###### Abstract  
Wireless Sensor Networks (WSNs) is a major sensing technology that has revolutionized the way information is collected, processed, and used in many smart cities' applications that rely on sensing technologies for event detection and monitoring. Despite the multiple benefits that such technology offers, the quick depletion of sensors' battery power represents a major concern, mainly due to the extensive computational tasks and communication operations performed by individual sensors. Indeed, the cost of replacing batteries can be prohibitively expensive, especially when sensors are deployed in areas where access is difficult, in urbanized cities. To extend sensors' lifetime, this paper proposes a new variant of LEACH protocol named LEACH enhanced with probabilistic cluster head selection (LEACH-PRO). LEACH-PRO introduces several measures to extend WSNs nodes' lifetime such as cluster head node selection using a probabilistic function based on maximum residual energy and minimum distance to the sink. The obtained simulation results have proven the supremacy of LEACH-PRO over LEACH and direct transmission protocol in terms of the achieved network lifetime and the generated traffic overhead. Most importantly, LEACH-PRO will significantly extend the sensors' lifetime, which would make this type of deployment more viable in smart city scenarios. wireless sensor networks; energy-efficiency; smart cities; LEACH +
Footnote †: journal: Sensor and Actuator Networks  
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WSNs are deployed in remote sensing fields where each node is equipped with a non-replaceable battery and consumes an amount of energy while sensing, aggregating and transmitting data [4]. Hence, communication among sensor nodes must be efficient for faster relief operations in emergencies. In some situations, like areas where accessibility is difficult, it is almost impossible or too costly to replace the exhausted batteries [5]. Since the lifetime of a sensor node depends on its battery or power source capacity, which is consumed through communication and sensing activities, it is necessary to design energy-aware solutions to increase the lifetime of WSNs [6]. The design of energy-efficient routing techniques for WSNs is very challenging task due to the limited computational and storage capacities in such tiny and energy-constrained sensors [7, 8]. In this paper, we propose a new protocol called LEACH-PRO (LEACH enhanced with probabilistic cluster head selection), which represents an enhanced version of LEACH (low energy adaptive clustering hierarchy), in order to maximize WSNs' lifetime. The main contribution of this paper is to overcome LEACH's related issues, outlined in Section 5, by designing a new probabilistic mechanism in which CHs selection is made based on two metrics: The maximum residual energy and the minimum distance to the base station. While LEACH-PRO has similar design logic as LEACH, the main difference lies in the CH selection process and the fact that sensors located at the border of the sensing field are excluded from participating in the CH selection process under certain conditions, making LEACH-PRO more energy efficient than LEACH. An extensive performance evaluation is performed under varying network densities by measuring several metrics of interest and the results have proved the effectiveness of LEACH-PRO. Moreover, one of the distinguishing features of LEACH-PRO is its compatibility with other state of the art approaches, such as those concerned with the determination of the number of clusters and could therefore be used jointly to complement them. The remainder of this paper is organized as follows. In Section 2, we provide a brief overview of the importance of wireless sensor networks in smart cities. In Section 3, we present an overview of LEACH routing protocol followed by the literature review in Section 4.