International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Binary PCM/FM has been widely adopted as a standard by the telemetry community. It offers a reasonable balance between detection efficiency and spectral efficiency, with very simple implementation in both the transmitter and receiver. Current technology, however, allows practical implementations of more sophisticated demodulators, which can substantially improve the detection efficiency of the waveform, with no changes to the modulator. This is accomplished by exploiting the memory inherent in the phase continuity of the waveform. This paper describes the implementation and performance of a noncoherent multi-symbol demodulator for PCM/FM. Sensitivity to offsets in carrier frequency, timing, and modulation index is also examined. Simulation results are presented which demonstrate improvements in detection efficiency of approximately 2.5 dB over traditional noncoherent single symbol detectors.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / It has been shown that a multi-symbol detector can improve the detection efficiency of PCM/FM by 3 dB when compared to traditional methods without any change to the transmitted waveform. Although this is a significant breakthrough, further improvements are possible with the addition of Forward Error Correction (FEC). Systematic redundancy can be added by encoding the source data prior to the modulation process, thereby allowing channel errors to be corrected using a decoding circuit. Better detection efficiency translates into additional link margin that can be used to extend the operating range, support higher data throughput, or significantly improve the quality of the received data. This paper investigates the detection efficiency that can be achieved using a multisymbol detector and turbo product coding. The results show that this combination can improve the detection performance by nearly 9 dB relative to conventional PCM/FM systems. The increase in link margin is gained at the expense of a small increase in bandwidth and the additional complexity of the encoding and decoding circuitry.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / It has been previously shown, through computer simulations, that a multiple symbol detector can provide substantial gains in detection efficiency (nearly 3 dB) over traditional PCM/FM detectors. This is accomplished by performing correlations over multiple symbol intervals to take advantage of the memory inherent in the continuous phase PCM/FM signal. This paper presents measured hardware results, from a prototype developed for the Advanced Range Telemetry (ARTM) Project, that substantiate the previously published performance and sensitivity predictions. Furthermore, this work confirms the feasibility of applying this technology to high-speed commercial and military telemetry applications.

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / The performance of telemetry systems may be strongly affected by diverse sources of perturbations. Among them, multipath channels and transmission noise are the most critical. While the effects due to the multipath channels can be attenuated thanks to equalization, the effects of the noise are limited if forward error correction is used. This paper first proves that the combination of blind equalization and forward error correction can strongly improve bit error rates. The other objective of the paper is to show that reasonably powerful codes like Reed-Solomon codes are sufficient to enable quasi-error free transmissions in a large majority of propagation channel scenarios.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / Transmitter mobility and multipath propagation make the telemetry channel both time and frequency selective, which results in telemetry link errors, sometimes in crucial flight phases. Only part of these impairments are compensated by various diversity techniques, but a fast converging adaptive channel equalization is probably the best suited and most cost effective solution. This paper first presents an analysis of mobile multipath propagation in telemetry based on recorded operational signals, both at the transmitter and at the receiver sides. Then it provides performance evaluation of a novel blind equalizer, assessed by offline processing of the recorded signals. The paper focuses on typical environments at a flight test centre, which exhibit critical multipath channel characteristics, namely during parking, taxiway and flight. The channel analysis exploits the recorded signals as well as the time frequency response of the novel equalizer filter. Performance evaluation shows that the equalizer outperforms state of the art Constant Modulus Algorithm (CMA). In particular, it is shown to significantly increase the telemetry link availability even in severe conditions, sometimes from nearly 0% to almost 100%, whereas the CMA fails to improve the signal quality as soon as the channel varies in time.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper will present the results of experiments to characterize the performance of a blind, adaptive constant modulus algorithm (CMA) equalizer in simulated telemetry multipath environments. The variables included modulation method, bit rate, received signal-to-noise ratio, delay of the indirect path relative to the direct path, amplitude of the indirect path relative to the direct path, and fade rate. The main measured parameter was bit error probability (BEP). The tests showed that the equalizer usually improved the data quality in the presence of multipath.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Improving the spectral-efficiency of aeronautical telemetry has been a principal area of research over the last several years due to the increasing demand for more data and the limitation of available spectrum. These efforts have lead to the development of the ARTM Tier 1 SOQPSK and Tier II Multi-h CPM waveforms which improve the spectral efficiency by two and three times, as compared to legacy PCM/FM, while maintaining similar detection efficiency. Now that more spectrally efficient waveform options are becoming available, another challenge is to further increase the detection performance. Better detection efficiency translates into additional link margin that can be used to extend the operating range, support higher data throughput, or significantly improve the quality of the received data. It is well known that Forward Error Correction (FEC) is one means of achieving this objective at the cost of additional overhead and increased receiver complexity. However, as mentioned above, spectral efficiency is also vitally important meaning that the FEC must also have a low amount of overhead. Unfortunately, low overhead and high coding gain are generally conflicting trades, although recent work has shown that Turbo Product Codes (TPC) are a particularly attractive candidate. Computer simulations predict that very impressive gains in detection performance are possible for a relatively small increase in bandwidth. The main drawbacks are the additional complexity of the decoding circuitry and an increase in receive side latency. This paper presents the latest simulation and hardware performance results of PCM/FM, SOQPSK, and Multi-h CPM with TPC.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / It is widely recognized that telemetry channels, particularly airborne channels, are afflicted by multipath propagation effects. It has also been shown that adaptive equalization can be highly effective in mitigating these effects. However, numerous other factors influence the behavior of adaptive equalization, and the type of modulation employed is certainly one of these factors. This is particularly true on modulations that exhibit different operating bandwidths. Computer simulations using the Constant Modulus Algorithm (CMA) have recently been reported for PCM/FM, ARTM Tier 1 SOQPSK, and Tier II SOQPSK. These encouraging results have led to a hardware implementation of a CMA equalizer. This paper presents the latest results from this work.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / This paper will present the results of some experiments with non-coherent, single symbol detection of pulse code modulation (PCM)/frequency modulation (FM) where the receiver intermediate frequency (IF) bandwidth is much wider than the bit rate. The experiments involved varying the peak deviation and measuring the bit error probability (BEP) at various signal energy per bit to noise power spectral density ratios (E(b)/N(o)). The experiments showed that the optimum peak-to-peak deviation was about 0.7 to 0.8 times the –3 dB IF bandwidth and that the E(b)/N(o) required for a given BEP increased as the ratio of IF bandwidth to bit rate increased. Further, bi-phase-level/FM performed slightly better than non-return-to-zero-level (NRZ-L)/FM with an ac coupled RF signal generator and IF bandwidths much wider than the bit rate.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / This paper compares telemetry link performance of the PCM/FM waveform when simultaneously transmitting in two different frequency bands, S-Band and C-Band. A description of the aircraft and ground station is presented followed by flight test results. These results are presented in the form of received signal strength and accumulated bit errors, versus time and link availability, over the flight paths. Conclusions are drawn based upon the presented flight test results.