An application of a proposed airdrop planning system

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.Includes bibliographical references (p. 117).The United States military has always had an increasing need for more accurate airdrops, whether the drops are being implemented for various special operations missions, or for basic humanitarian relief. Improving the delivery accuracy of airdrops will result in numerous benefits. In attempting to improve airdrop accuracy, it is helpful to know what errors will arise throughout the course of a drop. This information is effective in revealing to the airdrop personnel what steps can be taken to improve the airdrop, as well as what the expected landing accuracy of the airdrop will be. This research converges on tools to assist in the estimation and improvement of airdrop landing errors. Wind estimation was studied to better understand the landing errors that stem from different wind prediction methods, as well as from onboard wind measurement systems. Other uncertainties, throughout each phase of an airdrop, are also known to produce landing errors, such as uncertainties in release conditions and parachute dynamics. These errors were implemented in airdrop simulations, for both unguided air release planning systems and guided airdrop systems, to determine the effects of these uncertainties on landing error. Error in wind estimation was found to be the largest source of error in the airdrop simulations. Guided systems were hypothesized to have much smaller landing errors than the unguided systems, and that hypothesis was confirmed in this study. One major benefit of using guidance was the ability to implement onboard wind measurement systems. Using the data from the simulation results, this information was combined to produce an airdrop planning aid to assist airdrop personnel in their aerial deliveries.(cont.) While the tool developed in this study is not a complete product, it represents a template on which to base further airdrop planning aids.by Lucas Jonathan Fortier.S.M

Error Control Mechanisms over Correlated Fading Channels

This paper considers the application of Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ) schemes over correlated wireless channels. In particular the depth of the interleaver and its influence on the frame-error-rate and transmission delay in the presence of Correlated fading and delay constraints is investigated. It is found that an increased interleaver depth in a correlated channel, although improving the Bit-Error-Rate, does not always improve the Frame-Error-Rate (FER). Further it is shown that in case of bursty channels a large interleaver depth is required to improve the FER, thus negatively influencing the delay. In this case the use of a retransmission scheme can improve delay performance