This thesis describes the analysis, design, simulation, evaluation and implementation of an optimized network protocol and its software system for 'little LEO' satellite networks to support an efficient digital store and forward (S&F) global data deliyery service. Many protocols have been proposed for 'little LEO' satellite S&F communication net""orks. These protocols fall into two categories. One category is the protocols which have been implemented in the real world, such as MSG2 and P ACSA T. These protocols were designed under constrained conditions and concentrated more on real world implementation. Another category is the protocols which are still proposals, such as LAMSLM, LAMS-DLC, variable-length information frame-type random access scheme and so on. These protocols were designed under some idealized conditions and concentrated only on some aspects. All these protocols are evaluated on their capability to handle the dominating problems in a typical LEO satellite S&F communication system, such as message addressing, multiple access control, multiplexing, and error control. Some problems in the design of these protocols are identified from real world statistics and others by simulation or analysis. To solve the problems, an optimized network layer protocol (called LEONET) is developed. LEONET provides an optimized and integrated solution to the dominating problems in 'little LEO' satellite S&F networks. Several improvements over previous protocols have been achieved in LEONET. On the up-link, LEONET defines a ne"" multiple access control protocol which allocates the number of reservation time slots according to dynamic network requirements, and therefore reduces collisions and leaves more up-link resource to upload messages. On the down-link, LEONET adopts a new message addressing and multiplexing mechanism which eliminates the directory downloading and can dO\\lnload more messages. The message uploading and downloading are scheduled by a novel routing optimization algorithm which can further improve the network performance. Simulation models are built for both pervious protocol and proposed protocols to evaluate their performance. It shows that LEONET can better use the 'little LEO' satellite network resource and provide much better performance, especially when the offered load is heavy orland the user population is large. An object-oriented software model for the proposed protocol is built. A software system of the proposed protocol is generated from the model and verified by OPNET.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:301291 |
| Date | January 1999 |
| Creators | Cheng, Baozhong |
| Publisher | University of Surrey |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://epubs.surrey.ac.uk/804469/ |
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