Unmanned Aerial System Traffic Management with WAVE Protocol for Collision Avoidance

The hierarchical unmanned aerial systems (UAS) traffic management (UTM) is proposed for UAS operation in Taiwan. The proposed UTM is constructed using the similar concept of ATM from the transport category aviation system. Based on the airspace being divided by 400 feet of altitude, the RUTM (regional UTM) is managed by the local government and the NUTM (national UTM) by the Civil Aeronautical Administration (CAA). Under construction of the UTM system infrastructure, this trial tests examine the effectiveness of UAV surveillance under 400 feet using automatic dependent surveillance-broadcast (ADS-B)-like on-board units (OBU). The ground transceiver station (GTS) is designed with the adoptable systems. In these implementation tests, five long-range wide area network (LoRa) gateways and one automatic packet reporting system (APRS) I-Gate are deployed to cover the Tainan Metropolitan area. The data rates are set in different systems from 8 to 12 s to prevent from data conflict or congestion. The signal coverage, time delay, data distribution, and data variance in communication are recorded and analyzed for RUTM operation. Data streaming and Internet manipulation are verified with cloud system stability and availability. Simple operational procedures are defined with priority for detect and avoid (DAA) for unmanned aerial vehicles (UAVs). Mobile communication and Zello broadcasts are introduced and applied to establish controller-to-pilot communication (CPC) for DAA. The UAV flight tests are generally beyond visual line-of-sight (BVLOS) near suburban areas with flight distances to 8 km. On the GTS deployment, six test locations examine communication coverage and effectiveness using ADS-B like OBUs. In system verification, the proposed ADS-B like OBU works well in the UTM infrastructure. The system feasibility is proven with support of receiving data analysis and transceiver efficiency. The trial test supports RUTM in Taiwan for UAV operations.

The development of an unmanned aircraft system (UAS) traffic management (UTM) system for the safe integration of unmanned aerial vehicles (UAVs) requires pre-flight conflict detection and resolution (CDR) methods to provide collision-free flight paths for all UAVs before takeoff. A popular solution consists in adapting multi-agent path finding (MAPF) techniques. However, standard MAPF solvers consider only a fixed takeoff time and fixed uniform speed for each UAV flight path, which can lead to inefficiencies in the resolution of instances. Therefore, in this article, we propose incorporating scheduling elements into MAPF solvers, which allows us to adjust the takeoff times and speeds of each UAV to solve conflicts. We introduce two time-related resolution techniques: 1) takeoff scheduling, whereby the start time of a UAV agent is delayed, and 2) speed adjustment, wherein the speed of a UAV agent is decreased over a segment on its flight path. Importantly, we present a distinction of conflict types, which enables us to combine replanning resolution to the aforementioned temporal resolution techniques. We evaluate our proposed approaches on a realistic, high-density UAV delivery scenario in Tokyo, Japan. We show that the combination of takeoff scheduling, replanning, and speed-adjustment resolution techniques improves the efficiency of route planning by reducing the average delay per flight path and the number of rejected flight paths.

Providing quality-of-service- (QoS-) guaranteed video on demand (VOD) services over wireless access in vehicular environments (WAVEs) is a challenge as WAVE adopts enhanced distributive channel access (EDCA), a contention-based channel access mechanism, for air interface access control. This paper proposes a selective downlink scheduling (SDS) algorithm to enhance the quality of VOD for WAVE networks. According to the importance of video decoding, video packets are categorized into high and low priorities. The categorized packets are put into different queues in roadside units (RSUs) to contend for transmission opportunities. Aiming to improve video playback quality and reduce video playback delay, the proposed SDS algorithm schedules video packets based on their importance, playback deadline, and their real-time parameters of receiving onboard units (OBUs), such as velocity and remaining dwelling time. The effectiveness of SDS algorithm is verified by simulations.

NASA's Unmanned Aerial System (UAS) Traffic Management (UTM) project aims at enabling near-term, safe operations of small UAS vehicles in uncontrolled airspace, i.e., Class G airspace. A far-term goal of UTM research and development is to accommodate the expected rise in small UAS traffic density throughout the National Airspace System (NAS) at low altitudes for beyond visual line-of-sight operations. This paper describes a new capability referred to as ICAROUS (Integrated Configurable Algorithms for Reliable Operations of Unmanned Systems), which is being developed under the UTM project. ICAROUS is a software architecture comprised of highly assured algorithms for building safety-centric, autonomous, unmanned aircraft applications. Central to the development of the ICAROUS algorithms is the use of well-established formal methods to guarantee higher levels of safety assurance by monitoring and bounding the behavior of autonomous systems. The core autonomy-enabling capabilities in ICAROUS include constraint conformance monitoring and contingency control functions. ICAROUS also provides a highly configurable user interface that enables the modular integration of mission-specific software components.

WAVE(Wireless Access in Vehicular Environments) designed for vehicle communication has the features of a short initial link, low latency and high mobility. The success of data transmission in WAVE is affected by the priority and size of data and how many nodes are transmitting the data. In this paper, we tested and analyzed how the success rate of data transmission of each node varies according to the number of nodes, priority and size of data in various cases. Based on the simulation results, it is possible to confirm the success rate of data transmission and delay time for each node and the entire channel, and it can be determined how channel resources should be efficiently used considering these results.

The research of vehicular networks has been studied for many years. In actual life, there are a few implementations of V2X communication system, majority of them are extremely expensive. Most importantly, detailed insight implementation procedure hasn't been provided for researches. In this paper, an efficient V2X communication system based on the IEEE 802.11p/1609.X protocol stack, also known as the Wireless Access in Vehicular Environment (WAVE) standard has been designed. In this system, a Dedicated Short Range Communication (DSRC) unit using low-cost and commercial hardware which can support the vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications is developed. Some specific driver adjustments based on the IEEE 802.11a driver are taken to assure compliance with the IEEE 802.11p protocol. Besides, the development of networking layer protocol is accomplished based on IEEE 1609.3. Furthermore, three safety applications and a performance evaluation subsystem have been developed on this platform. The subsystem can test the comprehensive performance of the communication unit in terms of Packet Loss Rate (PLR), throughput and end-to-end delay. Meanwhile enormous experiments are conducted to evaluate the performance of the communication prototype and different scenarios were designed to validate the practical function of the safety applications.

The vehicular ad-hoc network (VANET) is a promising technology in near future. VANET allows vehicles to communicate with each other and with roadside units (RSUs). Wireless Access in Vehicular Environment (WAVE), defined by IEEE, provides the Internet connectivity for vehicles as well as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. RSUs can form a wireless mesh network (WMN) as a backbone infrastructure to enhance the performance of VANET. However, WAVE supports only one-hop communications for IP packets in VANET, and existing researches do not consider the compatibility between VANET and WMN infrastructure formed by RSUs. We propose the extended WMN (ExWMN) which has the feasibility to extend WMN to VANET domain. In ExWMN, the vehicles can send IP packets to an access router by using the multi-hop capability of WMN. ExWMN uses the addressing scheme of WMN for the extended VANET domain and exploits geographical routing protocols instead of existing routing protocols of WMN due to VANET characteristics such as mobility and dynamically changing network topologies. ExWMN supports the compatibility between the extended VANET and a WMN infrastructure due to RSUs, which provide a bridging function between them. This paper presents the architecture and the detailed procedures of the ExWMN.

Dedicated Short Range Communications (DSRC) is a wireless communication standard intended for high speed secure communication between vehicles and the infrastructure. In order to overcome the limitations that vehicular environment imposes such as high mobility, IEEE published the 802.11p amendment widely known as Wireless Access in Vehicular Environment (WAVE). To the best of our knowledge, most of the WAVE stack implementations and studies that are carried out till now are simulator based. This paper majorly focuses on the implementation of IEEE 1609 WAVE /DSRC stack on a Linux based system that forms the backbone of vehicular communication. It dives deep into the changes and the development of new modules that have to be made in Linux kernel to cater the need for vehicular communication. We also discuss in brief about the various challenges faced and design decisions that were made in this process. Finally, we conclude by depicting the performance of our developed stack in comparison with commercially available stack in terms of packet losses.

To improve the throughput performance of the Wireless Access in Vehicular Environment (WAVE) system, we propose a multi-channel MAC protocol that is able to adaptively adjust the intervals of Control Channel (CCH) and Service Channel (SCH) according to the probability distribution of the reservation time for service packet in CCH Interval. Numerical results show that our protocol can significantly improve the performance of WAVE system.

Recently, the IEEE 1609.4 Standard for Wireless Access in Vehicular Environments (WAVE) has been proposed to enhance the performance of vehicular networks with multi-channel operations that allow for the coexistence of safety-related and non-safety related vehicular applications. However, while the benefits of the multi-channel approach are clear, the impact of the IEEE 1609.4 channel scheduler on the performance of delay-constrained vehicular applications remains to be well explored by researchers. At present, the evaluation of 1609.4-based Vehicular Ad Hoc Networks (VANETs) constitutes an open issue due to the lack of simulation tools that can provide a complete modeling of the IEEE WAVE 802.11p/1609.4 stack. In this paper, we provide three key contributions pertaining to multi-channel VANETs. First, we describe our implementation of the IEEE 1609.4 protocol in the ns2 simulator, and we detail its current integration with the existing ns2 implementation of the 802.11p MAC protocol. Second, using our simulation model we propose an evaluation study of 1609.4-based VANETs, and we show that the tight channel synchronization issues foreseen by the protocol might have a dramatic impact on the performance of safety-related applications with strict delivery ratio and delay requirements. Third, we propose two new enhancements for the WAVE protocol stack to favor the dissemination of safety messages in multi-channel VANETs. The suggested algorithms are shown to greatly improve packet delivery ratio and delay of safety applications in single and multi-hop topologies, while preserving the synchronization scheme of the IEEE 1609.4 protocol.

The Unmanned Aircraft System (UAS) Traffic Management (UTM) effort at NASA aims to enable access to low-altitude airspace for small UAS. This goal is being pursued partly through partnerships that NASA has developed with the UAS stakeholder community, the FAA, other government agencies, and the designated FAA UAS Test Sites. By partnering with the FAA UAS Test Sites, NASA's UTM project has performed a geographically diverse, simultaneous set of UAS operations at locations in six states. The demonstrations used an architecture that was developed by NASA in partnership with the FAA to safely coordinate such operations. These demonstrations—the second or Technical Capability Level (TCL 2) National Campaign of UTM testing—was performed from May 15 through June 9, 2017. Multiple UAS operations occurred during the testing at sites located in Alaska, Nevada, Texas, North Dakota, Virginia, and New York with multiple organizations serving as UAS Service Suppliers and/or UAS Operators per the specifications provided by NASA. By engaging various members of the UAS community in development and operational roles, this campaign provided initial validation of different aspects of the UTM concept including: UAS Service Supplier technologies and procedures; geofencing technologies/conformance monitoring; ground-based surveillance/sense and avoid; airborne sense and avoid; communication, navigation, surveillance; and human factors related to UTM data creation and display. Additionally, measures of performance were defined and calculated from the flight data to establish quantitative bases for comparing flight test activities and to provide potential metrics that might be routinely monitored in future operational UTM systems.

An Unmanned Aircraft System (UAS) Traffic Management System (UTM) relies significantly on automation, introducing the need for efficient and accurate trajectory computation to enable coordination and safety. The main objective of this paper is to present and to organize prior work and relevant concepts with the goal of developing a framework for UAS trajectory prediction in the presence of anomalous events. Literature documenting UAS safety and risk assessment has provided multiple pointers for identification and characterization of system failures that cause trajectory deviations or changes to its associated qualities. A UAS trajectory modeling framework considering endogenous and exogenous factors affecting the trajectory is introduced and used in this exposition. In addition, a general formulation of the trajectory computation challenge is presented along with key requirements for potential solution approaches.

The FAA and NASA are developing an Advanced Air Mobility (AAM) capability defining an Unmanned Aircraft Systems (UAS) Traffic Management (UTM) architecture. The combined scale and density of the expected air traffic, as well as the algorithmic complexity of maintaining safe separation, are driving a consensus that a structured airspace will eventually be required. Against this background, a lane-based airspace structure is proposed here whose motivation is to reduce the computational complexity of strategic deconfliction by providing UAS agents with a set of pre-defined airway corridors called lanes. To achieve complexity reduction, an airspace is defined that is composed of a directed graph where every node has either input or output degree equal to one, and flight plans consist of a scheduled sequence of lane traversals. The major results are: (1) the creation and layout of lane structures, (2) an efficient lane-based strategic deconfliction scheduling algorithm, (3) lane-network performance analysis tools, and (4) a tactical deconfliction protocol to handle dynamic contingencies (e.g., failure to follow the nominal flight plan). In conclusion, this approach provides efficient scheduling of safe flight paths, straightforward analysis of stream properties of the transportation system, an effective contingency handling protocol, and scalability to thousands of flights over urban areas.

Dedicated short range communication (DSRC) is the key component in intelligent transportation systems (ITS). The goal of this technology is to help driver and passengers getting multimedia services via wireless communication equipment during the movement of vehicle, so as to improve the traffic safety and enhance the transportation efficiency. The paper is focus on the DSRC baseband technical analysis and the application development. Based on the WLAN 802.11a architecture, we develop a new adaptive channel estimation algorithm that uses two kinds of feedback tracking and pilot aid to enhance wireless access ability in vehicular environments.

Vehicular ad hoc networks (VANETS) are simply a collection of onboard units (OBUs) and roadside units (RSUs) that communicate using dedicated short-range communications (DSRC) utilizing 75 Mhz in 5.9 GHz frequency band for wireless access in vehicular environment (WAVE). The frequency channel layout of WAVE has been divided into seven channels, with one channel for service safety applications and the remaining for service non-safety applications. The nature of the VANET environment being dynamic, it is most likely that packet forwarding over varied time intervals may be disconnected, causing network delays. In such a case the message containing information needs to be with the current vehicle until a new intelligent node becomes active. Extensive studies have been conducted on the propagation of messages in vehicular networks. Although conventional methods are mainly focused on similar traffic, in this only high, low-density traffic is considered. The intelligent mobile node structure in NS-3 has been designed in such a way as to support 802.11 MAC with a single channel. However, this intelligent mobile node is not appropriate for WAVE multi-channel operation.