Intelligent Reflecting Surface Assisted Transmission Optimization Strategies in Wireless Networks

Wireless Power Transfer(WPT)technology can provide real-time power for many terminal devices in Internet of Things(IoT)through millimeterWave(mmWave)to support applications with large capacity and low latency.Although the intelligent reflecting surface(IRS)can be adopted to create effective virtual links to address the mmWave blockage problem,the conventional solutions only adopt IRS in the downlink from the Base Station(BS)to the users to enhance the received signal strength.In practice,the reflection of IRS is also applicable to the uplink to improve the spectral efficiency.It is a challenging to jointly optimize IRS beamforming and system resource allocation for wireless energy acquisition and information transmission.In this paper,we first design a Low-Energy Adaptive Clustering Hierarchy(LEACH)clustering protocol for clustering and data collection.Then,the problem of maximizing the minimum system spectral efficiency is constructed by jointly optimizing the transmit power of sensor devices,the uplink and downlink transmission times,the active beamforming at the BS,and the IRS dynamic beamforming.To solve this non-convex optimization problem,we propose an alternating optimization(AO)-based joint solution algorithm.Simulation results show that the use of IRS dynamic beamforming can significantly improve the spectral efficiency of the system,and ensure the reliability of equipment communication and the sustainability of energy supply under NLOS link.

On Differentiation Among Pilot Signals of Multiple Mobile Targets in Retro-Reflective Beamforming for Wireless Power Transmission

An experimental study is conducted on several retro-reflective beamforming schemes for wireless power transmission to multiple wireless power receivers(referred to herein as“targets”).The experimental results demonstrate that,when multiple targets broadcast continuous-wave pilot signals at respective frequencies,a retro-reflective wireless power transmitter is capable of generating multiple wireless power beams aiming at the respective targets as long as the multiple pilot signals are explicitly separated from one another by the wireless power transmitter.However,various practical complications are identified when the pilot signals of multiple targets are not appropriately differentiated from each other by the wireless power transmitter.Specifically,when multiple pilot signals are considered to be carried by the same frequency,the wireless power transmission performance becomes heavily dependent on the interaction among the pilot signals,which is highly undesirable in practice.In conclusion,it is essential for a retro-reflective wireless power transmitter to explicitly discriminate multiple targets’pilot signals among each other.

Wireless Self-Powered Vibration Sensor System for Intelligent Spindle Monitoring

In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great impact on the product quality.It is necessary to monitor the status of equipment and to predict fault diagnosis.At present,most of the condition monitoring devices for mechanical equipment have problems of large size,low precision and low energy utilization.A wireless self-powered intelligent spindle vibration acceleration sensor system based on piezoelectric energy harvesting is proposed.Based on rotor sensing technology,a sensor is made to mount on the tool holder and build the related circuit.Firstly,the energy management module collects the mechanical energy in the environment and converts the piezoelectric vibration energy into electric energy to provide 3.3 Vfor the subsequent circuit.The lithium battery supplies the system with additional power and monitors’the power of the energy storage circuit in real-time.Secondly,a three-axis acceleration sensor is used to collect,analyze and filter a series of signal processing operations of the vibration signal in the environment.The signal is sent to the upper computer by wireless transmission.The host computer outputs the corresponding X,Y,and Z channel waveforms and data under the condition of the spindle speed of 50∼2500 r/min with real-time monitoring.The KEIL5 platform is used to develop the system software.The small-size piezoelectric vibration sensor with high-speed,high-energy utilization,high accuracy,and easy installation is used for spindle monitoring.The experiment results show that the sensor system is available and practical.

Design of intelligent detecting system based on wireless transmission

An intelligent detecting system based on wireless transmission is designed. Its hardware includes the card reading module, the wireless digital transmission module, the LCD module, the random password keyboard module and a 16×16 lattice word database based on e-Flash MM36SB020. Its software is a communication protocol between the central control computer and the entrance management base station. To resolve the conflicting problems occurred during the data transmission, a method of delaying time at random is proposed.

Wearable multilead ECG sensing systems using on-skin stretchable and breathable dry adhesives

Electrocardiogram(ECG)monitoring is used to diagnose cardiovascular diseases,for which wearable electronics have attracted much attention due to their lightweight,comfort,and long-term use.This study developed a wearablemultilead ECG sensing system with on-skin stretchable and conductive silver(Ag)-coated fiber/silicone(AgCF-S)dry adhesives.Tangential and normal adhesion to pigskin(0.43 and 0.20 N/cm2,respectively)was optimized by the active control of fiber density and mixing ratio,resulting in close contact in the electrode–skin interface.The breathableAgCF-S dry electrodewas nonallergenic after continuous fit for 24 h and can be reused/cleaned(>100 times)without loss of adhesion.The AgCF encapsulated inside silicone elastomers was overlapped to construct a dynamic network under repeated stretching(10%strain)and bending(90°)deformations,enabling small intrinsic impedance(0.3,0.1 Hz)and contact impedance variation(0.7 k)in high-frequency vibration(70 Hz).All hard/soft modules of the multilead ECG system were integrated into lightweight clothing and equipped with wireless transmission for signal visualization.By synchronous acquisition of I–III,aVR,aVL,aVF,and V4 lead data,the multilead ECG sensing system was suitable for various scenarios,such as exercise,rest,and sleep,with extremely high signal-to-noise ratios.

Optimal Design of Wireless Power Transmission Systems Using Antenna Arrays

Three design methods for wireless power transmission(WPT)systems using antenna arrays have been investigated.The three methods,corresponding to three common application scenarios of WPT systems,are based on the method of maximum power transmission efficiency(MMPTE)between two antenna arrays.They are unconstrained MMPTE,weighted MMPTE,and constrained MMPTE.To demonstrate the optimal design process with the three methods,a WPT system operating at 2.45 GHz is designed,simulated,and fabricated,in which the transmitting(Tx)array,consisting of 36 microstrip patch elements,is configured as a square and the receiving(Rx)array,consisting of 5 patch elements,is configured as an L shape.The power transmission efficiency(PTE)is then maximized for the three application scenarios,which yields the maximum possible PTEs and the optimized distributions of excitations for both Tx and Rx arrays.The feeding networks are then built based on the optimized distributions of excitations.Simulations and experiments reveal that the unconstrained MMPTE,which corresponds to the application scenario where no radiation pattern shaping is involved,yields the highest PTE.The next highest PTE belongs to the weighted MMPTE,where the power levels at all the receiving elements are imposed to be equal.The constrained MMPTE has the lowest PTE,corresponding to the scenario in which the radiated power pattern is assumed to be flat along with the Rx array.

Stability analysis and stabilization of wireless networked control systems based on deadband control scheduling

The stability analysis and stabilization problems of the wireless networked control systems(WNCSs) with signal transmission deadbands were considered. The deadbands were respectively set up at the sensor to the controller and the controller to the actor sides in the WNCS, which were used to reduce data transmission, furthermore, to decrease the network collision and node energy consumption. Under the consideration of time-varying delays and signal transmission deadbands, the model for the WNCS was presented. A novel Lyapunov functional which took full advantages of the network factors was exploited. Meanwhile, new stability analysis and stabilization conditions for the WNCS were proposed, which described the relationship of the delay bounds, the transmission deadband bounds and the system stability. Two examples were used to demonstrate the effectiveness of the proposed methods. The results show that the proposed approach can guarantee asymptotical stability of the system and reduce the data transmission effectively.

Gradient based restoration of coal mine images obtained by underground wireless transmissions

Curvature-driven diffusion (CDD) principles were used to develop a novel gradient based image restora- tion algorithm. The algorithm fills in blocks of missing data in a wireless image after transmission through the network. When images are transmitted over fading channels, especially in the severe circum- stances of a coal mine, blocks of the image may be destroyed by the effects of noise. Instead of using com- mon retransmission query protocols the lost data is reconstructed by using the adaptive curvature-driven diffusion (ACDD) image restoration algorithm in the gradient domain of the destroyed image. Missing blocks are restored by the method in two steps: In step one, the missing blocks are filled in the gradient domain by the ACDD algorithm; in step two, and the image is reconstructed from the reformed gradients by solving a Poisson equation. The proposed method eliminates the staircase effect and accelerates the convergence rate. This is demonstrated by experimental results.

Battery Charger for Electric Vehicles based on a Wireless Power Transmission

In this paper,the case of a battery charger for electric vehicles based on a wireless power transmission is addressed.The specificity of every stage of the overall system is presented.Based on calculated and measured results,relevant capacitive compensations of the transformer and models are suggested and discussed in order to best match the operating mode and aiming at simplifying as much as possible the control and the electronics of the charger.

Theoretical Design of Energy Harvesting Module or Wireless Power Transmission Receiver Using Magnetic Field of 0.2 mT at 60 Hz

This paper presents a theoretical design method for a magnetic energy harvesting module. This module consists of an air-core coil and resonant capacitor. With a simple RLC circuit model, it can derive an equation of harvesting energy as a function of coil size. In order to demonstrate the magnetic field, a uniform magnetic field is generated by the developed coil system. From the experimented results, it is successfully demonstrated 100 mW of energy harvesting from a magnetic field of 0.09 mT at 60 Hz. This value is in good agreement with the estimated results. Harvested energy is proportional to the square of the magnetic flux density. However, ICNIRP2010 provides a guideline that an acceptable level for human health in a public space is 0.2 mT at power-line frequency. This paper also discuss the possibilities of several applications related with both magnetic energy harvesting and wireless power transmission.

Retro-reflective Beamforming Technique with Applications in Wireless Power Transmission

Retro reflective beamforming technique has the potential of enabling efficient wireless power transmission over long distance(on the order of meters and even kilometers).In retro reflective beamforming,wireless power transmission is guided by pilot signal:Based upon pilot signal broadcasted by a wireless power receiver,a wireless power transmitter delivers focused microwave power beam(s)onto the location of wireless power receiver.When the wireless power receiver’s location is not fixed or when the wireless power receiver’s location is unknown to the wireless power transmitter,the microwave power beam would follow the wireless power receiver’s location dynamically as long as the wireless power receiver broadcasts pilot signal periodically.This paper reviews our research endeavors in recent years on retro reflective beamforming technique targeting three applications:(1)wireless charging for low power mobile/portable electronic devices,(2)space solar power satellites(SSPS)application,and(3)wireless charging in fully enclosed space.The feasibility and potential of retro reflective beamforming technique with applications in wireless power transmission are demonstrated by some preliminary experimental results.

A high rectification efficiency Si_(0.14)Ge_(0.72)Sn_(0.14)-Ge_(0.82)Sn_(0.18)-Ge quantum structure n-MOSFET for 2.45 GHz weak energy microwave wireless energy transmission

The design strategy and efficiency optimization of a Ge-based n-type metal-oxide-semiconductor field-effect transistor(n-MOSFET)with a Si_(0.14)Ge_(0.72)Sn_(0.14)-Ge_(0.82)Sn_(0.18)-Ge quantum structure used for 2.45 GHz weak energy microwave wireless energy transmission is reported.The quantum structure combined withδ-doping technology is used to reduce the scattering of the device and improve its electron mobility;at the same time,the generation of surface channels is suppressed by the Si_(0.14)Ge_(0.72)Sn_(0.14) cap layer.By adjusting the threshold voltage of the device to 91 mV,setting the device aspect ratio to 1μm/0.4μm and adopting a novel diode connection method,the rectification efficiency of the device is improved.With simulation by Silvaco TCAD software,good performance is displayed in the transfer and output characteristics.For a simple half-wave rectifier circuit with a load of 1 pf and 20 kΩ,the rectification efficiency of the device can reach 7.14%at an input power of-10 dBm,which is 4.2 times that of a Si MOSFET(with a threshold voltage of 80 mV)under the same conditions;this device shows a better rectification effect than a Si MOSFET in the range of-30 dBm to 6.9 dBm.

Wireless sensing system for environmental humidity and temperature monitoring

Aiming at the actual demand for monitoring environmental information,a wireless sensing system for temperature and relative humidity(RH)monitoring based on radio frequency(RF)technology and mobile network was designed.This paper introduces the architecture of the system.The system uses AVR micro controller unit(MCU),KYL-1020U RF module and SHT71 to complete real-time temperature and humidity monitoring,and uses SIM900A module to realize remote alarming and monitoring with short message system(SMS)through global system for mobile communication(GSM).Experimental results show that the designed system has good stability of measurement and real-time performance,and it can be used in some small temperature and humidity monitoring occasions.

Design and application of wireless signal strength measurement system on the near-ground

The wireless communication system's performance is greatly constrained by the wireless channel characteristics,especially in some specific environment.Therefore,signal transmission will be greatly impacted even if not in a complicated topography.Testing results show that it is hardly to characterize the radio propagation properties for the antenna installed on the ground.In order to ensure a successful communication,the radio frequency(RF)wireless signal intensity monitor system was designed.We can get the wireless link transmission loss through measuring signal strength from received node.The test shows that the near-ground wireless signal propagation characteristics still can be characterized by the log distance propagation loss model.These results will conduce to studying the transmission characteristic of Near-Earth wireless signals and will predict the coverage of the earth's surface wireless sensor network.

A Radio⁃Frequency Loop Resonator for Short⁃Range Wireless Power Transmission

A microstrip loop resonator loaded with a lumped capacitor is proposed for short-range wireless power transmission applications.The overall physical dimensions of the proposed loop resonator configuration are as small as 3 cm by 3 cm.Power transmission efficiency of greater than 80%is achieved with a power transmission distance smaller than 5 mm via the strong coupling between two loop resonators around 1 GHz,as demonstrated by simulations and measurements.Experimental results also show that the power transmission performance is insensitive to various geometrical misalignments.The numerical and experimental results of this paper reveal a bandwidth of more than 50 MHz within which the power transmission efficiency is above 80%.As a result,the proposed microstrip loop resonator has the potential to accomplish efficient wireless power transmission and high-speed(higher than 10 Mbit/s)wireless communication simultaneously.

Reliability Strategies for Data Transmission in Wireless Mesh Network

Wireless Mesh Network (WMN) is a new-type wireless network. Its core idea is that any of its wireless equipment can act as both an Access Point (AP) and a router. Each node in the network can send and receive signals as well as directly communicate with one or several peer nodes. One important issue to be considered in wireless Mesh networks is how to secure reliable data transmission in multi-hop links. To solve the problem, the 3GPP system architecture proposes two functionalities: ARQ and HARQ. This paper presents two HARQ schemes, namely hop-by-hop and edge-to-edge, and three ARQ schemes: hop-by-hop, edge-to-edge, and last-hop. Moreover, it proposes three solutions for WMNs from the perspective of protocol stock design: layered cooperative mechanism, relay ARQ mechanism and multi-hop mechanism.

Design and validation of wireless strain test system for bridge based on the resistance strain sensor

In order to achieve an access to strain sensor data with wireless transmission in bridge engineering structure testing, a wireless strain test system is presented based on the resistance strain sensor of networks. The wireless bridge strain test system composed of master station and substation adopts the wireless method to realize the high accuracy data acquisition between the master station and the substation under a reliable communication protocol. The system has been tested in contrast with the present strain apparatus. Results show that the wireless system is high-reliable, and has many characteristics such as high efficiency, good precision, high stability with low cost, and good flexibility, without using the present communication network.

A shock wave overpressure test system based on WLAN

Due to short transmission distance and low transmission speed when testing the shock wave overpressure with storage test method based on ZigBee technology, a new test method based on wireless local area network （WLAN） technology is proposed, which can monitor remote test nodes. Moreover, the wireless network is designed based on 802. 11b/g protocol, which is helpful for reading the data of the test nodes quickly. Therefore, the accessibility of distributed test system can be improved greatly. The field test results show that the test system performance is good and the transmission speed is high.

Game Theoretical Secure Wireless Communication for UAV-assisted Vehicular Internet of Things

With the ever-expanding applications of vehicles and the development of wireless communication technology,the burgeoning unmanned aerial vehicle(UAV)assisted vehicular internet of things(UVIoTs)has emerged,where the ground vehicles can experience more efficient wireless services by employing UAVs as a temporary mobile base station.However,due to the diversity of UAVs,there exist UAVs such as jammers to degenerate the performance of wireless communication between the normal UAVs and vehicles.To solve above the problem,in this paper,we propose a game based secure data transmission scheme in UVIoTs.Specifically,we exploit the offensive and defensive game to model the interactions between the normal UAVs and jammers.Here,the strategy of the normal UAV is to determine whether to transmit data,while that of the jammer is whether to interfere.We then formulate two optimization problems,i.e.,maximizing the both utilities of UAVs and jammers.Afterwards,we exploit the backward induction method to analyze the proposed countermeasures and finally solve the optimal solution.Lastly,the simulation results show that the proposed scheme can improve the wireless communication performance under the attacks of jammers compared with conventional schemes.

Efficient Broadcast Retransmission Based on Network Coding for InterPlaNetary Internet

In traditional wireless broadcast networks,a corrupted packet must be retransmitted even if it has been lost by only one receiver.Obviously,this is not bandwidth-efficient for the receivers that already hold the retransmitted packet.Therefore,it is important to develop a method to realise efficient broadcast transmission.Network coding is a promising technique in this scenario.However,none of the proposed schemes achieves both high transmission efficiency and low computational complexity simultaneously so far.To address this problem,a novel Efficient Opportunistic Network Coding Retransmission(EONCR)scheme is proposed in this paper.This scheme employs a new packet scheduling algorithm which uses a Packet Distribution Matrix(PDM)directly to select the coded packets.The analysis and simulation results indicate that transmission efficiency of EONCR is over 0.1,more than the schemes proposed previously in some simulation conditions,and the computational overhead is reduced substantially.Hence,it has great application prospects in wireless broadcast networks,especially energyand bandwidth-limited systems such as satellite broadcast systems and Planetary Networks(PNs).