This paper summarizes the analysis of bit error rate data captured during flight tests designed to compare data-aided equalizers with SOQPSK-TG to unequalized and currently available blind, adaptive equalizers with SOQPSK-TG. The number of bit errors,on a second-by-second basis, are analyzed. The results are different for each test point. Given the uncertain behavior of the preamble detector for the data-aided equalizer and the differing channel conditions between the data-aided equalizer channel and the conventional serial streaming telemetry channel, we are unable to draw any firm comparative conclusions.

This paper describes the results of flight tests designed to compare data-aided equalization to blind, adaptive equalization using SOQPSK-TG in aeronautical telemetry. The flight tests were conducted on 3 June 2016 at the Air Force Flight Test Center, Edwards AFB, at upper L band (1801.5 MHz) and at C band (4711.5 MHz). Five data-aided equalizers were implemented and compared to a commercially available blind equalizer. In addition, all equalized bit streams were compared to an unequalized reference. The results show that the blind equalizer tends to be either really good or really bad. In contrast, the data-aided equalizers tend to exhibit more graceful degradation. Which equalization method is “best” is not clear as of this writing. The answer depends on a number factors that will become clear as more data from the experiments is analyzed.

This paper deals with the problem of producing the best bit stream from a number of input bit streams with varying degrees of reliability. The best source selector and smart source selector are recast as detectors, and the maximum likelihood bit detector (MLBD) is derived from basic principles under the assumption that each bit value is accompanied by a quality measure proportional to its probability of error. We show that both the majority voter and the best source selector are special cases of the MLBD and define the conditions under which these special cases occur. We give a mathematical proof that the MLBD is the same as or better than the best source selector.

This paper presents algorithms for estimating the frequency offset, multipath channel coefficients, and noise variance of iNET-formatted SOQPSK-TG. The estimators compare the received signal samples corresponding to the iNET preamble and attached sync marker (ASM) bits to a locally stored copy of the SOQPSK-TG samples corresponding to the same. The mean and variance of the three estimators over ten test channels derived from channel sounding experiments at Edwards AFB is presented. The results show that usable estimates are achievable.

The iNET preamble can be used to estimate the frequency offset and multipath channel in an aeronautical telemetry link. To accomplish this, the receiver must be able to identify the start of the preamble within the received data stream in the presence of uncompensated frequency offset and unknown multipath channel. In this paper, we explore the performance of seven candidate preamble detectors in the presence of a frequency offset and over multipath channels typically encountered in aeronautical telemetry. A non-coherent post-detection integration (NCPDI) detector considered in this paper demonstrates the best detection performance for a reduced complexity.