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 investigates the performance of a multiple-input multiple-output (MIMO) digital communication system, when the transmitter is located on a spinning vehicle. In particular, a 2x2 MIMO system is used, with Alamouti coding at the transmitter. Both Rayleigh and Rayleigh plus line-of-sight, or Rician, models combined with a deterministic model to simulate the channel. The spinning of the transmitting vehicle, relative to the stationary receive antennas, modulates the signal, and complicates the decoding and channel parameter estimation processes. The simulated system bit error rate is the primary performance metric used. The Alamouti channel code is shown to perform better than the maximal ratio receiver combining (MRRC) and single receiver (2x1) system in some circumstances and performs similarly to the MRRC in the broadside case.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In this paper, we extended the matched filter bound (MFB) of time-discrete multipath Rayleigh fading channels derived in [1,2] for multiscale wavelet signaling communication.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Data from ARTM channel sounding test flights is examined to characterize the dynamic channel behavior of aeronautical telemetry channels. The dynamic behavior is characterized using the Doppler power spectrum. The width of the Doppler power spectrum is the Doppler bandwidth of the channel which indicates the required bandwidth of adaptive detection techniques such as adaptive equalization, adaptive modulation, adaptive channel selection and adaptive error control coding. Data collected from ARTM Flight 11 suggest a Doppler bandwidth exceeding 6.7 Hz for the channel, but greater accuracy and resolution will only be possible with more data.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The presence of multipath fading has been shown to degrade the performance of a wireless channel. This paper quantifies the effects of multipath interference on signal performance based on the estimated parameters of the multipath signal. Theoretical results are compared with actual results obtained through the Advanced Range Telemetry (ARTM) program.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A non-feedback adaptive equalizer based on Feher Equalizer (FE) is presented and its performance is evaluated. By artificially adding notch/notches to the corrupted spectrum resulted from selectively faded LEO environments, an artificial symmetry is created and as a result the BER/BLER is improved. The location and the depth of artificial additive notches are based on the shape of the spectrum of the corrupted signal. By measuring the power in narrow bands around certain frequencies the existence of notches around those frequencies are predicted. Based on this information notches with proper depths are added to the main spectrum which results in more symmetry in the spectrum. The selection process of artificial notch/notches are based on the shape of the signal spectrum, which means that this equalizer unlike most conventional equalizer does not need any feedback. The nonfeedback nature of this equalizer improves the adaptation time over that of alternative equalizers The results presented in this paper are based on both MatLab simulations and laboratory hardware measurements.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Dynamic hardware and software schemes for trajectory based simulation of LEO satellite channel are presented and evaluated. The simulation models are based on the practical LEO satellite channels and change dynamically with the trajectory using the latitude and longitude of the LEO satellite as input. The hardware simulator is consisted of a trajectory based selective fade generator, a trajectory based Doppler shifter, trajectory based time shadowing simulator and a standard channel for addition of noise, ACI and CCI. A FQPSK modulated signal is passed through a trajectory based dynamic fade generator and the spectrum is distorted. Then the resulting signal is exposed to a trajectory based dynamic Doppler Shifter, simulating the passage of the satellite overhead. Then the proper AWGN, ACI or CCI is added to the signal. At the final stage the signal is passed through a trajectory based time Shadowing simulator. The software simulator is a dynamic real time simulator written in MatLab and its structure is similar to the hardware simulator.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper will discuss the use of a specialized telemetry signal simulator for pre-mission verification of a telemetry receiving system. This will include how to configure tests that will determine system performance under “real time” conditions such as multipath fading and Doppler shifting. The paper will analyze a telemetry receiving system and define tests for each part of the system. This will include tests for verification of the antenna system. Also included, will be tests for verification of the receiver/combiner system. The paper will further discuss how adding PCM simulation capabilities to the signal simulator will allow testing of frame synchronizers and decomutation equipment.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / A series of RF channel flight characterization tests were recently run to benchmark multi-path performance of high-speed quadrature amplitude modulation (QAM) over the ocean surface. The modulation format was differential-phase/absolute-amplitude two level polar 16 QAM. The bit rate was 100 Megabits per second with a symbol period of 40nS. An aircraft radiated the test signal at 5 different altitudes. It made two inward flights, on two different days, at each altitude with vertical and horizontal polarization, respectively. Receivers, using circular antenna polarization, were in two different locations. Analysis of the resulting data shows flat fading and frequency selective fading effects.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Data collected during July 1999 at Edwards EAFB by the Advanced Range Telemetry (ARTM) program is examined to characterize the dynamic behavior of multipath interference in an aeronautical telemetry channel. Multipath fade events are analyzed in the frequency domain to show how these fades appear, evolve, and disappear from the channel. A channel model and examples from the channel sounding data are used to show the dynamic nature of these fade events. The Doppler power spectrum is used to quantify the exact time-varying nature of the multipath fade events. The coherence time, or the amount of time the channel can be viewed as unchanging, is obtained from the Doppler power spectrum and is calculated to be 100 ms in the data sets examined in this paper. This implies that adaptive multipath mitigation techniques must have an adaptation bandwidth of 10 Hz.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy