Traffic alert and collision avoidance coding system

摘要

A system for coding and transmitting traffic alert and collision avoidance data between vehicles (A, B and C) traveling within a given airspace (12). The airspace is divided into a grid of volume elements (14a, 14b . . . 14i), each of which is assigned a unique pseudonoise (PN) code. A vehicle (A) traveling through the airspace determines its position using signals from Global Positioning System (GPS) satellites. The vehicle's position places it within one of the volume elements in the airspace. A Traffic Alert and Collision Avoidance System (TCAS) transmitter (38) on the vehicle creates a navigation message that describes the position of the vehicle. A collision avoidance signal is then generated by modulating a carrier signal with the PN code representing the volume element containing the transmitting vehicle and with the navigation message. The collision avoidance signal is transmitted on a common communications channel using time-multiplexing based on a pseudorandom sequence. Other vehicles operating within the same airspace use a TCAS receiver to receive the collision avoidance signals broadcast from each vehicle. Each receiving vehicle in the airspace only tracks collision avoidance signals produced by vehicles located in its own and surrounding volume elements to determine if an impending collision is likely. Specifically, only the navigation messages from vehicles in the same or surrounding volume elements are decoded to determine the position of the other vehicles. Based on calculated vehicle paths, a warning of an impending collision or instructions on how to avoid a collision are provided to the operator of the receiving vehicle.