To reduce the end-to-end delay in EH-WSNs (energy-harvesting wireless sensor networks), medium access control protocols using pipelined-forwarding have been introduced and studied. In real-life applications, there are several situations where it is difficult to harvest more energy than the energy consumed. Therefore, it is crucial to design a MAC protocol that allows nodes to efficiently relay data without exhausting the power in pipelined-forwarding multihop transmission. In this paper, we propose a PP-MAC (priority-based pipelined-forwarding MAC) protocol that determines the priority of relay nodes based on the residual power and energy-harvesting rate. The proposed protocol determines the probability of a node becoming a relay node based on the priority of the node and attempts to access the channel in a distributed manner. Furthermore, the PP-MAC protocol controls the sleep interval based on the power conditions of the nodes. It also minimizes the power exhaustion problem by controlling the sleep interval based on the priority of the nodes. The performance of the proposed PP-MAC was evaluated via computer simulation, and the results indicated that PP-MAC could improve the network lifetime by mitigating the power imbalance of nodes.
A compact model for depletion-mode p-type cylindrical surrounding-gate nanowire field-effect transistors (SGNWFETs) is proposed. The SGNWFET model consists of two back-to-back Schottky diodes for the metal-semiconductor (MS) contacts and the intrinsic SGNWFET. Based on the electrostatic method, the intrinsic SGNWFET model was derived from current conduction mechanisms attributed to bulk charges through the center neutral region, in addition to accumulation charges through the surface accumulation region. The authors' previously developed Schottky diode model was used for the M-S contacts. The new model was applied to an advanced design system (ADS), whereby the intrinsic part of the SGNWFET and the Schottky diode were developed using the Verilog-A language. The results of the simulation of the newly developed SGNWFET model reproduced the experiment results considerably well.
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