Next generation earth-to-space telecommand coding and synchronization: ground system design, optimization and software implementation

Ricard Abelló,Franco Chiaraluce,Filipe Carvalho,Enrico Paolini,Ricardo Fernandes,Marco Baldi,Ricardo Prata,Roberto Garello

doi:10.1186/s13638-021-02078-z

Abstract

The Consultative Committee for Space Data Systems, followed by all national and international space agencies, has updated the Telecommand Coding and Synchronization sublayer to introduce new powerful low-density parity-check (LDPC) codes. Their large coding gains significantly improve the system performance and allow new Telecommand services and profiles with higher bit rates and volumes. In this paper, we focus on the Telecommand transmitter implementation in the Ground Station baseband segment. First, we discuss the most important blocks and we focus on the most critical one, i.e., the LDPC encoder. We present and analyze two techniques, one based on a Shift Register Adder Accumulator and the other on Winograd convolution both exploiting the block circulant nature of the LDPC matrix. We show that these techniques provide a significant complexity reduction with respect to the usual encoder mapping, thus allowing to obtain high uplink bit rates. We then discuss the choice of a proper hardware or software platform, and we show that a Central Processing Unit-based software solution is able to achieve the high bit rates requested by the new Telecommand applications. Finally, we present the results of a set of tests on the real-time software implementation of the new system, comparing the performance achievable with the different encoding options.

Highlights

Space Telecommand (TC) systems from ground stations to space vehicles have traditionally been characterized by well-established requirements, which may be summarized as transmission of short messages, very high reliability, and receiver simplicity [1]
We focus on a target output bit rate of 2.048 Mbps, which is currently considered realistic by the European Space Agency (ESA) for the new applications described in Sect
5 Results and discussion Taking into account the output target bit rate of 2.048 Mbps at the TC Synchronization and Channel Coding sublayer, this section describes the achieved results for the three encoding methods presented in Sect. 3, running on the selected platform

Summary

Introduction

Space Telecommand (TC) systems from ground stations to space vehicles have traditionally been characterized by well-established requirements, which may be summarized as transmission of short messages (mostly for command and emergency), very high reliability (to prevent the execution of wrong commands), and receiver simplicity (to limit the on-board complexity) [1]. 5, we present the results for the real-time software implementation of the new TC Synchronization and Channel Coding sublayer and we quantify the bit rate improvement achieved by the two encoding methods for the two different LDPC codes.

Results

Conclusion