An efficient transmission of 4D Trajectory short messages on LDACS1

In order to support a 4-Dimensional Trajectory (4DT) based Air Traffic Services (ATS), aircraft should update trajectory data back to a ground control center with aeronautical short messages (ASM). An efficient transmission mechanism for 4DT-ASM is developed in this study. The proposed approach firstly divides aircraft into groups by spatial diversity. Then, if one airborne station (AS) requests resource for sending ASM, the control will allocate the corresponding radio resources to all group members including this AS. Thanks to the space division multiple access (SDMA), all aircraft in the same group could transmit ASM randomly without causing any collision. The capacity of 4DT-ASM hereby will be improved and the request time delay of other AS nodes in this group can be saved, i.e., the real-time performance enhancement. Furthermore, a low complex selection algorithm for grouping aircraft is detailed analyzed, with which the control could group aircraft under SINR constraints. Simulation results prove that SDMA based collision free random access (CFRA) can improve the spectrum efficiency and reduce average time delay remarkably.