Abstract
The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission threshold for all sensor nodes in advance. The method did not take link quality and delay requirement into account, which decreases the probability of a packet passing its delivery path within a given deadline. This paper investigates the problem of finding optimal retransmission thresholds for relay nodes along a delivery path in a sensor network. The object of optimizing retransmission thresholds is to maximize the summation of the probability of the packet being successfully delivered to the next relay node or destination node in time. A dynamic programming-based distributed algorithm for finding optimal retransmission thresholds for relay nodes along a delivery path in the sensor network is proposed. The time complexity is , where is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and Δ is the given upper bound of the transmission delay of the delivery path. If Δ is greater than the polynomial, to reduce the time complexity, a linear programming-based -approximation algorithm is proposed. Furthermore, when the ranges of the upper and lower bounds of retransmission thresholds are big enough, a Lagrange multiplier-based distributed -approximation algorithm with time complexity is proposed. Experimental results show that the proposed algorithms have better performance.
Highlights
Wireless Sensor Networks (WSNs) have been increasingly deployed for a wide variety of real-time applications, such as industrial Internet-of-Things, emergency response, critical infrastructure monitoring and process measurement and control
The time complexity is O (n∆ · max1≤i≤n {ui }), where ui is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and ∆ is the given upper bound of the transmission delay of the delivery path
Due to the transmission uncertainties, wireless link dynamics and the queueing dynamics, wireless link qualities in sensor networks can vary at a wide range of timescales [5,6], which results in node failures and connectivity varying over time [7]
Summary
Wireless Sensor Networks (WSNs) have been increasingly deployed for a wide variety of real-time applications, such as industrial Internet-of-Things, emergency response, critical infrastructure monitoring and process measurement and control. Most protocols set the same retransmission threshold for all sensor nodes in advance without considering the delay requirement and link quality, so that the delivery performance in terms of latency and reliability is decreased. If the protocol is set by a high retransmission threshold, such as 29, in the CTPprotocol [15], without the consideration of delay requirement, the probability for successfully transmitting the first packet through the link S → B can be significantly improved. A dynamic programming-based distributed algorithm for solving the problem is proposed It can be run on a sensor node and enables the node to adaptively set the optimal retransmission threshold based on the link quality and the remaining time to deadline. In the case of the ranges of the upper and lower bounds of the retransmission thresholds being big enough, a Lagrange Multiplier-based Distributed Approximation Algorithm (LMDAA) with time complexity O(1) is proposed.
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