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

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

Fonaments matemàtics, febrer 2010

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Fonaments matemàtics, febrer 2010

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Fonaments matemàtics, febrer 2010

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Coded transmissions for space links affected by solar scintillation: Baseband analysis

Summary A thorough analysis of the behavior of error-correcting codes over space links affected by solar scintillation is presented. The relevant channel parameters are fixed through the development of a model based on real missions' data. Both telecommand and telemetry links are considered in fast and slow fading conditions. Besides classical coherent modulation schemes, the possibility to use noncoherent modulation schemes is considered, to eliminate the problem of phase tracking. For the case of channels with very slow fading, the use of external interleavers or erasure coding is proposed to cope with error bursts