Robust modem design for satellite communications in emergency scenarios

Abstract

Aiming at increasing the satellite link performance, advanced modulation techniques have been thoroughly studied. On the other hand, reliable transmission techniques with a low computational overhead are pursued for many applications in critical scenarios such as: control operation of a satellite while it is placed into its orbit, the disposal of a satellite at the end of its life or the deep-space missions. In these specific mission critical scenarios, fast and correct data reception is even more important than high channel capacity. An unknown and fast variable channel state condition, with large Doppler shifts and low available power require incoherent and light computationally modulation techniques. This paper introduces a whole digital implementation of a receiver, based on the Double Differential PSK (DD-PSK) modulation, that is perfectly compliant with these requirements.

Effective Doppler Mitigation in Critical Satellite Communications

“…In this section the performance of the proposed receiver will be compared with those obtained by DD-PSK [5]. The performance are evaluated in three different scenarios.…”

“…Section 3 proposes a complete description of the modem architecture and an analytical analysis of its operative principles Sect. 4 compares the performance of the whole receiver architecture with the one proposed in [5]. Finally, conclusive remarks are given in Sect.…”

“…The operative frequency is in S-Band: in particular ITU radio regulation and satellite standard [17] reserves the following sub-ranges: The satellite is usually equipped with a hemispherical patch antenna that is dedicated to the TM/TC link and placed on yaw satellite's face. When the satellite correctly points to Ground, the received power is easily computed by means the link budget equation; a detailed case study is described in [5].…”

“…The features of a receiver which is based on Delay and Multiply (D&M) estimator will be compared with a receiver implementing an incoherent Double Differential PSK whose performance and implementation have been described in a previous contribution [5].…”

“…The reliability and robustness are key features for a satellite communication system, particularly during critical satellite mission phases, like the early operations after separation from upper launcher stages or the end of life manoeuvres [3,4]. In these scenarios, the spacecraft may have reduced functionalities and uncontrolled attitude and consequently, the communication link could be weak, unstable and with a rapid variability e.g., signal's amplitude could drop down or go up according to satellite tumbling rate [5,6]. In this context, the communication becomes bursty and the link reliability harms the bit rate performance.…”