Afran, Shah; Saquib, Mohammad; Rice, Michael (International Foundation for Telemetering, 2018-11)
In this paper, we explore a carrier frequency offset (CFO) estimation scheme with sparsity-constraint
(SC) on the aeronautical telemetry channels. This SC CFO estimator is implemented in two steps.
In the first step, channel support is recovered by combining compressed sensing techniques with
the CFO estimate based on the non-sparsity constraint (NSC) on the channel. Next we use the
estimated channel support to derive the SC CFO estimator. Simulations are performed to compare
the performance of the SC CFO estimator against the existing NSC CFO estimators using shaped
offset QPSK version TG (SOQPSK-TG) modulated iNET-formatted data over an aeronautical test
Rice, Michael; Hogstrom, Christopher; Nash, Chris; Ravert, Jeff; Saquib, Mohammad; Afran, Md. Shah; Cole-Rhodes, Arlene; Moazzami, Farzad; Perrins, Erik; Temple, Kip (International Foundation for Telemetering, 2017-10)
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.
Afran, Md. Shah; Saquib, Mohammad; Rice, Michael (International Foundation for Telemetering, 2017-10)
This paper investigates the performance of sparse minimum mean squared error (MMSE) equalizer for generalized time-reversed space-time block codes (GTR-STBC) in aeronautical telemetry. GTR-STBC equipped with MMSE equalizer performs the best trade-off between the signal-tonoise ratio and inter-symbol interference by allocating unequal power over aeronautical telemetry channels. However, aeronautical telemetry channels are in general consists of larger delay spreads which make the MMSE equalization of aeronautical channels with GTR-STBC computationally complex. Interestingly enough, in spite of larger delays aeronautical channels are made of few sparsely distributed multipaths and therefore their MMSE equalizers are highly compressible. In this paper, compressed sensing based greedy algorithm is used for the design of sparse MMSE equalizer and a convex curve-ﬁtting algorithm is used to ﬁnd the sub-optimum power allocation parameter at the same sparsity level for GTR-STBC. Our simulation results show that 75-90% of the non-zero equalizer taps can be reduced with a slight relaxation of the mean-squared error (or equivalentlyslight degradationof bit-errorrate performance). It isalso observedthat the optimum transmitter power proﬁle for the sparse MMSE equalizer is different than that of the non-sparse equalizer.
Rice, Michael; Narumanchi, Gayatri; Saquib, Mohammad (International Foundation for Telemetering, 2011-10)
This paper compares the bit error rate performance of a single channel equalizer with the bit error rate performance of a multi-channel equalizer (in the form of the time-reversed space-time block code) using channels derived from multipath channel measurements at Edwards AFB, California, and Cairns Army Airfield, Ft. Rucker, Alabama. The results show that the performance of the multi-channel equalizer is better than the single channel equalizer over the weaker channel, but worse than the performance of the single channel equalizer over the stronger channel. We conclude that the best approach for the informed transmitter is to apply all available power to a single antenna, whereas the best approach for the uninformed transmitter is to apply equal power with transmit diversity to the two available antennas.
Rice, Michael; Hogstrom, Christopher; Nash, Christopher; Ravert, Jeffrey; Cole-Rhodes, Arlene; Moazzami, Farzad; Saquib, Mohammad; Afran, Md. Shah; Perrins, Erik; Temple, Kip (International Foundation for Telemetering, 2016-11)
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.
Saquib, Mohammad; Popescu, Otilia; Popescu, Dimitrie C.; Rice, Michael (International Foundation for Telemetering, 2006-10)
In this paper we describe a new method that is applicable to mitigating both multipath interference and adjacent channel interference (ACI) in aeronautical telemetry applications using ARTM Tier-1 waveforms. The proposed method uses a linear equalizer that is derived using Kalman filtering theory, which has been used for channel equalization for high-speed communication systems. We illustrate the proposed method with numerical examples obtained from simulations that show the bit error rate performance (BER) for different modulation schemes.
Afran, Md. Shah (International Foundation for Telemetering, 2015-10)
This paper presents a frequency domain equalization (FDE) technique for aeronautical telemetry channels. The FDE has significantly lower computational complexity compared to its time-domain counterpart, however both are found to exhibit almost identical performance. A cyclic prefix is generally needed to implement the FDE. In this paper, we exploit the repetition of iNET preamble and ASM bits in place of cyclic prefix.
Rice, Michael; Narumanchi, Gayatri; Saquib, Mohammad (International Foundation for Telemetering, 2012-10)
This paper investigates a fractionally-spaced decision-feedback equalization technique for Shaped Offset Quadrature Phase Shift Keying (SOQPSK). The kernel of the block-based feedback algorithm is to estimate the intersymbol interference and cancel it from the samples used to make the bit decisions. This process refines the bit estimates sequentially, thereby increasing the probability of obtaining accurate estimates. The simulated bit error rate performance of the decision-feedback technique shows a 1 dB improvement over MMSE-equalized SOQPSK-TG over channels derived from multipath channel measurements at Cairns Army Airfield, Ft. Rucker, Alabama and Edwards AFB, California.
Ali, Tariq M.; Saquib, Mohammad; Rice, Michael (International Foundation for Telemetering, 2005-10)
This paper describes and interference cancellation technique appropriate for ARTM Tier-1 waveforms. The technique requires the estimators for the bit sequences for the adjacent channels as well as the power levels of the adjacent channels. Simulation results show that the interference canceller allows a more dense “channel packing” thereby creating a channel utilization 67% ~ 100% greater than the current IRIG 106 recommendations.
Rice, Michael; Saquib, Mohammad; Perrins, Erik (International Foundation for Telemetering, 2014-10)
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.
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