The deep space network, volume 18

The objectives, functions, and organization of the Deep Space Network are summarized. The Deep Space Instrumentation Facility, the Ground Communications Facility, and the Network Control System are described

Overcoming CubeSat downlink limits with VITAMIN: a new variable coded modulation protocol

Thesis (M.S.) University of Alaska Fairbanks, 2013Many space missions, including low earth orbit CubeSats, communicate in a highly dynamic environment because of variations in geometry, weather, and interference. At the same time, most missions communicate using fixed channel codes, modulations, and symbol rates, resulting in a constant data rate that does not adapt to the dynamic conditions. When conditions are good, the fixed date rate can be far below the theoretical maximum, called the Shannon limit; when conditions are bad, the fixed data rate may not work at all. To move beyond these fixed communications and achieve higher total data volume from emerging high-tech instruments, this thesis investigates the use of error correcting codes and different modulations. Variable coded modulation (VCM) takes advantage of the dynamic link by transmitting more information when the signal-to-noise ratio (SNR) is high. Likewise, VCM can throttle down the information rate when SNR is low without having to stop all communications. VCM outperforms fixed communications which can only operate at a fixed information rate as long as a certain signal threshold is met. This thesis presents a new VCM protocol and tests its performance in both software and hardware simulations. The protocol is geared towards CubeSat downlinks as complexity is focused in the receiver, while the transmission operations are kept simple. This thesis explores bin-packing as a way to optimize the selection of VCM modes based on expected SNR levels over time. Working end-to-end simulations were created using MATLAB and LabVIEW, while the hardware simulations were done with software defined radios. Results show that a CubeSat using VCM communications will deliver twice the data throughput of a fixed communications system

Design and testing of a real time simulation for Trellis Coded Modulation

Bibliography: leaves 75-76.The aim of this project is to build and test a real time simulation for Trellis Coded Modulation(TCM). The tests to be performed are a comparison between Ungerboeck and pragmatic codes and varying and observing different Viterbi decoder parameters for coded 8PSK. TCM is coded modulation which means the choice of modulation scheme is linked with the encoding technique. Convolutional codes are important for an understanding of TCM. They are described by the rate (which is the number of inputs over the number of outputs) and the number of memory elements, v. For TCM schemes, soft decision decoding, based on euclidean distance, rather than hard decision decoding, based on hamming distance, is used. Ungerboeck developed a mapping of encoder bits to channel signals on a constellation diagram. The mapping is called mapping by set partitioning and aims to find the smallest free euclidean distance for a given code. The free euclidean distance is the minimum euclidean distance between output sequences in a code. The asymptotic coding gain is a measure of coding gain based on the free euclidean distance

Advanced constellation and demapper schemes for next generation digital terrestrial television broadcasting systems

206 p.Esta tesis presenta un nuevo tipo de constelaciones llamadas no uniformes. Estos esquemas presentan una eficacia de hasta 1,8 dB superior a las utilizadas en los últimos sistemas de comunicaciones de televisión digital terrestre y son extrapolables a cualquier otro sistema de comunicaciones (satélite, móvil, cable¿). Además, este trabajo contribuye al diseño de constelaciones con una nueva metodología que reduce el tiempo de optimización de días/horas (metodologías actuales) a horas/minutos con la misma eficiencia. Todas las constelaciones diseñadas se testean bajo una plataforma creada en esta tesis que simula el estándar de radiodifusión terrestre más avanzado hasta la fecha (ATSC 3.0) bajo condiciones reales de funcionamiento.Por otro lado, para disminuir la latencia de decodificación de estas constelaciones esta tesis propone dos técnicas de detección/demapeo. Una es para constelaciones no uniformes de dos dimensiones la cual disminuye hasta en un 99,7% la complejidad del demapeo sin empeorar el funcionamiento del sistema. La segunda técnica de detección se centra en las constelaciones no uniformes de una dimensión y presenta hasta un 87,5% de reducción de la complejidad del receptor sin pérdidas en el rendimiento.Por último, este trabajo expone un completo estado del arte sobre tipos de constelaciones, modelos de sistema, y diseño/demapeo de constelaciones. Este estudio es el primero realizado en este campo

Telemetry coding study for the international magnetosphere explorers, mother/daughter and heliocentric missions. Volume 2: Final report

A convolutional coding theory is given for the IME and the Heliocentric spacecraft. The amount of coding gain needed by the mission is determined. Recommendations are given for an encoder/decoder system to provide the gain along with an evaluation of the impact of the system on the space network in terms of costs and complexity

Remote Science Operation Center research

Progress in the following areas is discussed: the design, planning and operation of a remote science payload operations control center; design and planning of a data link via satellite; and the design and prototyping of an advanced workstation environment for multi-media (3-D computer aided design/computer aided engineering, voice, video, text) communications and operations