential Approaches

  IEEE Communications Magazine · 2026-01-01

  article

  Frequency-division duplexing (FDD) remains the de facto standard in modern low Earth orbit (LEO) satellite communication (SatCom) systems, such as SpaceX's Starlink, OneWeb, and Amazon's Project Kuiper. While time-division duplexing (TDD) is often regarded as superior in today's terrestrial networks, its viability in future LEO SatCom systems remains unclear. This article details how the long propagation delays and high orbital velocities exhibited by LEO SatCom systems impedes the adoption of TDD, largely due to challenges involving the frame structure and synchronization. We then present potential approaches to overcome these challenges, which vary in terms of spectral efficiency and operational/ device complexity and thus may likely be application- specific. We conclude by assessing the performance of these proposed approaches, putting into perspective the tradeoff between complexity and performance gains over FDD. Overall, this article aims to motivate future investigation into the prospects of TDD in LEO SatCom systems and solutions to enable such, with the goal of enhancing future systems and unifying them with terrestrial networks.

  PublisherDOI

• Satellite Selection for In-Band Coexistence of Dense LEO Networks

  IEEE Transactions on Wireless Communications · 2026-01-01 · 1 citations

  article

  We study spectrum sharing between two dense low-earth orbit (LEO) satellite constellations, an incumbent primary system and a secondary system that must respect interference protection constraints on the primary system. In particular, we propose a secondary satellite selection framework and algorithm that maximizes capacity while guaranteeing that the time-average interference and absolute interference inflicted upon each primary ground user never exceeds specified thresholds. We solve this NP-hard constrained, combinatorial satellite selection problem through Lagrangian relaxation to decompose it into simpler problems which can then be solved through subgradient methods. A high-fidelity simulation is developed based on public FCC filings and technical specifications of the Starlink and Kuiper systems. We use this case study to illustrate the effectiveness of our approach and that explicit protection is indeed necessary for healthy coexistence. We further demonstrate that deep learning models can be used to predict the primary satellite system associations, which helps the secondary system avoid inflicting excessive interference and maximize its own capacity.

  PublisherDOI

• Phase-Sensitive Dynamic Filters: A Conceptual Model for Energy-Preserving, Instantaneously Tunable, Symbol-Level Signal Processing Using Complex IIR Filters

  IEEE Access · 2026-01-01

  articleOpen access

  Filters used for modulated RF signals are often matched bandpass filters that have larger bandwidths than that of the modulation. Therefore, the time constants of the filters must be shorter than the symbol periods. This paper presents an idealized theoretical model for Phase-Sensitive Dynamic Filters (PSDF), a class of emerging filters that can be tuned in real time, as fast as the symbol rate of a signal but with time constants longer than the symbol periods. With the foreknowledge of the frequency and phase shifts of a given signal, such filters are capable of filtering across multiple symbols of a constant envelope and compressing the noise bandwidth to a fraction of the modulated signal bandwidth. The transient response of the filters can be longer than the symbol rate of the signal. This can mathematically be modeled by infinite impulse response (IIR) filters with long time constants yet fast time-varying complex coefficients in the feedback path. Phase-sensitive dynamic filters preserve energy across symbols and also exhibit phase-sensitivity. The proposed models indicate that PSDFs can be employed in applications such as rejection of self-interference in the front ends of full-duplex communications systems. Such systems pave the way for the possibility of higher isolation and robustness compared to other prototypical approaches in dynamically changing systems.

  PublisherDOI

• Site-Specific Beamforming for Full-Duplex Massive MIMO Systems via Implicit Channel Estimation

  ArXiv.org · 2026-05-20

  articleOpen accessSenior author

  Beamforming has proven to be valuable in enabling full-duplex massive MIMO base stations, but doing so effectively often requires knowledge of the self-interference channel matrix H. Estimating this high-dimensional channel is costly in practice, however, since it requires a prohibitive number of measurements, especially in fast-fading conditions. In this work, we overcome this dilemma by designing full-duplex beams using implicit channel knowledge gathered from a relatively small number of measurements across H. These measurements are collected by the base station using a sequence of beams tailored to both the deployment environment and the particular users being served. This is accomplished through site-specific training of a transformer-based deep learning model that learns to efficiently probe portions of H most relevant to the particular users being served by exploiting the underlying structure of the surrounding environment. The deep learning model then uses these probing measurements to design transmit and receive beams that couple low self-interference while delivering high gain to a pair of downlink and uplink users. For favorable multi-user scaling, a single set of probing measurements can be used by the model to serve several users throughout the coherence time of H by leveraging correlations across those users' channels. Simulation results using ray-tracing demonstrate that our proposed approach exceeds the best possible performance with explicit channel estimation across a wide range of scenarios, especially with large antenna arrays.

  PublisherOA PDF

• Nonlinear Self-Interference Cancellation With Adaptive Orthonormal Polynomials for Full-Duplex Wireless Systems

  IEEE Transactions on Wireless Communications · 2025-03-17 · 5 citations

  article

  Nonlinear self-interference cancellation (SIC) techniques are essential for enabling full-duplex communication systems, which can offer spectral efficiencies twice that of traditional half-duplex systems. The challenge of nonlinear SIC is similar to the classic problem of system identification in adaptive filter theory, whose crux lies in constructing the optimal nonlinear basis functions of a nonlinear system. This becomes especially difficult when the system input has a non-stationary distribution, as is the case in practical wireless systems. In this paper, we propose a novel algorithm for nonlinear digital SIC that adaptively constructs orthonormal polynomial basis functions according to the non-stationary moments of the transmit signal. By combining these basis functions with the least mean squares (LMS) algorithm, we introduce a new SIC technique, called the adaptive orthonormal polynomial LMS (AOP-LMS) algorithm. To reduce computational complexity for practical systems, we augment our approach with a precomputed look-up table, which maps a given modulation and coding scheme to its corresponding basis functions. Numerical simulation indicates that our proposed method surpasses existing state-of-the-art SIC algorithms in terms of convergence speed and mean squared error when the transmit signal is non-stationary, such as with adaptive modulation and coding. Experimental evaluation with a wireless testbed further confirms that our proposed approach outperforms existing digital SIC algorithms in practical systems.

  PublisherDOI

• Analog Beamforming Codebooks for Wideband Full-Duplex Millimeter-Wave Systems

  2025-06-08

  articleSenior author

  In full-duplex millimeter-wave (mmWave) systems, the effects of beam squint and the frequency-selectivity of self-interference exacerbate over wide bandwidths. This complicates the use of beamforming to cancel self-interference when communicating over bandwidths on the order of gigahertz. In this work, we present the first analog beamforming codebooks tailored to wideband full-duplex mmWave systems, designed to both combat beam squint and cancel frequency-selective self-interference. Our proposed design constructs such codebooks by minimizing self-interference across the entire band of interest while constraining the coverage provided by these codebooks across that same band. Simulation results using computational electromagnetics to model self-interference suggest that a full-duplex 60 GHz system with our design enjoys lower self-interference and delivers better coverage across bandwidths as wide as 6 GHz, when compared to similar codebook designs that ignore beam squint and/or frequency-selectivity. This allows our design to sustain higher SINRs and spectral efficiencies across wide bandwidths, unlocking the potentials of wideband full-duplex mmWave systems.

  PublisherDOI

• A Survey on Advancements in THz Technology for 6G: Systems, Circuits, Antennas, and Experiments

  IEEE Open Journal of the Communications Society · 2025-01-01 · 56 citations

  articleOpen accessSenior author

  Terahertz (THz) carrier frequencies (100 GHz to 10 THz) have been touted as a source for unprecedented wireless connectivity and high-precision sensing, courtesy of their wide bandwidth availability and small wavelengths. However, noteworthy implementation challenges persist, ranging from limitations in semiconductor device technologies to antenna design and packaging, as well as system-level issues such as high path loss, complex beam management, and regulatory constraints. In this paper, we survey recent advancements on 6G networks using THz frequencies, with a particular emphasis on the 200–400 GHz frequency range and the IEEE 802.15.3d standard. This band offers a compelling balance by providing ample bandwidth for high data-rate communications, while also exhibiting lower atmospheric absorption for longer-range transmission, and can be viably realized using current semiconductor technologies. Unlike other existing surveys in this domain, we provide a comprehensive and holistic overview of THz systems, circuits, device technology, and antennas while also highlighting recent experimental demonstrations of 6G networks using THz frequencies. Throughout this paper, we review the state-of-the-art in 6G network implementation using THz, and call attention to open problems, future prospects, and areas of further improvement in THz communication technologies to fully realize their potential in next-generation wireless connectivity.

  PublisherDOI

Frequent coauthors

• Jeffrey G. Andrews

  The University of Texas at Austin

  31 shared

• Sriram Vishwanath

  The University of Texas at Austin

  28 shared

• Hardik Jain

  15 shared

• Thomas Novlan

  AT&T (United States)

  9 shared

• Eunsun Kim

  The University of Texas at Austin

  8 shared

• Aditya Chopra

  Amazon (United States)

  7 shared

• Tawfik Osman

  Arizona State University

  3 shared

• Ahmed Alkhateeb

  3 shared

Labs

• Wireless LabPI

  The Wireless Lab conducts research on wireless communication and sensing in the Department of Electrical and Computer Engineering at UCLA.

Education

• B.S., Electrical Engineering

  Missouri University of Science and Technology

  2018

• M.S., Electrical and Computer Engineering

  University of Texas at Austin

  2020

• Ph.D., Electrical and Computer Engineering

  University of Texas at Austin

  2023

Awards & honors

• 2023 Andrea Goldsmith Young Scholars Award