Showing papers by "Mihail L. Sichitiu published in 2023"

Spectrum Activity Monitoring and Analysis for Sub-6 GHz Bands Using a Helikite

Abstract: In this paper, we report sub-6 GHz spectrum measurement results at multiple ground fixed nodes and a helikite flying at altitudes up to 500 feet. Measurements are carried out at the NSF AERPAW platform in Raleigh, NC. We first describe our measurement methodology using software defined radios (SDRs) and explain the details of the measurement environment. Subsequently, we analyze the impact of terrain, measurement altitude, measurement frequency, and the time of the day on spectrum measurements for various different sub-6 GHz bands. In particular, we present spectrum occupancy results from various different LTE bands first in a rural environment, and then in an urban campus environment. Results show that for both environments, measured power at a given spectrum band increases with altitude up to 500 feet. On the other hand, in the urban environment, an abrupt increase in the aggregate received power is observed in all considered bands as the helikite rises above the buildings, when compared with the more gradual increase of the received power in same bands for the rural environment.

Spectrum Monitoring and Analysis in Urban and Rural Environments at Different Altitudes

Abstract: —Due to the scarcity of spectrum resources, the emer- gence of new technologies and ever-increasing number of wireless devices operating in the radio frequency spectrum lead to data congestion and interference. In this work, we study the effect of altitude on sub-6 GHz spectrum measurement results obtained at a Helikite flying over two distinct scenarios; i.e., urban and rural environments. Specifically, we aim at investigating the spectrum occupancy of various long-term evolution (LTE), 5 th generation (5G) and citizens broadband radio service (CBRS) bands utilized in the United States for both uplink and downlink at altitudes up to 180 meters. Our results reveal that generally the mean value of the measured power increases as the altitude increases where the line-of-sight links with nearby base stations is more available. SigMF-compliant spectrum measurement datasets used in this paper covering all the bands between 100 MHz to 6 GHz are also provided.

Open RAN Testbeds with Controlled Air Mobility

Abstract: —With its promise of increasing softwarization, im- proving disaggregability, and creating an open-source based ecosystem in the area of Radio Access Networks, the idea of Open RAN has generated rising interest in the community. Even as the community races to provide and verify complete Open RAN systems, the importance of verification of systems based on Open RAN under real-world conditions has become clear, and testbed facilities for general use have been envisioned, in addition to private testing facilities. Aerial robots, including autonomous ones, are among the increasingly important and interesting clients of RAN systems, but also present a challenge for testbeds. Based on our experience in architecting and operating an advanced wireless testbed with aerial robots as a primary citizen, we present considerations relevant to the design of Open RAN testbeds, with particular attention to making such a testbed capable of controlled experimentation with aerial clients. We also present representative results from the NSF AERPAW testbed on Open RAN slicing, programmable vehicles, and programmable radios.

SDR-Based 5G NR C-Band I/Q Monitoring and Surveillance in Urban Area Using a Helikite

Abstract: In this paper, we report experimental results in collecting and processing 5G NR I/Q samples in the 3.7 GHz C-band by using a software-defined radio (SDR)-mounted helikite. We use MATLAB's 5G toolbox to post-process the collected data, to obtain the synchronization signal block (SSB) from the I/Q samples, and then go through the cell search, synchronization procedures, and reference signal received power (RSRP) and reference signal received quality (RSRQ) calculation. We plot these performance metrics for various physical cell identities as a function of the helikite's altitude. Furthermore, building on our experience with the collected and post-processed data, we discuss potential vulnerabilities and challenges for the 5G NR systems to surveillance, spectrum coexistence with existing services, jammina attacks, and post-quantum era attacks.

LTE I/Q Data Set for UAV Propagation Modeling, Communication, and Navigation Research

Abstract: Recently, unmanned aerial vehicles (UAVs) have been receiving significant attention due to their wide range of potential application areas. To support UAV use cases with beyond visual line of sight (BVLOS) and autonomous flights, cellular networks can serve as ground connectivity points, and they can provide remote control and payload communication for UAV links. However, there are limited data sets to study the coverage of cellular technologies for UAV flights at different altitudes and develop machine learning (ML) techniques for improving UAV communication and navigation. In this article, we present raw LTE I/Q sample data sets from physical field experiments in the Lake Wheeler farm area of the NSF AERPAW experimentation platform. We fly a UAV that carries a software-defined radio (SDR) at altitudes ranging from 30~m to 110~m and collect raw I/Q samples from an SDR-based LTE base station on the ground operating at 3.51 GHz. We adopt a standard metadata format for reproducing the results from the collected data sets. The post-processing of raw I/Q samples using MATLAB's 4G LTE toolbox is described and various representative results are provided. In the end, we discuss the possible ways that our provided data set, post-processing sample code, and sample experiment code for collecting I/Q measurements and vehicle control can be used by other ML researchers in the future.

A Millimeter-Wave Software-Defined Radio for Wireless Experimentation

Abstract: In this study, we propose a low-cost and portable millimeter-wave software-defined radio (SDR) for wireless experimentation in the 60 GHz band. The proposed SDR uses Xilinx RFSoC2x2 and Sivers EVK06002 homodyne transceiver and provides a TCP/IP-based interface for companion computer (CC)-based baseband signal processing. To address the large difference between the processing speed of the CC and the sample rate of analog-to-digital converters, we propose a method, called waveform-triggered reception (WTR), where a hard-coded block detects a special trigger waveform to acquire a pre-determined number of IQ samples upon the detection. We also introduce a buffer mechanism to support discontinuous transmissions. By utilizing the WTR along with discontinuous transmissions, we conduct a beam sweeping experiment, where we evaluate 4096 beam pairs rapidly without compromising the flexibility of the CC-based processing. We also generate a dataset that allows one to calculate physical layer parameters such as signal-to-noise ratio and channel frequency response for a given pair of transmit and receive beam indices.

Kriging-Based 3-D Spectrum Awareness for Radio Dynamic Zones Using Aerial Spectrum Sensors

Abstract: Radio dynamic zones (RDZs) are geographical areas within which dedicated spectrum resources are monitored and controlled to enable the development and testing of new spectrum technologies. Real-time spectrum awareness within an RDZ is critical for preventing interference with nearby incumbent users of the spectrum. In this paper, we consider a 3D RDZ scenario and propose to use unmanned aerial vehicles (UAVs) equipped with spectrum sensors to create and maintain a 3D radio map of received signal power from different sources within the RDZ. In particular, we introduce a 3D Kriging interpolation technique that uses realistic 3D correlation models of the signal power extracted from extensive measurements carried out at the NSF AERPAW platform. Using C-Band signal measurements by a UAV at altitudes between 30 m-110 m, we first develop realistic propagation models on air-to-ground path loss, shadowing, spatial correlation, and semi-variogram, while taking into account the knowledge of antenna radiation patterns and ground reflection. Subsequently, we generate a 3D radio map of a signal source within the RDZ using the Kriging interpolation and evaluate its sensitivity to the number of measurements used and their spatial distribution. Our results show that the proposed 3D Kriging interpolation technique provides significantly better radio maps when compared with an approach that assumes perfect knowledge of path loss.