Dynamic link budget simulation

A new simulator named DLBS (Dynamic Link Budget Simulator) was written to simulate the time-varying communication link between a vehicle that re-enters the atmosphere from the outer space, and a ground station. During the vehicle descent trajectory, communications blackouts typically occur due to the effects of plasma that forms around the vehicle. A companion simulator, AIPT (Antenna In Plasma Tool), evaluates the electric field at the input of the ground station antenna, taking into consideration the vehicle structure, its antenna, the characteristics of plasma at some specified points along the vehicle trajectory, and the obtained values are stored in a file. DLBS processes the data read from the AIPT output file and evaluates the corresponding channel transfer functions. DLBS then allows to simulate the typical telemetry and telecommand links, using both CCSDS standardised and some non standard channel encoding schemes and modulations. For each generated frame, DLBS uses a channel transfer function obtained by adequately interpolating the two nearest transfer functions evaluated in the initial phase. DLBS includes realistic frame, frequency, phase and bit synchronisation, so that synchronisation errors are also included as source of performance degradation, and measures both the average bit and frame error rates, and the bit error rate at frame level, so that it is possible to appreciate the dynamic system behaviour. The paper will show the results obtained for a case stud