TAILIEUCHUNG - Smart Wireless Sensor Networks Part 9

Tham khảo tài liệu 'smart wireless sensor networks part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 13 A Reliable and Flexible Transmission Method in Wireless Sensor Networks Dae-Young Kim and Jinsung Cho Kyung Hee University S. Korea 1. Introduction Recent advances in wireless communication have enabled multifunctional tiny nodes to construct a wireless network by themselves Akyildiz et al. 2002 . The network is called a wireless sensor network. The tiny sensor nodes are densely deployed in a physical space. They monitor physical phenomena deliver information and cooperate with neighbor nodes Aky-ildiz et al. 2002 Culler et al. 2004 Hac 2003 Zhao and Guibas 2004 Chong and Kumar 2003 . The communication systems in end-to-end data transmission of wireless sensor networks employ a recovery mechanism for lost data during data transmissions because reliable data transmissions are required for various sensor network applications. Two types of retransmission have been proposed for the recovery namely end-to-end loss recovery E2E and hop-by-hop loss recovery HBH . In these mechanisms lost packets are retransmitted from a source node or an intermediate node. If a retransmit request for lost packets is sent to a source node the end-to-end delay may increase because channel error accumulates exponentially over multi-hops Wan et al. 2002 . The well-known HBH mechanisms are PSFQ Wan et al. 2002 and RMST Stann Heidemann 2003 . PSFQ is based on ACK message and RMST is on NACK message. In HBH when intermediate nodes cache data packets into storage retransmissions can be requested to an intermediate relay node to reduce end-to-end delays. Because sensor nodes have limited resources however it is difficult for all sensor nodes to find sufficient space in their routing paths to cache data packets. There is therefore a tradeoff between end-to-end delays and memory requirements. Because data traffic on sensor networks requires a variety of levels of communication reliability CR depending on the application a loss recovery method to guarantee the desired CR should be provided. .

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