Showing papers on "Interference (wave propagation) published in 2022"

Dynamic deformation measurement of dual-wavelength arbitrary phase-shifting digital holography with automatic phase-shift detection

Abstract: Dual-wavelength arbitrary phase-shifting digital holography with automatic phase-shift detection is first proposed in this study. Holograms with two wavelengths and the interference fringes used to detect the phase-shifting amount for each wavelength were simultaneously recorded in one image using the space-division multiplexing technique. Compared with conventional methods, the proposed approach can achieve simultaneous phase shifting of the reference beams of two wavelengths, which substantially reduces recording time and does not require excessive phase-shifting device precision. The proposed and conventional methods were quantitatively evaluated with numerical simulations, and a dynamic deformation measurement was obtained using the system. In the quantitative evaluation of the simulation, the root-mean-square errors of amplitude and phase images reconstructed by the proposed method were reduced by 12% and 19% compared to the conventional method, respectively. Both numerical simulations and experiments verified the effectiveness of the proposed method.

NOMA-Based LPWA Networks

Abstract: Non-orthogonal multiple access (NOMA) is used in the uplink for LPWAN for providing services to users or nodes requiring a different set of services. The LoRa nodes usually suffer from inter-cluster and intra-cluster interference. In this article, both are minimized by assigning spreading factor (SF) depending upon their channel coefficient. The assignment of different SF and use of NOMA allows successive interference cancellation (SIC) which itself reduces interference while decoding the signals. In numerical results, several LoRa nodes are varied to calculate the number of packets transmitted, percentage collisions, and throughput, which shows that the use of NOMA enhances the performance considerably. The proposed algorithm allocates channels to LoRa nodes based on their channel gains and distance which reduces collisions and increases throughput.

Investigation on Metasurface for Dual-Band RF Energy Harvesting Without Mutual Interference

Abstract: A dual-band (2.45 and 12 GHz) and wide-angle MS (short for metasurface) for RF (short for radio frequency) energy harvesting is proposed in this research. This structure can maintain a high efficiency over 90% at 2.45 GHz for electromagnetic wave harvesting as conventional ones, and can operate in another frequency band with efficiency of at least 90%. For verification, a prototype is fabricated and measured in an anechoic chamber. The experimental results corroborate the proposed MS performs well with the efficiency of more than 80% for wide-angle incident waves in all frequency bands. Isolated by a wide band between both resonances points, the MS structure can provide alternative sources to wireless sensor network (WSN) without mutual interference.

Cooperative Diversity for Resource Optimisation in Cognitive Radio Networks

Abstract: The problem of interference is arguably the biggest problem that may hinder or limit cognitive radio networks’ realisation. Recently, the concept of cooperative diversity is being introduced and employed to help mitigate the effects of interference, and in providing improved resource allocation solutions for end-to-end communication in the cognitive radio network. The use and significance of cooperative diversity in the resource allocation optimisation for cognitive radio networks are discussed in this chapter. Some important results are presented to show the marked improvement in resource optimisation for the cognitive radio network when cooperation is incorporated in the network design.

PD Detection and Analysis of Cross-Bonded Cable Based on Broadband Sensor and Three-Phase Amplitude Relation Analysis Method

Abstract: The power cable is one of the most important transmission equipment. The long cable common use the cross-bonded grounding method to reduce the loss of shielding layer and decrease the voltage rise at the end of cable. Therefore, it is difficult to diagnosis the PD detection result of cross-bonded cable in field because the PD signals will be influenced by both the environment electromagnet interference and the interference among different phases. The broad band sensor is used to detect the PD of cross-bonded cable in field in this paper. The waveform of the PD pulse, PRPD, and 3PARD diagrams are analyzed to diagnose the results. The results have shown that the broadband sensor can anti the environment electromagnet interference because it can obtain more information of PD signal. The 3PARD diagrams can division the interference among different phases.

Antenna Selection in Cognitive Radio for MIMO System

Abstract: Cognitive radio is the most important and emerging technologies of today, as it solves spectral scarcity in highly traffic channels. The main aim of CR is to reduce the interference as low as possible of the secondary user at primary user. Multiple input–output systems are implemented with CR to enhance diversity gain. However, all the antenna used at the same time in the system is wastage of transmitter power and also increases the interference. The better way to deal with this problem is to select a few groups of antennas which optimize the system performance in a dynamically varying channel environment. Here, this issue is considered as an optimization issue where the main objective function is to maximize data transmission rate, and constraints are to minimize total transmission power and interference.