2,558 research outputs found
Massive MIMO-based Localization and Mapping Exploiting Phase Information of Multipath Components
In this paper, we present a robust multipath-based localization and mapping
framework that exploits the phases of specular multipath components (MPCs)
using a massive multiple-input multiple-output (MIMO) array at the base
station. Utilizing the phase information related to the propagation distances
of the MPCs enables the possibility of localization with extraordinary accuracy
even with limited bandwidth. The specular MPC parameters along with the
parameters of the noise and the dense multipath component (DMC) are tracked
using an extended Kalman filter (EKF), which enables to preserve the
distance-related phase changes of the MPC complex amplitudes. The DMC comprises
all non-resolvable MPCs, which occur due to finite measurement aperture. The
estimation of the DMC parameters enhances the estimation quality of the
specular MPCs and therefore also the quality of localization and mapping. The
estimated MPC propagation distances are subsequently used as input to a
distance-based localization and mapping algorithm. This algorithm does not need
prior knowledge about the surrounding environment and base station position.
The performance is demonstrated with real radio-channel measurements using an
antenna array with 128 ports at the base station side and a standard cellular
signal bandwidth of 40 MHz. The results show that high accuracy localization is
possible even with such a low bandwidth.Comment: 14 pages (two columns), 13 figures. This work has been submitted to
the IEEE Transaction on Wireless Communications for possible publication.
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Terminal Orientation in OFDM-based LiFi Systems
Light-fidelity (LiFi) is a wireless communication technology that employs
both infrared and visible light spectra to support multiuser access and user
mobility. Considering the small wavelength of light, the optical channel is
affected by the random orientation of a user equipment (UE). In this paper, a
random process model for changes in the UE orientation is proposed based on
data measurements. We show that the coherence time of the random orientation is
in the order of hundreds of milliseconds. Therefore, an indoor optical wireless
channel can be treated as a slowly-varying channel as its delay spread is
typically in the order of nanoseconds. A study of the orientation model on the
performance of direct-current-biased orthogonal frequency-division multiplexing
(DC-OFDM) is also presented. The performance analysis of the DC-OFDM system
incorporates the effect of diffuse link due to reflection and blockage by the
user. The results show that the diffuse link and the blockage have significant
effects, especially if the UE is located relatively far away from an access
point (AP). It is shown that the effect is notable if the horizontal distance
between the UE and the AP is greater than m in a typical
m indoor room.Comment: This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may no
longer be accessibl
On real time optical wireless communication channel emulator design with FPGAs
This paper discusses the implementation details of a channel emulator suited for optical wireless communications (OWC) systems. The channel emulator comprises functional blocks able to model the transmitter, the receiver and the channel. It is in this sense a valuable tool for system performance evaluation. The proposed design uses field programmable gate arrays (FPGAs) as supporting hardware platform, enabling flexible and expedite interconnection with other system blocks. The achieved design operates in real time, allowing timely and realistic assessment of the channel and terminal equipment impairments on the overall system. Achieved results demonstrate the feasibility to address channel emulation with 500ps time resolution, with negligible quantization errors when compared to the predefined channel coefficients.publishe
Frame-based multiple-description video coding with extended orthogonal filter banks
We propose a frame-based multiple-description video coder. The analysis filter bank is the extension of an orthogonal filter bank which computes the spatial polyphase components of the original video frames. The output of the filter bank is a set of video sequences which can be compressed with a standard coder. The filter bank design is carried out by taking into account two important requirements for video coding, namely, the fact that the dual synthesis filter bank is FIR, and that loss recovery does not enhance the quantization error. We give explicit results about the required properties of the redundant channel filter and the reconstruction error bounds in case of packet errors. We show that the proposed scheme has good error robustness to losses and good performance, both in terms of objective and visual quality, when compared to single description and other multiple description video coders based on spatial subsampling. PSNR gains of 5 dB or more are typical for packet loss probability as low as 5%
Radio frequency channel characterization for energy harvesting in factory environments
This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature
and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant.
In addition, wideband measurements obtained from a machine workshop are presented in this thesis. The power delay profile of the wireless channel was obtained by using a frequency domain channel sounding technique. The measurements were compared with
an equivalent ray tracing model in order to validate the suitability of the commercial propagation software used in this work.
Furthermore, a novel technique for mathematically recreating the time dispersion created by factory inventory in a radio frequency channel is discussed. As a wireless receiver
design parameter, delay spread characterizes the amplitude and phase response of the radio channel. In wireless sensor devices, this becomes paramount, as it determines the
complexity of the receiver. In reality, it is sometimes difficult to obtain full detail floor plans of factories for deterministic modelling or carry out spot measurements during
building construction. As a result, radio provision may be suboptimal. The method presented in this thesis is based on 3-D fractal geometry. By employing the fractal overlaying algorithm presented, metallic objects can be placed on a floor plan so as to
obtain similar radio frequency channel effects. The environment created using the fractal approach was used to estimate the amount of energy a harvesting device can accumulate
in a University machine workshop space
A Site-Specific Indoor Wireless Propagation Model
In this thesis, we explore the fundamental concepts behind the emerging field of site-specific propagation modeling for wireless communication systems. The first three chapters of background material discuss, respectively, the motivation for this study, the context of the study, and signal behavior and modeling in the predominant wireless propagation environments. A brief survey of existing ray-tracing based site-specific propagation models follows this discussion, leading naturally to the work of new model development undertaken in our thesis project. Following the detailed description of our generalized wireless channel modeling, various interference cases incorporating with this model are thoroughly discussed and results presented at the end of this thesis
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