2,342 research outputs found
Contact-Free Multitarget Tracking Using Distributed Massive MIMO-OFDM Communication System:Prototype and Analysis
Wireless-based human activity recognition has become an essential technology that enables contact-free human-machine and human-environment interactions. In this article, we consider contact-free multitarget tracking (MTT) based on available communication systems. A radar-like prototype is built upon a sub-6-GHz distributed massive multiple-input and multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) communication system. Specifically, the raw channel state information (CSI) is calibrated in the frequency and antenna domain before being used for tracking. Then, the targeted CSIs reflected or scattered from the moving pedestrians are extracted. To evade the complex association problem of distributed massive MIMO-based MTT, we propose to use a complex Bayesian compressive sensing (CBCS) algorithm to estimate the targets' locations based on the extracted target-of-interest CSI signal directly. The estimated locations from CBCS are fed to a Gaussian mixture probability hypothesis density (GM-PHD) filter for tracking. A multipedestrian tracking experiment is conducted in a room with a size of 6.5 × 10 m to evaluate the performance of the proposed algorithm. According to the experimental results, we achieve 75th and 95th percentile accuracy of 12.7 and 18.2 cm for single-person tracking and 28.9 and 45.7 cm for multiperson tracking, respectively. Furthermore, the proposed algorithm achieves tracking purposes in real time, which is promising for practical MTT use cases.</p
Directional Antenna Diversity for Mobile Devices: Characterizations and Solutions
We report a first-of-its-kind realization of directional transmission for smartphone-like
mobile devices using multiple passive directional antennas, supported by only one RF
chain. The key is a multi-antenna system (MiDAS) and its antenna selection methods that
judiciously select the right antenna for transmission. It is grounded by two measurementdriven
studies regarding 1) how smartphones rotate during wireless usage in the field and
2) how orientation and rotation impact the performance of directional antennas under
various propagation environments.
We implement MiDAS using the WARP platform, and evaluate it usmg a
computerized motor to rotate the prototype according to traces collected from smartphone
users in the field. Our evaluation shows MiDAS achieves median of 3dB increase in link
gain. Combined with rate adaptation and power control, MiDAS also improves goodput
and power saving. MiDAS does not require any changes to the network infrastructure,
and is therefore suitable for immediate deployment
Wireless sensor systems in indoor situation modeling II (WISM II)
fi=vertaisarvioimaton|en=nonPeerReviewed
Sub-Nyquist Sampling: Bridging Theory and Practice
Sampling theory encompasses all aspects related to the conversion of
continuous-time signals to discrete streams of numbers. The famous
Shannon-Nyquist theorem has become a landmark in the development of digital
signal processing. In modern applications, an increasingly number of functions
is being pushed forward to sophisticated software algorithms, leaving only
those delicate finely-tuned tasks for the circuit level.
In this paper, we review sampling strategies which target reduction of the
ADC rate below Nyquist. Our survey covers classic works from the early 50's of
the previous century through recent publications from the past several years.
The prime focus is bridging theory and practice, that is to pinpoint the
potential of sub-Nyquist strategies to emerge from the math to the hardware. In
that spirit, we integrate contemporary theoretical viewpoints, which study
signal modeling in a union of subspaces, together with a taste of practical
aspects, namely how the avant-garde modalities boil down to concrete signal
processing systems. Our hope is that this presentation style will attract the
interest of both researchers and engineers in the hope of promoting the
sub-Nyquist premise into practical applications, and encouraging further
research into this exciting new frontier.Comment: 48 pages, 18 figures, to appear in IEEE Signal Processing Magazin
Probabilistic Framework for the Positioning Of a Vehicle in a Combined Indoor-Outdoor Scenario
The development in technology has given
us all sophistications but equal amounts of
threats too. This has brought us an urge to
bring a complete security system that
monitors an object continuously. Consider
a situation where a cargo vehicle carrying
valuable material is moving in an area
using GPS (an outdoor sensor) we can
monitor it but the actual problem arises
when its movement involves both indoor
(with in the industry) and outdoor because
GPS has its limitations in indoor
environment. Hence it is essential to have
an additional sensor that would enable us a
continuous monitoring /tracking with out
cutoff of the signal. In this paper we bring
out a solution by combining Ultra wide
band (UWB) with GPS sensory information
which eliminates the limitations of
conventional tracking methods in mixed
scenario(indoor and outdoor) The same
method finds application in mobile robots,
monitoring a person on grounds of
security, etc
Innovative Wireless Localization Techniques and Applications
Innovative methodologies for the wireless localization of users and related applications
are addressed in this thesis.
In last years, the widespread diffusion of pervasive wireless communication
(e.g., Wi-Fi) and global localization services (e.g., GPS) has boosted the interest
and the research on location information and services. Location-aware
applications are becoming fundamental to a growing number of consumers (e.g.,
navigation, advertising, seamless user interaction with smart places), private and
public institutions in the fields of energy efficiency, security, safety,
fleet management, emergency response. In this context, the position of the user - where
is often more valuable for deploying services of interest than the identity of the
user itself - who.
In detail, opportunistic approaches based on the analysis of electromagnetic
field indicators (i.e., received signal strength and channel state information) for
the presence detection, the localization, the tracking and the posture recognition
of cooperative and non-cooperative (device-free) users in indoor environments are
proposed and validated in real world test sites. The methodologies are designed
to exploit existing wireless infrastructures and commodity devices without any
hardware modification.
In outdoor environments, global positioning technologies are already available
in commodity devices and vehicles, the research and knowledge transfer
activities are actually focused on the design and validation of algorithms and
systems devoted to support decision makers and operators for increasing efficiency,
operations security, and management of large fleets as well as localized
sensed information in order to gain situation awareness. In this field, a decision
support system for emergency response and Civil Defense assets management
(i.e., personnel and vehicles equipped with TETRA mobile radio) is described in
terms of architecture and results of two-years of experimental validation
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