Low-Power Beam-Switching Technique for Power-Efficient Collaborative IoT Edge Devices

Collaborative beamforming (CB) enables uplink transmission in a wireless sensor network (WSN) composed of sensors (nodes) and far-away access points (APs). It can also be applied to the case where the sensors are equipped with beam-switching structures (BSSs). However, as the antenna arrays of the BSSs are randomly headed due to the irregular mounting surface, some sensors form beams that do not illuminate a desired AP and waste their limited energy. Therefore, to resolve this problem, it is required to switch the beams toward the desired AP. While an exhaustive search can provide the globally optimal combination, a greedy search (GS) is utilized to solve this optimization problem efficiently. Simulation and experimental results verify that under certain conditions the proposed algorithm can drive the sensors to switch their beams properly and increase the received signal-to-noise ratio (SNR) significantly with low computational complexity and energy consumption

Optimized Combination of Local Beams for Wireless Sensor Networks

This paper proposes an optimization algorithm to determine the optimal coherent combination candidates of distributed local beams in a wireless sensor network. The beams are generated from analog uniform linear arrays of nodes and headed toward the random directions due to the irregular surface where the nodes are mounted. Our algorithm is based on one of the meta-heuristic schemes (i.e., the single-objective simulated annealing) and designed to solve the objective of minimizing the average interference-to-noise ratio (INR) under the millimeter wave channel, which leads to the reduction of sidelobes. The simulation results show that synthesizing the beams on the given system can form a deterministic mainlobe with considerable and unpredictable sidelobes in undesired directions, and the proposed algorithm can decrease the average INR (i.e., the average improvement of 12.2 dB and 3.1 dB are observed in the directions of π 6 and 2 π 3 , respectively) significantly without the severe loss of signal-to-noise ratio (SNR) in the desired direction

On-demand frequency tunability of fluidic antenna implemented with gallium-based liquid metal alloy

We investigated frequency tunability of a microfluidic-based antenna using on-demand manipulation of a gallium-based liquid metal alloy. The fluidic antenna was fabricated by polydimethylsiloxane (PDMS) and filled with the gallium-based liquid metal alloy (Galinstan®). It is composed of a digital number “7”-shaped feedline, and a square-shaped and a digital number “6”-shaped patterns, which are all implemented with the liquid metal. The gallium-based liquid metal was adhered to the channel surface due to its viscous oxide layer originating from the gallium oxide forming when it exposed to the air environment. We treated the liquid metal with hydrochloric acid solution to remove the oxide layer on the surface resulting in easy movement of the liquid metal in the channel, as the liquid metal surface has been transformed to be non-wettable. We controlled the physical length of the liquid metal slug filled in feedline with an applied air pressure, resulting in tuning the resonant frequency ranging from 2.2 GHz to 9.3 GHz. The fluidic antenna properties using the liquid metal’s electrical conductivity and mobility were characterized by measuring the return loss (S11), and also simulated with CST Microwave Studio