A Traffic Information Service-Broadcast model for mixed-equipage Aircraft Simulation

Abstract

The use of new Air Traffic Management (ATM) concepts built upon the capabilities afforded by the Automatic Dependent Surveillance-Broadcast (ADS-B) system in NextGen airspace aims to provide substantial improvements in system capacity and throughput without compromising safety relative to today's ground-directed ATM based on Secondary Surveillance Radar (SSR). These concepts rely on airborne based surveillance and include the use of airborne systems and procedures to perform traffic monitoring, self-separation, and merging and spacing. The Traffic Information Service-Broadcast (TIS-B) system is intended to provide the crucial bridge for ADS-B aircraft to employ some of these concepts during the transition phase. Although TIS-B surveillance is not expected to be of the same quality as ADS-B surveillance, it still provides aircraft state and velocity information required so that airborne systems can provide airborne separation assistance/assurance and airborne spacing capabilities (with increased separation margins). While simulation studies of these NextGen concepts in the end-state system are already underway [1], additional simulation models will be needed to represent the intermediate state system where not all aircraft will be equipped with ADS-B. The suitability of new ATM concepts for use in the transitional NextGen airspace with mixed equipage (Mode C, Mode S, and Mode S Extended Squitter (ES)) aircraft can be studied using simulation tools such as NASA Langley's Airspace and Traffic Operations Simulation (ATOS) enhanced with the TIS-B model described in this paper. ATOS is a distributed, Human in the Loop (HITL) simulation consisting of multiple, mid-fidelity, desktop cockpit simulators called ASTOR (Aircraft Simulation for Traffic Operations Research). This paper describes the RTCA standards-based design of the TIS-B model developed for use in ATOS. This model consists of ground and aircraft subsystems with a focus on the models of TIS-B system functional elements such as Ground Surveillance Processing (GSP), TIS-B Target Report Distribution Function (DF), Ground Link Specific Processing (GLSP), Airborne Link Specific Processing (ALSP), and Target Tracking and Report Assembly (RA). The modeling of SSR data processing functions in the GSP, including position and altitude measurement, state estimation, radar tracking, and computation of Navigation Accuracy Category (NAC) and Navigation Integrity Category (NIC) of aircraft position is discussed at length. This paper also describes how Target reports are extrapolated (to account for data latency), generated, and distributed by the DF model. A Ground Based Transceiver (GBT) model implements the GLSP functions that include generation of TIS-B messages and suppression of TIS-B messages corresponding to aircraft producing ADS-B signals being received by the GBT. Modeling of the reception of ADS-B transmissions by the GBT is included using the ADS-B reception model developed for ASTOR air-to-air reception modeling [2, 3]. Finally, this paper describes the modeling of the ALSP and RA functions within the ASTOR. The paper also presents and discusses the preliminary model validation test results obtained from the simulation by comparing truth and TIS-B message derived track data and provides insights into how the TIS-B model can be used to support NextGen concept studies.