193 research outputs found
Beam Squint Assisted User Localization in Near-Field Integrated Sensing and Communications Systems
Integrated sensing and communication (ISAC) has been regarded as a key
technology for 6G wireless communications, in which large-scale multiple input
and multiple output (MIMO) array with higher and wider frequency bands will be
adopted. However, recent studies show that the beam squint phenomenon can not
be ignored in wideband MIMO system, which generally deteriorates the
communications performance. In this paper, we find that with the aid of
true-time-delay lines (TTDs), the range and trajectory of the beam squint in
near-field communications systems can be freely controlled, and hence it is
possible to reversely utilize the beam squint for user localization. We derive
the trajectory equation for near-field beam squint points and design a way to
control such trajectory. With the proposed design, beamforming from different
subcarriers would purposely point to different angles and different distances,
such that users from different positions would receive the maximum power at
different subcarriers. Hence, one can simply localize multiple users from the
beam squint effect in frequency domain, and thus reduce the beam sweeping
overhead as compared to the conventional time domain beam search based
approach. Furthermore, we utilize the phase difference of the maximum power
subcarriers received by the user at different frequencies in several times beam
sweeping to obtain a more accurate distance estimation result, ultimately
realizing high accuracy and low beam sweeping overhead user localization.
Simulation results demonstrate the effectiveness of the proposed schemes.Comment: This paper has been accepted by IEEE Transactions on Wireless
Communications (TWC) on 18 September 202
Embodied Scene-aware Human Pose Estimation
We propose embodied scene-aware human pose estimation where we estimate 3D
poses based on a simulated agent's proprioception and scene awareness, along
with external third-person observations. Unlike prior methods that often resort
to multistage optimization, non-causal inference, and complex contact modeling
to estimate human pose and human scene interactions, our method is one stage,
causal, and recovers global 3D human poses in a simulated environment. Since 2D
third-person observations are coupled with the camera pose, we propose to
disentangle the camera pose and use a multi-step projection gradient defined in
the global coordinate frame as the movement cue for our embodied agent.
Leveraging a physics simulation and prescanned scenes (e.g., 3D mesh), we
simulate our agent in everyday environments (libraries, offices, bedrooms,
etc.) and equip our agent with environmental sensors to intelligently navigate
and interact with scene geometries. Our method also relies only on 2D keypoints
and can be trained on synthetic datasets derived from popular human motion
databases. To evaluate, we use the popular H36M and PROX datasets and, for the
first time, achieve a success rate of 96.7% on the challenging PROX dataset
without ever using PROX motion sequences for training.Comment: Project website: https://embodiedscene.github.io/embodiedpose/
Zhengyi Luo and Shun Iwase contributed equall
A delta-doped quantum well system with additional modulation doping
A delta-doped quantum well with additional modulation doping may have potential applications. Utilizing such a hybrid system, it is possible to experimentally realize an extremely high two-dimensional electron gas (2DEG) density without suffering inter-electronic-subband scattering. In this article, the authors report on transport measurements on a delta-doped quantum well system with extra modulation doping. We have observed a 0-10 direct insulator-quantum Hall (I-QH) transition where the numbers 0 and 10 correspond to the insulator and Landau level filling factor ν = 10 QH state, respectively. In situ titled-magnetic field measurements reveal that the observed direct I-QH transition depends on the magnetic component perpendicular to the quantum well, and the electron system within this structure is 2D in nature. Furthermore, transport measurements on the 2DEG of this study show that carrier density, resistance and mobility are approximately temperature (T)-independent over a wide range of T. Such results could be an advantage for applications in T-insensitive devices
Corrigendum to: The TianQin project: current progress on science and technology
In the originally published version, this manuscript included an error related to indicating the corresponding author within the author list. This has now been corrected online to reflect the fact that author Jun Luo is the corresponding author of the article
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