| The Advanced Orbiting System(AOS) has been adopted and realized in many aero-space missions in our country such as manned spacecraft projects etc., and it will be used more extensively in future aerospace plans like moon exploration projects, tracking and data relay satellites. Most advanced orbiting systems used in our country, so far, have only chosen to transfer their data in a mega data rate by grade 2 or 3 service in space link layer. However, spotted in highspeed aerospace communication environment for the future, their space link layer performance must be further improved according to the newly imposed demands.In this dissertation, the requirements on space link layer performance of AOS from the target highspeed aerospace communication instance are first fully explored, and then after the factors that affect the throughput and delay performance are systematically discussed, a number of optimization conditions for these two metrics are brought out by theoretical analysis and formula induction. Especially, two key algorithms which will be elaborated on are outlined: virtual channel scheduling algorithm and space link ARQ algorithm (SLAA).For virtual channel scheduling, a condition is brought out which would optimize the delay performance of the target source during its virtual channel scheduling process, and a combined scheduling algorithm is proposed accordingly on the basis of analyzing the drawbacks of three commonly-used scheduling algorithms: periodical polling scheduling, queue-length based asynchronous scheduling and priority based asynchronous scheduling.For SLAA, the LACW field used for ACK report is carefully designed as a prerequi-site, and then that the improved combined acknowledgement-SR ARQ outperforms single acknowledgement-SR ARQ and accumulated acknowledgement-SR ARQ is theoretically proved.In the last part, an OPNET model for AOS protocol is built, and the advantages of the improved SR-ARQ algorithm are proved again by two simulation scenarios. |
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