A Wi-Fi dual-band directional antenna is presented herein. The proposed antenna consists of a bent ground-backed slot-loop structure to form a directional antenna. The aperture of the antenna element ...and the offset from the ground plane have opposing functional variation for the beamwidth adjustment. By utilizing both factors, a consistent Wi-Fi dual-band beamwidth is achieved. The antenna has high radiation efficiency over both bands. The proposed antenna achieves H-plane dual-band beamwidth consistency, which varies within 5° over the two bands. The gain is 9 and 9.5 dBi, respectively, in the 2.4 and 5 GHz bands, and a stable H-plane beamwidth of 66°-71° over the operating bands is achieved. The proposed antenna can be used for the sectorized Wi-Fi access point application or as an element to form an array.
Antenna design plays a prominent role when we consider the far-field patterns when compared with near field patterns. By using a PIN diode (which has a wide intrinsic region when compared with normal ...diode) as a switch and a capacitor as a filter we are proposing an antenna design that able to radiate far field regions. The reason behind choosing capacitor as a filter means that we are designing antenna to transfer high frequency signals. For antenna deign simulations we have different software’s (like FEKO, ZELAND IE 3D etc.,) but the preferred software for this antenna design is Computer Simulation Technology Microwave Studio (CST MWS) as we are operating in a frequency band of 2 to 2.54GHz and the diameter of the antenna 20X20cm. Based on the diameter chosen the antenna is able to switch direction of signalling by using a switch with four different angles. The material used for antenna design FR-4 which is a Composite material composed of fibre glass cloth with an epoxy resin blinder i.e. frame resistance and SMB connectors with 75Ω impedance.
Radio spectrum is a scarce resource. To meet demands, new wireless technologies must operate in shared spectrum over unlicensed bands (coexist). We consider coexistence of Long-Term Evolution (LTE) ...License-Assisted Access (LAA) with incumbent Wi-Fi systems. Our scenario consists of multiple LAA and Wi-Fi links sharing an unlicensed band; we aim to simultaneously optimize performance of both coexistence systems. To do this, we present a technique to continuously estimate the Pareto frontier of parameter sets (traces) which approximately maximize all convex combinations of network throughputs over network parameters. We use a dimensionality reduction approach known as active subspaces to determine that this near-optimal parameter set is primarily composed of two physically relevant parameters. A choice of two-dimensional subspace enables visualizations augmenting explainability and the reduced-dimension convex problem results in approximations which dominate random grid search.
A circularly-polarized (CP) wideband 4-port Multi-input multi-output (MIMO) antenna is proposed. The novel contribution of the proposed work lies in achieving CP through an L-shaped feedline and a ...carefully engineered orthogonally placed slotted ground plane geometry leading to a defected ground structure (DGS). A single-fed CP antenna structure is then converted to the 4-port MIMO antenna that achieves higher isolation due to polarization diversity. The MIMO antenna demonstrated an impedance bandwidth (IBW) spanning 65.01 % (from 3.81 GHz to 7.48 GHz), along with an axial ratio bandwidth (ARBW) of 20.10 % (from 5.47 GHz to 6.70 GHz). The 4-port CP MIMO antenna shows decent MIMO diversity performance. The measured results of the fabricated structure displayed good agreement with the simulated results. Antenna having both MIMO capability and circular polarization helps in reducing the multipath fading effect while increasing the latency. Thus, the proposed antenna having a wide overlapping Axial Ratio (AR) and Impedance Bandwidth (IBW) can be a very good choice for future devices using the Wireless Fidelity (Wi-Fi) 6E band.
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As result of the development of technology, most of modern computer and smartphones are Bluetooth and Wi-Fi direct wireless technologies enabled. While those wireless technologies come with the ...benefits of interconnecting devices without the need access point or central base station. However, computer and smartphones connected via Bluetooth based or via Wi-Fi Direct connection does not guarantee intercommunication or data transmission in meaningful way. Therefore, third party software is always needed to help for achieving data transmission. In this research an effort is done to design and develop P2P software applications and web based application by using C# and ASP.net MVC programming languages as features of Visual Studio 2017. Application would facilitate P2P communication of interconnected devices via the same channel. Built software system has been tested based on functional testing method, and usability testing. The result from functional testing shows that P2P communication meets functional requirements while usability testing has an average score of 72.2% from System Usability Scale method. The results from SUS scores brands our proposed P2P communication system to be good and highly accepted.
Over the past decade, the demand and research for indoor localization have burgeoned and Wi-Fi fingerprinting approach has been widely considered because it is cheap and accessible. However, most ...existing methods lack in terms of positioning accuracy and high computational complexity. To cope with these issues, we formulate a two-stage, coarse and accurate positioning narrow-down approach (NDA). Furthermore, a three-step source domain refinement (SDR) scheme that involves outlier removal, stable AP’s weight enhancement, and a data averaging technique by applying the K-means clustering algorithm is also proposed. The collaboration of SDR scheme with the training data selection, area division, and overlapping schemes reduces the computational complexity and improves coarse positioning accuracy. The effect of the proposed SDR scheme on the performance of the support vector machine (SVM) and random forest algorithms is also presented. In the final/accurate positioning phase, a set of lightweight neural networks (DNNs), trained on different sub-areas, predict the user’s location. This approach significantly increases positioning accuracy while reducing the online computational complexity at the same time. The experimental results show that the proposed approach outperforms the best solutions presented in the literature.
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Motivated by the recent efforts in extending long term evolution (LTE) to the unlicensed spectrum, we propose a novel spectrum sharing framework for the coopetition (i.e., cooperation and ...competition) between LTE and Wi-Fi in the unlicensed band. Basically, the LTE network can choose to work in one of the two modes: in the competition mode, it randomly accesses an unlicensed channel, and interferes with the Wi-Fi access point using the same channel; in the cooperation mode, it onloads the Wi-Fi users' traffic in exchange for the exclusive access of the corresponding channel. We design a second-price reverse auction mechanism, which enables the LTE provider and the Wi-Fi access point owners (APOs) to effectively negotiate the operation mode. Specifically, the LTE provider is the auctioneer (buyer), and the APOs are the bidders (sellers) who compete to sell the rights of onloading the APOs' traffic to the LTE provider. In Stage I of the auction, the LTE provider announces a reserve rate, which is the maximum data rate that it is willing to allocate to the APOs in the cooperation mode. In Stage II of the auction, the APOs submit their bids, which indicate the data rates that they would like the LTE provider to offer in the cooperation mode. We show that the auction involves allocative externalities, i.e., the cooperation between the LTE provider and one APO benefits other APOs who are not directly involved in this cooperation. We characterize the APOs' unique equilibrium bidding strategies in Stage II, and analyze the LTE provider's optimal reserve rate in Stage I. Numerical results show that our framework improves the payoffs of both the LTE provider and the APOs comparing with a benchmark scheme. In particular, our framework increases the LTE provider's payoff by 70% on average, when the LTE provider has a large throughput and a small data rate discounting factor. Moreover, our framework leads to a close-to-optimal social welfare under a large LTE throughput.
The rapid development of Internet of Things has led more realization of digital twins (DT), such as healthcare, smart homes, virtual reality, etc, gesture recognition is a fundamental component of ...DT. Its implementation can provide users with personalized services or improved human-computer interaction, such as smart home control, in-car interaction, etc, most of existing gesture recognition methods are based on vision or wearable device. However, the vision-based methods face the problem of privacy breach, whereas the wearable-based methods may bring inconvenience to users. With the wide deployment of Wi-Fi networks, lots of consumer devices are widely accessible in people's homes. Motivated by the fact that Wi-Fi signal propagation can be affected by human motion, the opportunity to use Wi-Fi signals for gesture recognition can be further explored. However, the challenge is that the received Wi-Fi signal shows great differences when the same person performs the same gesture in different environments or different person performs the same gesture in the same environment. Therefore, the signal alignment across different domain needs to be solved. In this paper, we propose a gesture recognition system named Phase-Attention-based-Conv-CSI (PAC-CSI), which consists of two modules: data processing and gesture recognition. In the data processing module, we eliminate random phase noise in channel state information (CSI) and perform phase calibration. In the gesture recognition module, we feed the processed phase sequence into a lightweight deep neural network for gesture recognition. PAC-CSI can obtain the gesture category in about 200ms, which can meets the real-time requirements of DT. The gesture recognition accuracy of our proposed system in a single domain is 99.46%, and its performance across new locations, orientations, users, and environments is 98.77%, 98.90%, 97.54%, and 96.47%, respectively.
Currently, there is a growing tendency of research on leveraging Wi-Fi signals as sensors for various IoT applications. We observe that most studies deal with the behavior of wireless signals for ...regular structures in indoor environments. But there is a lack of investigation on Wi-Fi signals behavior for a complex structure like collapsed buildings. This study investigates the possible Wi-Fi signal penetration for collapsed structures. We consider two objectives of this study. Firstly, there is a need to figure out the most common collapsed environments and then to select the best frequency selection concept from available license-free ISM bands to have better coverage. We achieve the first goal through a field survey of an earthquake hit area followed by a debris model constituent of brick and concrete materials. To address the second objective, we have employed two methods for selection of the best frequency. Firstly, we use theoretical bijective soft set approach to select the best available concept and then a modified path loss termed as PL-Collapsed has been introduced to estimate the losses encountered to the wireless signal under debris while providing the best possible coverage with available ISM bands for Wi-Fi. We then compare signal coverage for Wi-Fi bands with each other to finally select the possibly best frequency. Simulation results show that newly introduced Wi-Fi Halow operating at sub 1GHz has relatively better coverage which is also cross-verified by the theoretical bijective soft-set approach. This study triggers the application of wireless signals under collapsed structures where there is a need to rescue the lives. Furthermore, this also prompts new dimensions in IoTs hence emphasizing more ubiquitous systems.
•This paper investigates the behavior of Wi-Fi signals for collapsed structures.•The paper is based on real-field survey of an earthquake hit area.•This paper discusses two techniques for selection of the best frequency concept.•The core techniques are bijective soft set theory and signal path loss models.•This paper simulates models for Wi-Fi signal coverage in collapsed structures.•Finally, the paper validates the best suited Wi-Fi frequency in collapsed structures.
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