We propose SKYLOCK, a unified multi-layer authentication and key management framework for 6G non-terrestrial networks (NTNs) spanning space–air–ground segments. SKYLOCK comprises a quantum-resistant authentication protocol (QRAP), a hierarchical key management system (HKMS), and a fast handover security protocol (FHSP) that jointly deliver low-latency, formally reasoned security under NTN constraints. Evaluation indicates up to 42% lower authentication latency in LEO, 38% in MEO, and 42% in GEO compared to 5G-AKA, and 56% lower handover latency with 79% fewer packet losses. We provide a threat model, formal properties, and implementation guidance for standardisation and deployment.

A dual-layer frequency-power slicing framework is developed for resource allocation in Unmanned Aerial Vehicles(UAV)-assisted Non-Orthogonal Multiple Access (NOMA) networks. The approach integrates the physical relationship between transmission power and service coverage by introducing the concept of power-circle radii, enabling interpretable boundaries for slice differentiation. Frequency slices manage frequency distribution among UAVs, while power slices dynamically adjust transmission power to support heterogeneous user pairs within each NOMA cluster. A Quality-of-Service (QoS)-aware convex optimization model is formulated to jointly coordinate frequency, power, and user-type allocations under service constraints for ultra-Reliable Low-Latency Communication(URLLC), enhanced Mobile Broadband (eMBB), and massive Machine-Type Communication (mMTC) users. The convex formulation ensures global optimality and computational efficiency within the CVX framework. Simulation results indicate significant improvement in URLLC and eMBB throughput without an increase in total transmission power, accompanied by a physically meaningful layered coverage structure that validates the slice-priority design. The proposed framework establishes a mathematically grounded and physically interpretable foundation for joint frequency-power resource orchestration in dynamic UAV-enabled networks.

Integrated sensing and communications (ISAC) has emerged as a promising technology for future wireless networks, particularly for aerial platforms where efficient waveform designs are indispensable for joint communication and sensing. In this paper, we investigate the waveform characteristics of orthogonal time frequency space (OTFS) and orthogonal frequency division multiplexing (OFDM) signals modulated with Zadoff–Chu (ZC) sequences. We construct two-dimensional (2D) ZC sequence codewords for OTFS modulation and a truncated ZC sequence for OFDM, and analyze their delay–Doppler (DD) domain behavior using the ambiguity function. The analytical results show that both waveforms exhibit symmetric resolution properties in the delay and Doppler dimensions, while numerical evaluations demonstrate that ZC-modulated OTFS (ZC-OTFS) achieves a narrower mainlobe, a higher peak-to-sidelobe ratio (PSLR), and more stable sidelobes compared to ZC-modulated OFDM (ZC-OFDM), and simultaneously maintains a low peak-to-average power ratio (PAPR). In addition, the simulation results further confirm the DD symmetry of both waveforms.

This paper proposes an integrated sensing and communication (ISAC) waveform design using the Zadoff-Chu (ZC) sequence based on orthogonal frequency division multiplexing (OFDM). The correlation property of the ZC sequence is utilized to achieve the target range (root mean square error (RMSE) can reach approximately 0.3m) and velocity (RMSE can reach approximately 0.2m/s) detection. This proposal also implements a fixed-angle beam-scanning method to obtain the targets' 3D positions. This scheme is simulated with different bands and numerologies to verify its versatility.

With the increasing adoption of Vehicle-toEverything (V2X) communication in next-generation intelligent transportation systems, ensuring cybersecurity in vehicular networks has become a critical challenge. Machine Learning (ML)-based Intrusion Detection Systems (IDS) have been widely proposed to detect anomalous and malicious activities in V2X networks. However, these systems are vulnerable to adversarial attacks, where an attacker subtly manipulates input data to evade detection. This study investigates the impact of adversarial attacks on ML-based IDS using the CICIoV2024 dataset, which includes diverse cyber threats targeting V2X networks. We evaluate Fast Gradient Sign Method (FGSM), Projected Gradient Descent (PGD), Carlini & Wagner (CW), and DeepFool attacks against ML models such as Random Forest (RF), Support Vector Machines (SVM), Convolutional Neural Networks (CNN), and Transformer-based IDS. Our results demonstrate that adversarial attacks significantly degrade IDS performance, reducing detection accuracy by up to 40%, thereby exposing critical vulnerabilities in V2X cybersecurity frameworks. Furthermore, we assess defence mechanisms, including adversarial training and feature squeezing, and analyze their effectiveness in mitigating adversarial threats. The findings highlight the urgent need for robust, adversarially-aware IDS to safeguard V2X networks from evolving cyber threats. Future research directions include realworld deployment, federated learning-based IDS, and adversarially robust AI architectures for V2X security.

Radio-frequency (RF) signal transmission is highly susceptible to environmental factors such as the properties of materials. This paper presents an analysis of an ultra-high frequency (UHF) radio-frequency identification (RFID) system under various conditions, primarily focusing on signal quality in the presence of different materials and fluid levels. Multiple scenarios are analyzed using Ansys High Frequency Structure Simulator (HFSS) software, which utilizes the finite element method (FEM) for analysis. Scattering parameters (S-parameters) are key metrics to assess RF signal quality. The study shows that RF signal absorption is significantly influenced by the relative position of RFID tags to the water level, and the amount of water further aggravates signal attenuation. Furthermore, there is a clear trend of scattering parameter minimum shifting as the water level arises. Additionally, signal absorption is also affected by the container material, both PVC plastic and aluminum containers are analyzed in this paper. The results show that metal materials effectively reduce RF signal attenuation caused by water inside containers. This study offers valuable insights for improving RFID system performance in smart refrigerators and other complex environments.

This paper investigates a spatial division multiple access (SDMA) enabled non-orthogonal multiple access (NOMA) integrated sensing and communications (ISAC) framework. A dual-functional base station serves multiple communication users via SDMA and transmits a superimposed NOMA-ISAC signal for radar sensing. A transmit beamforming optimization problem is formulated to maximize the sensing signal-to-interference-plus-noise ratio (SINR). To address the non-convexity, a two-level iterative algorithm based on the Dinkelbach method and semidefinite relaxation (SDR) is proposed. Numerical results show the performance gain of combining SDMA into the NOMA-ISAC system and the trade-off between sensing and communications.

This paper presents a Deep Q-Network (DQN)-based algorithm for NOMA-aided resource allocation in smart factories, addressing the stringent requirements of Ultra-Reliable Low-Latency Communication (URLLC). The proposed algorithm dynamically allocates sub-channels and optimizes power levels to maximize throughput while meeting strict latency constraints. By incorporating a tunable parameter$\lambda$, the algorithm balances the trade-off between throughput and latency, making it suitable for various devices, including robots, sensors, and controllers, each with distinct communication needs. Simulation results show that robots achieve higher throughput, while sensors and controllers meet the low-latency requirements of URLLC, ensuring reliable communication for real-time industrial applications.

In most Internet of Vehicles (IoV) scenarios, intelligent vehicle terminals are required to cope with a multitude of heterogeneous tasks, each of which is subject to increasingly strict constraints on delay and energy consumption. Task offloading is an efficient way to tackle this issue. However, due to performance constraints, a single or two-tier offloading strategy can not enable fine-grained task allocation and flexible service deployment. To address the above problems, we propose a collaborative cloud-edge-end task offloading scheme for IoV scenarios. Since traditional single-agent Deep Reinforcement Learning (DRL) makes it difficult to coordinate multiple objectives of dynamic services simultaneously, we propose a task offloading strategy based on multiagent Deep Deterministic Policy Gradient (DDPG), to jointly consider service delay and energy consumption. We further introduce attentive experience replay (AER) to mitigate the issue of insufficient experience sampling in the DDPG algorithm caused by the catastrophic forgetting problem. Through simulation of IoV scenarios, our proposed model significantly enhances task offloading effectiveness and concurrently reduces delay by 10.6% and energy consumption by 8.1% compared to other state-of-the-art baseline algorithms.

According to the World Health Organization, an estimated 1.28 billion adults aged 30–79 years worldwide have hypertension. 46% of adults with hypertension are unaware that they have the condition. The only way to know is to get your blood pressure checked. Typically, we use a blood pressure monitor (cuff) at home. However, this method can be uncomfortable and stressful. This paper proposes a non-contact method for estimating blood pressure using 2.4GHz microwave signals. We conduct experiments aimed at capturing the pulse waveform through the reflection of microwave signals. In our previous paper, we only estimated the SBP and focused on increasing the number of features value. In this paper, we estimate both SBP and DBP, and clarify which feature values are important to estimate blood pressure. Also, we attempt the real-time detection of blood pressure. Our studies show that both SBP and DBP can be estimated at a chest. This paper is to achieve predicted blood pressure values that meet the accuracy standards defined by the Japanese Industrial Standards (JIS).

Smartphone can be used to operate IoT devices and access services such as smartphone game, but prolonged use cause gaming disorder. Gaming disorder was published as an international disease in 2022 by World Health Organization (WHO). Gaming disorder is a symptom of an inability to control the amount of time spent playing games daily. In recent years, the number of patients with gaming disorder has been increasing and there are not enough hospitals to treat them, so it is necessary to cure gaming disorder by oneself without visiting hospitals. Therefore, it is necessary to understand the stress that users are under while playing games, and to provide remedial measures such as encouraging rest within a reasonable range. Since this paper is an initial study, stress evaluation of users during smartphone game playing. To evaluate the stress using biometric information, we obtain temporal changes in radio wave intensity by reflecting radio waveform in the 2.4 GHz band to the chest, and pulse wave and respiration waveforms by signal processing, from which 17 parameters that are attributable to stress. From the one-month smartphone usage logs, 16 subjects with short average game time per month and 18 subjects with long average game time per month are extracted. Since it can be assumed that the stress state during game play differs between the groups with short and long average game time, comparison of the difference in variation during game play using stress-induced parameters and binary classification using machine learning to evaluate the user's stress state. Since this method uses two antennas in the 2.4GHz band, it will be possible to measure stress using smartphones in the future, contributing to the understanding of stress that is likely to be held unconsciously.

Mobile healthcare has attracted significant attention in recent years as people have become more health -conscious. Furthermore, there is an increasing demand for non-contact and non-invasive diagnostic methods to reduce the risk of infection and pain. This study proposes a healthcare system that detects pathological symptoms by utilizing speech audio. Existing methods for the detection of COVID-19 have relied on cough recordings. To investigate the potential application of this method in the real use case, this study utilizes speech audio instead of cough recording. Our target is to alleviate the burden on the medical field and help medical workers by implementing this mobile healthcare system. This method uses transfer learning to address the problem of limited data. We evaluate the accuracy with transfer learning and random forest classification utilizing the specific features extracted in such a spectrum and spectrogram.

Atherosclerosis is an extremely common and serious health problem that is often asymptomatic. Typically, symptoms of atherosclerosis do not appear in the early stages, making timely diagnosis difficult. This paper proposes a non-contact method for estimating arteriosclerosis using 2.4GHz microwave signals. From the gained waveforms, we calculated the pulse wave velocity (PWV) as an index of arteriosclerosis. As an evaluation method for the experiment, we conducted a Bland-Altman and Four-Quadrant analysis and a T-test to determine if there was a significant difference between the data of healthy subjects and hypertensive subjects and evaluated it using the p-value. It was found that the speed of the PWV of hypertensive subjects was higher than the speed of the PWV of healthy subjects. The p-value was less than 0.05 when using a pulse waveform. These results indicate the potential to detect arteriosclerosis using microwaves. Traditionally, detecting arterial stiffness has required undergoing tests at hospitals. By measuring at the same frequency as Wi-Fi, in the future, it may be possible to measure blood pressure with a smartphone and easily assess the risk of arteriosclerosis, potentially preventing serious illnesses.

This paper discusses the novel technique which investigates the fusion of Radio Frequency (RF) signal and Fisheye camera to improve object detection to further the future realization of Autonomous vehicles and their safety on roads. A technique in which Direction of Arrival (DOA) of signal is computed through the Time of Arrival (TOA) - Trilateration method. The evaluation is done for the same-side DOA and opposite-side DOA on road. Then, this DOA value is utilized to select the Region of Interest (ROI) in the panoramic view made by the images captured by the Fisheye camera from all the directions. Then, dataset is created by using these ROI-selected images which are used to train the YOLO model to perform detection. This is the first work that talks about the fusion of RF signals with vision sensors. This Fusion will not only improve the overall classification but also reduce the computational time for the detection. The results have shown that the computation time has reduced by 10 percent, along with 17 percent improvement in confidence score for ROI-selected images resulting in accurate detection of targeted vehicles on the road.

Orthogonal time frequency space (OTFS) has been identified as an effective approach for addressing delay and Doppler shifts inherent in the physical transmission character-istics of low earth orbit satellite (LEO-Sat) communications. In this paper, we investigated the performance of zero-forcing (ZF) and linear minimum mean square error (LMMSE) equalizers in OTFS LEO-Sat unmanned aircraft systems (UAS)-assisted multi-hop system. We analytically derived the signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) for these equalizers. Further, we developed the multi-hop ZF and LMMSE equalizers tailored for the multi-hop Amplify-and-Forward (AF) relay scheme. Utilizing the aforementioned expressions, we derived the SNR for multi-hop Decode-and-Forward (DF) relay and multi-hop AF relay schemes. Simulation results indicate that, with appropriate link combining selection, the use of multi-hop AF relay scheme is feasible. Moreover, in LEO-Sat multi-hop scenarios, strict adherence to the equalization sequence is crucial for optimal performance.

Application of Unmanned Aerial Vehicles (UAVs) as small airborne base stations is gradually becoming a research hotspot in the field of wireless communications. With the flexible deployment, wide coverage and low cost, UAV communications show great potential in the fields of emergency rescue, environmental monitoring and military operations. In particular, the easier availability of line-of-sight (LOS) links for UAVs makes its combination with millimetre wave (mmWave) technology significantly enhance the communication bandwidth and data transfer rate. However, the very limited coverage of mmWave communications greatly affects the actual data rates provided by small aerial base stations of mmWave UAVs, especially considering user movement on the ground. In this paper, we study the joint optimisation problem of UAV deployment, user association, spectrum resource allocation in millimetre-wave heterogeneous networks, and explore the impact of different user movement models on system performance. Given that this problem is NP-hard, our paper proposes an MCR-SAC method to maximize the network’s total throughput. Simulation results demonstrate an average 18% improvement in total transmission rate compared to the conventional.

Integrating autonomous vehicles (AVs) within our transportation ecosystem presents exciting possibilities and introduces intricate challenges. Systemic failures due to cyberattacks on AVs could have far-reaching consequences, impacting safety and financial stability. This paper emphasizes the interdependence of stakeholders, particularly within the financial and insurance sectors. We propose a proactive approach, focusing on three objectives: (1) Systemic Risk Mitigation, (2) Premortem Analysis with a focus on cascading failures, and (3) Integration of Cybersecurity Standards tailored for autonomous electric vehicles (EVs). By addressing EV-specific vulnerabilities in charging infrastructure and telematics systems, we aim to significantly enhance the security of safety-critical cyber-physical systems, strengthen the resilience of interconnected industries, and contribute to broader economic stability.

Orbital Angular Momentum (OAM) has attracted significant attention in the field of wireless communications due to its potential for high-capacity data transmission through mode multiplexing. However, OAM experiences severe performance degradation due to inter-mode interference (IMI) caused by antenna misalignment. In this paper, we propose a novel method to suppress IMI caused by misalignment for uniform circular array (UCA)-based OAM multiplexing. We discovered that IMI can be minimized when the IQ data of each OAM mode are close to each other in the constellation, enhancing robustness to misalignment. Therefore, we propose a method, where the IQ data of one OAM mode (reference OAM mode) is selected from the entire constellation range, and the IQ data of the other OAM modes are selected from a range close to this reference OAM mode. The proposed method is shown to prevent system capacity degradation compared to traditional method when the antenna is tilted. Moreover, in the proposed method, the reference OAM mode stream shows minimal performance degradation when the antenna is tilted. Furthermore, our proposed method is well-suited for adaptive modulation, effectively adjusting to varying communication conditions to maintain optimal performance.

Joint Radar Communication (JRC) system achieves radar detection and communication transmission using a shared hardware platform, making it more suitable for integration, miniaturization, and efficient spectrum utilization compared to traditional standalone radar or communication devices. Due to the mutual interference between the two subsystems, there is growing interest in reducing negative impacts and optimizing the overall performance of JRC systems. Among various approaches, optimizing resource scheduling strategies within JRC systems to balance the performance of each subsystem in different environments and enhance system Quality of Services (QoS) values has become a significant research direction. In this paper, we propose a deep learning-based optimization framework tailored for JRC systems. By analyzing the current application environment of JRC systems, the proposed method dynamically adjusts the energy resource allocation strategy within the JRC system. This approach aims to balance the subsystems’ performance concerning the current system environment and demands, achieving self-optimization to adapt to the current application scenarios. Simulation results indicates that our proposal could improved the JRC average performance under different application scenarios.

With the increasing demand for sensing functions in the 6-th generation (6G) wireless communication networks, waveform design has become critical. The waveform must ensure a high quality of service in communication and achieve high precision in sensing; thus, interference between these two functions should be minimized. This paper proposes a power division waveform design for integrated sensing and communication (ISAC) based on orthogonal frequency division modulation (OFDM). This waveform design utilizes the Zadoff-Chu (ZC) sequence as the symbol sequence for sensing. The probability of detection for this method can reach approximately 0.8. The properties of the ZC sequence make it easy to implement in LTE and NR base stations and allow it to be effectively eliminated through successive interference cancellation. Additionally, the potential of this waveform in channel estimation (CE) is also analyzed, demonstrating an accuracy of CE under 3.5 × 10−3.

The number of terminals connected to the satellite network is expected to increase, influenced by the recent increase in communication requirements. Since the delay time cannot be ignored in links between geostationary orbit satellites and ground stations, a multiple access scheme that can accommodate many stations while minimizing retransmissions is required. In this paper, we propose a protocol for mobile satellite communications that aims to achieve low latency and high reliability by applying Successive Interference Cancellation (SIC) to Power Level Division Multiple Access (PDMA) using power and time domains. As one of the use cases, an urban model with traffic signals and buses as relay stations was assumed. First, we conducted a theoretical evaluation of communication quality and confirmed that PDMA achieves higher spectrum efficiency than conventional schemes. Then, we conducted simulations assuming the actual urban environment based on the Line of Sight duration and other factors to compare the performance of the proposed method with that of other multiple access schemes. The results showed that the proposed method reduced the delay by about 70% and reached higher throughput compared to the conventional scheme, even when using a lower level primary modulation scheme.

Fractional Doppler is always treated as a technical barrier in Orthogonal Time Frequency Space (OTFS) transmission, for it will lead to extra Doppler spread. In this paper, we view fractional Doppler from a new perspective that it can be utilized for high-resolution Doppler-only positioning and adopt it in high-speed railway scenarios for positioning and velocity detection. The proposed method uses only Doppler shifts for positioning, instead of delay or any other angle-related measurement, and can effectively work without massive antenna arrays or large bandwidth. Correlation-based Doppler estimation, which is adopted for OTFS channel estimation, is adopted to obtain high-resolution fractional Doppler measurement. Then the Doppler-only positioning problem is transformed into a non-linear equation and solved by the Halley method. The simulation results verify that the proposed method, with just normal bandwidth as commercial communication systems, shows better performance than integer Doppler-based positioning and ultra-wide-band (UWB) time-of-arrival (TOA)-based method.

With increased sophistication, robots tend to become bigger and heavier as it requires greater processing power and complexity. However, the increase in size and weight of robots can reduce efficiency and mechanical flexibility. Therefore, the removal of wires inside robots is proposed to reduce them. Signals are to be wirelessly propagated via waveguide structures fitted inside the robotic structure. In this paper, we discuss an improved waveguide model to fit inside a robotic leg structure and bending via the incorporation of a rotary joint is also investigated electromagnetically. For comparison, both rectangular and circular waveguide models are designed. In conclusion, it is found that the rectangular waveguide model is optimal for the proposed system, which operates between 2.83 GHz to 3.76 GHz.

The typical measurement method using a cuff is physiologically stressful for many, especially the elderly people. In order to eliminate the burden and realize comfortable measurements, a non-contact method for monitoring blood pressure is necessary. This paper proposes a non-contact method to detect the human pulse, acceleration pulse waveform and in turn, predict blood pressure. In the experiment, microwave signals were transmitted against, and reflected from the chest and wrist, upon which the time-varying Insertion loss of Scattering parameter(S21) was acquired. Pulse, respiration rate and Augmentation Index(AIx) are first estimated via postprocessing of acquired raw data. Further signal processing also detects the acceleration pulse waveform. Blood pressure is then predicted via Machine Learning (ML) methods with parameter values derived from the detected pulse waveform, respiration waveform and acceleration waveform. Our works indicate that our proposed non-contact method is practical and has great potential for future smart health solutions.

This study proposes a salvage transmission (ST) scheme for 5G networks using device-to-device (D2D) communication. In mobile networks, communication is disabled when issues emerge in the core network or base station of the operator. To address this problem, the proposed scheme provides mobile communication services via D2D communication to user equipment (UE) that cannot use cellular networks. The users of an operator that is unable to provide service due to communication failure transmit signal using D2D communication with the closest UE of another operator. This ST scheme enables the mitigation of communication failures. In addition, this study introduced the basic protocols of ST with Wi-Fi Direct (IEEE 802.11) and 5G networks. Furthermore, we verified the effectiveness of the ST scheme in the case of communication failures via a simulation study.

Reconfigurable Intelligent Surface (RIS) is a competitive technology for future communication systems owning its capability of artificially manipulating the Electro-Magnetic (EM) environment at a low energy cost. Self-sustainable RIS, as a practical design, further enhance the ease of deploying and maintaining the devices. In this paper, we discuss the joint active and passive beamforming design of a Wireless Power Transfer (WPT) powered self-sustainable RIS aided Non-Orthogonal Multiple Access (NOMA) system. An RIS-NOMA transmission scheme and a corresponding min-max fairness problem are proposed. To address the problem and tackle the non-convexity caused by the coupling of active and passive beamforming parameters, we discuss an Alternating Optimization (AO) based solution. Results show the tradeoff between self-sustainability and Spectrum Efficiency (SE) under different RIS settings. It is also determined that self-sustainable RIS and NOMA are mutual beneficial and allow higher SE compared with the combination with traditional OMA schemes.

Orthogonal Time Frequency Space (OTFS) has been proven to have strong robustness to Doppler shifts and is regarded as a potential candidate for Orthogonal Frequency Division Multiplexing (OFDM) in the next generation wireless communication. However, narrowband interference (NBI) may become a headache for OTFS-based wireless systems. In OTFS, NBI will be spread over the whole delay-Doppler (DD) domain, and thus cause serious interference. Such interference is very dangerous in OTFS-based high-mobility communication for it will let the fast-moving user equipment (UE) in danger of losing control. Previous work infers OTFS to have natural robustness to NBI. In this work, we conduct further analysis and come to the conclusion that such robustness is only capable when NBI is weak, but when NBI gets stronger, OTFS exhibits vulnerability to it. Then we propose an NBI suppression scheme for OTFS to detect and eliminate NBI with a low computation load. Simulation results prove our analysis and indicate the proposed scheme can prevent serious interference resulting from NBI to some extent.

The use of space elevators is being considered as a new possibility for satellite communications. However, there has been no research on communication using space elevators. In this study, we evaluated the communication performance using space elevators. In particular, we studied the installation altitude of the space elevator at low-altitude stations. As a use case of communication, wireless communication was assumed to be used in the downlink of communication from the space elevator to the ground. The communication performance in wireless communication is mainly determined by the received power. The received power is mainly affected by transmit power, distance attenuation, shadowing, and fading. Among them, fading affects the received power due to different communication models depending on whether direct waves are available for communication or not. Since space elevator-based communications can be regarded as low earth orbit satellite communications and fixed communications due to the nature of space elevators, fading models are an important factor in evaluating the communications performance of space elevators, assuming actual communications. In this study, a communication model for each city model was obtained from data of real cities. Using the communication model, the communication performance of the space elevator was evaluated for each city model.

Non-terrestrial network (NTN), especially HighAltitude Platform Station (HAPS), is a popular choice because of low latency, deployment flexibility, and disaster resilience. In order to increase the availability of HAPS, a new multiple access system that improves performance, such as throughput and user fairness, is required. Although Non-Orthogonal Multiple Access (NOMA) is a promising technology for improving spectral efficiency, there are significant differences in transmission rate according to power levels for NOMA. Since ground-HAPS links are the end part of NTN and the HAPS network is expected to be used for the mobile network, the user fairness of NOMA should be improved. Thus, to increase throughput guaranteeing user fairness and transmission accuracy for HAPS, we implement Power Level Division Multiple Access (PDMA) which power levels of users are randomly switched in each timeslot. In this paper, we propose a new system applying PDMA for ground-HAPS uplink network with hybrid Free Space Optics (FSO) / millimeter wave communication. In our system, it switches optical and millimeter waves according to the channel state of users. By simulation results, the throughput of PDMA is higher than that of Orthogonal Multiple Access (OMA), and its user fairness is significantly improved compared with NOMA.

In modern robotics, one of the topics is to remove or reduce the cables inside the robot, which can improve flexibility, decrease the maintain demand, and make the robot easier to build up. Therefore, wireless communication would provide a solution that can replace these cables for the above issue. In this paper, we propose a hybrid Medium Access Control (MAC) scheme for different wireless sensors communication based on our previous work, the Orthogonal Frequency subcarrier-based Multiple Access (OFSMA) scheme. For general sensors, we use the OFSMA scheme to ensure URLLC standards. As for audio sensors and video sensors. There are many spaces inside the robot structure. We set a goal to transmit the signal directly through these small spaces as an internal waveguide to achieve wireless communication. Therefore, we design a model to simulate the realistic situation of robots using High-Frequency Simulation Software (HFSS) and find out the possibility of signal propagation directly through the robot.

With the increasing number of 4K/8K channels and the development of broadcasting technology, the frequency used for the intermediate frequency (IF) signal keeps increasing. Using fiber to replace cable is proved to achieve lower signal loss and reduces the noise sensitivity in 4k/8k broadcasting systems. Power-over-fiber (PoF) is chosen for the power supply. In this research, a 4K/8K broadcasting system using double-clad fiber (DCF) to maintain power and signal transfer simultaneously is proposed. DCF has three layers and can achieve Single-Mode and Multi-Mode transmission simultaneously. The breakthrough we make is using HPLD for energy supply to combine RoF and PoF together.

In recent years, hypertension has become a leading cause of diseases worldwide. Despite the recommendation from medical experts to measure blood pressure on a daily basis, only a small few do so. The main reason for this is that the typical measurement method using a cuff is physiologically stressful for many, especially for physically handicapped people, and the elderly. In order to eliminate the burden during measurement, a non-contact method for monitoring blood pressure is necessary. This paper proposes a non-contact method to detect the human pulse and in turn, estimate blood pressure. In the experiment, 2.4GHz microwave signals were transmitted against, and reflected from the body, upon which the time-varying reflection intensity was acquired. Pulse rates are first estimated via post-processing of acquired raw data. Blood pressure is then estimated via Machine Learning (ML) methods with parameter values derived from the detected pulse waveform. Experiments indicate that our proposed method is practical and has great potential for future smart health solutions.

GPS is known to be vulnerable to GPS spoofing. This can be divided into three stages based on technical aspects: Simplistic, Intermediate, and Sophisticated [1]. Intermediate spoofing is a feasible and threatening technology. However, most of the existing research on mobile device spoofing focuses only on the Simplistic spoofing, which is the least threatening, and there are few experimental-based studies specifically on Intermediate spoofing. In this article, we conduct an experiment of Simplistic and Intermediate spoofing on mobile terminals using an open-source GPS signal generation simulator and analyze the threats.

Resource allocation of 5G cellular network slicing has been gaining huge interest recently. However, it is not well-explored under the Multi-tenant and Multi-service Coexistence Network scenario. This paper proposes a dynamic network slicing scheme for the 5G Coexistence Network, which considers tenants, priority, baseband resources, slice granularity, service characteristics, quality of service (QoS), and fairness index. The framework of the network slicing scheme consists of a group-level, which performs clustering preprocessing, setting the priority of service, and filtering the desired characteristic service groups; and a slice-level, which performs radio resource allocation among services and follows the changes in the network environment closely. The simulation results show that the proposed scheme can achieve higher goal service group QoS, fairness, and overall QoS compared with three kinds of baseline schemes.

Intelligent Reflecting Surface (IRS) is a planar surface that allows the signal transmission to be artificially manipulated. Communication aided by multiple IRSs is proven to be more effective in aspects such as transmission rate and signal coverage, but it raises complex coordination in issues such as channel estimation, resource allocation, and active/passive beamforming design problems for the Base Station (BS), IRSs and User Equipments (UEs). In this paper, we discuss the cooperative passive beamforming problem for multiple IRSs. First, we develop a multi-user communication scenario, in which multiple discrete phase shift IRSs are deployed to assist the transmission. Then, we formulate the cooperative passive beam-forming problem to maximize the sum transmission rate within a cellular multi-user network. To address this problem, we discuss a Reinforcement Learning (RL) approach, i.e., to transform the problem into a Multi-agent Markov Decision Process (MA MDP) and raise a Q-learning-based solution. Three different designs of the reward function are tested. Simulation results regarding the performance under different IRS and RL settings are given, which show that the proposed algorithm is capable of reaching a favorable passive beamforming solution in limited iterations and is effective in both convergence and long-term performance.

This research investigates the use of a hybrid technique to locate vehicle positions on a 2D plane solely via other vehicles to further the future realization of Vehicle-to-Vehicle (V2V) communication. An approach in which trilateration and Time Difference Of Arrival (TDOA) are combined to estimate the Direction Of Arrival (DOA) of an incoming signal is considered. By using TDOA measurements of receivers on the Receiver Vehicle (RV), estimation regions are constructed to robustly obtain the Transmitter Vehicle (TV) position. This proposal not only creates a method for TDOA to be directly used in V2V communication but compared to other localization methods such as TOA (Time Of Arrival), the proposed technique does not need to consider time synchronization between the TV and RV, allowing for usage in a larger variety of on-road scenarios. A regression model is also implemented to further improve the accuracy of the estimation. Evaluation of the proposal is conducted for same side DOA and opposing side DOA. The DOA estimation was compared with a theoretically ideal scenario incorporating TOA. For further clarification of the methods utility and to mimic the transmission signal in road environments, the proposal is also tested in a ray tracing propagation model. The simulations show that the proposed solution accompanied with the regression model estimated the DOA in a 1 nanosecond (ns) time step environment to 1.92° accuracy and 0.08°accuracy in a 0.1ns time step environment.

We designed an in-vehicle communication system using wavelength division multiplexing and investigated its characteristics under various environments. Since a single optical fiber can communicate multiple wavelengths of light, it is assumed that this will lead to a reduction in the number and weight of cables required for communication compared to conventional coaxial cables. As a result, vehicle maintenance and fuel efficiency were improved. Using data from coaxial cables as a reference, the transmission characteristics of single-mode fiber (SMF), the wavelength division multiplexing (WDM) systems, and the transmission characteristics of optical fibers were measured and compared in an in-vehicle environment.

Terahertz (THz) band is a frequency range starting from 0.1 THz to 10 THz. It is considered a new frequency band resources for future communication systems. However, the high absorption attenuation of THz waves in the atmosphere makes utilizing this frequency range very difficult. Current research on THz has rarely focused on satellites, aircraft, or other long-distance communications. Moreover, due to the channel model’s limitations, some research cannot easily be applied to the entire THz band. So in this paper, we analyze the atmospheric attenuation on the propagation of THz waves in the long-distance scenario with a universal model. Then we propose a new non-orthogonal multiple access (NOMA) scheme (direct NOMA) according to the atmospheric attenuation. Through simulation, we analyzed the system capacity and the bit error rate of the three multiple access schemes (conventional NOMA, direct NOMA, and OMA) in this scenario. The simulation result verified the feasibility of THz in this scenario, and it points out that direct NOMA can increase the capacity and reliability of this system.

In this work, a channel estimation method for OTFS using superimposing pilot is proposed. The pilot is superimposing on the first transmitter data symbol, yielding an enhanced frequency domain of Delay-Doppler domain pattern at the receiver end. A deep convolution neural network is proposed to de-noise the interfered channel matrix. Simulation results show that the bit error rate performance of the proposed method is better than that of the existing methods at low pilot energy.

The authors have been proposed a wireless multihop routing method inspired by the behavior of the slime mold. The previous methods iteratively calculate bandwidth allocation for each link based on the maximum bandwidth, the transmission delay, and the required communication volume by the source node. However, the appropriate number of calculation iterations and the actual calculation time for bandwidth allocation vary depending on various factors. In addition, the allocation results cannot be reflected until the calculation is completed, thus the allocation results may not be suitable for the network conditions at the end of the calculation. In this paper, the authors propose an adaptive wireless multi-hop routing with reduced impact of processing delay by sequentially using values that are convergence processes as indicators for route selection.

Wireless power transmission via radio frequency (RF) attracts attention as a power source for small devices such as wireless sensor networks (WSN). Among these, the method using RF waves have the advantage that power can be transmitted over long distances about several meters. Because RF waves can transmit power from a single power supply over a wide area simultaneously. RF can also drive a wireless sensor network semi-permanently. However, simply transmitting radio waves will cause problems such as interference and reflection, then it will reduce efficiency. In this paper, we propose an efficient wireless power transmission scheme by controlling the phase using an all-pass filter (APF). APF is a filter that acts only on the phase of the signal and realizes interference mitigation by controlling the phase difference. Experimental results show that the application of APF to wireless power transfer increased the voltage across WSN devices.

Gesture recognition has been a popular research field under the trend of IoT and intelligent devices. Air-writing is the most challenging and crucial topic in the gesture recognition field. In this paper, we propose a wearable air-writing system that makes users can write the English alphabet in the three-dimensional space without any write rules. The proposed system is based on the Inertial Measurement Unit (IMU), and it uses dynamic time warping (DTW) as the main recognition algorithm. In addition, to improve the recognition accuracy and take a better advantage of the DTW algorithm, we present an adjustment system that gives some new optimization methods to the application of IMU and DTW. In the experiment, the accuracy of recognition is 84.6% for the uppercase alphabet (from `A' to `Z') in user-dependent case. And we also confirmed that the recognition method only based on the DTW algorithm is one kind of user-dependent methods, which means this method is heavily dependent on personalization.

Non-Orthogonal Multiple Access (NOMA) is attracting attention as a key technology for 5G because of its high spectral efficiency and high throughput. In addition, satellite communication, especially Low Earth Orbit (LEO), is popular choice for global communication because of its high global connectivity. In this paper, we apply uplink and downlink NOMA for inter-satellite communication to achieve delay suppression and increased throughput. We analyze the BER and transmission rate of the proposed system by simulation.

Non-invasive Blood Glucose Measurement (NGM) technology is a crucial challenge for not only academic communities but also industrial communities. Therefore, finding an applicable and accurate NGM technology is supportive and desired for patients with hyperglycemia or hypoglycemia. Among various NGM technologies, infrared is considered as the most popular and prospective method. In this paper, the mid-infrared spectroscope is used in the experiment, there are significant differences in transmittance in the range of 3000 ~ 3500 cm−1(3333 ~ 2857 nm). The association between mid-infrared spectroscopy transmittance and blood glucose concentration is presented. The infrared with a peak wavelength of 3000 ~ 3500 cm−1could be a good solution to measuring the physical signals in the experiment. Besides, an NGM prototype that aims to improve self-management motivation is designed and presented. Mid-infrared is very potential and prospective in NGM research. Also, further investigation and consideration ear needed in future work.

The low power consumption in mW of the IEEE802.15.4/ZigBee standard is one of its feature, even though it requires the exchange of batteries. The cost of battery exchange for wireless sensors is considered as one of the critical problems for wireless sensor networks (WSN). Sediment microbial fuel cell (SMFC) can be a promising technology to replace conventional energy sources by renewable energy sources for wireless sensors, which has the potential to supply sustainable WSN without a replacement of batteries. However, SMFC cannot drive a microcontroller directly since it only provides ultra-low voltage and ultra-low current. In addition, from a general perspective, SMFC is costly to build for wireless sensors due to its materials costs. Considered about those challenges, this paper proposed a novel energy harvesting system for the ZigBee network which consists of the SMFC sensor and a power management circuit to accumulate adequate energy for load. Intermittent data transmission between the ZigBee end-device and coordinator is conducted with the designed energy harvesting system. The experimental results showed that the SMFC-powered ZigBee sensor device is eligible to enable intermittent communication in replacement of conventional battery.

Currently, non-invasive blood pressure monitoring with using a cuff is commonly used. However, this monitoring method is not suitable for some people who cannot wear the cuff and who might feel uncomfortable and troublesome. Non-contact measurement method provides a safer and more comfortable way to measure blood pressure. This paper describes the research on a non-contact pulse and blood pressure monitoring system. The frequencies of millimeter waves used in this experiment are 28GHz and 32GHz, which are the same as 5G millimeter wave signal. In this experiment, the millimeter waves are transmitted and reflected to the body and measure the reception intensity. As the results, we can detect pulse by utilizing millimeter waves, however, the relationship between blood pressure and millimeter waves needs further investigation.

Although there have been extensive works on artificial-noise-aided (AN-aided) secure transmission schemes for multi-antenna systems, there is still lack of study on the AN-aided scheme employing the widely used linear zero-forcing beamforming (ZFBF) for systems with multiple distributed users. Particularly, there is no analytical secrecy performance for general system settings with neither perfect nor imperfect channel state information of the legitimate users at the transmitter (CSIT). This paper considers the AN-aided ZFBF based on the quantized CSIT for secure communication in the downlink multiuser multi-antenna systems with an external multi-antenna eavesdropper. We develop an approximated closed-form lower bound on the ergodic rate of each legitimate user (LU), and also a closed-form upper bound on the maximum achievable ergodic rate for each LU's messages over the eavesdropper's channel without assuming any asymptotes for system parameters. Then, an approximated closed-form lower bound on the ergodic secrecy rate of each LU follows. Simulation results validate our analytical secrecy performance results and also the effectiveness of AN in enhancing the secrecy performance of linear ZFBF.

In this paper, we propose a system for visualization of radio signal using drone in the field. It is possible to measure the directivity of antennas if we use anechoic chamber. However, it is difficult to obtain the directivity of antennas in the field. In order to get the directivity of antennas in the field, we propose the system which uses detector circuits which convert radio signals to light, receive antennas, and drone. To obtain the directivity in the field, we carried out an experiment. In this experiment, we used Yagi-antennas. The results show that precision of the system is a moderate match to the directivity obtained from the chamber. The results also confirm the proposed system is practical in the field.

This paper introduces a novel Vehicular Ad Hoc Networks (VANET) clustering scheme, titled “Normalized MultiDimensional Parameter based Affinity Propagation Clustering (NMDP-APC).” The similarity function of NMPD-APC consists of normalized multi-dimensional parameters in order to represent VANET's motion dynamics. This similarity function is the key in the Affinity Propagation Clustering (APC) scheme to adequately representing the homogeneity of traffic dynamics of VANET. In contrast to the previous research on APC scheme for VANET, our proposal does not associate any un-stable future prediction term. We also applied recently introduced Cellular V2X radio capability in this study, which significantly contributed to the reduction of communication latency. In conducting simulations, Gazis-Herman-Rothery (GHR) car following model was applied on the real sampled traffic data. The simulation resulted remarkable effects on the normalized multidimensional parameters along with successful VANET clustering. The simulation also demonstrated required minimum number of iterations for the clustering and controllability of clustering granularity in the proposed NMDP-APC scheme on the real traffic data.

In this paper, a cooperative traffic light controlling algorithm for urban road network aiming at reducing traffic congestion is proposed. Dedicated Short Range Communications (DSRC) is applied to detect the real time traffic flow. Based on the traffic flow at the current traffic light cycle and the historical data, we use machine learning technique to predict the variation of the traffic flow at the next traffic light cycle. With the purpose of reducing the road network's average waiting time and balancing the traffic pressure between different intersections, the traffic light control system adjusts the timing plan cooperatively. The genetic algorithm is used to calculate the optimum traffic light timing plan. In addition, a novel state transition model of the road network for dynamic numerical simulation is utilized to verify the effectiveness of the proposed algorithm. According to a 4-nodes road network simulation result, the vehicles in the traffic flow with congestion problems will have a shorter waiting time while the vehicle in the other traffic flows will have an increased waiting time. More importantly, the average waiting time of the road network declines.

In this paper, we propose a power control algorithm dedicated for machine type communications (MTC) in future non-orthogonal multiple access (NOMA) networks employing game theory. In MTC networks, communication reliability should be considered prior to power consumption or energy efficiency. Once the reliability is satisfied, discussions about power consumption makes sense. We build a cost function for each device based on a non-cooperative game model. The cost function reflects the power consumption as well as received signal-to-interference plus noise ratio (SINR) of each device. Since we assume the devices are battery-driven, the objective is to minimize the power consumption as much as possible provided that the received SINR of each device is kept beyond an acceptable level so that the reliability can be guaranteed. We derive the power control algorithm function and prove the convergence of this iteration algorithm and the unique existence of Nash equilibrium as well. The simulation results show that under the same constraints of maximum power consumption and minimum acceptable SINR, the proposed algorithm outperforms the conventional algorithms in terms of power consumption and power efficiency.

This paper explores a cooperative partnership and data forwarding model in wireless sensor networks using unmanned aerial vehicle (UAV) with the goal of enhancing the data collection efforts. A UAV-based data acquisition architecture is presented to suppress the limitations of the traditional wireless sensor network. For this, we introduce a flexible and fast approach to collect data by taking into consideration the mobility of the mobile sink (UAV) and sensor nodes in the network. In other words, leveraging the mobility of the UAV and the location of sensor nodes, we adopt a novel frame selection technique that classifies sensor nodes into different frames. Then we present a cooperative partnership model that allows sensor nodes in the network to individually pair with their peers and thus transmitting data simultaneously. We also aim to alleviate the packet loss originated from certain sensor nodes located in the rear edge-side of the UAV's coverage area. This situation happens when the UAV is moving in the forward direction while collecting data. Thus, to alleviate these packet losses while guaranteeing a higher success rate of packet reception ratio, we propose a novel data forwarding scheme to closely integrate with the aforementioned partnership model. We conduct simulations to verify our proposed framework, and results show huge performance gain is obtained over the traditional data collection technique.

This paper presents a novel ticket gate system employing optical wireless communication used at a train station in Japan. The proposed system needs two optical wireless card readers attached to two inner sides of the gate. According to our study, we found that the proposed system has higher received power compared to the conventional train ticket gate system. It also has higher probability of success as long as the communication distance is less than 0.28 meters. As a result, the proposed system has a better performance compared to the conventional one and its availability is guaranteed.

In this paper, we propose a system for detection of the missing people employing UAV which is able to move quickly and has a wide view from the air in the disaster area. However, an airplane type UAV does not always have a stable flight due to strong wind, rolling, and pitching. In order to detect and to respond the missing people promptly using the UAV, we propose the system which uses a phased array antenna and an angle detector. To implement the system, we assemble the phased array antenna and carry out an experiment to measure the characteristics of directivity, the directivity control characteristics, the return loss of the antenna, and the received power level to compare using and not using the phased array antenna in terms of efficiency and functionality. The experiment results show that the proposed system increase the received power level by adjusting the directivity of the antennas with short delay time. The results also confirm that the proposed system is practical in decreasing victims of disasters.

This paper proposes novel multiple access schemes for a swarm of Unmanned Aerial Vehicles (UAVs). In a super dense aerial sensor network, small UAVs communicate and transmit data from one to another, and thus leading to unavoidable packet collisions among actors. In light of that, this work introduces a novel proposal of multiple access scheme based on a hybrid collision coordination technique, a combination of CSMA/CA and TDMA protocols. The newly proposed MAC protocol is named as CC-MAC in this paper. Besides, a system model considered in this paper focuses on a swarm of UAVs in a super dense network environment. These UAVs are used to sense and collect a real-time data from a disaster area. The information is then transmitted from joint UAV nodes to a more powerful node called a master UAV. Moreover, this paper also adopts a spatial diversity technique and introduces a simultaneous data transmission scheme based on a partnership of two nearby UAVs. Thus, nodes in a network allocation vector state (NAV) of CC-MAC can simultaneously transmit their packets without any delay or collision. Simulation results show that both proposed MAC protocols offer a huge performance improvement in average throughput and delay compared to an IEEE 802.11 CSMA/CA.

This paper investigates the performances of a nonorthogonal single user multiplexing scheme employing multiple power levels. In this work, we employ different power levels for different signals from a single user. The single data stream from a single user was divided into several data blocks and each data block employed a non-uniform multiple power levels. The system performances were evaluated using two different modulation schemes of 16QAM and 64QAM. Two data blocks case gave us a better performance with flexibility in power allocation compared to four data blocks case where the complexity of power allocation was high. The proposed scheme with interference cancellation and multiple power levels offer effective improvement even with some error in cancellation compared to no cancellation scheme.

In recent years, short range wireless communications have been used more and more frequently in our life. But the electromagnetic fields waves also have some disadvantages. One of these disadvantages is health problems. Many studies shows the electromagnetic field waves using for communication may damage our health. And in most hospitals, they also have bans on the use of mobile phones and wide area networks because of Electromagnetic Interference. So in this paper, we studied the use of ultrasound for wireless communication in air, instead of using electromagnetic field wave. An Alternating-Direction Implicit Finite-Difference Time-Domain (ADI-FDTD) method is developed to simulate the ultrasonic wave communication system. The ADI-FDTD simulations make it possible to better understand the behavior of an ultrasonic signal. Experimental data is also presented to compare with simulation. The results show that such a system is feasible in principle for communications using ultrasound.

This paper proposes a self-optimizing based energy-efficient scheme with a dynamic coverage expansion of femtocells in the macro-femto two-tier networks. High SINR and low power consumption can be benefited by coordinating downlink cross-tier interference and intra-interference with a neuron control based adaptive power adjustment when sleep mode is involved in the macro base station (MBS). Moreover, by allowing open access in the hybrid femtocells, more near-indoor macro user equipments (MUEs), especially located around the edge of the macrocell can be served by indoor femto access point (FAP), which results in MBS having more of a probability to maintain sleep mode when the traffic is low. Many related performances are evaluated with a comparison of utility-based power control (UBPC) scheme, the energy impact of both MBS and FAP can be largely improved with optimal transmit power, which means the sleep mode technology can be enhanced, as shown in the simulation.

This paper proposes the effective data gathering and energy efficient communication scheme for Wireless Sensor Networks employing Unmanned Aerial Vehicle. In this scheme, we minimize the number of redundant sensors communicating with UAV by assigning the sensors inside the coverage area of UAV's beacon signal into different priority groups. Once the priority segments, Circularly Optimized Frame Selection (COFS), are defined, data communication is handled from higher to lower transmission priority frame sequentially. The work presented in the paper is based on multi-hop approach. Therefore, the plausible algorithms employing the scheme COFS are proposed to engage in effective data collection. As a result, both the proposed scheme and algorithms are significant to obtain low energy consumption as well as increase the lifetime of sensors inside the network. The energy consumption model is also presented. This study is confirmed by simulating the WSN-UAV system employing our proposed model.

In this paper, we determine accurate expressions for the probability of success of handshake-type network mechanisms in a wireless ad hoc network modelled by a Poisson point process. Handshake-type mechanisms form the basis for the implementation of Quality of Service into wireless ad hoc networks (e.g, to guarantee packet delivery). However, to our knowledge, their analysis using a stochastic model has not been yet presented in the literature. In order to address this issue, we consider a deployment model in which the interference situations of both nodes composing a link are defined explicitly. Our results, verified by comparison to simulated data, find applications in the joint design of Medium Access Control and routing protocols for wireless ad hoc networks.

In this paper, we analyze the performances of the Medium Access Control protocol Multi-slot-ALOHA in a wireless ad hoc network modelled by a Poisson Point Process (PPP). By giving to nodes access to the medium for several time slots, Multislot ALOHA strengthens the reliability of transmissions, which is the main weakness of MAC protocols without acknowledgements. To our knowledge, this protocol has not been the subject of a stochastic analysis of its performances yet, hence the motivation for the present work. All the approximate theoretical expressions proposed in this paper are verified by comparison to simulated data.

This paper presents an optical wireless identification (OWID) scheme utilizing high-energy harvesting thinfilm embedded onto the corner cube retroreflector (CCR). We apply optical wireless communication (OWC) for transmitting information. The thinfilm is used as a rechargeable battery that absorbs the power when the incident light beam goes through the CCR and reflects On-Off-Keying (OOK) modulated signals back to the reader. The energy harvested during the transmission is used to drive the CCR inside the tag to modulate the OWC signals back to the reader. The proposed system is proved to be more secure and having much higher available stored energy. The performance of the proposed scheme is evaluated based on the simulations and the results are discussed. According to the simulations, by using a 550nm wavelength with 0.4W of the transmitted power, the scheme achieves a data rate of 100bps and about 0.19W of the harvested power while the communication distance is up to 0.25m.

In this paper, we investigate the optimal solution of power savings for femtocell cluster deployments in the sleep mode involved macro-femto two-tier scenarios. The proposed scheme aims at achieving high SINR with optimal transmit power of femto access point (FAP) by coordinating downlink cross-tier interference and intra-interference with utility and traffic based power control (UTPC) when macro base station (MBS) is under sleep activation. Since the optimal radius of femtocells can be obtained according to dynamic coverage extension, several sleep patterns can be defined for open access permitted hybrid femtocells. In this case, more FAPs can be switched into sleep mode and managed by the main active FAPs in the cluster. As a result, the number of active femtocells can be controlled in accordance with dynamic cell configurations, which can effectively reduce the energy impact of the femtocell cluster. The simulation results show that our proposed scheme enable positive influence on power efficiency and interference coordination for femtocell cluster in the two-tier heterogeneous networks, especially during the night zone.

In this paper, we propose a new model to determine subgraph probabilities in a Random Geometric Graph(RGG). A subgraph in a RGG can be used to model various scenarios involving a given number of nodes in a multihop ad hoc network. We determine the probabilities for the two essential cases of complete subgraphs with three and four vertices, respectively, which have not yet been addressed correctly in the literature. Our theoretical results are confirmed by simulation and thus represent a significant step towards the quantitative analysis of complex scenarios, such as cooperative communications, in multi hop ad-hoc networks.

In this paper, we propose an energy saving solution for mobile systems based upon dynamic cell configuration for different scenarios. To characterize the optimal energy savings of base stations, we propose an active cell rotating scheme to control the number of active cells with regard to different work patterns switching among three states (active, receive and sleep). A recovery mechanism is enabled by scheduling a receiving-only function if sudden traffic occurs within the cell group. We consider an improved-Markov based birth-death process in order to modeling the instantaneous random traffic variance and state transitions, which is used to evaluate the performance of the proposed approach with a positive influence on power savings, especially during the night zone.

Global warming is a very serious problem which is becoming ever worse as the growth in the number of vehicles. This paper presents a real time traffic lights control scheme for reducing vehicles CO2emissions based on the Electronic Toll Collection (ETC) installed vehicles. Real time road conditions are obtained by wireless communication between the vehicles and the traffic lights based on the Dedicated Short Range Communication (DSRC) technology. A decision tree classification algorithm is used to calculate optimal average waiting time, then to calculate the CO2reductions. Compared with fixed-time control, simulation results indicate that more than 26.9% idling time CO2emissions can be reduced when traffic flow is heavy, meanwhile vehicles have a 0.07 higher probability to pass the intersection by non-stop when traffic flow is light.

This paper presents a novel position based access scheme for indoor optical wireless communication systems. In this scheme, we apply the Intensity Modulation-Direct Detection (IM/DD) with Quadrature Phase Shift Keying (QPSK) modulation. The I (in-phase) and Q (Quadrature) signal are transmitted separately in Additive White Gaussian Noise (AWGN) channel. The probability of error is analyzed with consideration of different mode numbers of the radiation lobe of Lambertian source, and position of the transmitters. The analytical result of this paper demonstrates that high level security for optical wireless communication systems can be achieved by specifying the receivers' position where the signal can be demodulated successfully.

As the precondition of dynamic spectrum access (DSA), the accuracy and efficiency of spectrum sensing (SS) have an important impact on performance of cognitive networks. However, the performance of energy-aware SS is greatly compromised by the accompanying inter-channel interference (ICI). Aiming to alleviate ICI, this paper proposes an energy-aware cooperative SS method with ICI cancellation. The proposed method consists of two parts: the determination of the optimal threshold and the ICI cancellation. The optimal threshold is obtained by minimizing the sum of probabilities of false alarm and missed detection. The ICI cancellation is implemented indirectly by solving a non-homogeneous linear equation set with a coefficient matrix depending only on the distances between the secondary users and the transmitters of primary users. Simulation shows that the proposed SS method can efficiently cope with the ICI and can achieve much better performance in the range with low signal to interference-plus-noise ratio.

This paper proposes a novel and promising MAC protocol applied for the new wireless sensor network based data collection applications that coordinate with an unmanned aerial vehicle (WSN-UAV). In this system, before communicating with the UAV by the CDMA-based transmission technique, the active sensors are divided into a number of sub groups with an appropriate priority each. We named the protocol as a Prioritized Frame Selection based CDMA MAC protocol (PFSC-MAC). The PFSC-MAC protocol incorporates both of the beacon signal receiving power and the variation trend of this factor. The simulation results have demonstrated that PFSC-MAC provides a low Packet-Error-Rate (PER) compared to the other schemes. In addition, the optimal number of priority groups has also been derived in order to obtain the minimal PER at each pair of the number of sensor in the network and the altitude of the UAV.

This is a study on the effect of reflected light on optical code-division multiple-access (CDMA) system over indoor optical wireless communication (OWC). The indoor propagation channel model which takes multiple reflecting surfaces into account was addressed. Theoretical analysis of the pulse response of direct light and reflected light is given. Bit error rate (BER) of this system is analyzed considering reflected light, background light, avalanche photo-diode (APD) noise, thermal noise, and multi-user interference. The results prove that the BER of the system is influenced by the reflected light and the effect of reflected light is related to the room size and receiver position. With the increase of user number, the effect of reflected light becomes stronger and it is a significant source of inter-symbol interference. It becomes clear that when OCDMA is used to an indoor optical wireless system, the effect of reflected light is a key issue to be considered.

We propose a partnership-based cooperative MAC protocol (PC-MAC) based on the distributed coordination function (DCF) protocol in wireless networks. The contribution of this paper is twofold. First, we introduce a cooperative interframe space (CIFS) for latency reduction and second, we introduce a control frame called request to cooperate (RTC) for on-demand packet relaying for error recovery. We compare PC-MAC with the non-cooperative DCF protocol. The analysis results show that using cooperation improves the theoretical maximum achievable throughput and the saturation throughput.

In Wireless Sensor Networks (WSNs), current intrusion detection systems (IDSs) work in isolation from access control. The lack of interoperation between these components can not provide enough security for WSNs. To address this, we propose a new framework to integrate access control and intrusion detection (ID) to improve the security of WSNs. Moreover, we perform access control based on usage control (UCON), so that our scheme can provide mutable attributes and continuous access decision. We also develop an adaptive decision tree construction mechanism for intrusion detection. Besides normal attacks, our scheme can defense against sophisticated ongoing attacks and unknown attacks in WSNs. An instance of policy is simulated to evaluate the overhead coursed by our scheme. The implementation results support the feasibility of using our scheme in WSNs. Also, the security evaluation is done. The results show that the proposed scheme can provide higher security than traditional security schemes.

Security access is one of the key concerns for wireless sensor networks (WSNs). The secure authentication protocols of the most current security access schemes are complex. Moreover, the access control models of existing schemes have no concept of attribute mutability and can not perform continuous access decisions. In this paper, we propose a new security access scheme that deal with the requirements of low-complexity authentication and continuous access decision. The authentication protocol and access control mechanism is designed based on security token and usage control (UCON) respectively. An instance of UCON is implemented. The implementation results support the feasibility of using UCON in WSNs. The authentication protocol in our scheme presents several advantages including the low expenses in calculation, storage and communication. Moreover, our scheme also can perform access control with attribute mutability and decision continuity.

This paper introduces a new kind of communication system that is proposed for oceanic air traffic control, especially works under the high air traffic conditions. The aircraft position reports are sent to the ground controllers by relaying them via other aircrafts. To do so, multi-hop ad-hoc networks that are based on these aircrafts is proposed to use. In addition, a proper multiple access scheme with optimal values is also proposed that allows the aircrafts to operate autonomously in a valid region. Furthermore, with accurate time obtained from equipped means, the Position aided-autonomous idle timeslot reuse scheme (PA-AITR) is proposed to reuse the idle timeslots caused by the sparse aircraft distributions. And another scheme, that is proposed to improve the connectivity under sparse aircraft distributions; which is aided by interference power in the feedback information (IB-NS). In all, the combined conditions and schemes show the applicability to utilize this system for future air traffic control communications.

This paper proposes a reliable system to overcome the weakness of current HF radio communication system for oceanic aeronautical flight routes. This system uses only one aeronautical VHF channel with air-to-air radio relay system based on local mobile Ad-hoc networks. For access of all aircrafts in the system, a TDMA (Time Division Multiple Access) scheme is proposed to be used where each aircraft is assigned with one time slot during its presence in the system in order to transmit its own packet by itself or to be relayed its packets by neighbor aircrafts. These packets contain aircraft position, ID, relative direction and all of which are used to build a routing table at each aircraft. In addition, several algorithms for relaying packets and a scheme to reduce the packet-loss-ratio have been proposed. This system strengthens the reliability of oceanic aeronautical communication and increases situational awareness of all oceanic flights as an effective solution to operate more flights on the oceans but in higher safety.

This paper presents a wireless relay scheme for indoor healthcare communication system, in which an optical relay link, instead of a traditional radio frequency (RF) relay link, is established between the relay station (RS) and the mobile terminal (MT). To simplify the structures of RS and the additional optical parts that shall be installed in the MT, the subcarrier-modulation based intensity-modulated direct- detection (IM/DD) is also adopted for both the up-link and the down-link. The proposed relay scheme not only enhances the transmission power, but also creates safe signal propagation environment, which is much meaningful for wireless and pervasive healthcare communication. Simulation results show that the proposed interference-reduced relay scheme provides a stable and high quality communication link when the average optical receiving power is larger than -25 dBm.

In this paper we introduce a new MAC protocol called Continuous Contention-Assisted Transmission (CAT) for wireless Ad-hoc network. This proposed protocol is based on Carrier sense multiple access with collision avoidance (CSMA/CA) but we have modified the ACK packet and re-designed mobile stations behavior so that they could continuously transmit data without contention. Our proposed algorithm tries to keep collision in the network as low as possible by allowing wireless stations to form a sequence of transmission among stations that have data to send. Analytical results are compared with simulations. The analysis model is quite accurate in predicting network throughput.

This paper presents an optical intensity-modulated direct-detection (IM/DD) based relay scheme for indoor optical wireless communication system. Multiple distributed optical relay links are set up between relay stations (RS) and mobile terminals (MT) to create multiple safe signal propagation links for wireless communication so that at least one link is available for data streaming. Different from conventional relay scheme, the phase shift of RF signals is pre-adjusted based on maximum ratio transmission (MRT) technique, and then relayed from multiple distributed optical transmitters which are set up in different places. The proposed relay scheme not only enhances signal power and achieves diversity, but also avoids possible obstruction of line-of-sight (LOS) signal. Furthermore since propagation phase variation of incoherent optical signal can be neglected, the propagation space becomes a non-directional scalar space, resulting in a much simpler system structure, where multiple optical antenna elements can be freely arranged, phase shift due to different transmitting paths is solely decided by the distance between transmitter and receiver, etc. The paper presents these features and also provides computer simulation results to demonstrate the performance. Simulation results show that the proposed relay system is much feasible and attractive, and it would be one of the promising candidates for future wireless and pervasive healthcare communication systems.

This paper proposes a reliable communication system for high air-traffic oceanic flight routes in aeronautical industry. This proposal uses a single aeronautical VHF channel with an air-to-air radio relay system based on local ad-hoc networks. A TDMA (Time Division Multiple Access) is proposed to be used for multiple access in a wide-area where each aircraft is assigned with one time slot and kept during its presence in the system in order to transmit its own packet by itself or to relay its packets by neighbor aircrafts. By transmitting in each three frame- periods, each aircraft's position, ID and direction are all used to build a routing table at each neighbor aircraft. Several methods of relaying packets are discussed to reduce packet-loss-ratio occurred from relaying process. In addition, the method to deal with the sparseness of aircrafts in some periods of time was also proposed to make the packet-loss-ratio lower. This system is an effective way not only to allow aviation authority to give more flights but also increase the safety by providing situational awareness frequently for all flights on the oceanic routes.

Recently, the frequency resource for a future wide-band communication system in Air Traffic Control (ATC) at advanced airports has become a vital issue of aeronautical industry, many studies on new frequency bands coupled with high-bit-rate- transmission schemes have been carried out. However, almost all evaluations were done by theoretical analysis and computer simulations. But in this paper, an air-to-ground channel characteristic in a new and wide band, in 5-GHz, is studied for ATC communication in all periods when aircraft was near the airport by practical experiments and measurements. These periods include takeoff/landing, taxi and parking. First, the path-loss and fading-channel models have been studied for each period; then, the performance of MC-CDMA system employing the studied channel characteristics at these periods are evaluated. MC-CDMA has shown its robustness in a high Doppler shift and deep multi-path fading channels during these periods of flight. This paper provides a wide-band communication system in 5-GHz band that is essential for air traffic control communication at any advanced airport.

In this paper, we propose a new duplex scheme based on the multi-carrier transmission technology, multi-carrier division duplex (MCDD). MCDD exploits a time-spreading technique, the aim of which is reducing an impact of inter-link interference due to loss of orthogonality. When MCDD exploits the time-spreading with one of spreading factor, we regards this one as orthogonal frequency division duplex (OFDD), which we proposed in our previous literatures. On the other hand, when MCDD exploits greater than one of spreading factor, we regards this one as multi-carrier code division duplex (MC-CDD). We investigate how time-spreading improves the performance of MCDD system in the presence of carrier frequency offset by computer simulation. From the results, we confirm that OFDD is tolerable to the inter-link interference due to the normalized carrier frequency offset of up to 0.1. We also confirm that MC-CDD with time-spreading reduces the impact of inter-link interference and improves the performance even when the normalized carrier frequency offset is 0.5.

High-Altitude Platform Station (HAPS) is one of the promising wireless communication infrastructures in the future. The major factor affecting its communication channel is environment. An accurate characterization of shadowing caused by the environment is needed for this new wireless infrastructure. This paper is, therefore, designed to address and evaluate the shadowing characteristics from urban physical structures for HAPS communications. Experiments are first conducted in urban areas of Japan and then we present the results of shadowing characteristics at various conditions in each specific area. Second, an analytical model is developed to evaluate the shadowing condition for HAPS channel based on the environmental characteristic data derived from the experimental areas and a geometrical model. Finally, comparisons between empirical studies and the analytical model are made. The comparison results show that the proposed analytical model is reliably practical in characterizing shadowing in urban areas by using the environmental statistical data and the geometrical model.

This paper evaluates fixed step algorithm of closed loop power control and investigates an optimum step size for WCDMA communication employing high altitude platforms (HAPs). In CDMA, power control must be used to overcome near-far effect, shadowing and multipath fading. Users who are distributed within HAPs coverage will have different channel characteristic depending on their elevation angle. Therefore, parameter of power control algorithm should be designed to comply with the channel characteristic. Step size is one parameter in fixed step closed loop power control that will be investigated in this paper. Considering the measured HAPs channel characteristic, this paper investigates an optimum step size that will resulting a minimum power control error (PCE). Computer simulation shows that optimum step size depends on user's elevation angle. The higher the elevation angles the smaller the optimum step size of the power control.

In our previous work, power time differential detection (PTDD) has been proposed for finger identification scheme (FIS), which is an application of intra-body communication. In this paper, phase detection is proposed to realize FIS with low implementation cost. The identification probabilities of FIS models by employing PTDD and phase detection are evaluated experimentally and statistically. The results show that FIS using phase detection perfectly identifies fingers at carrier frequency of 1.2 GHz. Moreover, time difference enhancement method (TDEM) is proposed and theoretically analyzed. Both phase detection and TDEM have the possibility to reduce the implementation cost of FIS as well as to improve the performance of FIS.

In this paper, Iterative Unequal Length Search (ULS) Syndrome Decoding for Product Codes is proposed by introducing an idea of unequal length search space. The principle and realization of the algorithm is presented. Moreover, a mathematical performance and decoding complexity analysis is illustrated. Compared to the conventional Equal Length Search (ELS) Syndrome algorithm, experimental results indicate that the iterative ULS syndrome decoding algorithm, not only significantly reduces the decoding complexity, but also improves the error-correcting performance. Because of the balance between the odd and even circuits, the speed of parallel processing is increased and hardware resources are saved accordingly. Simulations results have shown that the proposed algorithm leads to a decrease of 25%~30% of search complexity and a gain of 0.3 dB in the BER performance for various subcodes.

M-ary Elliptical Phase Shift Keying (M-EPSK) have been proposed and evaluated through simulations in our previous works. According to the simulation results, M-EPSK (M=4,8) can achieve better noise performance than MPSK; in particular, M-EPSK can adaptively realize trade-offs between bandwidth efficiency and power efficiency by varying the eccentricity. Eccentricity is the main modulation variable that makes M-EPSK distinctive comparing with conventional MPSK. Substantial effects of eccentricity to performance of M-EPSK have been verified in simulations; however, prior to exploring applications of M-EPSK in communication systems, principle behind the effects of eccentricity to performance needs to be further studied. In this paper, we theoretically evaluate effects of eccentricity to decision parameters of performance, and then explore a novel solution based on approximate treatment to derive closed-form BER approximations of M-EPSK over an AWGN channel. In the BER approximations, the effects of eccentricity to both error performance and bandwidth efficiency of M-EPSK are mathematically derived. In addition, the theoretical results agree with simulation results.

In this paper, a new and wide frequency band was proposed for air traffic control communication (ATC), C band, which could be a supplement to its conventional VHF band. The radio propagation characteristics at this band under ATC conditions were studied through several experiments and theoretical analysis. For this communication channel, Nakagami-Rice distribution was used to extract Rice factor. This study also shows received power level of radio signal for the conical area above the ground antenna system was very weak and was not good enough for a reliable communication. A new antenna model was proposed to increase signal power in this area by reflecting the side lobe of antenna beam pattern at the ground system. This paper concluded the feasibility of utilizing a wideband communication for the next generation of ATC communication.

There has been many developments in long distance optical wireless communication between buildings using rooftop- mounted units over Point-to-Point wireless links. We propose an Angle Division/Time Division Multiple Access scheme to perform Point-to-Multi-Point communication employing reflectors. A single reflector controlled by a stepping motor and an array of fixed reflectors were used. The width of the beam of the infrared rays is measured and the relationship between the width and the stepping angle deviation of the motor are demonstrated. Moreover, the received power, the bit error rate, and throughput of the proposal scheme are measured. The angle of the reflector and the reflection characteristics when using one or two reflectors were compared. In addition, the throughput characteristics of the proposal scheme were made clear by experiments.

We propose a contention based multiple access scheme that enables packet level cooperation in wireless packet network, where the idle nodes help the source nodes by offering relay of the failed packet. Also a prioritization scheme is implemented to optimize to the contention whose complexity is added by participation of relay nodes. Throughput and delay performance improvement is confirmed by computer simulations considering wireless links that have different packet error rates according to the radio condition which suffer from propagation loss and Rayleigh fading. Analysis shows that the addition of active nodes for cooperation rather eases the number of waiting nodes in the contention, and that the reduction of retries needed for transmission reduces the average delay.

The intra-body communication method attracted more attention since the development of ubiquitous communication. IBC is the technology to use the human body as communication transmission channel and the exchanges of information can be realize more naturally, easily and safely. This paper proposes a new application to recognize the finger movement by using intra-body communications that we call finger identification scheme. Finger identification scheme aims to detect the finger being used when a person is using touch panel devices. Performance has been evaluated by experiments and each finger was able to be distinguished by using a detection method that we have named power time difference detection, where the finger detection is performed based on the difference in time and power of the electromagnetic signals propagating through the body. From this result, using power time difference detection method, it is possible to confirm in the receiver side which finger is being used reliably.

We propose a new space division multiplexing-orthogonal frequency division multiplexing system using reduced-complexity-and-latency detection and channel estimation algorithms. It is important to reduce a latency from receiver processing because the latency degrades performances of wireless systems in a mobile fading environment. In this paper, we evaluate and discuss bit error rate performance and computational complexity of the proposed system. From simulation results, we observe that our proposed estimation scheme improves the accuracy more than conventional minimum mean square error based schemes, and that the proposed system outperforms a maximum likelihood detection based system in a mobile fading environment. Moreover, we confirm that the proposed system is superior to the conventional schemes from the points of not only the performance but also the complexity.

We propose an analysis of CDMA multispot beam for reverse link multiple stratospheric platforms (SPF). Evaluation on the CDMA system capacity of this technology has not been much reported especially for multiple SPF scenarios. This paper addresses all possible multiple access interference including the effects of channel fading and shadowing in order to evaluate the system capacity. The analysis is based on perfect power control and imperfect power control. The results indicate that in SPF systems the reverse link CDMA capacity is significantly reduced because of the power control imperfections. In multiple SPF model the interference caused by the users in overlapped region is not trivial. Because of this problem the capacity is reduced for both speech and real-time data applications even though the assumption of perfect power control can be made.

We have proposed a multi-carrier based duplexing, or orthogonal frequency division duplex (OFDD), that realizes the flexible radio resource management. In this paper, we propose a new OFDD system using an analog filter bank. The aim of the analog filter bank is moderating the difficulty of analog circuit designs and solving the signal dynamic range problem in the OFDD. The OFDD system approaches a practical one with the help of the analog filter bank. In this paper, we investigate the sub-carrier configuration for OFDD and evaluate the effect of the analog filter bank. Then, we evaluate the bit error rate performance of the OFDD using the analog filter bank in the presence of carrier frequency offset by computer simulations. From the results, we observe that four null sub-carriers are sufficient for a given analog filter bank to avoid the nonlinear degradation at the analog circuit. We also observe that the OFDD system almost achieves the ideal bit error rate performance when the normalized carrier frequency offset is 10-2.

One major concern of energy constrained WSN technology is to design energy efficient communication protocol. Clustering the whole network is an efficient solution to increase its life time. This paper proposes a clustering based communication protocol for periodical data gathering application in wireless sensor network. It uses the scheduled rotation of cluster heads, which eliminates the problem with the variability of the number of clusters generated in the dynamic, distributed and randomized protocol. Proposed protocol shows more energy efficiency by only triggering the cluster formation when cluster heads energy level falls below a certain threshold. In the simulation, our protocol shows better performance than that of LEACH (low energy adaptive clustering hierarchy) protocol in respect of energy dissipation and number of survival nodes. Furthermore this protocol performs higher number of rounds than that of LEACH in case of the first node and 60% nodes die in the network.

Intra-body communications based on near-field radio signals is a short range communication solution suitable for body area networks wherein the human body is used as the transmission medium. This paper proposes a statistical model for the intra-body propagation channel based on experimental data of the human body transmission characteristics. The channel models are presented over three measurements configurations with several transmitter and receiver locations and considering two common scenarios: the human body not moving and walking. We define the statistical models in terms of most fitting probability density function to the experimental data of the received signal power among 15 families of probability distributions. These general models should be useful for simulating propagation effects in the laboratory and, therefore, we believe that these models will play a significant role in the design and evaluation of intra-body communication systems.

Abstract — Body area networks (BAN) will become increasingly important in the future personal communication systems. We believe that intra-body communications (IBC) based on near field electromagnetic waves is a suitable solution for BAN. This paper presents experimental measurements of the frequency and time domain responses in order to investigate the transmission characteristics of the human body as a conductor of low power high frequency radio signals (up to 3GHz). In the measurements, several distances between transmitter and receiver (up to a long distance from the head to the foot) and six test people (to study the possible variation results due to physiological body effects) have been considered. Besides analyzing the intra-body channel response, we also aim to define a suitable frequency range for IBC. Finally, this paper also presents an initial evaluation study of several digital modulation schemes in order to investigate the optimal technique for IBC. Keywords- body area networks, intra-body communications, body transmission characteristics, body channel, blind people guidance application I.

This paper considers the downlink performance of mobile communication channel based on a novel wireless infrastructure that is called stratospheric platforms (SPF). The SPF has been recently proposed as an alternative method for delivering mobile communication services such as IMT -2000 in parallel with cellular tower-based terrestrial system or satellite. Channel performance evaluation is now becoming a matter of urgency in the designing of communication link between the platform and mobile user. We first evaluate propagation characteristic in urban area in order to obtain propagation parameters in terms of path loss model and Rice factor. Due to their unique positioning, elevation and azimuth angle are considered as main parameter in SPF environment compared with terrestrial tower-based system. The propagation parameters are then used in order to evaluate downlink performance for IMT -2000 services served by the SPF. Different applications refer to different information bit rate that is carried by IMT -2000 system are considered in the analysis. In all scenarios, downlink performance decreases as the service bit rate increases and it becomes worse when elevation angle lower than 40deg.

Recently, there are of great interests on employing stratospheric platform as a new means of providing IMT-2000. One important issue that has not been much investigated is the propagation characteristic of its link. This paper aims at evaluating the impact of elevation and azimuth angles variation to the propagation mechanism in urban environment for mobile communication link. In order to examine the propagation loss experienced by this system in urban area, we developed the building block model and the ray tracing tool for simulation. We then apply the ray tracing tool with respect to the angle variations. As a result, propagation loss as a function of elevation and azimuth angles is obtained. We compared the result with a physical-statistical model for verification. Finally, link budget analysis and estimation to the required transmitted power at several transmission rates for the application of IMT-2000 is observed. Different scenario, which means different azimuth angles clearly show the critical limitations for mobile communication using a concept of stratospheric platform.

Intra-body communications is a short range communication solution suitable for Body Area Networks wherein the human body is used as the transmission medium. Currently, some studies have succeeded to transmit and receive simple information. However, intra-body communications could also provide broadband applications such as video streaming which will need high data rates. In this paper, firstly we investigate the propagation characteristics of the human body as a conductor of radio frequency signals. Afterwards, we evaluate five digital modulation schemes for intra-body communications. In the experiments, several distances between transmitter and receiver, symbol rates and frequency carriers are considered to investigate the optimal modulation scheme and the maximum transmission rate achievable. Constellation and eye diagrams and error vector magnitude are the performance parameters measured to evaluate the modulation accuracy.

We propose a new multiple-QR-decomposition assisted group detection (multi-QRD-GD) algorithm for the development of reduced-complexity-and-latency multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) receivers. In addition, we investigate an effect of adaptive grouping (AG) based on received signal-to-noise power ratio for multi-QRD-GD. In this paper, we describe the functions of the multi-QRD-GD algorithm and AG scheme. Then, we compare bit error rate (BER) performances of the proposed multi-QRD-GD and conventional detection algorithms by computer simulations. In addition, we compare the computational complexities of the algorithms

We believe that near-field radio intra-body communications, wherein human body is used as the transmission medium, will be a very suitable solution for body area networks with many interesting applications towards a ubiquitous communication world. This paper presents some potential new applications of great usefulness for handicapped people. Moreover, we have also envisioned applications inside train coaches where the use of mobile phones is restricted in countries such as Japan. On the other hand, we present the system model designed to carry out these applications by using intra-body communications. Finally, in order to investigate the feasibility of this kind of communication, we analyze experimentally the characteristics of the intra-body propagation channels and we evaluate the performance of several digital modulation schemes

By replacing a circle with ellipses in constellations of MPSK (M=2,4,8), this paper propose several modulation schemes defined as M-ary elliptical phase shift keying (M-EPSK, M=2,4,8). Both mathematical analysis and computer simulations show that M-EPSK can improve power efficiency over MPSK, and have high flexibility to make trade-offs on power efficiency and bandwidth efficiency by varying eccentricities

This work aimed to evaluate some modulation methods, which have been defined based on elliptical modulation scheme, namely are eccentricity shift keying (ESK), inclination angle shift keying (IASK) and elliptical phase shift keying (EPSK). In this paper, signal characteristics of these three modulation schemes and effect of eccentricity to the waveforms have been demonstrated and analysed, through observing real signals generated by using DSPs, both in time-domain and frequency-domain; performances of IASK, 4-EPSK and 8-EPSK, as three modulation methods capable of 1-bit, 2-bit and 3-bit information transmission under the same carrier frequency respectively, have been evaluated through Matlab simulation in terms of BER. Advantages over existing modulation schemes suggested that the newly proposed modulation schemes can contribute to the improvement of wide-band wireless communication systems.

Most of current wireless communications take sinusoidal waveforms derived from circles. In this paper, new modulation schemes using elliptical circles, instead of usual circles, are proposed. Several schemes proposed in this paper can be described as "elliptical modulation" which modulates the signals by varying the geometrical characteristics of ellipses. The elliptical modulation method involves variables such as eccentricity, rotation, revolution frequencies and offset inclination angles. In this paper, several schemes based upon elliptical modulation have been proposed. A performance evaluation of the proposed scheme is shown as well. The proposed schemes seem to open up a new research area of telecommunication field in the future.

The authors examine the structural relationship between load and blocking probability for a fully connected homogeneous nonhierarchical network when blocked messages cause retrial and when different alternate routing strategies are employed to overcome congestion. The model employed for analysis is based on the flow approximation. It is found that retrials push the stable equilibrium state away from the zero blocking state, thereby aggravating congestion. The alternate routing strategies accommodate the stable equilibrium state close to the zero blocking state. However, both the retrials and the alternate routing strategies do not alter the fundamental structure of the system, namely, the fold catastrophe. By solving the degenerate equation, the value of appropriate control parameters can be obtained. According to the present model, it is only under schemes with no alternate routing that the system attains stability, in the mathematical sense of the term.>

A global message communication network for low-density traffic, using satellites at low altitudes, is described. This network affords around-the-clock service to any part of the globe, including the polar regions. Such a network can accommodate static and mobile user terminals simultaneously. The oblate globe is modeled as a regular polyhedron with 12 facets for setting up the orbits. Satellites are positioned uniformly in low-altitude symmetrical orbits. The symmetrical orbits are those whose axes are symmetrical in the three-dimensional space. The authors study the coverage aspects of the 6-orbit scheme and the 10-orbit scheme, each with satellites deployed at an altitude of 5000 km. At this altitude, the terrestrial user terminals can access satellites at a grazing angle of 45 degrees . The method of access over the crosslinks is the slotted ALOHA scheme. For low-density traffic, the downlink and uplink throughput rates are estimated. Simulation results agree with these analytical estimates for low values of network offered load.>

Stability and throughput are investigated for a combined random-reservation access scheme employed in a satellite-based very small aperture terminal (VSAT) packet communication network. The analysis is based on the use of catastrophe theory by which the system behavior is characterized by the cusp catastrophe. A stable region is given in terms of system and user parameters such as packet generation rate, retransmission rate, channel division ratio and propagation delays. A numerical example is given to illustrate the analysis developed. Simulation results agree with the steady-state throughput of the model.>