Browsing by Author "Brown, T."
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- Adaptive power control as a fade countermeasure on satellite linksSweeney, Dennis G. (Virginia Tech, 1993)Satellite systems in the 20/30 GHz band are very susceptible to outages due to rain-induced fades. In order to reduce the impact of these fades, it has been proposed that the power of the uplink station transmitter be adjusted during the fade to compensate. This dissertation will explore some of the issues involved in implementing this uplink power control (ULPC). Fade slope is examined as a parameter to predict signal strength during a fade. A fade slope model based on fade physics is presented, but it strongly suggests that fade slope is not an appropriate parameter for ULPC. Real time scaling of attenuation from the downlink to the uplink shows more promise for ULPC. Differences in drop size distributions during a rain storm will result is different scaling factors. If the downlink attenuation is limited to 6 dB at 20 GHz, real time scaling can be accomplished. A scaling type ULPC algorithm driven by downlink attenuation is tested on 66 hours of OLYMPUS 20/30 GHz fade data. A similar algorithm driven by uplink attenuation is tested and the performance of the two algorithms is presented and compared.
- Development of Human Factors Guidelines for ATIS and CVO Identify Strengths and Weaknesses of Alternative Information Display FormatsHulse, Melissa C.; Dingus, Thomas A.; Mollenhauer, Michael A.; Liu, Y. C.; Jahns, Steven K.; Brown, T.; McKinney, B. (United States. Federal Highway Administration, 1993-10)This report is one of a series produced as part of a contract designed to develop precise, detailed, human factors design guidelines for Advanced Traveler Information Systems (ATIS) and Commercial Vehicle Operations (CVO). The goals of the work covered in this report were to: (1) identify information format alternatives for ATIS devices for both private drivers and CVO applications, and (2) identify research issues that must be addressed in order to develop effective information format guidelines. To achieve these goals, and to make the greatest progress possible toward the ultimate project goal of guideline development, the project developed the strategy of turning the current state of knowledge into tools applicable to any ATIS design. Four primary design-decision tools were developed. These tools are intended to help either professional or nonprofessional human factors designers make appropriate tradeoff decisions in designing effective ATIS displays. The four tools are: (1) Sensory Modality Allocation, (2) Trip Status Allocation, (3) Display Format Allocation, and (4) Display Location.