Real-Time Digital Video Streaming at Low-VHF for Compact Autonomous Agents in Complex Scenes

This paper presents an experimental investigation of real-time digital video streaming in physically complex Non-Line-Of-Sight (NLoS) channels using a low-power, low-VHF system integrated on a compact robotic platform. Reliable video streaming in NLoS channels over infrastructure-poor ad-hoc radio networks is challenging due to multipath and shadow fading. In this effort, we focus on exploiting the near-ground low-VHF channel which has been shown to have improved penetration, reduced fading, and lower power requirements (which is critical for autonomous agents with limited power) compared to higher frequencies. Specifically, we develop a compact, low-power, low-VHF radio test-bed enabled by recent advances in efficient miniature antennas and off-the-shelf software-defined radios. Our main goal is to carry out an empirical study in realistic environments of how the improved propagation conditions at low-VHF affect the reliability of video-streaming with constraints stemming from the limited available bandwidth with electrically small low-VHF antennas. We show quantitative performance analysis of video streaming from a robotic platform navigating inside a large occupied building received by a node located outdoors: bit error rate (BER) and channel-induced Peak Signal-to-Noise Ratio (PSNR) degradation. The results show channel-effect-free-like video streaming with the low-VHF system in complex NLoS channels.Comment: Accepted for publication in 2019 IEEE 89th Vehicular Technology Conferenc

Performance assessment of lower VHF band for short‐range communication and geolocation applications

The focus of this paper is to characterize near‐ground wave propagation in the lower very high frequency (VHF) band and to assess advantages that this frequency band offers for reliable short‐range low‐data rate communications and geolocation applications in highly cluttered environments as compared to conventional systems in the microwave range. With the advent of palm‐sized miniaturized VHF antennas, interest in low‐power and low‐frequency communication links is increasing because (1) channel complexity is far less in this frequency band compared to higher frequencies and (2) significant signal penetration through/over obstacles is possible at this frequency. In this paper, we quantify the excess path loss and small‐scale fading at the lower VHF and the 2.4 GHz bands based on short‐range measurements in various environments. We consider indoor‐to‐indoor, outdoor‐to‐indoor, and non‐line‐of‐sight outdoor measurements and compare the results with measurements at higher frequencies which are used in conventional systems (i.e., 2.4 GHz). Propagation measurements at the lower VHF band are carried out by using an electrically small antenna to assess the possibility of achieving a miniaturized, mobile system for near‐ground communication. For each measurement scenario considered, path loss and small‐scale fading are characterized after calibrating the differences in the systems used for measurements at different frequencies, including variations in antenna performance.Key PointsLow VHF has favorable short‐range characteristics and low signal distortionPenetration through many layers of building walls is possible at low VHFNovel miniaturized VHF antennas with reasonable performance have been designedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111943/1/rds20240.pd

Low Frequency Multi-Robot Networking

Autonomous teams of unmanned ground and air vehicles rely on networking and distributed processing to collaborate as they jointly localize, explore, map, and learn in sometimes difficult and adverse conditions. Co-designed intelligent wireless networks are needed for these autonomous mobile agents for applications including disaster response, logistics and transportation, supplementing cellular networks, and agricultural and environmental monitoring. In this paper we describe recent progress on wireless networking and distributed processing for autonomous systems using a low frequency portion of the electromagnetic spectrum, here defined as roughly 25 to 100 MHz with corresponding wavelengths of 3 to 12 meters. This research is motivated by the desire to support autonomous systems operating in dense and cluttered environments by harnessing low frequency propagation, where meters long wavelengths yield significantly reduced scattering and enhanced penetration of obstacles and structures. This differs considerably from higher frequency propagation, requiring different low frequency propagation models than those widely employed for other bands. Progress in use of low frequency for autonomous systems has resulted from combined advances in low frequency propagation modeling, networking, antennas and electromagnetics, geolocation, multi-antenna array distributed beamforming, and mobile collaborative processing. This article describes the breadth and the depth of interaction between areas, leading to new tools and methods, especially in physically complex indoor/outdoor, dense urban, and other challenging scenarios. We bring together key results, models, measurements, and experiments that describe the state of the art for new uses of low frequency spectrum for multi-agent autonomy