With the development of the Internet of Things, new devices need more diversified input methods. Gesture recognition has become a hot research field, and air-writing [1] is a significant part of the field of gesture recognition. In our previous air writing recognition system, we proposed an input system that measures dynamic data based on an inertial measurement unit that uses a dynamic time warping (DTW) algorithm for recognition. In this paper, cDTWw algorithm, KNN & DTW classification algorithm and fastDTW algorithm are used for comparative experiments. In order to improve the actual recognition ability of the air writing system, save the recognition time as much as possible , and optimize the recognition accuracy. We found that the cDTW w algorithm has a faster recognition speed than the fastdtw algorithm in the air writing recognition system. KNN & DTW class fication algorithm significantly improves the recognition accuracy in the air writing recognition system.

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.

There is a growing trend to utilize satellite networks for the construction of 5G and Beyond 5G high-capacity systems. The power division scheme used in non-orthogonal multiple access (NOMA), which is a key technology for terrestrial networks, can contribute to improving the system capacity of satellite networks. In this paper, we propose a direct sequence spread spectrum-power level division multiple access (DSSS-PDMA) scheme that combines non-orthogonal PDMA with DSSS technology to mitigate the depletion of communication resources and interference to terrestrial terminals. Finally, simulation results with ETS-9 as the high throughput satellite (HTS) and active electronically scanned array (AESA) antenna as the earth station validate the effectiveness and superiority of the proposed schemes as compared with several existing schemes.

Inter-Satellite Optical Wireless Communication (Is-OWC) is regarded as the best choice for satellite communication because of its large throughput, low transmission power and high immunity to interference. To increase the availability of Is-OWC, it is required to implement a communication scheme that realizes lower latency and handles more traffic. In this paper, we propose a new Is-OWC system that uses multi-layer satellite constellation that applies uplink Non-Orthogonal Multiple Access (NOMA) to achieve delay suppression and increased throughput. In our proposed scheme, to distribute packets and reduce queue delay in each satellite, each communication path is adapted to the distance between the terrestrial transmitter and receiver. Simulation results validate the performance of our NOMA model is better than that of the conventional OMA model. Furthermore, the results showed that the BER of our model is improved by introducing the original algorithm to optimize the transmission power and the allocated sub-band of each satellite for the NOMA transmission. As a result, comparison of the latency between the proposed model using LEO and MEO satellites and the conventional model using only LEO satellites, the proposed model realizes delay suppression. The difference between the two models becomes more significant as the number of sessions in the entire network increases.

This paper presents a sensor-based data acquisition glove for gesture recognition in Japanese Sign Language (JSL), which uses five flex sensors and an inertial measurement unit (IMU) to detect finger flexion and hand motion information. The detected data is sent from the Arduino Micro to a computer. We collected data from the "A"to "Ta"lines of the Japanese (kana) syllabary and using four different machine learning algorithms: Support Vector Machine (SVM), Decision Tree (DT), Random Forest (RF), and K-Nearest Neighbor (KNN) to recognize them. RF and KNN have the highest average accuracy, reaching 99.75%. Also, SVM and DT had an average accuracy of 99% and 94.25% respectively. The experimental results show that the proposed system has great potential for gesture recognition in Japanese Sign Language.

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.

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.

Uniformed circular array antenna (UCA) based orbital angular momentum (OAM) communication system has some disadvantages, such as not being suitable for long-distance multiplexing and requiring a high degree of synchronization between the transmitting and receiving antennas. To achieve non-line-of-sight (NLoS) communication using OAM radio waves, we propose an inter-mode interference (IMI) cancellation method for intelligent reflecting surface (IRS)-Assisted OAM multiplexing to eliminate the IMI from all OAM modes. We also propose a L2-ba11 projection method to optimize the transmit power allocation for OAM modes to increase the system capacity of IRS-assisted OAM communication systems. The IMI cancellation method and the L2-ball projection method are shown to achieve increasing the maximum system capacity as compared to the L1-ball projection method when the IRS is located closer to the middle between the transmitter UCA and receiver UCA.

The sign language recognition system plays an important role in the field of human-computer interaction. In the daily life of hearing-impaired people, sign language is used as the main tool to communicate with the world. Although sign language can satisfy simple conversation, it is difficult to deal with in some situations where a lot of conversation is required such as medical emergencies or educational consultation. This paper proposes a sign language recognition system based on Wi-Fi to improve the life of the disabled The proposed system collects the Channel State Information (CSI) due to the change of hand movement. Through the analysis of all subcarriers, the amplitude of CSI is determined to reflect the characteristics of different sign languages, some high-frequency noise is removed in the amplitude of CSI to obtain a smoother signal Gesture feature. We propose a gesture feature extraction method based on the variance of time series and DTW algorithm is used to recognize nine common Japanese sign language gestures. We set two daily conditions to test the system, and the experimental results show that the system performs well in different conditions.

Nowadays it is recommended to do blood pressure measurements on a daily basis at home to prevent diseases caused by high blood pressure. Blood pressure measurements methods using a cuff is most commonly used. However, it is a burden for hypertensive patients and the elderly to put on a blood pressure cuff repeatedly for the multi-metering of blood pressure. Non-contact measurement will provide a comfortable and easy method to monitor blood pressure and pulse rates continuously. This paper proposes a non-contact method to measure both pulse rates and blood pressure simultaneously. In the experiment, microwave signals were transmitted to the body and the reception intensity was measured. The microwave frequencies used in this experiment were 2.4GHz and 5.6GHz. The pulse rates and the blood pressure can be estimated by processing the data obtained from microwave reflection. The experiment results show that the 2.4GHz microwave signals have better estimation accuracy. It indicates that our proposed system is practical and has great potential for the future smart health monitoring system.

In this paper, we propose a sensor-based data acquisition glove for Japanese Sign Language (JSL) hand gesture recognition. Five flex sensors, an Inertial Measurement Unit (IMU), and three Force Sensing Resistors (FSRs) are used to detect the bending degree of fingers and hand movement information. The detected data are transmitted to the computer by an Arduino Micro. The average accuracy of the hand gesture recognition for a single subject, using the Support Vector Machine (SVM) based and the Dynamic Time Wrapping (DTW) based algorithm are 96.9% and 94.5%, respectively. Our proposed system also achieves an average recognition accuracy of about 82.5% for the cross-recognition among three subjects. The experimental results indicate that our proposed system has great potential for JSL hand gesture recognition.

In our paper, we proposed an Energy Borrowing (EB) transmission scheme which is used to conserve the battery life of user equipment (UE), such as a mobile phone. EB is based on device-to-device (D2D) communication and cellular networks, particularly, on out-band D2D (Wi-Fi Direct, IEEE 802.11) and 5G networks. Since D2D offers higher energy efficiency than cellular networks, in this scheme, a UE with low remaining battery power establishes a D2D connection with a nearby UE, and the nearby UE transfers the low remaining battery UE's packets to/from gNB (5G-base station). As nearby UE plays an active role in the low remaining battery UE's connection with gNB. Therefore, we can rephrase that a UE with low battery power is virtually borrowing the battery resources of a nearby UE. This paper introduces the operation protocol and procedure followed by EB with the use of Wi-Fi Direct and 5G networks. Experiments and simulations demonstrate that EB can extend terminal battery lifetime (a valuable characteristic for long-lasting batteries), and it is more effective as compared with the existing scheme that uses only the cellular network.

Non-orthogonal multiple access (NOMA) with power domain multiplexing and successive interference cancellation (SIC) is one of the promising technologies for future wireless communication. The performance of NOMA is highly dependent on resource allocation such as power allocation and channel assignment. In this paper, we investigate the power allocation (PA) scheme, to optimize the weighted maximin fairness (MMF) for 2-user and 3-user clusters. We utilize the particle swarm optimization (PSO) based algorithm for power allocation due to its promising behavior. Application area of NOMA is becoming broader, then, we considered a cellular network, assisted by an unmanned aerial vehicle (UAV) as the base station (BS) which is integrated with the NOMA system. The PA for weighted MMF problem in NOMA is non-convex, it is difficult to find out the optimal solution directly. Simulation results show the performance of PSO-based algorithm in different adaptive weights and its convergence characteristics. We have also shown that the rate and fairness tradeoff using weighted maximin fairness. Numerical results compare the performance of NOMA and orthogonal multiple access (OMA) and prove the significance of the proposed algorithm.

This paper proposes a Hybrid Access Scheme (HAS) aiming to convert a future robot's backend communication system by a finite number of sensors instead of using a lot of wires. To replace this communication, the HAS needs to assure higher reliability within stringent low latency packet transmission. In this paper, the HAS utilizes the packet diversity principle and forward multiple copies of the same packet over the massive number of subcarrier channels. The HAS assigns the random accessing to select a subcarrier channel for general packet transmitting sensors. The audio and video sensors transmit packets over the dedicated channels to avoid collisions. The HAS system allows transmitting audio, video and general sensors simultaneously. The minimum number of subcarriers to satisfy the URLLC reliability requirement of 99.999% is evaluated for different packet duplications over different arrival condition. The HAS system's reliability and collision probability are evaluated in MATLAB simulator for different packet duplication over different arrival condition. Moreover, the signal propagation expressions are captured using ANSYS HFSS software for rectangular and circular transmission medium over the 900 MHz, 2.4 GHz, 24 GHz, and 55 GHz frequency bands for different structural configurations.

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.

The dynamic phase control system for the stable long distance high frequency (HF) communication is evaluated in this paper by the ionospheric propagation simulations. The radio wave in HF band reaches to the very far side on the Earth by ionospheric propagation. It is efficacious to low latency long distance communication and emergency communication, but the ionospheric propagation is the cause of a phase fluctuation and power attenuation, the affects lead to ionospheric fading that is the sharp drop of the received power. We have reproduced the HF band propagation in a computer simulation and calculated the received power at the receiving station. The results show the improvement of the received power and fading reduction by the appropriate phase control at transmission station.

In this paper, a novel triple-band antenna with reflector surface which has the property of both artificial magnetic conductor (AMC) surface and perfect electric conductor (PEC) for WLAN and Sub-6G 5G applications is proposed. The presented antenna is composed of two parts: the AMC surface and the microstrip-fed printed dipole. Baluns are used to excite the dipoles. This antenna design combines the advantages of AMC and PEC. In lower band and middle band, the inserted board works as AMC surface. This AMC surface can help the antenna to achieve unidirectional radiation pattern and low-profile characteristics. While at upper band the antenna works as PEC surface. PEC surface increases the gain of the antenna in upper band. As a result, the proposed antenna can offer an impedance band from 2.39 GHz to 2.63 GHz and from 3.61 GHz to 3.72 GHz and from 5.61 GHz to 5.84 GHz when the S11 is less than - 10dB. Stable radiation patterns with peak gain of 5.6 dBi, 6.5 dBi and 9.6 dBi are obtained in lower band, middle band and upper band, respectively. The proposed antenna can be used for multiband base stations for WLAN and 5G applications.

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.

This article proposes a novel chunk-based caching scheme known as the Progressive Popularity-Aware Caching Scheme (PPCS) to improve content availability and eliminate the cache redundancy issue of Information-Centric Networking (ICN). Particularly, the proposal considers both entire-object caching and partial-progressive caching for popular and non-popular content objects, respectively. In the case that the content is not popular enough, PPCS first caches initial chunks of the content at the edge node and then progressively continues caching subsequent chunks at upstream Content Nodes (CNs) along the delivery path over time, according to the content popularity and each CN position. Therefore, PPCS efficiently avoids wasting cache space for storing on-path content duplicates and improves cache diversity by allowing no more than one replica of a specified content to be cached. To enable a complete ICN caching solution for communication networks, we also propose an autonomous replacement policy to optimize the cache utilization by maximizing the utility of each CN from caching content items. By simulation, we show that PPCS, utilizing edge-computing for the joint optimization of caching decision and replacement policies, considerably outperforms relevant existing ICN caching strategies in terms of latency (number of hops), cache redundancy, and content availability (hit rate), especially when the CN’s cache size is small.

This paper we provide a tractable system for 2-tier users, wearable device terminals (WTDs) are in tier 2 and under the control of tier 1 users. Tier 1 user works as full-duplex relay to charge the WTDs on the downlink (DL) based on wireless power transfer (WPT), then help WTDs to transmit the information on the uplink (UL). Both of the users and picocell base stations (BS) are randomly distributed based on homogeneous poison point process (HPPP). We only considered the user association for the tier 1 users that tier 1 users always connect to the closest BS on UL since WTDs tier 2 users are close enough to tier 1 users. In this paper, we analyzed the processes of wireless power transfer on DL and information transmission on UL. We derived analysis of the average harvested energy on DL for both 2-tier users, the average ergodic rate and outage probability on UL for WTDs tier 2 users. According to the analytical results, it is observed that with the density of the picocell base stations increased, the average harvested energy increased, but the average ergodic rate and UL outage probability degraded significantly because of the UL performance decreased.

Nowadays, within the concept of Internet of Things (IoT), smart homes, smart factory, intelligent transportation among others are infrastructure systems that connect our world to the Internet. However, wireless communications technology are considerably constrained by complicated structures, and lossy media in complex environments. Fundamental limitations on the transmission range have been treated to connect IoT devices in such Radio Frequency (RF) challenging environments. In order to extend the transmission range in complex environments, Magnetic Induction (MI) communication has been proved to be an efficient solution. In this paper, a Multilayered Metamaterial low profile antenna (MMLPA) using Magnetic Induction communication scheme is proposed for IoT applications. The system model of the MMLPA is analyzed. Then an MMLPA system is designed by using a circular loop antenna backed with isotropic metamaterial which is considered as a Defected Ground Structure (DGS) as well as with anisotropic metamaterial for the purpose of a dielectric uniaxial metamaterial. By using a full-wave finite-element method, the proposed analysis is supported with simulation results where good agreement is achieved compared to the measurement results after realizing four prototypes of the MMLPA antennas. The effect of the presence of metal in the vicinity of the transceivers is also analyzed.

This paper studies the emerging wireless energy harvesting algorithm dedicated for machine type communication (MTC) in a typical cellular network where one transmitter (e.g. the base station, a hybrid access point) with constant power supply communicates with a set of users (e.g. wearable devices, sensors). In the downlink direction, the information transmission and power transfer are conducted simultaneously by the base station. Since MTC only transmits several bits control signal in the downlink direction, the received signal power can be split into two parts at the receiver side. One is used for information decoding and the other part is used for energy harvesting. Since we assume that the users are without power supply or battery, the uplink transmission power is totally from the energy harvesting. Then, the users are able to transmit their measured or collected data to the base station in the uplink direction. Game theory is used in this paper to exploit the optimal ratio for energy harvesting of each user since power splitting scheme is adopted. The results show that this proposed algorithm is capable of modifying dynamically to achieve the prescribed target downlink decoding signal-to-noise plus interference ratio (SINR) which ensures the high reliability of MTC while maximizing the uplink throughput.

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.

Recently, the 3rd Generation Partnership Project (3GPP) proposes to extend the Long Term Evolution Advanced (LTE-A) to the unlicensed spectrum, named Long Term Evolution Unlicensed (LTE-U), which enables LTE to operate in both the licensed band and the unlicensed band. In this paper, we consider how to make LTE-U get even higher throughput in the high traffic unlicensed band. In order to achieve this target, there is a big challenge to make LTE-U a good neighbor to the existing wireless communication technologies in the unlicensed band, such as WIFI system in the 5 GHz band. In our research, we assume two carriers aggregated, one is from licensed band, and the other is from unlicensed. We also define two kinds of frequency resources in the unlicensed band. One is the normal frequency resource that has not been utilized by the WIFI systems, and the other is the special frequency resource that has been utilized by the WIFI systems already. We propose a novel hybrid resource allocation algorithm by combining two different frequency sharing schemes (Underlay and Interweave) and apply different resource allocation algorithm to achieve higher throughput for all kinds of user equipment (UE) from LTE-U when the WIFI system’s traffic is heavy. We also consider the fairness for all UEs from LTE-U system and guarantee that the interference to the WIFI UEs (WUEs) is acceptable.

By 2020, 5G era will be commercially available. The smart city construction will also make great progress. Compared to current situation, more than thousand times of devices will connect to the cellular networks. For the operators, in order to analyze overall network performance, it is a key factor to estimate the user equipment (UE) radio frequency (RF) condition. However, practical RF estimation scheme is based on UE data log which can only observe UE that is at the top-serving cell with good RF condition. However, according to the comparison of actual UE data log and the scanner data log, potential RF problems may still exist since the UE will not always be served by the top-1 cell. In this paper, we propose a novel estimation scheme by integrating machine learning (ML) algorithm to analyze the scanner data logs from the target estimation zones where the mobility problems may occur. A hypothesis is obtained from learning step by various kinds of RF condition as input features. The numerical results show that the proposed estimation algorithm integrated ML can estimate probability of the potential mobility problems accurately.

This paper studies the emerging wireless power transfer for the Internet-of-Things (IoT) network, where one hybrid access point (H-AP) with constant power supply communicates with a set of IoT devices. This H-AP is assumed to work in a full-duplex mode, which transmits/receives signals to/from these IoT devices simultaneously during the whole frame. The IoT devices are capable of harvesting energy from the received signals broadcast by the H-AP. And the harvested energy is used to support the uplink transmission. Since time-division multiple access is used in uplink transmission, one IoT device keeps harvesting energy till its own uplink time slot. The objective of this paper is to maximize the total surplus energy, which is defined as the gap between available energy and consumed energy for uplink transmissions, by exploiting the optimal time allocation scheme for each device. A distributed non-cooperative and a bargaining cooperative game-based algorithms are proposed to solve this problem. In addition, the well-known KKT condition approach is adopted as a comparison. The numerical results show that the bargaining cooperative algorithm outperforms the distributed non-cooperative algorithm (DNCA) and KKT algorithm (KKTA) in terms of total surplus energy and fairness index. The performance of DNCA is better than that of KKTA in terms of total surplus energy while KKTA is fairer than DNCA.

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 studies the emerging wireless power transfer for machine type communication (MTC) network, where one hybrid access point (AP) with constant power supply communicates with a set of users (i.e., wearable devices and sensors) without power supply. The information and energy are transferred simultaneously in downlink direction. For MTC networks, most devices only receive several bits control data from AP in downlink transmission. So it is possible to utilize part of the received power to execute energy harvesting provided that the transmission reliability is guaranteed. Since we assume that all devices are without power supply or battery, the power of uplink transmission is entirely from energy harvesting. After converting electromagnetic wave to electricity, the devices are able to transmit their measured and collected data in uplink. Based on these considerations, a non-cooperative game model is formulated and a utility function involving both downlink decoding signal to noise ratio (SNR) and uplink throughput is established. The existence of Nash equilibrium (NE) in the formulated game model is proved. The uniqueness of NE is discussed and the expected NE is selected based on fairness equilibrium selection mechanism. The optimal splitting ratio within the feasible set, which maximizes the utility function, is obtained by an iterative function derived from this utility function. The numerical results show that in addition to ensuring the downlink decoding SNR and maximizing uplink throughput of an individual device, our proposed algorithm outperforms the conventional algorithm in terms of system performance.

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, a visible light communications (VLC) system prototype using organic light emitting diode (OLED) with dimming support was realized and tested. Frequency response and driving range of OLED were measured and discussed. Considering practical applications of OLED, variable pulse position modulation (VPPM) signal was used to support data transmission under dimming condition. Our prototype was able to transmit up to 85 kbps data rate using an OLED with only 7 kHz 3 dB modulation bandwidth. For the target BER=10-3 with FEC, the luminous flux could be varied within 5-8 lm.

In this paper, a visible light communications (VLC) system prototype using OLED was realized and tested. Using simple DPPM technique and comparator, our prototype was able to transmit up to 127.5 kbps data rate using an OLED with only 7 kHz 3 dB modulation bandwidth. Exploiting the frequency response of OLED, we were able to achieve a better data rate to modulation bandwidth ratio than other recent reports using OLED for VLC.

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.

Satellite clusters have been satisfactorily implemented in a number of applications, such as positioning and sensor networks, with the purpose of improving communication system capabilities. However, because the use of clusters requires good management of the resources, those solutions imply new challenges for communication systems. This paper focuses on improving the data management between network elements by considering a network formed by satellite clusters. Satellite clusters work in cooperation to provide real-time and non-real-time services in different footprint areas. This study proposes the adjustable energy consumption access scheme (AECS) as one possible solution response to particular necessities of communication and at the same time, as a way of decreasing the system energy consumption. Energy consumption is a key issue that concerns green network operations and it is directly linked to the cooperation and coordination between network elements. On the other hand, we support the implementation of Optical Inter-Satellite Links (OISL) for communication between cluster elements. The analysis involves the study of energy consumption, transmission delay, specific link margins, bit error rate (BER) and QoS.

Based on the use of multi-beams, high throughput satellites (HTSs) provide high data rates to a large number of users. In this context, the distribution of frequency resources among multi-beams plays an important role. This is because unsuitable distributions might cause the wastage or the starvation of frequencies and bring about low throughput rates. This paper proposes a solution to mitigate the unsuitable allocations of frequency resources in an HTS. The solution is the priority code scheme (PCS), which seeks to respond to users' demands by dynamically scheduling frequency resources for precise satellite footprint areas. The key is to assign a priority code and an efficiency indicator to every multi-beam deployed on the system. The PCS algorithm involves the association of the efficiency indicator with the bandwidth utilization per beam to detect and correct arbitrary bandwidth allocations among the beams. Due to the PCS's cyclical repetition of its algorithm, the concurrence time of the scheme and the tardiness of the algorithm form part of the evaluation of the PCS. Furthermore, we support the implementation of the frequency-reuse process to enhance the exploitation of frequency resources. To evaluate the PCS performance, the analysis delves into the study of the bandwidth utilization, the interference among beams, the concurrence time, and the algorithm tardiness.

This paper proposes the Piggyback schemes between each User Equipment (UE) in cellular networks. This scheme is able to reduce a communication traffic volume of base station by each UE cooperates with other one. Therefore, it can make a smaller load in base station. Each UE establishes an independent connection and communication in current mobile network. When a UE accesses a base station, the UE receive data from other UEs nearby by device-to-device communication and the UE sends its own uplink data with the received data in this proposed method. We name the method a "Piggyback scheme". Here we introduce two methods; one is "real-time active calling based piggyback scheme". The calling UE receives uplink data from other UEs and the UE sends the data in free white space of its own real-time active call channel while using call function in this scheme. The second one is "Data aggregation piggyback scheme". In this scheme, when the UE sends its own uplink data to base station, the UE informs that it can piggyback execute for nearby UEs, and the UE receives data from the nearby UEs. And the UE sends data that includes its own and other's data. And piggyback request UEs use broadcast scheme in searching piggyback execution UE and it choice the best condition piggyback execution UE every time with plural evaluation criteria. In this paper, we confirm that performances of the proposed schemes have an effect on the load reduction of cellular network as it has been shown in the simulations.

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.

In this paper, we propose an optical wireless communication service for indoor environment. To seamlessly cover the target area and keep the received signal power strength at an acceptable level, we send the signal from multiple diffused optical emitters and achieve possible transmit diversity. With the proposed diversity scheme, the effective coverage range of the proposed system can be significantly enlarged with a guaranteed BER performance. Simulation results show a 13.4 m2 area can be effectively covered by two optical emitters with optical emitter spacing of 3 m and average transmit optical power of 28 dBm. © 2012 Springer Science+Business Media, LLC.

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. © 2013 IEEE.

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

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. © 2012 IEEE.

We present a study on evaluating the effects of multipath dispersion on indoor optical code division multiple access (CDMA) systems over optical wireless communication. The indoor propagation channel model which takes multiple reflecting surfaces into account is addressed. Theoretical analysis of the pulse response of direct light and reflected light is given. The bit error rate (BER) of this system is analyzed considering reflected light, background light, avalanche photo-diode noise, thermal noise, and multi-user interference. The results prove that the BER of the system is influenced by reflected light and that the effect of reflected light is related to room size and receiver position. With an increase in the number of users, the effect of reflected light becomes stronger and is a significant source of inter-symbol interference. It becomes clear that when optical CDMA is used in an indoor optical wireless system, the effect of reflected light is a key issue to be considered. © 2009-2012 OSA.

This paper presents a free space visible light communication (VLC) system using an image sensor as a receiver to acquire position related timely information. Since the atmospheric turbulence affects the communication quality, the analysis of atmospheric turbulence is very important for designing a practical communication system. In this paper, the atmospheric turbulence channel is analyzed. The method of characterizing and quantifying the influence of atmospheric effect to image sensor communication is presented. The noise model of the system using CMOS image sensor as a receiver is given. Furthermore, the bit error probability of the system using OOK modulation considering atmospheric turbulence is studied. © 2012 IEEE.

Developments in outdoor free space optical (FSO) communication between buildings using rooftopmounted units are limited by Point-to-Point wireless links. We propose a space and 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 are used. The reflection characteristics of the reflector are measured. The relationship characteristics between the static angle error of the stepping motor, the beam fluctuation, and the communication distance are demonstrated. The received optical powers are compared on using one or two reflectors while considering the angle of incidence at the surface of the reflector. Moreover, the received power, the bit error rate and the throughput of the experiment system are measured. In addition, the throughput characteristics of the proposal scheme are made clear by experiments. The result of the experiment shows that the new scheme can provide a low-cost and efficient method for Point-to-Multi-Point FSO communication 1. © 2006 IEEE.

This paper proposes a new kind of communication system for air traffic control over the oceans; it is particularly effective at handling high air traffic loads due to many oceanic flights. In this system, each aircraft position report is sent to its relevant ground station by forwardly relaying them via a multi hop ad-hoc network that is formed by the aircraft between this aircraft and the ground station. In addition, an effective multiple access scheme with optimal values is also proposed. This scheme enables the various aircraft involved in relaying the signal to operate autonomously in a flight-route airspace. Furthermore, two useful schemes are proposed for efficient timeslot reuse and timeslot assignment in cases of low aircraft densities: the position aided timeslot reuse (PATR) and distance based timeslot assignment (DBTA), respectively. Finally, another scheme is proposed to improve the achievable relayed packet rate under low aircraft densities, which is called interference-based node selection (IB-NS). In all, the proposed system combined with those three schemes show the availability to utilize this system for air traffic control communications, specifically on high traffic ocean routes.

This paper has conducted a practical experiment to investigate the transmission characteristics between the two aircrafts on the air in aeronautical VHF frequency band. Based on that, a proper scheme combining the two typical features in any avionics application, space and time domains respectively. Space-Time Division Multiple Access (S-TDMA) scheme is incorporated were each sub frame is considered for each sub area. With high accuracy timing derived from other applications, all aircrafts in each sub area are operated autonomously from transmitting, broadcasting its own position information or relaying the neighbor's position information. In addition, against the unevenly distributed aircrafts, ADS-TSR (Autonomous Distance Based-Time Slot Reuse) scheme is proposed to enhance spectrum usage and system performance as well. The system shows the capability in enabling a new generation of widening the view for cockpit display not only for nearby area but also beyond the horizon and contribute to the feasibility of the future trend, a concept of free flight in aviation industry.

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.

本論文では,端末にルータの機能をもたせるマルチホップ無線ネットワークに着目し,圏外エリアに所在する端末がマルチホップを用いてネットワークを構築し,基地局にアクセスを行うモバイル通信モデルについて考察する.マルチホップのルーチングアルゴリズムにAODV方式を適用し,モバイル通信を計算機シミュレーションにより評価した結果,通話可能エリアの拡大が図れることが示されたが,一方でパケット衝突や中継端末数の増加,チャネル負荷等,マルチホップ特有の問題が生じることも明らかとなった.そこで,このような問題を解決すべく,新たにグルーピングという概念を提案し,これに基づきルーチングを行うことで,より効果的にルートを形成できるようなモバイル通信モデルの構築を行う.結果として,本論文が提案するバーチャルマップモデルは,既存のAODV型モデルに比べ同等の通信性能を維持しつつ,パケット衝突,端末の負担増加等の問題を改善できることを示す.

一般的に,電車車内では医療機器への影響があるため,携帯電話の使用は控えることが望ましいとされているが,筆者らが行ったアンケートによれば,電車車内でデータ通信を利用したいという意見が大半を占めており,電車車内では他の電気機器に対して安全な無線通信が期待されると考えられる.そこで,光無線通信が電波を利用せず車湾内の通信インフラに適している点に着目して,本論文では光無線通信を用いた車両内データアクセスシステムを提案する.また,電車車内で多く用いられているステンレス面やガラス面のような反射面による伝搬特性は,これまで光無線通信の伝搬特性に用いられてきたLambertian反射パターンではモデル化が困難なため,本論文ではステンレス面やガラス面についてモデル化された反射パターンを提案し,更に,提案する反射パターンのモデルを用いて車両内の遅延プロファイルを算出して,実際に車両内で測定した遅延プロファイルと比較検討する.

This paper considers the application of optical wireless Communications to mobile communications. We consider an optical mobile communications system using cycle emission cells and allowing a reduction of the shadowing effect, which is a problem in optical wireless communications. The proposed system uses multiple transmitters with cycle emissions (DTCE). By varying the number of transmitters, the error rate performance is compared via computer simulation. It is anticipated in particular that when the proposed method is applied to mobile communications, multiple transmitters will be placed in the service area, and the distance between the transmitters and the synchronization among the transmitters will greatly affect the error rate performance. The performance is calculated by varying these parameters via computer simulation, and the results are evaluated. Furthermore, the result is compared to other models which have been proposed in order to reduce the shadowing effect, and the effectiveness of the DTCE system regarding optical wireless mobile communications is demonstrated. (C) 2004 Wiley Periodicals, Inc.

3系統送受信同時運用を行う航空機搭載VHF通信システムの干渉障害発生メカニズムを検証した.低位相雑音VCOを用いて搬送波の純度を改善し,隣接チャネル漏れ電力(ACP:Adjacent Channel Leakage Power)に起因する干渉障害を減少させることを提案する.加えて,希望波をバスバンド内に保ち,干渉障害を与える非希望波をパスバンド外に排除する電子式自動同調回路とRF増幅段専用のAGC回路を備える強電界干渉対策電子同調プリセレクタを用いて干渉障害を減少させることを提案し,航空無線システムの信頼性向上を図る.

3系統送受信同時運用を行う航空機搭載VHF通信システムの干渉障害発生メカニズムを検証した.低位相雑音VCOを用いて搬送波の純度を改善し,隣接チャネル漏れ電力(ACP:Adjacent Channel Leakage Power)に起因する干渉障害を減少させることを提案する.加えて,希望波をバスバンド内に保ち,干渉障害を与える非希望波をパスバンド外に排除する電子式自動同調回路とRF増幅段専用のAGC回路を備える強電界干渉対策電子同調プリセレクタを用いて干渉障害を減少させることを提案し,航空無線システムの信頼性向上を図る.

本論文では光無線通信を移動体通信に適用した場合について考察を行った.本論文では,光無線通信で問題となるしゃへいを軽減可能な巡回発光セルによる光移動体通信のシステムについて検討した.提案方式は巡回発光する複数の送信器を用いる方式であるため,本論文ではその送信器数を変化させた場合について計算機シミュレーションにより誤り率特性の比較を行った.特に,提案方式を移動体通信に適用する場合にはサービスエリア内に複数の送信器が配置され,それぞれの送信器間の距離,送信器間の同期の状態が誤り率特性に大きく影響を及ぼすと考えられるため,これらパラメータの変化に応じた特性を計算機シミュレーションにより算出して評価を行った.更に,しゃへいを軽減する方式としてほかに提案されたモデルとの比較を行い,光無線移動体通信におけるDTCE方式の有効性を示した.

This paper presents a practical implementation scheme of the variable gain amplifier (VGA) using a Cds photo coupler (Cds PC) as a variable resister at the feedback loop. The fundamental design policies of IF amplifier stage in super-heterodyne receiver were described. We demonstrated the VGA's experimental results. The results indicated the excellent IIP3 of +25 dBm achieved by a gain of 15 dB, and the reasonable thermal stability and variable gain range. Third-order intermodulation distortion (IMD3) comparison between the proposed VGA and conventional PIN diode attenuation type VGA was evaluated and the result indicated that the proposed VGA surpassed the PIN VGA. The proposed VGA was practically fabricated in 455 kHz IF amplifier stage for an airborne VHF communication receiver in order to improve the large signal handling capability to eliminate numerous interferences resulting from the collocated airborne VHF communication systems on the aircraft.

Most of current wireless communications take sinusoidal waveforms derived from circles. In this paper, new modulation schemes using elliptical circles, in stead of usual circles, are proposed. Several schemes proposed in this paper can be described as "Elliptical Modulation" which modulates 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 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.

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.

HF通信とSATCOMに次ぐ第3の洋上航空路通信手段として,自律分散型アドホック無線による単一チャネルVHF空対空無線中継通信システムを提案する.経路情報は航空機がもつ位置情報を利用し,すべての航空機は決まった間隔で航空機識別符号と現在位置をブロードキャストする.また,広大な空域(Area)における無線アクセス方式は,隠れ端末に対して耐性を有する使用フレーム時間を航空路上の空域ごとに分ける空間時分割多重アクセス方式を用いる.飛行実験によりディジタルデータ伝搬特性及び空対空伝搬特性を取得し,実用的な1ホップの最大有効中継距離を検証した.

HF通信とSATCOMに次ぐ第3の洋上航空路通信手段として,自律分散型アドホック無線による単一チャネルVHF空対空無線中継通信システムを提案する.経路情報は航空機がもつ位置情報を利用し,すべての航空機は決まった間隔で航空機識別符号と現在位置をブロードキャストする.また,広大な空域(Area)における無線アクセス方式は,隠れ端末に対して耐性を有する使用フレーム時間を航空路上の空域ごとに分ける空間時分割多重アクセス方式を用いる.飛行実験によりディジタルデータ伝搬特性及び空対空伝搬特性を取得し,実用的な1ホップの最大有効中継距離を検証した.

HF通信とSATCOMに次ぐ第3の洋上航空路通信手段として,自律分散型アドホック無線による単一チャネルVHF空対空無線中継通信システムを提案する.経路情報は航空機がもつ位置情報を利用し,すべての航空機は決まった間隔で航空機識別符号と現在位置をブロードキャストする.また,広大な空域(Area)における無線アクセス方式は,隠れ端末に対して耐性を有する使用フレーム時間を航空路上の空域ごとに分ける空間時分割多重アクセス方式を用いる.飛行実験によりディジタルデータ伝搬特性及び空対空伝搬特性を取得し,実用的な1ホップの最大有効中継距離を検証した.

成層圏飛翔体のような高高度基地局と地上移動局間の通信では、相互の距離や相対的な仰角といったものが重要な要素となる.反射角入射角の性質により高仰角状況では直接波に対する散乱波の影響が少なく, 逆に低仰角状況では散乱波の影響を受けやすく, 伝搬特性も異なることが考えられる.そのため本稿では仰角の違いにより多重波電波伝搬が具体的にどの程度変動するかを, 飛翔体試作機を飛行させ, 様々な条件で実測実験を行った.また実測実験データを計算機シミュレーション上に導入し, 都市別, 仰角別の特性評価を行った.

In recent years, several global network systems using non-stationary satellites have been proposed. Some of them are announced to start services within years. We also have several experimental systems with stratospheric aircrafts. In the future, the radio communication system using stratospheric aircrafts will be one of the promising media for personal communications. The question of how to establish the optimal communication under such circumstance seems to be still open. In this paper, performance evaluations of wireless communication systems using LEO satellites and stratospheric aircrafts are proposed. We will show some proper communication parameters to improve competence of mobile communication in the such systems as well.

本論文では, 地上局の送信電力を制御し複数局間で受信電力差をつけることで捕捉効果を発生させ, 衛星通信網構成制御を行う制御方式を提案し, その性能評価を行った.まず, 使用した実験システムの機器概要と, 本研究で構築した衛星回線監視/制御システム, インバウンド衛星通信網制御システムおよびアウトバウンド衛星通信網制御システムの概要を示す.つぎに, 実衛星を用いた捕捉効果に関する実験結果を示し, 衛星回線における捕捉効果利用の可能性について考察する.また, 衛星通信網構成制御を行ううえで必要な捕捉効果を利用した局切換え方式を提案し, その性能評価を示す.更に, 捕捉効果の新たなる利用法として内送という概念を構築し, 内送を用いた方式として送出要求内送付衛星回線切換え方式を提案し, その可能性を検証する.

複数メディアを組み合わせたマルチメディア通信への需要が高まり, さまざまな情報源から送出される多様な性質のデータを同一チャネル上で通信するネットワークシステムの構築が重要視されている.可変長データを分割して転送する方式はチャネル有効利用率に関して有効である反面, 分割されたブロックごとに付加されるオーバーヘッドが増大するといった問題等が残されている.本論文では, 分割転送を行わず簡易な制御システムにおいてチャネルの有効利用を図るため, 可変長データを固定長スロットに送出した場合に生じる空白区間を有効活用し, 広い負荷領域において優れた特性を示す捕捉効果を利用した可変長データ転送方式(VDAC方式:Variable length Data Access with Capture)を提案する.再送を行う際のデータ長分布の変化を考慮した理論解析による性能評価の結果, 従来方式より特性が向上することを示す.

本論文では, 地上局の送信電力を制御し複数局間で受信電力差をつけることで捕捉効果を発生させ, 衛星通信網構成制御を行う制御方式を提案し, その性能評価を行った.まず, 使用した実験システムの機器概要と, 本研究で構築した衛星回線監視/制御システム, インバウンド衛星通信網制御システムおよびアウトバウンド衛星通信網制御システムの概要を示す.つぎに, 実衛星を用いた捕捉効果に関する実験結果を示し, 衛星回線における捕捉効果利用の可能性について考察する.また, 衛星通信網構成制御を行ううえで必要な捕捉効果を利用した局切換え方式を提案し, その性能評価を示す.更に, 捕捉効果の新たなる利用法として内送という概念を構築し, 内送を用いた方式として送出要求内送付衛星回線切換え方式を提案し, その可能性を検証する.

通信系における安定性を解明することは重要であり,さまざまなシステムについて研究がなされている. しかし今までの研究の大部分は,システムに均一な負荷がかかる場合についてのみ行われており,不均一な負荷がかかる場合についての研究は不十分である. しかし,実際のネットワークでは負荷が均一に加わることはまれであり,不均一に負荷が加わる場合の解析が必要である.本論文では,不均一な負荷がかかるシステム解析の一手法を示す.情報ネットワークにおける情報の流れに着目し,状態方程式を求めリヤプノフ関数を用いて安定性を議論する.本解析手法の適用例として完全結合型網を取り上げ,トラヒック集中が起こる場合について平衡状態の安定性を検討し,ふくそうを起こさないための呼の発生率のしきい値を示す.

いかなるネットワーク利用状態においても優れた特性を示すアクセス方式を開発することは,今後ますます多様化するネットワーク状況に対応するうえで重要である.先に筆者らが提案した割当ウィンドウアクセス方式(FAWA方式 : Fixed Assignment based Window Access)は,ウィンドウ値を変えることで, ALOHA 方式に近い性質をもつ方式から固定割当方式に近い性質をもつ方式まで設定可能である.FAWA方式を使用した場合, ALOHA方式と固定割当方式の中間の特性が得られるが,両方式より優れた特性を示す負荷領域は狭い.本論文では,スループット・平均遅延特性の向上を目指し,FAWA人方式より有効となる負荷範囲を拡大するために,送信電力制御により発生する捕捉効果を用いた割当ウィンドウアクセス方式(FAWA方式 : Fixed Assignment based Window Access with Capture)を提案する.理論解析による性能評価の結果,FAWA方式は中負荷から高負荷の負荷範囲でALOHA方式,固定割当方式, FAWA人方式より良好な特性が得られることを示す.

The TDMA scheme, a typical multiple‐access scheme, can provide secure transmission
but its efficiency is poor under low traffic conditions. By contrast, the random access scheme, represented by the ALOHA scheme, has a small‐delay characteristic under low traffic conditions but a stability problem under heavy traffic conditions. This paper presents a new multiple‐access scheme in which each station is assigned a slot in every frame and stations are assigned to a slot at different power levels to obtain the capture effect. Therefore, the proposed scheme can adapt itself under various traffic conditions with channel status monitoring based control. Different models of capture effect are proposed, and the performance of the models is analyzed both by theory and by computer simulation. Copyright © 1993 Wiley Periodicals, Inc., A Wiley Company