• A NOVEL FFT-BASED TECHNIQUE FOR RAPID ACQUISITION OF HIGH DYNAMIC DSSS SIGNAL

      Ming, Wang; Taotao, Liang; Guoning, Ma; Yudong, He; Institute of Electronic Engineering, China Academy of Engineering Physics (International Foundation for Telemetering, 2019-10)
      High dynamic direct sequence spread spectrum (DSSS) signal acquisition process is a two-dimensional signal replication process no matter what acquisition methods are used. In this paper, acquisition methods in dynamic surroundings are researched. The analysis tells that, serial acquisition methods cannot meet the requirement of flight application, which requires correct signal capturing possibility of weak signal and less acquisition time. A new improved acquisition approach using partial correlator and Fast Fourier Transform (FFT) is introduced. The method can search Doppler and calculate C/A code phases in parallel. Matlab simulation indicate that, the FFT-based algorithm can work well in high dynamic DSSS receiver.
    • DESIGN OF PROBING WAVEFORMS IN SOFTWARE-DEFINED SENSING AND IMAGING SYSTEMS

      Lee, Hua; Univ California Santa Barbara, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      The probing waveforms play a crucial role in the performance of software-defined sensing-imaging systems. The characteristics of the probing waveforms govern both the computation complexity and accuracy of the estimation. This paper describes the concepts of the design and utilization of the probing waveforms for sensing and imaging applications.
    • CHANNEL AND SPECTRUM ESTIMATION FOR SOFTWARE DEFINED RADIO

      Lee, Hua; Sanchez, Connor D.; Radzicki, Vincent R.; Univ California Santa Barbara, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      Software defined radios are rapidly increasing in both research and commercial usage for many different applications. As the number of deployed systems increase, a difficult problem that remains is efficient usage of the Radio-Frequency (RF) spectrum to be shared among all these devices. Two key tasks for the radio to perform here include spectral estimation of the RF environment and channel estimation of the communication channel for which the data will be transmitted. These two steps are linked as the communication channel can change over different portions of the RF-spectrum. In this work, an algorithmic approach is presented for passive and active channel estimation procedures for wideband software-defined radios. The algorithm is comprised of first channel quality estimation followed by communication channel planning to optimize the overall performance.
    • INTERFERENCE MITIGATION OF ADJACENT RADIO FREQUENCY SIGNALS ON A FLEXIBLE SOFTWARE-DEFINED RADIO TESTBED PLATFORM

      Gonzalez, Virgilio; Elahi, Mirza M.; Sandoval, Jose C.; Corral, Pabel; Yasuda, Susumu; Univ Texas, Computational Science Program; Univ Texas, Dept Electrical and Computer Engineering; White Sands Missile Range, U.S. Army Test and Evaluation Command (International Foundation for Telemetering, 2019-10)
      The radio frequency (RF) spectrum is crowded with users and adjacent frequency users are facing an increase in interference from each other. The spectrum governing body Federal Communications Commission (FCC) has the difficult task of allocating spectral bands for new users for mobile devices using 4G LTE technology. Telemetry (TM) is affected by the adjacent band 4G LTE users in terms of signal degradation. To minimize the interference between adjacent frequency users, several methods can be used. A common but inefficient method separates adjacent band frequencies using guard bands which leaves a big portion of the spectrum unused. Alternatively, adjacent RF signals can be separated using digital filtering techniques with the signal of interest being unharmed and reducing the signal power of the interfering signal. A digital filtering technique includes bandpass filter (BPF) rejection, which has the ability to filter out adjacent interfering signals. This is accomplished by designing bandpass digital filters where the passband and stopband frequencies are adjusted to achieve maximum signal power and reject the interfering signal by reducing its power. A flexible software-defined radio testbed is set up to experiment and analyze this scenario with ease and effective measures.
    • CLASSIFICATION STYLE REGRESSION FOR SPECTRAL OPENING PMF ESTIMATION

      Fosdick, Garrett; Marefat, Michael; Bose, Tamal; Univ Arizona, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      Dynamic spectrum allocation (DSA) permits unlicensed users to access spectrum owned by a licensed user given they do so without interference to the primary user. To avoid interference with other users, the unlicensed user needs to be aware of channel availability. Spectrum sensing allows a radio to find spectrum holes, but costs energy and time. Predictive methods can be used to decrease the amount of spectrum sensing needed to find an available channel. We designed a novel neural network architecture for spectrum hole prediction. This neural network is capable of creating probability mass functions (PMF) estimates of the length of channel openings with no assumptions of the initial probability distribution or prior knowledge about the traffic. This architecture is shown to work through a mathematical proof, and its performance is measured through simulation.
    • Peak-to-Average Power Ratio (PAPR) Reduction for OFDM

      Moazzami, Farzad; Dean, Richard; Zegeye, Wondimu K.; Morgan State University, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      The telemetry community has been challenged in its search for additional spectrum for its aeronautical mission. With a fixed amount of spectrum the challenge becomes focused on increased spectrum efficiency. Today’s best solution for spectrum efficiency is Orthogonal Frequency Division Modulation (OFDM). This approach has proven effective with both cellular LTE as well as IEEE 802.11 wireless LAN systems. OFDM has seen limited use in telemetry systems in part due to issues related to high peak to average ratio of OFDM signals. This paper reviews approaches to resolving these issues and proposes a scheme for peak conditioning of OFDM signals to reduce the peak to average ratio. Results of preliminary experimental work are promising.
    • Neuro-OSVETA: A Robust Watermarking of 3D Meshes

      Vasic, Bata; Raveendran, Nithin; Vasic, Bane; Univ Arizona, Dept Electrical and Computer Engineering; Univ Nis, Electronic Dept (International Foundation for Telemetering, 2019-10)
      Best and practical watermarking schemes for copyright protection of 3D meshes are required to be blind and robust to attacks and errors. In this paper, we present the latest developments in 3D blind watermarking with a special emphasis on our Ordered Statistics Vertex Extraction and Tracing Algorithm (OSVETA) algorithm and its improvements. OSVETA is based on a combination of quantization index modulation (QIM) and error correction coding using novel ways for judicial selection of mesh vertices which are stable under mesh simplification, and the technique we propose in this paper offers a systematic method for vertex selection based on neural networks replacing a heuristic approach in the OSVETA. The Neuro-OSVETA enables a more precise mesh geometry estimation and better curvature and topological feature estimation. These enhancements result in a more accurate identification of stable vertices resulting in significant reduction of deletion probability.
    • USING TENA AND JMETC FOR TELEMETRY APPLICATIONS

      Hudgins, Gene; Secondine, Juana; TENA Software Development Activity (SDA) (International Foundation for Telemetering, 2019-10)
      Often, TM requires operators on location with receive system(s) or at a remote console (with a remote antenna control unit), resulting in TDY for operators and possibly a shortage of operators to support all scheduled operations. A remote-control capability could eliminate existing personnel requirements at both the local system antenna site as well as the control facility, greatly reducing operational costs. TENA provides for real-time system interoperability, as well as interfacing existing range assets, C4ISR systems, and simulations; fostering reuse of range assets and future software systems. JMETC is a distributed, LVC capability using a hybrid network solution for all classifications and cyber. TENA and JMETC allow for the most efficient use of current and future TM range resources via range resource integration, critical to validate system performance in a highly cost-effective manner.
    • AN IMPROVED LOG-DOMAIN BELIEF PROPAGATION ALGORITHM OVER GRAPHS WITH SHORT CYCLES

      Raveendran, Nithin; Srinivasa, Shayan G.; Vasic, Bane; Univ Arizona, Dept Electrical and Computer Engineering; Indian Institute of Science, Dept Electronic Systems Engineering (International Foundation for Telemetering, 2019-10)
      We present a modified belief propagation (BP) algorithm for decoding low density parity check codes having graphs with short cycles. The modified algorithm in log domain is superior in terms of numerical stability, precision, computational complexity and ease of implementation when compared to the algorithm in the probability domain. Simulation results show improvement in decoding performance for the modified BP compared to the original algorithm. The modified approach is also generalized for graphs with isolated cycles of arbitrary length by considering the statistical dependency among messages passed in such cycles.
    • CYBERDEFENSE AND DATA SECURITY IN FLIGHT TEST APPLICATIONS

      Weir, Malcolm; Ampex Data Systems Corporation (International Foundation for Telemetering, 2019-10)
      Specialist test establishments have historically placed significant reliance on “security through obscurity”. With increasing “always on” connectivity and the drive to leverage commercial products, the threat space has widened significantly while the sophistication of attack vectors has evolved. Access through vulnerabilities embedded within a platform’s communications, flight controls, or other on-board access points leave organizations vulnerable to attack, exploitation, and loss of revenue or property. Cyber and operational security associated with all aspects of aircraft technologies is becoming increasingly critical. This paper investigates techniques and procedures by which aircraft and space vehicles can be compromised by and protected against cyber-attacks.
    • MITIGATION OF ANTENNA POLARIZATION TRANSFORMATIONS CAUSED BY AIRFRAME REFLECTIONS

      Geoghegan, Mark; Nusair, Marwan; Quasonix (International Foundation for Telemetering, 2019-10)
      The majority of aircraft telemetry antennas transmit a linearly polarized wave. These linearly polarized signals are often received by two orthogonal (left and right hand) circularly polarized receive antennas, each of which has 3 dB polarization loss. Under nominal conditions, a diversity combiner can be used to coherently add the two received signals, thereby restoring the 3 dB loss. Recent flight tests have revealed that the signals radiating from the aircraft are actually elliptically polarized or even circularly polarized, leading to degraded combiner performance. This paper describes how the transmit polarization can be transformed from linear to circular, why this degrades combiner performance, and how to mitigate this effect.
    • ON CARRIER FREQUENCY AND PHASE SYNCHRONIZATION FOR CODED 16-APSK IN AERONAUTICAL MOBILE TELEMETRY

      Rice, Michael; Redd, Bryan; Briceno, Ximena; Brigham Young University, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      This paper examines the problem of carrier phase and frequency estimation for coded 16-APSK in aeronautical mobile telemetry. Given the fact that coded systems tend to operate at lower signalto-noise ratios than uncoded systems, the synchronizer must operate at these lower signal-to-noise ratios. For a 30 kHz frequency offset and a 10 Mbit/s 16-APSK signal, the conventional phase lock loop (PLL) system does not achieve consistent lock to be a useful approach. Consequently, a blind feed-forward approach, based on the FFT, and an initialized feedback approach based on the PLL were examined. The feed-forward estimator is capable of achieving BER ideal performance for Eb/N0 ≥ 6 dB using 1024 symbols. The feedback estimator, initialized using a feed-forward estimate based on 1024 symbols is also capable of achieving BER ideal performance for Eb/N0 ≥ 6 dB. Both synchronizers require a sufficiently good blind estimate: the estimate based on 2014 symbols appears to be the minimum value to achieve good performance.
    • BLOCK GENERALIZED SPATIAL MODULATION FOR MASSIVE MIMO SYSTEMS

      Borah, Deva K.; Curry, Elam; New Mexico State University, Klipsch School of Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      Spatial modulation techniques have the ability to convey information by both the positions of active antennas as well as the symbols they transmit. Such techniques include the generalized spatial modulation (GSM) that can provide high spectral efficiency. In general, however, the total number of available symbols in GSM is not a power of two. Therefore, selection of a symbol alphabet from the available symbols is needed. This is a numerically complex problem. In this paper, we propose to significantly reduce the complexity of the GSM symbol set selection problem by grouping antennas together to form blocks, thus producing block GSM (BGSM) symbols. A previously developed iterative combinatorial method is extended to BGSM symbol selection. The effects of the Rician K-factor, BGSM symbol block size, and antenna configuration on the performance and design complexity are studied. The algorithm is found to significantly reduce the complexity of the BGSM symbol set selection problem.
    • POLARIZATION DIVERSITY AND EQUALIZATION OF FREQUENCY SELECTIVE CHANNELS IN TELEMETRY ENVIRONMENT FOR 16APSK

      Rice, Michael; Arabian, Farah; Brigham Young University, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      Providing RHCP and LHCP outputs from the antennas vertical (V) and horizontal (H) dipoles in there sonant cavity within the antenna feeds is the current practice of ground-based station receivers in aeronautical telemetry. The equalizers on the market, operate on either LHCP or RHCP alone, or a combined signal created by co-phasing and adding the RHCP and LHCP outputs. In this paper, we show how to optimally combine the V and H dipole outputs and demonstrate that an equalizer operating on this optimally-combined signal outperforms an equalizer operating on the RHCP, LHCP, or the combined signals. Finally, we show how to optimally combine the RHCP and LHCP outputs for equalization, where this optimal combination performs as good as the optimally combined V and H signals.
    • RESILIENT PNT / TSPI ALTERNATIVE SOLUTIONS FOR TELEMETRY DURING GNSS OUTAGE TEST SCENARIOS

      Fischer, John; Perdue, Lisa; Orolia (International Foundation for Telemetering, 2019-10)
      GNSS is key to effective situational awareness, providing critical Positioning, Navigation and Timing (PNT) telemetry data for mobile military operations. Yet GPS/GNSS jamming and spoofing attacks are on the rise. The combination of low-cost hardware, open source software, and tutorials on YouTube have fostered the proliferation of these malicious acts. Beyond intentional disruption, other factors such as environmental conditions and conflicts with other electronic systems can result in unreliable or even unavailable GNSS data. The disruption of GNSS for increasing periods of time through jamming/spoofing must now be an essential test component in most test scenarios today. How can one still provide reliable Time-Space Position Information (TSPI) during periods of GNSS denial? Key mobile military operations that rely on continuous and trusted PNT telemetry data from GNSS include: SatCom on the Move (SOTM), Command, Control, Communications, Computer, Intelligence, Surveillance and Reconnaissance (C4ISR), Airborne Communications Relay, Synthetic Aperture Radar, and Combat Search and Rescue (CSAR). Techniques and technologies used in battlefield systems to provide alternative sources of PNT data during a GNSS outage, can also be used on the test range. This paper will identify technologies, best practices and strategies for GNSS jamming/spoofing detection and protection systems and testing protocols to maintain a state of PNT readiness.
    • Adaptive OFDM for Aeronautical Channels

      Moazzami, Farzad; Dean, Richard; Zegeye, Wondimu K.; Alam, Tasmeer; Morgan State University, Dept Electrical and Computer Engineering (International Foundation for Telemetering, 2019-10)
      Previous work modeled the cruise phase of an aeronautical channel and showed how the channel varied as a function of height, distance, and speed. What was apparent from that analysis was that the ``cruise" channel was remarkable stable and varied slowly and predictably over time. The steady state channel reflected a 2-ray multipath model which exhibits deep nulls in the spectrum which affects serial tone modems significantly. Further the application of parallel tone modulation improves performance except for that portion of the band which was degraded by the null. This points to the use of Adaptive OFDM (AOFDM) structure wherein tones are only sent in portions of the band which are strong and not areas where the signal is weak. This work develops a method for capturing a profile of the Signal to Distortion Ratio (SDR) for each tone for each frame and over time. It also develops a method for converting the SDR per tone to estimate the optimum QAM modulation scheme for each tone for application in Link Dependent Adaptive Radio (LDAR).
    • AN APPROACH FOR BER DETERMINATION USING LOGGED AERONAUTICAL TELEMETRY DATA

      Tamakuwala, Jimmy B.; Sonar, Souvik; Jena, Avijit; Integrated Test Range, DRDO Chandipur; Defense Research and Development Organization (International Foundation for Telemetering, 2019-10)
      BER is regarded as the link-performance metric in a digital communication system. It is a function of Eb/N0 and is dependent on the modulation scheme used. This relation is often used in prediction of ground telemetry systems performance for a mission configuration. However, there is no objective way of comparing the post flight results, as BER measurement in a flight test is not practically feasible for want of transmitting sufficient reference bit patterns. In this paper, an indirect way of computing BER and, in turn, link Eb/N0 is proposed for a PCM/FM link based on the frame synchronised data logged by the ground telemetry equipment. Using known quantities like bit rate and frame rate, a quantity defined as frame loss rate is computed. Applying the relations between frame loss probability, frame sync pattern and SFID information in the PCM format, an approach for bit error probability is demonstrated based on field data. By using a sliding window over a fixed length of data, BER for the entire flight duration can be determined as a function of flight time with the step size of the length of data window.
    • DUAL-CHANNEL RECEIVER PERFORMANCE USING BESTCHANNEL SELECTION: FIELD TEST RESULTS

      Uetrecht, Jim; Quasonix, Inc. (International Foundation for Telemetering, 2019-10)
      Best-Channel Selection (BCS) uses real-time data quality metrics (DQM) to select the best demodulated bits from Channel 1, Channel 2, and the Combiner of dual-channel receivers. Laboratory testing has demonstrated a substantial reduction in bit error rate (BER) relative to individual channels (including the Combiner) under some synthesized link conditions, with no degradation in BER under the remainder of tested link conditions. This paper extends those results to real-world flight tests.
    • EFFECT OF ROTATING PROPELLERS ON TELEMETRY SIGNALS

      Geoghegan, Mark; Nusair, Marwan; Quasonix (International Foundation for Telemetering, 2019-10)
      The migration of aeronautical telemetry systems to C band has prompted a fresh look at many historically uninteresting facets of telemetry links. The effects of higher cable losses and smaller antenna beamwidths, for example, have been recognized and accounted for. Recent flight tests at Edwards AFB with a propeller-driven aircraft have revealed another such effect, which we have termed “prop chop”. Realtime data quality metric (DQM) values showed a periodic fluctuation in DQM, related to the aircraft engine speed. An investigation of this phenomenon using detailed electromagnetic simulation of a transmit antenna in the presence of a propeller shows a mechanism for this interference, both when the propeller is in front of the transmit antenna and when it is behind the transmit antenna. This paper compares the electromagnetic propagation simulation results to measured values from the field.
    • Implementation and Benefits of Best Source Selection

      Gerstner, Grant; Normyle, Dennis; NAVAIR Atlantic Division (International Foundation for Telemetering, 2019-10)
      A comprehensive guide to implementing best source selection at a test range. This paper uses the history of the Atlantic Test Range's implementation as a guide to show the steps needed to implement Best Source Selection. It also discusses the advantages to best source selection at all levels of implementation.