Due to the dynamic and uncertain behaviors of nodes in Wireless Sensor Networks (WSNs), reliable data delivery becomes challenging task. With the absence of global information and centralised decision maker, the nodes in distributed WSNs need to rely on the surrounding nodes. This reliance requires the nodes to select the most reliable partner to work with in relaying the packets. Thus, the evaluation criteria and evaluation process has become a crucial agenda. Recent approaches adopt the concept of trust in selecting the next forwarder. However, most of them are restricted to certain criteria and the evaluation are conducted for single node. Inefficient consideration on the factors involved and inability to have wider view of the network could lead to inaccurate selection of forwarder, which eventually causes packet loss or re-transmission that consumes more resources. In this paper, we present an Adaptive Trust-based Routing Protocol (ATRP) that encompasses direct trust, indirect trust, and witness trust that considers multiple factors (resources and security) in its trustworthiness using pairwise comparison. The proposed mechanism allows further evaluations on more potential nodes, at several hops that helps to balance the energy consumption and prolong the network lifetime. Simulation results demonstrate longer lifetime, less delay, less packet loss and low energy consumption when compared to existing protocols. INDEX TERMSAdaptive routing, trust-based, routing protocol, multi criteria, WSNs.

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Non-uniform node distribution in a randomly deployed network causes inefficient routing when some abnormality or events at certain parts of the network cannot be detected due to a coverage hole problem. Existing works to improve routing efficiency in randomly deployed network utilise mobile sink to prolong nodes lifetime is either centred around the static sink or movement through random patterns. Few works had considered multiple mobile sinks to route packets in such network distribution. In fact, important aspect such as collaborations among mobile sinks is not well considered, where the decision made by each mobile sink in most existing approaches tend to maximise the individual sink's utility rather than benefiting wider parts of the network. Thus, a decision based on consensus may benefit more parties and eventually lead to better decision. A distributed collaboration mechanism may assist nodes mobility in improving routing efficiency. Thus, the authors proposed the consensusbased routing protocol, which aims to improve routing efficiency in randomly deployed network, by deciding relocation of mobile sinks based on coverage factor, in order to reduce energy consumption, providing more balance sinks distribution and better network coverage. Simulation results show good performances of proposed approach in terms of nodes lifetime, energy consumption, delay, packet delivery ratio and coverage hole, compared to other existing protocols. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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