| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 102 === In a wireless sensor network (WSN), packet errors could occur due to weak signal strength or signal interference. These erroneous packets may have to be recovered through retransmission. However, too many retransmissions can increase network load significantly. Hence, in this Thesis, we propose a packet interleaving algorithm (PIA) based on Reed-Solomon (RS) code to reduce the retransmissions in a WSN. First, the collected data are classified into two different types; high-reliability request (HRR) data and low-reliability request (LRR) data. In RS code, collected data are converted into symbols according to the symbol length. To improve the transmission reliability, in PIA, an HRR packet is encoded with a short symbol and an LRR packet with a long symbol. Once an HRR and an LRR packet are transmitted, respectively, to a upper layer sensor in a tree-structured WSN, they are interleaved on a symbol-by-symbol basis. Thus, the effect of burst errors (BE) is dispersed into small portions so that the uncorrectable probability of HRR packets can be reduced. Finally, two models, the Uniform Bit-Error Model (UBEM) and the On-off Bit-Error Model (OBEM) are built to analyze the packet uncorrectable probability. In the two models, we first change the lengths of BE, and then we vary the shift positions in a BE period, and finally we change the number of correctable symbols to observe the impact of the three factors on the uncorrectable probability of HRR and LRR packets.
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