A data-dependent algorithm was developed for estimating symbol signal-to-noise ratio (SNR) with a non-integral number of samples per symbol. The classical split symbol SNR estimator algorithm was adapted to incorporate the whole symbol by removing the data polarity.
The Whole Symbol Moments SNR Estimator (WSME) was developed for adaptive data rate (ADR) control, and is required to operate at all symbol rates between 1 and 4,096 ksps. This is particularly challenging at the highest symbol rates, especially when there is not an integer number of samples per symbol. For example, a nominal 19.18-MHz sampling rate and a 4,096-ksps symbol rate correspond to approximately 4.68 samples per symbol, in which case each symbol output from the symbol tracking loop (DTTL — data-transition tracking loop) will comprise either four samples (32% of the time) or five samples (68% of the time). Originally, it was envisioned that a split symbol SNR estimator could be used for ADR. However, given that each half-symbol at 4,096 ksps comprises only two or three samples, the resulting SNR estimates exhibit an extremely large variability that render this technique impractical for relay operations with the Mars Reconnaissance Orbiter (MRO). Consequently, a modification to the split-symbol SNR estimator has been developed that allows the utilization of whole symbols. This is accomplished by removing the data polarity of the BPSK (binary phase-shift keying) data symbols, thereby resulting in more samples used in generating the sample SNR estimates.
This algorithm provides a novel extension to the classical split-symbol SNR estimator by incorporating data over each entire symbol. This improves the stability of the algorithm, especially at high data rates.
This work was done by Igor Kuperman and Edgar H. Satorius of Caltech for NASA’s Jet Propulsion Laboratory.
The software used in this innovation is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
Whole Symbol Moments SNR Estimator Analysis and Implementation
(reference NPO-48004) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the Whole Symbol Moments SNR Estimator (WSME) analysis and implementation. It is part of the NASA Tech Briefs and is intended to disseminate results from aerospace-related developments that may have broader technological, scientific, or commercial applications.
The WSME is designed to estimate the Signal-to-Noise Ratio (SNR) for communication systems, particularly in the context of Adaptive Data Rate (ADR) control. The estimator is capable of operating effectively across various symbol rates, specifically targeting rates of 1024 ksps and below, with alternative configurations for higher rates of 2048 ksps and 4096 ksps. The implementation utilizes two independent lookup tables (LUTs) stored in the FPGA’s Distributed ROM, which are hard-coded to facilitate quick access to SNR estimates based on the received symbol rates.
The document includes technical details about the SNR estimator's architecture, including the use of a sum-and-dump filter and the relationship between sample size and SNR. It also provides insights into the bit energy estimator, which plays a crucial role in determining the energy per bit in the communication system.
Tables within the document present the current values of the SNR estimator’s primary and alternative lookup tables, showcasing the relationship between index ratios and corresponding SNR values in decibels. This information is critical for understanding how the estimator functions and how it can be applied in real-world scenarios.
The document emphasizes the importance of accurate SNR estimation in improving communication reliability and efficiency, particularly in challenging environments where noise can significantly impact signal quality. By providing a robust solution for SNR estimation, the WSME aims to enhance the performance of communication systems used in aerospace applications.
Overall, this Technical Support Package serves as a comprehensive resource for engineers and researchers interested in advanced communication technologies, offering insights into the design, implementation, and potential applications of the Whole Symbol Moments SNR Estimator. It underscores NASA's commitment to innovation and the dissemination of knowledge that can benefit a wide range of fields beyond aerospace.
