One of the main methods for link quality prediction is to predict the physical layer parameters first, and then evaluate the link quality based on the mapping models between such parameters and packet reception ratio (PRR). However, existing methods often ignore the temporal correlations of physical layer parameter series and rarely consider the influence of link fluctuations, which lead to more errors under moderate and sudden changed links with larger fluctuations. In view of these problems, this paper proposes a more effective link quality prediction method RNN-LQI, which adopts Recurrent Neural Network (RNN) to predict the Link Quality Indicator (LQI) series, and then evaluates the link quality according to the fitting model of LQI and PRR. This method accurately mines the inner relationship among LQI series with the help of short-term memory characteristics of RNN and effectively deals with link fluctuations by taking advantage of the higher resolution of LQI in the transitional region. Compared with similar methods, RNN-LQI proves to be better under different link qualities. Especially under moderate and sudden changed links with larger fluctuations, the prediction error reduces at least by 14.51% and 13.37%, respectively. Therefore, the proposed method is more suitable for low power wireless links with more fluctuations.

This paper proposes a novel zero-voltage-switching (ZVS) current-tripler DC/DC converter. Compared to the conventional phase-shifted ZVS full-bridge DC/DC converter with current-doubler rectifier, the proposed current-tripler DC/DC converter reduces the synchronous rectifier (SR) conduction loss as well as the transformer winding loss. Furthermore, the proposed transformer structure is very compact, and thus the power density of the converter could be greatly increased. Analysis and experimental results show that the proposed topology offers great advantages when the converter output current goes higher and the voltage goes lower, as demanded by future microprocessors and telecommunications systems. A 48 V/1.0 V, 100 A, 300 kHz prototype is implemented, and the experimental results show that it can achieve 87 % efficiency at full load.

Under high-frequency repetitive load transients, multiphase voltage regulators (VRs) suffer from beat-frequency oscillations of the phase currents. To investigate this issue, this paper develops a methodology based on the multifrequency model with describing functions. The influences from the interleaving operation are identified. After that, the analysis is extended to studying of the higher-order beat-frequency issue. Then, a solution by applying coupled inductors is proposed. Experimental and simulation results are presented as verification.

This paper offers a thorough analysis of the power delivery path. Based on the power delivery path model, the current slew rate of each loop is derived. The relationship between the slew rate of the inductor current of the voltage regulator (VR) and the bandwidth is also derived. Then, the level of the voltage spike across the capacitors of each loop is determined, after which the relationship between the bandwidth and the capacitance can be plotted. We find that for today's power delivery structure, the bulk capacitors can be eliminated as long as the bandwidth is pushed beyond 350 kHz. The experimental results of a 2 MHz two-stage 12 V VR verify this analysis.

Most existing unmanned aerial vehicle (UAV) assisted wireless sensor network (WSN) studies usually assume that using a large SNR or a short distance can ensure good link quality. However, they don't consider the actual characteristics of UAV assisted WSN. In this paper, spatial characteristics of wireless links, link quality indicating capabilities of physical layer metrics and symmetry of uplink and downlink are analyzed by comparing the measured data of UAV assisted WSN and traditional WSN. The results show that link characteristics of UAV assisted WSN have changed significantly compared with those of traditional WSN. Firstly, connected region of the three traditional communication regions (connected region, transitional region, and disconnected region) is significantly compressed and even no longer exists, which makes that short distance can no longer guarantee reliable communication. Secondly, traditional physical layer metrics such as RSSI, SNR and LQI are no longer valid and even become deceptive, which may lead to wrong judgment of link quality. Finally, there is obvious overall asymmetry between uplink and downlink of UAV assisted WSN, and the quality of downlink is significantly higher than that of the uplink. The discovery of these new features would have great significance on guiding the design of UAV assisted WSN.

Presented in this paper is a new method of increasing the output current of a quarter brick by integrating multiple gate drive and power windings on a single transformer core. Proposed is a two interleaved asymmetrical half-bridge structure that achieves ZVS on both legs and are mutually connected to an innovative transformer structure. The transformer structure transforms the two asymmetrical waveforms on the primary side to a symmetrical waveform on the secondary. This configuration is ideal for driving the synchronous rectifiers. The synchronous rectifiers are self-driven utilizing the same power transformer. A 750 kHz 1.2 V-80 A prototype is built in the quarter brick form factor that achieves 84.7% efficiency at 48 V input.