Wireless Mobile Terminals Research Articles

Effect of stability state transition of variable potential well in tri-hybridized energy harvesters

Energy harvesting is a crucial technology for self-powering wireless sensor nodes and mobile terminals. In addressing this, we utilized a variable potential well to create a tri-hybrid energy harvester that integrates piezoelectric effect, electromagnetic induction, and triboelectric effect. The compression and stretching of a compressible magnet-spring oscillator alter the system’s potential well, thereby promoting the operation of the piezoelectric unit (PU), electromagnetic unit (EU), and triboelectric unit (TU). A coupled electromechanical model using Hamilton’s principle was established. By calculating the static potential energy and restoring force, we discussed the stability state transition, revealing that when the magnet distance is less than 38 mm, the system transitions from a mono-stable to a bi-stable state. The experimental study investigated the impact of excitation and structural parameters on voltage and power. A high excitation level enhances all three units. The TU demonstrates excellent electrical performance under high potential energy in the bi-stable state, while the PU performs best in mono- and bi-stable switching structure. The EU shows relatively balanced electrical performance across various conditions. These findings offer new insights into enhancing energy harvesting capabilities for external circuits.

A True Random Number Generator Method Embedded in Wireless Communication Systems

To increase the number of wireless devices, e.g., mobile or IoT terminals, cryptosystems are essential for secure communications. In this regard, random number generation is crucial because the appropriate function of cryptosystems relies on it to work properly. This paper proposes a true random number generator (TRNG) method capable of working in wireless communication systems. By embedding a TRNG in such systems, no additional analog circuits are required and working conditions can be limited as long as wireless communication systems are functioning properly, making TRNG method cost-effective. We also present some theoretical background and considerations. We next conduct experimental verification, which strongly supports the viability of the proposed method.

A Model Based on Convolutional Neural Network for Online Transaction Fraud Detection

Using wireless mobile terminals has become the mainstream of Internet transactions, which can verify the identity of users by passwords, fingerprints, sounds, and images. However, once these identity data are stolen, traditional information security methods will not avoid online transaction fraud. The existing convolutional neural network model for fraud detection needs to generate many derivative features. This paper proposes a fraud detection model based on the convolutional neural network in the field of online transactions, which constructs an input feature sequencing layer that implements the reorganization of raw transaction features to form different convolutional patterns. Its significance is that different feature combinations entering the convolution kernel will produce different derivative features. The advantage of this model lies in taking low dimensional and nonderivative online transaction data as the input. The whole network consists of a feature sequencing layer, four convolutional layers and pooling layers, and a fully connected layer. Verifying with online transaction data from a commercial bank, the experimental results show that the model achieves excellent fraud detection performance without derivative features. And its precision can be stabilized at around 91% and recall can be stabilized at around 94%, which increased by 26% and 2%, respectively, comparing with the existing CNN for fraud detection.

4-Element Concentric Pentagonal Slot-Line-Based Ultra-Wide Tuning Frequency Reconfigurable MIMO Antenna System

In this communication, a novel, compact, ultrawideband tuning, concentric pentagonal slot-line-based frequency-reconfigurable multiple-input-multiple-output (MIMO) antenna system is presented. It consists of a four-element antenna design on a commercially available FR-4 substrate with the dimensions of $60\times 120\times 1.56$ mm3. All the antenna elements are planar in structure, which are etched out from ground plane. Frequency reconfigurability is achieved using varactor diodes by reactively loading the antennas. Each capacitance value of the varactor diode results in the triband operation. Proper capacitive reactance loading enables the antenna to resonate over a wide frequency band. The proposed MIMO antenna system is tuned over an ultrawide frequency band, and a smooth variation of the resonance frequencies is observed from 1.32 to 1.49 and 1.75 to 5.2 GHz. Moreover, the unique feature of the proposed antenna system is the effectiveness of reactively loading the slot over all the resonating bands. The proposed antenna system is compact and suitable to be used in wireless handheld devices and mobile terminals for cognitive radio applications. The envelope correlation coefficient did not exceed 0.186 in the entire operating band of the MIMO antenna operation. The maximum measured gain of the MIMO antenna is 4.5 dBi with a maximum efficiency of 81%.

Outage Performance Analysis for Wireless Non-Orthogonal Multiple Access Systems

Non-orthogonal multiple access (NOMA) is a promising air-interface technology for its ability to support massive wireless mobile terminals. In this paper, the outage performance for uplink NOMA systems employing the dynamic ordered successive interference cancellation receiver is analyzed under the independent but not identically distributed (i.ni.d.) fading environment. We theoretically reveal the general approach to derive the closed-form outage probability expression for an arbitrary number of serving users. Under the i.ni.d. fading environment, the probability for each possible decoding order is derived respectively based on the observation of the time-varying received power strength for each user. Furthermore, encountering the challenge of solving the multidimensional integration, a recursive method is proposed to deal with the conditional outage probabilities under a certain decoding order as a joint probability problem with the linear constraints of the decoding order and the required data rate. Finally, we derive the closed-form outage probability expressions. The simulations are performed to validate the accuracy of the theoretical results and reveal the superiority of the dynamic mode over the fixed one.

Planar UWB MIMO Antenna With Pattern Diversity and Isolation Improvement for Mobile Platform Based on the Theory of Characteristic Modes

This communication presents a planar ultra-wideband multi-input multi-output antenna with pattern diversity and isolation improvement based on the theory of characteristic modes. The proposed antenna (for new-generation wireless mobile terminals) consists of two ultra-wideband antenna elements—a compact quarter loop and a circular planar monopole located on the opposite edges of a rectangular ground plane. These two antenna elements are able to excite different modes in the ground plane and thus realize the desired diverse radiation patterns and high isolation without any additional decoupling structures. The experimental results show that both antenna elements are ultra-wideband with impedance bandwidths (return losses more than 6 dB for the quarter-loop antenna and more than 10 dB for the circular planar monopole antenna) of 130% (2–9.5 GHz). The isolation is over 20 dB with a peak value of 50 dB. The realized gains are above 1.5 dBi. The total efficiencies are above 70%. The envelope correlation coefficient is less than 0.03 assuming that the antenna operates in an isotropic channel.

A Two Concentric Slot Loop Based Connected Array MIMO Antenna System for 4G/5G Terminals

In this paper, an integrated design with a multiple-input multiple-output (MIMO) antenna system for fourth generation (4G) and fifth generation (5G) applications is presented. The proposed design contains a two-element slot-based MIMO antenna system for 4G and a connected antenna array (CAA)-based two-element MIMO antenna system for a potential 5G band. Two rectangular loops are etched on the periphery of the ground plane. The top and bottom portions of the thin loops act as the two 4G MIMO antennas, while parts of their sides are acting as 5G arrays. The antenna system is fabricated on a commercially available Roger 4350 substrate with $\epsilon _{r}$ equal to 3.5, while the dimensions of the board are $100\times 60 \times 0.76$ mm3 representing a typical smart phone back plane size. The integrated antenna system covers multibands at 4G with a combined bandwidth of 1.565 GHz (−6 dB BW) in addition to the band between 16.50 and 17.80 GHz for 5G. The design is planar, low profile, simple, and compact in structure making suitable for wireless handheld devices and mobile terminals. The measured gain at 3.46 GHz was at least 2.22 dBi and at 17 GHz was 8 dBi for the 4G and 5G MIMO antenna systems, respectively. The envelope correlation coefficient was also calculated from the measured 3-D patterns and showed good MIMO performance. This is the first integrated 4G/5G MIMO antenna system with below 6 GHz and above 10-GHz covered bands using CAA.

Exploitation of Dual-Polarization Diversity for 5G Millimeter-Wave MIMO Beamforming Systems

For the first time, to the best of our knowledge, this paper reports a complete millimeter wave (mmWave) wireless system, which coherently utilizes polarization diversity, multi-input multioutput (MIMO), and beamforming technologies applicable for upcoming fifth generation wireless mobile terminals. Using an interdisciplinary approach across the entire layers constituting of antennas, RF architecture, and digital modem, the polarization of the presented mmWave beamforming antenna system dynamically adapts to the channel environments and MIMO transmission modes. Empirical investigations, which are taken under real-life environments, ascertain that implementing switchable dual-polarized array antennas can alleviate the complexity of the beam searching procedure and MIMO channelization. In addition, experimental results acquired from intensive system level tests indicate more than 22 dB averaged cross-polarization discrimination under polarized MIMO channel conditions at the 60 GHz band. The beam selection algorithm that can be easily implemented based on power metric is confirmed to feature a 99.5% accuracy in comparison with the optimal selection algorithm derived from the theoretical maximal capacity.

Triboelectric-piezoelectric-electromagnetic hybrid nanogenerator for high-efficient vibration energy harvesting and self-powered wireless monitoring system

Energy harvesting is a key technology for the self-powered mode of wireless sensor nods and mobile terminals. A large number of devices have been developed to convert mechanical energy into electrical energy. Whereas great efforts have been made to improve the output performance, problems like energy dissipation, device life and response range still need to be addressed. Herein, we report a hybridized triboelectric-piezoelectric-electromagnetic nanogenerator efficiently harvesting vibration energy. Three harvest modes are integrated into a single device, whose core component is a magnetic levitation structure. On the one hand, it presents higher sensitivity than conventional spring or cantilever designs due to low energy loss, which favors the tiny energy harvesting like the slapping desk vibration and the running car vibration. On the other hand, the mechanical fatigue or damage can be avoided by the special structure design. Under 20Hz, triboelectric nanogenerator (TENG) can deliver a peak output power of 78.4μW, while the top (EMG2) and the bottom (EMG1) electromagnetic generator can provide a peak output power of 36mW and 38.4mW, respectively. Piezoelectric generator located at top (PEG2) and bottom (PEG1) can contribute a peak output power of 122mW and 105mW, respectively. The capacitor charge measurement reveals that unit combination performance is remarkably stronger than individual performance, and the combination of TENG+EMG1+EMG2+PEG1+PEG2 has the highest energy harvesting capacity. Finally, this device has been integrated into a wireless sensor system. Results show that the wireless sensor system can be activated and transmit temperature and vibration signal to control computer. This work has a vital significance to the development and application of the internet of things.

4G/5G antenna system with dual function planar connected array

An integrated design consisting of a multiple-input-multiple-output (MIMO) antenna system for fourth generation applications and a planar connected array (PCA) for fifth generation applications is presented. The proposed design contains a 4-element printed-inverted-F antenna-based MIMO antenna system and a slot-based PCA. The antenna system is fabricated on a commercially available RO-4350 substrate with er equal to 3.5. The dimensions of the board are 100 × 60 × 0.76 mm 3 representing a typical smart phone backplane size. The antenna system covers 2.1 and 12.5 GHz frequency bands via its MIMO and PCA parts, respectively. The design is planar, low profile and compact in structure that is suitable for wireless handheld devices and mobile terminals. The PCA also serves as a defected ground structure at 2.1 GHz thus having two functions. Isolation is improved by at least 4 dB. The PCA consists of a 4 × 3 radiating slots fed via a corporate feed structure. The measured gain and efficiency values at the centre frequency are at least 3.4 dBi and 74%, respectively, for the MIMO antenna system and 8 dBi and 80% for the PCA. The envelope correlation coefficient did not exceed 0.2824 for all antennas showing good MIMO performance.

Annular Slot-Based Miniaturized Frequency-Agile MIMO Antenna System

In this letter, a miniaturized annular slot-based multiple-input–multiple-output (MIMO) antenna system is presented. The proposed frequency-agile antenna exhibits wide tuning range operation by covering several well known wireless standards including GSM1800/LTE/UMTS/WLAN along with several others. The resonance frequency varies from 1.8 to 2.45 GHz. The structure of each antenna element consists of a combination of annular and circular slots, and the antenna is made reconfigurable using a varactor diode within its annular slot. Only one varactor diode is used in achieving this wide tuning band of operation. The four-element MIMO antenna system is realized on a $\text{60} \times \text{120}\times \text{0.76}$ -mm $^3$ RO4350 substrate. The proposed design is suitable for wireless handheld devices and mobile terminals as well as cognitive radio front ends. The measured results show maximum gain of 2.43 dBi and maximum efficiency ( $\eta$ ) of 73%. The envelope correlation coefficient did not exceed 0.186 across the complete operating bands.

Wide‐band frequency agile MIMO antenna system with wide tunability range

ABSTRACTIn this work, a 4‐element wide band frequency agile multiple‐input‐multiple‐output (MIMO) antenna system is presented. Frequency agility is achieved by loading the antenna elements with capacitive reactance using varactor diodes. The proposed MIMO antenna is a wide band antenna with very wide tunability range between 1610 and 2710 MHz, thus covering several well‐known wireless standards. Each tuned band has at least 470 MHz bandwidth. The proposed design is simple in structure with low profile antenna elements. The design is fabricated on an FR4 substrate with single element dimensions of 7.9 × 26.9 mm2 on a single board of dimensions 60 × 100 × 0.8 mm3. The proposed MIMO antenna system is highly suitable to be used in wireless handheld devices and mobile terminals within a cognitive radio platform. The antenna system is also characterized for MIMO performance metrics. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2276–2280, 2016

Implementing Smart Factory of Industrie 4.0: An Outlook

With the application of Internet of Things and services to manufacturing, the fourth stage of industrialization, referred to as Industrie 4.0, is believed to be approaching. For Industrie 4.0 to come true, it is essential to implement the horizontal integration of inter-corporation value network, the end-to-end integration of engineering value chain, and the vertical integration of factory inside. In this paper, we focus on the vertical integration to implement flexible and reconfigurable smart factory. We first propose a brief framework that incorporates industrial wireless networks, cloud, and fixed or mobile terminals with smart artifacts such as machines, products, and conveyors. Then, we elaborate the operational mechanism from the perspective of control engineering, that is, the smart artifacts form a self-organized system which is assisted with the feedback and coordination blocks that are implemented on the cloud and based on the big data analytics. In addition, we outline the main technical features and beneficial outcomes and present a detailed design scheme. We conclude that the smart factory of Industrie 4.0 is achievable by extensively applying the existing enabling technologies while actively coping with the technical challenges.

AT90s8535D CHIP APPLICATION FOR HEART RATE VARIABILITY DIAGNOSTIC SYSTEMS

By using wireless mobile communications and mobile information terminals, Internet and the linking of computers and information technology to human bodies effectively, mobile computing can play an important role in modern technology that can be used by anybody anytime, anywhere, and can reconsider new technology with physiological measurements and reconstruct it creatively. In particular, mobile computing can intervene in the process of inducing biometric changes before diseased symptoms develop into diseases in an aging society. Nevertheless, there are difficulties, such as data, treatment by many parameters, ambiguity of data standardization and difficulty of the simultaneous collection of data etc. Therefore, in this study, a system was embodied by excluding time limiting factors using mobile computing and selecting the mobile neural dynamic coding method based on bioelectric signals. As a result of the experiment, it could be a model for biomedical Signal Mobile Analysis Devices and mobile biometric measuring devices, whose self-measurement can be made possible by an academic approach. Furthermore, it became the research foundation of the atypical characteristics of the formation of bioelectrical signals based on mobile applications and could be modeled in the structure circuit form of a biosignal.

A cloud-based X73 ubiquitous mobile healthcare system: design and implementation.

Based on the user-centric paradigm for next generation networks, this paper describes a ubiquitous mobile healthcare (uHealth) system based on the ISO/IEEE 11073 personal health data (PHD) standards (X73) and cloud computing techniques. A number of design issues associated with the system implementation are outlined. The system includes a middleware on the user side, providing a plug-and-play environment for heterogeneous wireless sensors and mobile terminals utilizing different communication protocols and a distributed “big data” processing subsystem in the cloud. The design and implementation of this system are envisaged as an efficient solution for the next generation of uHealth systems.

IMS-based distributed multimedia conferencing services for next-generation mobile networks

Distributed architecture offers many advantages compared to centralized architecture in terms of providing multimedia services. However, as a trade-off, distributed architecture requires that peers contribute a portion of their bandwidth and computational capacity to maintain the mutual overlay interconnection. This requirement develops into a serious problem for mobile users and wireless infrastructure, as the radio resource in this network is tremendously expensive, based on 3gpp (2005), and is one of the reasons why distributed architecture has not been widely applied in next-generation (4G) networks. It is also the main reason why multimedia services such as video conference have to rely on a costly centralized architecture built over an expensive media resource function controllers via the Internet protocol (IP) multimedia subsystem (IMS). This research work proposes a new distributed architecture utilizing intelligence and extra capacity, currently available on LTE and WiMAX base stations to reduce the required bit rates that each peer has to provide in order to maintain the overlay network. This reduction saves valuable radio resources and allows a distributed architecture to provide video conferencing services on 4G networks, with all the advantages of a distributed architecture such as flexibility, scalability, smaller delay, and lower cost. In addition, this can be implemented with a minimum modification of the standardized IMS platform and the 4G infrastructure, thereby saving the operators and service providers from excessive investments. A prototype has been built to prove the feasibility of the proposed architecture and evaluate its performances. The results show that our proposed distributed video conferencing service can actually reduce the average bandwidth required for data and signaling messages at wireless mobile terminals while maintaining the main operations of a video conference session.

Design Flow for Silicon Chip Implementing Novel Platform Architecture for Wireless Communication

In current era of complex chip designs targeting wireless mobile terminals, architects and designers need to conform to tight design constraints – both in terms of performance (e.g. execution time, silicon area, energy consumption) and time-to-market. Further, additional flexibility is required in these designs to handle multiple wireless standards, sometimes even concurrently. To achieve these challenging goals, the authors introduce a platform architecture that uses a decentralized control to minimize communication and control overhead while keeping timing predictable by using state-of-the-art components and a novel interconnect. The authors demonstrate three main achievements in running multiple wireless standards on their platform: 1.053Gbps 4x4 80MHz WLAN 802.11ac receiver data path meeting the SIFS timing with a latency of 12.5µs, dual concurrent 173Mbps 2x2 20MHz Cat-4 3GPP-LTE receiver and platform reconfiguration from WLAN 11n receiver to 3GPP-LTE one in 52µs. Further the authors describe the design flow used to prepare main components of our platform architecture for a tape-out, while especially keeping a close eye on energy consumption. We believe that our chip design flow is generic and can be used in other custom processor chip designs even outside wireless domain.

A novel sampling synchronization scheme for OFDM-based system with unified reference clock

Due to the constraint of cost and size for mobile wireless communication terminals, many orthogonal frequency division multiplexing (OFDM)-based systems required the same crystal driving the sampling and the channel frequencies, which leads to the challenge of a more comprehensive sampling clock synchronization scheme needed. In this article, the effect of sampling clock error on the system performance was analyzed by dividing it into sampling clock frequency offset (SFO) and sampling timing error (STE) firstly. After that, we proposed a two-stage scheme of sampling clock synchronization based on theoretical derivation: the preliminary SFO was jointly acquired with the carrier frequency offset by using the improved preamble-aided algorithm firstly, the timing drift resulted from residual SFO and STE was tracked based on a phase looped lock in the second stage. The deviation properties of the estimation were achieved theoretically, which reveals that both the estimating variances of SFO and timing drift are in inverse proportion to signal-to-noise ratio and grow linearly by the number of total subcarrier. The results of the simulation show that the proposed synchronization scheme can introduce preferable tracking and robust synchronizing performance for this kind of OFDM-based system.

Experimental results from a MANET testbed in outdoor bridge environment considering BATMAN routing protocol

A set of wireless mobile terminals, which cooperate by routing packets to each other creates a Mobile Ad-hoc Network (MANET). MANETs are continuing to grow their interest in research environment and they are attracting attention for their potential use in several fields such as collaborative computing and disaster recovery environments. Considering mobility of the terminals, the topology changes rapidly and routing becomes a key process for operation of MANETs. In this paper, we analyze the performance of Better Approach To MANET (BATMAN) routing protocol in an outdoor bridge environment considering mobility and vertical communication. We implement two scenarios on our testbed and evaluate the performance in terms of throughput and packetloss.

Dynamic Bandwidth and Carrier Allocation for Video Broadcast/Multicast Over Multi-Cell Environments

Recently, broadcast/multicast over cellular networks has been actively discussed over commercial wireless mobile terminals. Compared to conventional terrestrial or satellite broadcasting systems, the quality-of-service (QoS) for edge users is an important issue due to inter-cell interference over multi-cell environments. In this paper, we introduce a dynamic bandwidth and carrier allocation (DBCA) technique by fully utilizing different visual importance of each layer in multi-layer video for broadcast/multicast services when the number of users is limited over macro/micro/femto cell environments. To ensure an acceptable video quality for edge users, the bandwidth and the loading ratio are dynamically controlled to enhance the utility through the radio resource control in accordance with the visual importance. The simulation results show that DBCA exhibits much better QoS by sending visually more important data with high priority in the cell border region.