Telemetry Modulation

11:00 AM – OTFS Modulation for the AMT Environment
Richard Simeon and Dr. Erik Perrins, University of Kansas

Orthogonal Time Frequency Space (OTFS) is a new modulation designed to operate in the high-mobility/high-Doppler environment that is closely related to 5G’s Orthogonal Frequency Division Multiplexing (OFDM). OFDM has been investigated for use in the next generation telemetry systems, but performance can suffer at high test article (TA) speeds due to rapid variations in the time-frequency channel response and inter-carrier interference (ICI) resulting from Doppler shifts. This paper presents an overview of OTFS and an exemplary OTFS system that can operate at high TA speeds in the Aeronautical Mobile Telemetry (AMT) environment to showcase advantages over OFDM such as resistance to ICI and jamming, lower peak to average power ratio (PAPR), and better spectral efficiency. Future areas of research unique to the AMT use case are discussed.

11:20 AM – Balancing Efficiency and Performance in Aeronautical Telemetry: A Study on Spectral Optimization Techniques for ARTM Codes
Andrew Cummins and David Mitchell, New Mexico State University; Erik Perrins, University of Kansas

In this work, we investigate the application of reinforcement learning (RL) to optimize artifical noise injection for enhancing physical layer security and reliability employing Low Density Parity Check codes over additive white Gaussian noise (AWGN) channels. We employ a Mutual Information Neural Estimator (MINE) to measure  information leakage to an eavesdropper, and a belief propagation (BP) decoder to estimate bit error rates (BER) across a range of SNR values. Using these tools, we explore the potential of an RL agents ability to learn how to adjust noise injection strategies with the goal of minimizing both information leakage and BER. Early experiments shows the potential of combining machine learning with physical-layer security techniques.

11:40 AM – Eliminating Undetected Errors in LDPC-CPM Decoders
Erik Perrins, University of Kansas

In error control coding, an undetected error occurs when the received code word passes the parity check even though errors are present. Such errors are a critical concern in many applications because a passed parity check at the receiver is taken to mean that the received code word is error free. In this paper, we outline the key operating principles and differences between the two constituent decoders in the system. Our high-level discussion reveals insights on two strategies that can be used in an LDPC-CPM decoder to eliminate undetected errors. The first is a brute-force approach of performing an additional decoding iteration to confirm (or rebut) a passed parity check. The second is a simple and elegant check-node-splitting approach that can be incorporated into the LDPC code itself. We provide numerical results and operating scenarios where these techniques are recommended for use.