In this thesis, we consider downlink data transmission in high density and large scale wireless sensor networks where the network coordinator is connected to a large number of child devices in a multi-hop passion. We first propose the use of a dynamic frame structure (DFS) comprising a management frame and a main frame at every beacon interval. During the management frame, parent and child devices can transmit and receive a control message to maintain the network connectivity and to utilize the main frame. During the main frame, only a pair of devices comprising a parent device and its child device can transmit/receive data packets while the other devices stay in an inactive mode to minimize power consumption. The proposed DFS can provide reliable transmission of control messages even in the presence of co-channel interference (CCI) by repeatedly transmitting beacon frames and data request messages. It can provide high transmission capacity in CCI environments by selecting an appropriate packet length and deferring packet transmission. We also design a resource allocation protocol that allows multiple networks nearby to work without collision. Finally, we consider an application of DFS to the IEEE 802.15.4e distributed synchronous multi-channel extension (DSME) protocol.
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Downlink data transmission structure for high-density and large-scale sensor networks
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