Available at: http://digitalcommons.calpoly.edu/theses/104
Date of Award
MS in Computer Science
Satellites are playing an increasingly important role in collecting scientific information, providing communication services, and revolutionizing navigation. Until recently satellites were large and very expensive, creating a high barrier to entry that only large corporations and government agencies could overcome. In the past few years the CubeSat project at California Polytechnic University in San Luis Obispo (Cal Poly) has worked to refine the design and launching of small, lightweight, and less expensive satellites called pico-satellites, opening space up to a wider audience. Now that Cal Poly has the launch logistics and hardware under control, a new problem has arisen. These pico-satellites are within communication range of a ground station only 40 minutes a day. This, combined with their 1200 bps communication speed, limits the usefulness of the satellite missions to those only transmitting small amounts of data back to Earth. This thesis proposes a novel protocol that allows a sparse network of pico-satellites to communicate among one another and to larger satellites called data mules, which relay the information back to the ground station at much higher speeds. The data mules are able to provide higher speeds because they are larger satellites with less power constraints. This protocol makes it possible for a pico-satellite to send more data over a given amount of time with less end-to-end delay. When every satellite has large amounts of data almost three times as much aggregate data can be sent through the network, and almost five times more data can be sent if only a single satellite has large amounts of data to send. The end-to-end delay is cut almost in half when sending 1 MB of data per day per satellite and is decreased by a factor of at least three when sending large amounts of data from only one satellite.