arXiv subjects

Aldebaro Klautau

Publications and source records attributed to Aldebaro Klautau.

25 records · Page 2Linked to original sources

arXiv2020

Virtualized C-RAN Orchestration with Docker, Kubernetes and OpenAirInterface

Virtualization is a key feature in Cloud Radio Access Network (C-RAN). It can help to save costs since it allows the use of virtualized base stations instead of physically deployment in different areas. However, the creation and management of virtual base stations pools is not trivial and introduces new challenges to C-RAN deployment. This paper reports a method to orchestrate and manage a container-based C-RAN. We used several instances of the OpenAirInterface software running on Docker containers, and orchestrated them using Kubernetes. We demonstrate that using Kubernetes it is possible to dynamically scale remote radio heads (RRHs) and baseband units (BBUs) according to requirements of the network and parameters such as the server resources usage.

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arXiv2020

LIDAR Data for Deep Learning-Based mmWave Beam-Selection

Millimeter wave communication systems can leverage information from sensors to reduce the overhead associated with link configuration. LIDAR (light detection and ranging) is one sensor widely used in autonomous driving for high resolution mapping and positioning. This paper shows how LIDAR data can be used for line-of-sight detection and to reduce the overhead in millimeter wave beam-selection. In the proposed distributed architecture, the base station broadcasts its position. The connected vehicle leverages its LIDAR data to suggest a set of beams selected via a deep convolutional neural network. Co-simulation of communications and LIDAR in a vehicle-to-infrastructure (V2I) scenario confirm that LIDAR can help configuring mmWave V2I links.

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arXiv2020

Downlink Fronthaul Compression in Frequency Domain using OpenAirInterface

This paper presents a compression scheme developed for the transport of downlink radio signals in packet fronthaul of centralized-radio access networks (C-RAN). The technique is tailored to frequency-domain functional splits, in which inactive LTE (or 5G NR) resource elements may not be transmitted in the packets. This allows decreasing the link data rate, especially when the cell load is low. The compression scheme is based on two parts: transmission of side information to indicate active and inactive resource elements of the LTE, and nonuniform scalar quantization to compress the QAM symbols of the active resource elements. The method was implemented in the OpenAirInterface (OAI) software for real-time evaluation. The testbed results show a significant reduction in link usage with a low computational cost.

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arXiv2019

Evaluation of Simplified Methodology for Obtaining mmWave MIMO Channels from Ray-Tracing Simulations

The use of higher frequencies and MIMO is important in many 5G use cases. However, the available channel models for millimeter waves (mmWaves) currently demand investigation and the number of measurements is still limited. Using simulators is a current practice in mmWave MIMO research and ray tracing is considered one of the most accurate techniques. Due to the relatively long time of ray tracing simulations, it is common practice to adopt a simplified simulation methodology in which omnidirectional antennas are simulated and, later, the results are used together with a geometrical model to consider that antenna arrays were used. This allows flexibility and decreases the overall time spent with simulations. This paper investigates the corresponding assumptions and how accurate are the results of the simplified methodology when compared to effectively using antenna arrays in the ray tracing simulation. The preliminary results indicate that the distance between transmitter and receiver needs to be sufficiently large.

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arXiv2019

C-RAN Virtualization with OpenAirInterface

C-RAN virtualization is a research topic with great interest since it allows to share baseband processing resources.Therefore, in this work, we report the implementation of a virtualized LTE testbed environment of C-RAN by integrating the OpenAirInterface (OAI) with Docker. Using the test bed,we conducted a workload study to understand the computation resource demand of C-RAN software. Virtualization in containers has proven to be effective in creating a functional 4G network which achieves realistic results to facilitate research.

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arXiv2019

Development and Evaluation of Least Square Satellite Tracking in Real Antenna Control System

This work describes the implementation of a satellite tracking technique in a real antenna control system. The technique uses least squares estimation to search for the best antenna pointing position to receive the satellite beacon signal tracked in the 2D region created by the motion axes. The work also presents the technique implementation results in the real system to prove its operation with the beacon signal intensity and the orbit obtained with the search over time.

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arXiv2018

Frequency Tracking: LMS and RLS Applied to Speech Formant Estimation (2000)

Introduction Several speech processing algorithms assume the signal is stationary during short intervals (approximately 20 to 30 ms). This assumption is valid for several applications, but it is too restrictive in some contexts. This work investigates the application of adaptive signal processing to the problem of estimating the formant frequencies of speech. Two algorithms were implemented and tested. The first one is the conventional Least-Mean-Square (LMS) algorithm, and the second is the conventional Recursive Least-Squares (RLS) algorithm. The formant frequencies are the resonant frequencies of the vocal tract. The speech is the result of the convolution between the excitation and the vocal tract impulse response [Rabiner, 78], thus a kind of "deconvolution" is required to recover the formants. This is not an easy problem because one does not have the excitation signal available. There are several algorithms for formant estimation [Rabiner, 78], [Snell, 93], [Laprie, 94

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