Energy-Efficient Method for Wireless Sensor Networks Low-Power Radio Operation in Internet of Things  
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1 Internet of Things Laboratory, 6514867953 Hamedan, Iran; [PERSON]SS]  
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consumption in a sensor node. Although the sensor network improves and enhances the performance of other technologies, it also presents challenges due to some of their inherent characteristics and location in a variety of environments. The nodes comprising a wireless sensor network are expected to be small, reliable, low cost, and low power. In some situations, the nodes are in hard-to-reach areas, so their power supply is usually battery or harvest energy from the environment. In both models of power supply the management of power consumption in the nodes is mandatory, in the former case to avoid battery replacement and in latter case to reduce the cost of the energy harvesting system [1; 2; 3]. Contiki OS is a well-known lightweight operating system that can be used to manage low-power wireless platforms based on wireless internet communication. In wireless networks, in many cases, it is necessary to relay data between nodes to reach the destination. The radio duty cycle (RDC) protocols available on Contiki OS allow end nodes and even relay nodes to sleep and save energy between each message sending or relay, so the network lifetime is increased. ContikiMAC is a radio duty cycling protocol available in Contiki OS based on the low power listening (LPL) mechanism [4]. It uses the periodic WakeUps method to monitor the communication medium for ongoing transmissions from neighbor nodes. ContikiMAC tries to reduce the amount of energy consumed by radio activities by using pairs of clear channel assessments (CCA) in every sleep and wake up sequence and providing a model of radio management. CCA identifies to recognize the difference interference by measuring the received signal strength indicator (RSSI) thresholds [5; 6]. The major power consumption in ContikiMAC is spent on the WakeUps of nodes. The WakeUp is known as a single radio check with a chance to detect the activity of a radio. The WakeUps can be considered in three categories, positive WakeUps, which results in the receipt of the packet, false WakeUps, which results in noise or interferences, and idle listening [7]. Idle listening occurs when the communication medium monitoring does not detect any activity on the radio. Implementing the CCA model on WSN hardware to recognize the different interference is extremely challenging due to the limitations of the low power radio, such as TI CC2420. The power consumption over radio listening mode (Rx) is unavoidable. Nodes should periodically listen to the radio channel to reduce the communication latency in-network, even if data traffic is slow [8]. In this paper, we carefully investigate the time factors associated with a radio WakeUp on the ContikiMAC and to reduce the radio power consumption by dynamic radio check time in WakeUps on the Rx mode. RSSI status check is an essential timing parameter during radio check-in nodes. Consequently, in this research particular attention has been paid to RSSI status check to enable an efficient manipulation of radio check within the limits during the Rx. The maximum timing of radio check is used when RSSI is either new or identified as a positive WakeUp. Otherwise, the false WakeUp or idle listening are associated with minimum timing of radio check. In the proposed method the radio check is essentially based on RSSI where the use of CCA is minimized. CCA is used only for the purpose of RSSI validation and classification. The rest of the paper is structured as follows. Section 2 provides an overview of related works. Section 3 identifies the hardware and software tools, as well as the scenario used in this paper. Section 4 highlights the challenge of ContikiMAC in WakeUps as a problem statement. Section 5 proposes a lightweight clear channel assessment (LW-CCA) method to reduce power consumption in WakeUp mode.