Reliable data delivery in wireless sensor networks

Wireless sensor networks (WSN) have generated tremendous interest among researchers these years because of their potential usage in a wide variety of applications. Sensor nodes are inexpensive portable devices with limited processing power and energy resources. Sensor nodes can be used to collect information from the environment, locally process this data and transmit the sensed data back to the user. This thesis proposes a new reliable data delivery protocol for general point-to-point data delivery (unicasting) in wireless sensor networks. The new protocol is designed that aims at providing 100% reliability when possible as well as minimizing overhead and network delay. The design of the new protocol includes three components. The new protocol adopts a NACK-based hop-by-hop loss detection and recovery scheme using end-to-end sequence numbers. In order to solve the single/last packet problem in the NACK-based approach, a hybrid ACK/NACK scheme is proposed where an ACK-based approach is used as a supplement to the NACK-based approach to solve the single/last packet problem. The proposed protocol also has a new queue management scheme that gives priority to new data. By introducing the idea of a Ready_Bit and newer packet first rule in the transmission queue, nodes can detect and recover lost packets in parallel with the normal data transmission process. The performance of the new protocol is tested in a Crossbow MicaZ testbed. Experimental results show that the new protocol performs well under various system and protocol parameter settings

Scalable and reliable data delivery in mobile ad hoc sensor networks

This paper studies scalable data delivery algorithms in mobile ad hoc sensor networks with node and link failures. Many algorithms have been developed for data delivery and fusion in static microsensor networks, but most of them are not appropriate for mobile sensor networks due to their heavy traffic and long latency. In this paper we propose an efficient and robust data delivery algorithm for distributed data fusion in mobile ad hoc sensor networks, where each node controls its data flows and learns routing decisions solely based on their local knowledge. We analyze the localized algorithm in a formal model and validate our model using simulations. The experiments indicate that controlled data delivery processes significantly increase the probability of relevant data being fused in the network even with limited local knowledge of each node and relatively small hops of data delivery