انتخاب سنسور بر اساس منطق فازی و تعادل بار در شبکه های حسگر بی سیم چند سینک Fuzzy Logic-Based Sink Selection and Load Balancing in Multi-Sink Wireless Sensor Networks

1 Introduction Wireless sensor networks or wireless sensor networks consist of many small, inexpensive, sensor nodes that communicate wirelessly. Each sensor node has a limited resource [1] and collaborates with other nodes to perform operations such as environment monitoring or target tracking etc. [2, 3]. Also, various applications of WSNs are proposed for E-Healthcare systems [4–6]. Limited battery power is one of the main limitations of the wireless sensor networks and almost all schemes and algorithms designed for these networks should consider this limitation [7–13]. When sensor nodes recognize any event in their perimeter they can forward their sensed data to the sink [14]. In this process, based on their distance to the sink and network topology, they may send their data to the sink, directly or through one or more relaying sensor nodes [15]. The sink node can transmit the sensor nodes data to other networks and even to a cloud-based system for further processing [16–19]. Regarding the number of sink nodes in the network, wireless sensor networks can be classified as single sink wireless sensor networks and multi-sink wireless sensor networks [20]. But wireless sensor networks, which utilize one sink node, are prone to hotspot problem near the sink and due to the high node density and converge cast communication pattern [21–23], congestion may happen in the sink node. Deployment of multiple sinks is a promising solution for wireless sensor networks to alleviate the congestion in the sink nodes and to improve the reliability of wireless sensor network communications [24]. Moreover, extra sink nodes help to mitigate the unbalanced energy consumption among the sensor nodes and improve the lifetime of the network [25]. Furthermore, multi-sink wireless sensor networks provide a higher level of fault tolerance and are able to tolerate the inaccessibility or failures of the sink nodes [26, 27]. Congestion is one of the critical problems in the sensor networks which increases the packet loss rate and the power consumption of network. In the wireless sensor networks, the congestion problem can happen because of irregular deployment of sensor nodes, buffer overflow, transmission channel contentions, transmission rate, dynamic time variation transmission channel and many-to-one data transmission schemes [28]. Generally, congestions can be classified as node-level congestions and link-level congestions. In the node-level congestion, the congestion is created because packet arrival rate is higher than the packet service rate. Also, node-level congestion can happen in the sensor nodes and in the sink nodes, in this paper, focus is on the latter case.