On the Use of PN Ranging With High-Rate Spectrally-Efficient Modulations in Satellite Payload Telemetry Links

Abstract

Pseudonoise (PN) ranging is a ranging technique that has been recently introduced in near-Earth space research missions. For these, at the state-of-the-art, the PN ranging signal is combined with a high-rate telemetry stream binary modulated in phase. The coupling of the two, together with the 10 MHz bandwidth constraint imposed for this class of missions, translates into a data rate bound of approximately 10 Mb/s. The purpose of this article is to prove the feasibility of overcoming the current data rate limitation by defining a communication architecture that foresees the coupling of the PN ranging signal with a high-order modulated telemetry stream. To achieve the goal, we study the feasibility of pairing the PN ranging with filtered high-order modulations that are standardized for satellite payload telemetry links and investigate the simultaneous demodulation of the telemetry stream while tracking the ranging sequence. Accordingly, we design a receiver scheme capable of performing a closed-loop parallel cancellation of the ranging and the telemetry signal reciprocally. From our analysis, we find that the nonconstant envelope property, characterizing the considered modulation set, causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be controlled and reduced by properly sizing the receiver loop bandwidth without limiting the timing synchronization dynamic. Our study proves the use of filtered high-order modulations combined with PN ranging to outperform the state-of-the-art in terms of spectral efficiency and achievable data rate while having comparable ranging performance.