Bridge inspection using drones has become considerably more attractive owing to the ability of drones to gather information safely in lesser time and at a lower cost than traditional inspection methods. However, one of the critical issues in drone-based bridge inspection is ensuring stable communication between the operation base and inspection drones. The inspection drone easily loses sight of the operation base because bridges have intricate structures. Therefore, this study developed a radio map-based flight planning method of autonomous repeater drones for bridge inspection in order to ensure stable communication. Based on the inspection scenario, the repeater drone needs to ensure the communication with a minimum movement even under position deviations caused by winds. First, we generated a three-dimensional radio map of the bridge. Then, under the assumption that the inspection drone adopted a predetermined path, we developed a path planning method for a repeater drone based on the radio map. Some path planning examples demonstrated that the generated path reduces the moving distance and is also robust against the position error, in addition to ensuring stable communication.

In order to measure the propagation channel characteristics in a factory environment, measurements were performed in the 2.4 GHz and 5.2 GHz bands to obtain the received power and delay spread at various locations. The received power at several fixed locations was recorded simultaneously to measure the long-term power fluctuations caused by the dynamic factory environment. Power fluctuations were also recorded from a receiver placed on an Automatic Guided Vehicle (AGV) which frequently moved around a fixed area within the factory. The probability distribution of the received power was compared with several distribution models, and results show that they can be modelled using the stable distribution. Furthermore, analysis of the relationship between delay spread and received power between several transmitter and receiver locations in the factory suggested that they are inversely correlated, where the delay spread increased when the received power decreased.

This paper proposes a concept of large-scale emulation and evaluation environment of wireless communication systems. The environment can build radio nodes called virtual node by software in cyberspace and provide interaction among the virtual nodes and the reconfigurable physical radio devices that are connected to the environment from the outside. The environment therefore enables preliminary investigations and evaluations for the highly advanced and complicated wireless systems in the future. Moreover, in the radio interactive emulation, the radio propagation parameters based on the preliminary obtained models are suitably referred. The proposed wireless emulation environment enables wireless emulations required in the six typical wireless systems that are further developed and promoted in B5G/6G society. The paper shows evaluation and consideration of the fundamental performances for the proposed wireless emulation environment that includes numerical investigation for the interconnection performances between the virtual nodes and the reconfigurable physical radio devices, as well as fundamental operation for the wireless emulation with suitable visualization functions.

Many technologies are implemented on the assumption that they will use a wireless environment. When evaluating these technologies, it is necessary to consider wireless links in various situations because the status of the wireless environment is affected by many physical phenomena and obstacles. Thus, it is not easy to evaluate these technologies. We have been studying and developing technology that enables us to evaluate software and hardware implementations for wireless technologies without transmitting radio waves by reproducing wireless sections on a wired network testbed. In this paper, we explain a detailed implementation of testbed middleware to easily introduce newly proposed technologies to the testbed. The architecture also enables us to introduce functions for wireless emulation to our testbed. Taking a small radio experiment as an example, we introduce a detailed implementation that enables wireless emulation in cooperation with the entire testbed.

In recent years, the importance of pre-verifying the status of wireless communications has increased for designing offices. Because wireless communication is used for various purposes in offices, this technology has become a basic infrastructure for business. Therefore, when building a new office or renovating an office, verifying the impact on radio waves while designing the workspace is paramount. However, no highly accurate simulation tools for radio waves are available that can be easily used by office planners, who do not possess expert knowledge of radio waves. To address this challenge, we propose smart office planning system that can be linked to a radio wave emulation system that can verify radio wave propagation and communication behavior with high accuracy and can be easily used by office planners. This paper presents the results of a usability evaluation of a smart office planning system. As a result, users could easily set simulation scenario by preparing a general-purpose template option and could evaluate the state of wireless communication by using 2 visualization strategies: a three-dimensional visualization that simultaneously presents the three-dimensional structure of the office space, radio propagation, and communication behavior, and a two-dimensional visualization that visualizes problems affecting the quality of work. Moreover, in the future, by integrating the smart office planning system with the radio wave emulation system, office planners will presumably be able to verify the effects of workspace design on radio waves in advance, thereby reducing the man-hours required for office construction and ensuring adequate communication quality in the workspace.

This article proposes a novel Airborne Internet of Things Network (AIN) system architecture for monitoring water quality, combining existing wireless technologies with the aid of a low altitude platform (LAP) to relay data over long distances in hilly terrain. The proposed system consists of water quality sensors, smart utility network (SUN) devices, long range (LoRa) wireless devices, an LAP air balloon, and Wi-Fi devices. A measurement campaign was conducted to assess the proposed system, focusing on the communication link reliability and the LAP stability and robustness. Several constraints, such as payload limit and safe weather conditions, were also highlighted for operating the LAP with extensive and reliable coverage. On the other hand, characterizing the wireless channel has become a crucial parameter for planning and deploying Internet of Things (IoT) applications. Accordingly, this work proposes a novel hybrid machine learning (ML)-based semi-empirical path loss (PL) model for LoRa wireless communication. The results validated the proposed system’s effectiveness, unique characteristics, and capability to monitor water quality in a harsh environment. Results also revealed a significant difference in packet delivery rate (PDR) for different gateway height and spreading factor (SF) configurations. For instance, switching SF7 to SF12 increased PDR by 28.7%. Meanwhile, increasing gateway height increased PDR by 29.2% for similar SF configurations. The evaluation also revealed that none of the established PL models are suitable to represent harsh tropical environments. Finally, the proposed model achieved nearly 90% prediction accuracy for testing samples and 95% accuracy for training and overall measurement samples, vastly outperforming conventional models.

Machine-to-machine (M2M) communication is an emerging communication paradigm, and it offers ubiquitous applications. Cellular M2M network has shown great potential. A well-established mobile cellular network seems to be the best option to provide connectivity for M2M communication, and this has attracted mobile network operators to host or deploy the M2M network on their existing infrastructure. However, one of the significant challenges to realize a cellular M2M network is its device density. In a cellular M2M network, millions of devices are connected to the mobile communication system in addition to the current mobile subscribers. The accommodation of a massive number of M2M devices would be a considerable burden for the mobile network system, as the signaling of M2M devices would cause channel congestion and undesirable signaling overheads due to mobility and session management. In this paper, we propose an efficient group-based mobility management mechanism for cellular M2M communication to mitigate the signaling cost for device mobility-related events.

Device-to-Device (D2D) communications in this paper refer to autonomous direct communications among end devices without central control. Wireless networks based on autonomous D2D communications are of resiliency feature. We developed a lifelog gathering system using such autonomous D2D communications towards elderly health monitoring in depopulated area, where creating wireless networks with coverage over entire area is costly. The developed system consists of three types of terminals, i.e., sensing terminal (s-terminal), delivering terminal (d-terminal), and gathering terminal (g-terminal). The s-terminal collects lifelog at objective’s house. The d-terminal can be placed in a moving car and it receives lifelog data when running within communication range of the objective’s house. Moreover, the lifelog is forwarded to the g-terminal when the d-terminal enters the communication range of facilities where the g-terminal is in operation. We conducted field experiments in a mountainous village. The measured results show that the developed system can successfully gather lifelog data even under non line-of-sight environments. Examples of observation from the gathered lifelog data are also presented.

It is expected that IEEE 802.11ad is used as intra-vehicle communications for high-speed transmission. Currently, since motion detection by frequency modulated continuous wave (FMCW) signals in mmW has been available, issues on interference between IEEE 802.11ad and FMCW signals have been raised. To solve the issues, an interference mitigation method applicable into IEEE 802.11ad against FMCW signals has been proposed. In this method, FMCW signals are detected by summation of the energy in frequency domain of interfered received signals. Interference suppression is achieved by nulling the frequencies where it is determined that FMCW signals are detected. The method does not require any changes of IEEE 802.11ad specifications. Simulation results show that significant improvement on BER has been achieved by introducing the method over SIR range from 0 dB to 8 dB. Experiment on the method has been conducted to evaluate performance of the method in a vehicle. The results obtained by the experiment have shown that the method successfully suppresses FMCW signals.

To further improve spectral efficiency for current wireless communication systems, we propose a new lazy learning-based cancellation approach to suppress self-interference (SI) sent from a base station and enable in-band full-duplex (IBFD) transmissions in cellular networks. Differ from the existing IBFD systems based on traditional approaches, our proposal consists of two phases: an offline phase for database generation and an online phase for data transmission. In the offline phase, the output before a 0/1 decision is previously measured without the desired signal input and recorded to a database with self-defined feature vectors (FVs). In the online phase, for the same system architecture with the desired signal input, a suitable result is sought from the generated database with the help of a learning method and the use of FV; then, the result is assigned as a value of SI cancellation. Computer simulation results indicate that the proposed cancellation approaches can achieve about 134 dB SI suppression and thus enables the IBFD transmissions in the considered systems.

IEEE 802.11ad is expected to be used as in-vehicle communications for high-speed transmission. Recently, radar systems using frequency modulated continuous wave (FMCW) signals in the 60 GHz band have been investigated for a child presence detection in a vehicle. Therefore, there is a concern that the in-vehicle radio communication system could be interfered with by the radar system. In this paper, transmission experiment of IEEE 802.11ad signals with existence of FMCW signals was conducted in a vehicle since the impact of the mutual interference has not been clarified. The results show that if the transmit antenna and the receive antenna face each other, the stable communication can be established in a vehicle even if the FMCW signal interferes. In addition, stable communications are confirmed by using reflection from the vehicle body as long as received signal power is beyond -33 dBm.

In this paper, we propose a novel efficient implementation of the optimal detector based on the minimum-mean-square-error criterion for orthogonally precoded orthogonal frequency-division multiplexing (OP-OFDM) systems. It enables the OP-OFDM to compensate for data rate loss reported in previous work with a reasonable receiver complexity. Numerical experiments show the proposed detector achieves outstanding error rate and throughput performances, and reduces the computational complexity by roughly 95 % from the conventional implementation in practical contexts where the OP-OFDM systems satisfy a strict spectral mask of 55 dB at band-edges.

In this paper, we propose a novel uplink non-orthogonal multiple access (UL-NOMA) for massive communications under the number of user equipments (UEs) that send signals simultaneously is larger than the number of receive antennas. The base station (BS) separates the superimposed signals through minimum mean square error (MMSE) spatial filtering with successive interference cancellation (SIC). In order to improve the signal separation performance, frequency domain-space time block coding (FD-STBC) is adopted as transmit diversity in the uplink. As FD-STBC, we examine two ways of transmit power allocation method for each UE. The proposed methods are evaluated by computer simulations and also experiments, which were performed under condition when up to 6 UEs transmit signals simultaneously. Performance evaluation is given by packet error rate (PER) by sending 16 bytes a packet as the signal. The results of the computer simulation and the experiments show good agreement, and the experimental results with the power difference for each UE, show that PER is less than 10% in single transmission without repetition when the number of UEs is up to 6. These are the results when the overloaded ratio, which is the ratio of the number of UEs to the number of the receive antennas, is up to 300%. And these results showed that it is effective to make a power difference for each UE.

This paper gives evaluation on MIMO communications by RF signals in seawater thorough analysis on channel capacity, simulations, and experiment in shallow water. The analysis on channel capacity reveals that near-bound capacity in MIMO communications is achieved by interference cancellation based on ZF by setting antenna spacing of more than a half of wavelength in seawater. Simulation results show that expected bitrate reaches at more than 10 bps/Hz and 20 bps/Hz by employing 2x2 and 4x4 MIMO communications, respectively, with 64QAM in frequency band of 10 MHz. Experiment in shallow water has been conducted on 2x2 MIMO communications with 64QAM, and 10-Mbps data transmission has been achieved, which is expected bitrate in wireless communications in seawater by RF signals.

It is expected that the highly-dense deployment of private fifth generation mobile communications system (5G) microcells will be further accelerated in order to meet the demands of a wide range of use cases in various environments. This motivates the need for spectrum sharing research in the mmWave spectrum. The use of array antennas in 5G systems opens the possibility for spectrum sharing in the angular domain in addition to the frequency domain. This paper investigates the use of compressive sensing (CS) to efficiently perform spectrum sensing over a wide bandwidth in the frequency and angular domains simultaneously using only a small number of compressed measurements. The CS problem is formulated using the Kronecker product of overcomplete dictionaries, where the overcomplete dictionary in the angular domain consists of frequency-dependent steering matrices. Modification of the Kronecker Orthogonal Matching Pursuit (Kron-OMP) algorithm is proposed, and group-sparsity is enforced over the frequency domain to improve detection of wideband signals. The effectiveness of the proposed approach for wideband spectrum sensing is confirmed through Monte Carlo simulation.

Spectrum sharing is known to improve the spectrum utilization efficiency. However, from the perspective of a spectrum owner, spectrum sharing implies renting some of its resources to the peers. With a concern for its users’ QoS, it is not trivial for the spectrum owner to decide whether or which amount of resources it should rent to the peers: as a matter of fact, sharing all of the free (un-used) spectrum may cause resource scarcity for its own users and harm the QoS; on the other hand, sharing no or less resources may hinder the improvement of spectrum utilization efficiency. To the best of our knowledge, no technical approach has been proposed to address this dilemma. In this regard, a ruin theory-based spectrum sharing mechanism is proposed. The objective of this proposed method is to allow the operator to wisely decide minimum resources that can ensure its users’ QoS and share only surplus resources. The required minimum resource is determined by the ruin probability which can be obtained by applying ruin theory. Hence, the proposed method can ensure the QoS of spectrum owner while improving the spectrum utilization efficiency. We also illustrate the benefits and robustness of the proposed method by citing some numerical examples.

In wireless communication for Internet-of-Things (IoT), a base station (BS) is required to efficiently accommodate radio signals transmitted from massive IoT devices. We have developed and demonstrated an uplink non-orthogonal multiple access (UL-NOMA) system, in which signals from the devices are multiplexed in the power domain without any spatial multiplexing or spreading. In the UL-NOMA strategy, precise transmit power control (TPC) methods are required to compensate for various fading fluctuation. For example, NOMA that multiplex devices' signals in the power domain utilize the difference of received signal power at BS to successfully achieve successive interference cancellation (SIC). To maintain the difference of received power at BS, the implementation of precise TPC is crucial. In the paper, a prediction method on the future fading condition from current conditions is useful to realize precise TPC in UL-NOMA in the power domain. The prediction method at IoT device side with the autoregressive (AR) model is proposed which utilizes received OFDM signals in the downlink. The proposed TPC is evaluated by computer simulations. Simulation results show that TPC with the proposed fading prediction improves the signal separation success rate of UL-NOMA with SIC. The ratio that the signals of all devices in multiplexing 5 devices are separated is improved from 39% to 66%.

In order to avoid the loss of separation or collision risk among unmanned aircrafts as well as manned aircrafts, we have developed a prototype system where the aircrafts autonomously exchange their location information obtained through the signal of the Global Positioning System (GPS) using device-to-device (D2D) communications. Based on the developed system, we have conducted an experiment that demonstrates its successful operation for maintaining the targeted separation between the drone and manned helicopter. This paper will report the details of our experimental results as well as describe our finding of the requirement in D2D communications so as to guarantee the sufficient separation among the aircrafts.

The 5G will not only offer high speed and greater capacity communication but also support the IoT. To support IoT, it is important that next generation NodeB (gNB) will be able to deal with massive uplink signals transmitted from IoT devices. Non-orthogonal multiple access (NOMA) is one of the effective methods to handle massive signals from the IoT devices. However, when NOMA is used for downlink, it is necessary to perform signal separation on the user equipment (UE), which suffers from heavy load on UE. We consider that it is better to employ orthogonal multiple access (OMA) for downlink to prevent too much computational cost and power consumption for UE. Hence, we have studied a system that uses NOMA for uplink and OMA for downlink. The feature of our system is that single carrier is used for uplink to reduce peak to average power ratio (PAPR). Although the single carrier transmission with NOMA will be in demand in the future, most of the research is computer simulation. In this paper, we demonstrated and evaluated our system using hardware. We measured the performance difference between uplink using NOMA and downlink using OMA in terms of packet error rate (PER) to obtain tips to improve uplink performance. From the result, we confirmed that uplink NOMA could be performed well in hardware. However, to improve reliability, it is necessary for the system to incorporate some techniques such as diversity with uplink NOMA. Without the techniques, the uplink with NOMA is less reliable than downlink with OMA so far.

Since IEEE 802.11af was standardized in 2013 as one of the standards for TVWS (TV white-spaces) communication, a variety of radio devices such as a high-power radio device al-lowing a transmission power of 1 W and a dongle-type com-pact radio device have been prototyped and demonstrated in field experiments. Meanwhile, since all the reported prototypes were limited to a single channel operation with a channel bandwidth of 6 MHz, achieved throughput was inferior to the commercialized WLAN (Wireless Local Area Network) systems with a channel bandwidth of 20 MHz or more. In this paper, to enhance the throughput of the IEEE 802.11af system, we de-sign and prototype a radio device based on IEEE 802.11af with a channel aggregation function. In addition, we evaluate fun-damental characteristics of the prototype radio device including radio performance and throughput.

It is of great interest to develop larger scale multiple-input multiple-output (MIMO) technology based on frequency division duplexing (FDD) for backward compatibility with existing standards and already deployed cellular networks. One hindrance to the FDD approach is the complexity of the codeword search performed by the receiver, which is known to scale with the number of transmit antennas N in a system. The codeword search complexity does not scale linearly and soon becomes infeasible even for the not-so-massive MIMO systems expected in the very near future. We address this problem by proposing a natural sequence-based orthogonal codebook and an intra-array interference magnitude (IIM) framework for MIMO beamforming based on quantized equal gain transmission that altogether tremendously simplifies the codeword search problem. We also present an assessment on the quality of the codeword selected by the proposed framework that explains it's near optimal performance, and, provide detailed codeword search complexity quantification. Finally, we provide simulation analyses of beamforming gain under time selective fading channels and an FDD MIMO system transmit delay model. Our analyses indicate that despite significantly reducing complexity, the proposed IIM framework executed by already commercialized processors is capable of approaching the ideal performance of an static system even in the presence of time-selectivity inherent to high-speed mobile communications. Our analyses also quantify the impact of feedback delay on average beamforming gain of moderately large transmit arrays.

The IEEE 802.11ad technology, which allows wireless devices to communicate in the unlicensed 60 GHz ISM band, promisingly provides multi-Gbps data rates for bandwidth-intensive applications. After years of research and development, we are now observing an increasing number of commodity IEEE 802.11ad radios that motivate researchers to exploit the IEEE 801.11ad capability for applications. This work first conducts an empirical study on the IEEE 802.11ad performance. In particular, we characterize the performance of IEEE 802.11ad links considering the variation of network parameters and interference. Secondly, we investigate the possibility of introducing IEEE 802.11ad to an evolving Wi-Fi network. The evaluation results show that our off-the-shelf IEEE 802.11ad hardware can achieve the Gbps level throughput of the transmission control protocol (TCP) and user datagram protocol (UDP). However, the evolvement is not trivial since the hardware can not well maintain the 60 GHz link. The main reason is lacking the fast switchover function between an IEEE 802.11ad and a legacy Wi-Fi link. We then seek the potential of multipath TCP (MPTCP) for the expected switchover. The default MPTCP, which enables data transmissions on both the IEEE 802.11ad and Wi-Fi links, is harmful to the IEEE 802.11ad throughput. Meanwhile, the backup mode of MPTCP, in which the Wi-Fi link acts as a backup for IEEE 802.11ad one, can maintain the comparable performance. Therefore, we propose to adopt MPTCP with the backup mode in the evolving Wi-Fi networks. The efficiency of MPTCP-based switchover is confirmed by conducting real experiments.

An important challenge to realize spectrum sharing through dynamic spectrum access in cognitive radio networks based on Orthogonal Frequency Division Multiplexing (OFDM) is to suppress high sidelobes of OFDM signals that interfere with the adjacent bands. Orthogonal precoding is a promising technique for sidelobe suppression where emitted OFDM signals must change their spectrum occupancy adaptively. However, the high computational complexity, quadratic in the number of subcarriers, has seriously prevented its application. To solve the problem, this paper proposes a novel orthogonal precoding with the compact WY representation. Numerical experiments show that the proposed method is significantly promising for implementation of the orthogonal precoding since it can achieve the efficiency of not only the coding operations (e.g., 5.1% of the multiplications in the conventional method) but also the precoder generation with remarkable numerical stability as keeping the attractive performances in the orthogonal precoding.

Decentralized synchronization among peer devices (PDs) for distributed device-to-device (D2D) wireless networks has been explored by many researches. A general way of performing decentralized synchronization is based on pulse-coupled methods. In which, all PDs are equal and each PD sends and receives synchronization packets as well as adjusts own clock accordingly to achieve mutual synchronization. A newly published standard of IEEE STD 802.15.8 (STD-15.8) provides a systematic process to achieve synchronization for distributed D2D. However, we find that the synchronization process of STD-15.8 may results in separated synchronization clusters. To solve this problem, we propose additional procedures to that of STD-15.8. Then, we conduct step-by-step simulations to reflect the lower MAC functions of real transceivers by employing multiagent model. The simulation results verify the effectiveness of our proposal on improving synchronization.

The 3rd generation partnership project (3GPP) has recently specified the non-standalone 5G New Radio (NR), in which the dual connectivity (DC) feature plays an essential role. A User Equipment (UE) with DC is able to concurrently connect to an evolved NodeB (eNB) (e.g., using LTE in a macro cell) and a next generation NodeB (gNB) (e.g., using 5G NR in a small cell) aiming to satisfy the 5G's required Key Performance Indicators (KPIs). In this work, we focus on the issue of concurrent transmissions on the 5G small cell, which potentially exploit the benefits of DC. With DC, an application is able to spread its traffic over different two paths (via eNB and gNB) between the UE and the LTE core network. The traffic over diverse paths may experience different delay since the conditions are generally different (e.g., due to wireless channel, background traffic). Therefore, one of the most important problems in efficient operation with DC is minimizing the end-to-end delay considering all the connections. To address that problem, we adopt the deterministic network calculus to first characterize the delay experienced by each connection; then to model the overall end-to- end delay in the 5G small cell. We then formulate an optimization problem that attempts to find the optimal traffic splitting over the connections while minimizing the delay. We derive the solution for the problem, as well as, present the numerical results.

The shared resource access wireless communication system is regarded as a paradigm that allows the mobile network operators (MNOs) to have extended coverage and allows them to satisfy their subscribers' high capacity demands while keeping the capital and operational expenditure in check. On the other hand, dual connectivity (DC), a small cell enhancement feature, allows the subscribers to have two simultaneous connections increasing throughput and enhancing mobility robustness. For the DC mechanism, the user needs to be under the coverage of multiple BSs concurrently. Because of random nature of the wireless links and distribution of BSs in a network, the practicability/operability of DC for a typical user under such random operating conditions (both topological and wireless link randomness) needs to be properly evaluated. In this paper, we perform stochastic analysis of DC in shared resource access high capacity wireless networks. We consider a fading-averaged signal propagation loss process, where the selection of the serving BS is perturbed shadowing, not by fading. The DC coverage probability is analyzed in terms of tractable, integral expressions. We have observed that the DC coverage probability is greatly affected by the density of the small cell BSs and the variance of the log-normal shadowing.

Our main aim is to develop and demonstrate energy saving technologies for mobile terminals (MTs) equipped with multiple wireless interfaces. We propose a new framework of device-to-device (D2D) cooperative virtual small-cell network in which a MT acts a virtual base station to take advantage of the good channel quality of long range link and the low energy consuming interface of short range link to save energy in MTs. In the proposed D2D cooperative virtual small-cell framework, how to select proxy MT which connects to the wide area network (WAN) and provides the local area network (LAN) connection to cooperated MTs is an important issue, and it is influenced by multiple factors such as channel quality both in WAN and LAN, throughput, battery lifetime, mobility of MTs. In this paper, the energy efficiency improvement is evaluated by a smartphone test-bed and the impacts of WAN channel condition and the number of cooperated MTs are discussed. The result shows that up to 66% improvement can be achieved by the proposal compared to the traditional systems without cooperation.

IR-UWB has been gaining attentions for its capability of providing high precision ranging and location-tracking. In responding to the changes of regulations, IR-UWB devices need to be implemented at UWB high band (6.0-10.6 GHz) instead of low band (3.14.9 GHz). To compensate the deficiency of high band in propagation, we propose an adaptive detection threshold at the receiver to improve receiving sensitivity. The proposed adaptive threshold is implemented by adding an additional circuit to a conventional detector. Evaluations are performed through measurements. The proposed structure improves receiving sensitivity by 7 dB compared to the conventional structure. Moreover, IR-UWB system with the proposed structure provides better positioning accuracy and precision than the conventional system.

We developed and deployed a testbed based on the concept of peer aware communication (PAC), where PAC is used to refer the fully distributed and self-coordinated device-to-device (D2D) wireless networks. The testbed was originally developed for information sharing at local community by employing in-operation community buses as main components. However, strong demands rise from the local community for obtaining bus location information. To enable the bus location features, a number of improvements are performed to the testbed such as increasing the robustness of wireless links, streamlining MAC frame format and data flow, etc. Examination is carried out on the improved testbed. The results show that the bus location information is obtained within acceptable time delay.

To make WiGig/IEEE 802.11ad backward compatible with the legacy Wi-Fi, a multi-band device that is capable of WiGig and Wi-Fi is necessarily equipped a function of fast switchover between the WiGig and Wi-Fi link. It is expected that the switching action is done as quickly as possible in order to minimize negative effects on an ongoing application. The IEEE 802.11ad standard defines the switching operation within the scope of fast session transfer (FST) protocol. To properly run FST, the device needs extra layer-2 entities that simultaneously manage the PHY/MAC states of multiple radios. Although introducing WiGig radios is a trivial task, installing those entities on an existing legacy Wi-Fi network is unfortunately a challenging one. This work presents an experimental feasibility study of achieving the backward compatibility without FST. We initially analyze the feasible capability of multipath transmission control protocol (MPTCP). We then setup a real- world testbed and evaluate different operational modes of MPTCP, aiming to find the most suitable one. Our experimental results show that the fast switchover between a multi-Gigabit WiGig and a legacy Wi-Fi link is achievable with the MPTCP's backup mode.

This paper investigates the aerial networks where the two unmanned aerial vehicles (UAVs) with different altitudes communicate with each other using the same spectral resources as the ground communication links. We propose a spectral sharing approach based on power control for aerial communication link such that the interference observed by the ground communication links is maintained below a predetermined threshold. Through theoretical analysis based on Nakagami-Rice fading channel model, the trade- off relationship between the acceptable interference observed by the ground terminals and the information rate achieved by the aerial communication link is elucidated.

We investigate an advanced two-phase shared spectrum access communication scheme as an efficient approach to enhance the spectral utilization of a network. In the first phase, we devise a spectrum-sharing policy based on demands, fairness, and so on, which utilizes a priority scheme in fulfilling operators' demands, and envision a secure operator-specific information sharing policy where no critical information is exchanged between the operators. In the second phase, a macro cell network (MCN) benefits through offloading services offered by small cell network (SCN). This allows the MCN to satisfy its users' capacity demands, improve its quality of services and coverage under Nakagami fading channel. As a repayment, the SCN is rewarded with licenses to share and operate on the spectrum originally owned by the MCN. We devise a density division-based shared spectrum access model, where the density of the licensee's SCN deployment is exploited as network resources. A fair division of the densities of the licensee operator's small cell base stations into fractions of licensed small cell base stations serving its own users and offloading small cells is presented. Unlike most of the previous research works that considered Poisson point process (PPP) to model the distribution of the network entities even when PPP modeling is not accurate for the networks, where the number of MCN/SCN base stations is definite and the number of MCN/SCN base stations in disjoint areas is not independent, we employ a more realistic network model known as binomial point process to perform an analytical analysis of the cumulative interference and performance of the system. Furthermore, we analyze the rate coverage and outage performances considering a wide range of values for path-loss exponent and fading severity parameter of Nakagami fading.

In this paper, we conceive an advanced small cells wireless network deployment framework within a managed space under shared spectrum access paradigm. We also conceive a complementary business model, referred to as neutral host micro operator (NH-μO), that leverages a single shared wireless infrastructure to mutually benefit μO (a third party service provider), the owner of the space/facility, and mobile network operators (MNOs). The model is composed of a μO slice, which delivers a venue with customized wireless services tailored to the its local service requirements, and an MNO slice, which facilitates improved wireless coverage to visitors/end-users with subscriptions to several different MNOs. The NH-μO is not biased to favor any specific client, which can be enforced through a concrete commercial agreement. A radio access network slicing concept is exploited to support and optimize both the slice instances (SIs) efficiently in a shared manner on a single physical network infrastructure. In addition, we devise an efficient architecture for the NH-μO small cell base station and dynamic spectrum assignment control unit, and their required functionalities supporting sustainable coexistence of different SIs in shared spectrum. We also devise both interSI and intra-SI dynamic spectrum allocation policies considering time-varying requirements of different SIs. These policies take care of application level priority by providing a proper mixture of users with guaranteed quality of service and best-effort users, while ensuring a healthy SI competition. The advantages of the proposed framework are twofold. It enables the venue owner to manage its wireless networks and consider its very specific requirements while capitalizing from the MNO slice. This, in turn, reduces the need for deployment of new infrastructure while providing improved wireless coverage and savings to MNOs. Finally, our proposed framework leverages efficient utilization of spectrum, physical infrastructure, and computational resources. The simulation results exhibit various important features of the proposed shared spectrum access policies.

This paper presents the experimental performance evaluation results of the IEEE 802.15.4/4g/4e Smart Utility Networks (SUN) in applications suited for outdoor environment. SUN is an advanced wireless communications network designed for reliable, low data rate, and low energy consumption networks for command-and-control applications like utility service, sensor network, and so on. IEEE 802.15.4g/4e is the international standard for SUN supported by multiple utility providers and product vendors. In this paper, a comprehensive field test was conducted by employing the implementation we have developed to evaluate the performance of the SUN devices based on IEEE 802.15.4/4g/4e standard. The output power of the implementation is 250 mW for extended range, reducible to 20 mW for short-range scalability and battery preservation. Results showed that in an outdoor line-of-sight environment, the achievable one-hop range of a 50 kbps SUN device was 450 m. Next, in a non-line-of-sight environment involving typical residential concrete building, the communications could be established penetrating obstructions to reach above the 11th storey, reaching the performance degradation limits at the 20th storey. Next, the network of the SUN system was proven to be capable of supporting a typical multihop tree network in a dense populated building, meeting the required performance by the standard.

This paper presents measurement and analysis results of power delay profiles and fading characteristics for “Public Broadband Wireless Communication (PBB) System” in VHF band. The PBB system was proposed to utilize a portion of vacant spectrum in VHF band due to the frequency reallocation plan in Japan, and the system was standardized as ARIB STD-T103 as well as IEEE802.16n. The purpose of this study is to evaluate the applicability of the system for non-line-of-sight urban environment and characterize the 200 MHz band broad band radio channel. The measurement is conducted by using a developed device which is compliant with the ARIB STD-T103 as a transceiver, and received signal is captured as complex IQ signals by using a signal analyzer. In order to obtain the power delay profile, impulse responses are analyzed by calculating sliding correlation between reference signal and measured signals. For the evaluation of delay characteristics, RMS delay spread is calculated using the power delay profile. In addition, fading characteristics is also shown to confirm the behavior of VHF band mobile propagation channel.

We have implemented a hierarchical mesh (HM) based routing protocol for data collection in an indoor environment. Devices are autonomously organized into a hierarchy based on a metric used to evaluate links between two devices, and end-to-end paths. The HM-based routing is implemented at the link layer over the MAC layer in a working WPAN (IEEE 802.15.4) and uses MAC addresses. A mesh root initiates the construction of the HM and acts as the data collector of the network. Data collection can begin as soon as the HM topology is established and does not require additional route establishment signaling. Devices select a next hop from a neighbor table and do not need to have knowledge of the entire path. We observe efficient routing with limited link layer retransmissions through our experiments. Additionally, the use of data concatenation reduces the number of transmissions in the network as well as the probability of collisions, providing a promising solution in high density and high traffic applications.

We consider a cognitive radio (CR) network consisting of a primary cellular system and a secondary cognitive machine-to-machine (M2M) system, and study the throughput enhancement problem of the latter system employing universal-filtered orthogonal frequency division multiplexing (UF-OFDM) modulation. The downlink transmission capacity of the cognitive M2M system is thereby maximized, while keeping the interference introduced to the primary users (PUs) below the prespecified threshold, under total transmit power budget of the secondary base station (SBS). The performance of UF-OFDM-based CR system is compared to the performances of OFDM-based and filter bank multicarrier (FBMC)-based CR systems. We also propose a near-optimal resource allocation method separating the sub-band and power allocation. The solution is less complex compared to optimization of the original combinatorial problem. We present numerical results that show that for given interference thresholds of the PUs and maximum transmit power limit of the SBS, the UF-OFDM-based CR system exhibits intermediary performance in terms of achievable capacity compared to OFDM- and FBMC-based CR systems. Interestingly, for a certain degree of robustness of the PUs, the UF-OFDM performs equally well as FBMC. Furthermore, the percentage rate-gain of UF-OFDM-based CR system increases by a large amount when UF-OFDM modulation with lower sidelobes ripple is employed. Numerical results also show that the proposed throughput enhancing method despite having lower computational complexity compared to the optimal solution achieves near-optimal performance.

In this paper, diversity receiver performance at base station for VHF-band broadband mobile communication systems is examined by using measurement results. Diversity gain of two RX antennas for link budget calculation has been calculated by using a selective combining and an equal gain combining schemes. By analyzing the diversity gain statistically, it is found that the diversity gain of selective combining and its variation are increased in larger antenna separation and shorter transmission range. On the other hand, the diversity gain of equal gain combining and its variation are decreased in larger antenna separation and in shorter transmission range. In addition, a path loss model has been developed for a link budget design. The path loss model parameters are extracted for over 1 km transmission range. By considering the path loss model with analytically-extracted constant diversity gains for BS antenna separation lengths of 1, 5, and 10 wavelengths, the system service coverage can be estimated.

Wireless Smart Utility Network (Wi-SUN) combining TV White Space (TVWS), which leverages the benefits of TVWS for Wi-SUN with a view to improvement associated with coverage, bandwidth, scalability of current Wi-SUN, receives overwhelming attention. The recently released standard IEEE 802.15.4m details techniques to enable Wireless Personal Area Network (WPAN) work in TVWS. We develop the first IEEE 802.15.4m compliant TVWS-Wi-SUN system, including the system design and prototype implementation. Furthermore, a series of laboratory experiments are performed to characterize the developed prototype transceiver performance. Any differences in performance between simulation and laboratory experiments are emphasized and analyzed. Laboratory experiment results provide the strong evidence that the developed prototype transceiver fulfills the requirements defined by IEEE 802.15.4m. Additionally, our work lays out a solid foundation for the practical application of the TVWS-Wi-SUN system.

This paper proposes geographical group MAC (G-MAC) for event-driven wireless sensor networks. G-MAC is a hybrid MAC protocol combined with the contention-based and contention-free MAC protocols. Collision avoidance is one major task in the contention-based MAC protocols. Collision is much significant as a channel is shared by a large number of contending hosts. If it is possible to reduce the number of contending hosts, collisions could be decreased. This is a basic idea of the proposed G-MAC. By diving the area covered by the sensing hosts into the multiple geographical groups and by separating the channel access time for each group, it could reduce the number of contending hosts. Also, G-MAC needs the time synchronization and channel access scheduling for the separating groups to avoid the interference with others. Simply to say, the proposed G-MAC works on the contention-based channel access for the hosts within a group, but operates on the contention-free channel access among the groups. Computer simulation is conducted to study the effects of the number of groups on collision, packet loss and delay. This paper presents that the proposed G-MAC has the superior performance of collision avoidance and packet loss compared to the contention-based MAC protocols.

Utilization of the TV white-spaces (TVWS), which are spatially or temporally unused frequency in TV bands, is promising technology to alleviate spectrum resource shortage. Services using the TVWS have been already started in the U.S.A., and the TVWS pilot program has been performed and test operation of qualified white-spaces database (WSDB) has been started by the Ofcom in the U.K. Authors have developed TVWS LTE (Long Term Evolution) system with white-space devices (WSDs) licensed by the Ofcom and WSDB qualified by also the Ofcom, and participated in the pilot program performed in the U.K. In this paper, developed TVWS LTE system is summarized and field experiment of throughput measurement is performed in the London urban area is described. As a result of the field experiment, maximum downlink throughput of 45.4 Mbps in the FDD mode and 19.5 Mbps in the TDD mode were obtained under the condition of SISO with a signal bandwidth of 20 MHz. This is the first report on the field experiment of the TVWS LTE system aiming for practical use.

This paper performs the world's first IEEE 802.11af based Wireless Local Area Networks (WLAN) operating in TV White Space (TVWS) indoor experiment in the Ofcom TVWS pilot program of the UK. The prototype system consists of TVWS Database (WSDB), Registered Location Secure Server (RLSS), and two prototype hardware for an Access Point (AP) and a Station (STA). The developed WSDB qualified by Ofcom TVWS pilot program of the UK. The prototype hardware meets to the transmission spectrum regulation of the European Telecommunication Standards Institute (ETSI). By using the developed system, a trial indoor experiment performed in the building of the King's College London (KCL), Denmark Hill Campus in London, UK. The prototype system and the experiment results show an effectiveness of the IEEE 802.11af and indicate the way to the practical application.

In recent years, there has been an increasing number of Software Defined Wireless Access Network (SDWAN) proposals aiming to cope with the proliferation of mobile devices, as well as, the novel Quality of Service (QoS) demands. One of the most important issues in the SDWANs is to maintain a scalable and robust OpenFlow channel through which the network control and update information (i.e., OpenFlow traffic) are exchanged. However, the standard channel does not well support those characteristics nor does it properly conform to the SDWAN environment. This paper seeks to remedy these problems by analyzing the requirements of SDWAN's OpenFlow channel. We then propose a novel OpenFlow channel named mOpenFlow, which is not only compatible with the SDWANs but also evolved with the OpenFlow standard. The advantage of mOpenFlow is using multipath communication for conveying OpenFlow traffic. Hence, both the robustness and the achievable throughput of the OpenFlow channel is significantly enhanced (i.e., scalable). Combining with the compatibility requirement, the multipath TCP is adopted in the mOpenFlow's design. We extensively evaluate the channel's performance in SDWANs including emulated SDN devices and a real controller. The results show that mOpenFlow outperforms the standard channel both in terms of robustness and scalability.

An IEEE 802.11af indoor trial experiment has been conducted in the Ofcom pilot program of the United Kingdom. This paper describes an indoor propagation characterization and throughput estimation method using prototype devices based on the IEEE 802.11af standard. Since the IEEE 802.11af is recent technology for TV white space (TVWS) spectrum sharing, indoor propagation measurements at TVWS band for WLAN usage are very seldom in the previous researches. Path loss model parameters has been extracted for each line-of-sight (LoS) and non-LoS (NLoS) situation on the same floor. Also a fluctuation of measured path loss is analyzed using the log-normal and the extreme value distributions. A developed path loss model is useful for the location design of access points and the interference risk estimation for IEEE 802.11af devices. As another modeling, a throughput estimation model has been developed using the exponential distribution derived from the cumulative probability distribution (CDF) of measured throughputs. By combination of the developed path loss model and the throughput estimation model, throughput can be estimated as a function in each LoS and NLoS situation.

In a white space communication system the database calculates and provides operational parameters to the device based on the device's specifications and geo-location. There is an option for the mobile device to submit an area where it may be located, then obtain the list of parameters that can be used anywhere within the submitted area. This paper addresses the effects of the area's size to the available channels and maximum transmission power. By using a database which passed the qualification tests for the Ofcom TV white space pilot, this paper shows the numerical results of spectrum availability in several locations in London corresponding to different area's sizes which are determined by the geo-location uncertainty.

This study evaluates the performance of a practical IEEE 802.15.4/4e/4g low‐rate (LR) wireless personal area network (WPAN) with multiple physical (PHY) layers and multi‐hop capabilities for smart utility networks, machine‐to‐machine networks and other advanced sensor networks. The proposal includes realistic design considerations addressing demands of practical applications, country‐specific regulatory requirements and technical specification in international standards. A cross‐layer open system interconnection model from the application, transport, network, medium access control, down to the multiple PHY layers is constructed based on the specification in IEEE 802.15.4 LR‐WPAN and other layer‐specific standards. Employing the cross‐layer model, extensive computer simulations were conducted to investigate the performance of the LR‐WPAN system in this application domain. As a result, the authors have successfully verified the simulated achievable average throughput in both PHY layer designs, multi‐rate and multi‐regional frequency shift keying (MR‐FSK) and multi‐rate and multi‐regional orthogonal frequency division multiplexing (MR‐OFDM) with the theoretical throughput by calculation. Secondly, in a multi‐PHY environment with the presence of 30 interferer devices, throughput degradation of the victim system is observed within 30%. Furthermore, when interferer devices transmit frames with interval beyond 1 s, the degradation to the victim system becomes negligible. Thirdly, MR‐FSK PHY has a simpler design with higher energy‐efficiency, whereas MR‐OFDM PHY is more complicated with more resilience to interference. They have found an interference tolerance capability difference of 15 dB between the MR‐FSK and MR‐OFDM systems. Fourthly, comparing with their single‐hop counterparts, multi‐hop systems have lower average throughput in MR‐FSK by 25% and MR‐OFDM by 10%. Finally, comparing with networks with periodical beacon transmissions, asynchronous networks have more inferior average throughput of 20% in MR‐FSK and 3% in MR‐OFDM, with the advantage of longer battery lifespan.

This paper proposes a novel routing protocol named Hierarchical Mesh Tree Protocol (HMTP) that achieves efficient routing at the MAC layer for multi-hop data collection in ad-hoc networks, wireless sensor networks, intelligent transportation system networks, etc. The proposed protocol enables the self-organization of a network into a hierarchical mesh tree topology. The mesh tree topology is used to select the optimal route from a terminal to the root of the tree among the different branches available in order to yield an efficient, scalable and robust routing. The HMTP also enables the terminals to autonomously maintain and update the network mesh tree topology. The hierarchical mesh tree (HMT) alleviates the drawbacks of the conventional cluster-tree proposed in the IEEE 802.15.4 standard and the quasi-mesh tree proposed in the IEEE 802.15.4m standard. The simulations results show that HMTP drastically improves the data collection performance in comparison with the mentioned conventional tree-based routing protocols.

This paper proposes a low-power multi-hop data frame transmission scheme to create a long-lived smart utility network (SUN), as standardized by IEEE 802.15 TG4g/4e. In the proposed scheme, low energy superframe structure with turned-off beacons are employed to reduce power wastage, thereby providing effective sleep periods for each device. Moreover, multi-hop frame transmission is easily realized by constructing a tree-shaped topology with incoming and outgoing superframes. Furthermore, in the proposed system, effective frame aggregation technology exploiting such low energy superframe structure is employed in order to solve the bottle neck problems that seriously degrade utility data collection performance in SUN. The results of computer simulations confirm that the proposed scheme enables a greater than 90% frame success rate without error control while holding a less than 0.4% active period ratio in feasible SUN usage situations.

This paper presents the evaluation on energy consumption of power saving mechanisms in recent IEEE 802.15.4 Low-Rate Wireless Personal Area Network (LR-WPAN) systems. The LR-WPAN applications share a common system requirement of high energy efficiency through power saving mechanisms to prolong battery lifespan. First, the recent IEEE 802.15.4 standard amendments including, but not limited to IEEE 802.15.4/4e/4f/4g/4j/4k/4m and their targeted applications are listed and discussed. Then, the applications are categorized based on different energy consumption models which are interconnected with the radio operations of the proposed power saving mechanisms. Next, addressing pervasive demands and respective energy consumption models in multiple application scenarios, three power saving mechanisms for LR-WPAN are proposed and evaluated taking into consideration realistic parameters. As a result, it is found that the power saving mechanisms are capable of supporting battery lifespan up to typically 3 years. Out of the three proposed mechanisms, two are found to be more suitable for deployment of symmetrical energy consumption model where all devices share similar burden of radio operations, while one is found to be otherwise, optimized for asymmetrical energy consumption model where some devices have larger burden as compared to others.

This paper presents the performance analysis of an IEEE 802.15.4g multi-hop orthogonal frequency division multiplexing (OFDM) system in a network with multiple physical (PHY) layer design. Identified usage models for the IEEE 802.15.4g standard are low energy wireless sensor network and smart grid/utility network applications. For that, a total of three PHY layer designs under a unified medium access control (MAC) are specified to address different market segments. The multi-PHY layer architecture has an advantage of covering a wide range of pervasive use case scenarios, at the expense of inter-PHY interference (IPI) among respective PHY layers. This paper focuses on the OFDM PHY that promises high data rate and superior propagation performance. To enable optimized operation in the targeted applications, a multi-hop MAC layer design is specified to extend the operating range of the network, while low energy features are designed to increase energy efficiency of the system. Additionally, an IPI mitigation technique is also developed to combat IPI generated from the interfering network. As a result, it is found that the average throughput of a multi-hop OFDM network is 8% lower than that of a single-hop OFDM network, but with larger achievable operating range. Secondly, with the proposed IPI mitigation technique, no degradation among devices with different PHY layer designs is observed to take place. Thirdly, with the energy-efficient non-beacon-enabled mode, devices are consuming less power, at the expense of immunity reduction against interferer.

This paper presents the network performance analysis of a low energy IEEE 802.15.4/4e/4m LR-WPAN operating in TV White Space. An energy-efficient mechanism optimizing the tradeoff between device sleep time and synchronization strategy is utilized to reduce the total power consumption in a non-beacon-enabled network. To evaluate the performance of the network, we have modeled a cross-layer system starting from the application, transport, network layers, to the MAC layer where the energy-efficient mechanism resides, to the PHY layer where the FSK PHY resides, down to the propagation channel where the VHF/UHF channels applies. Extensive computer simulations were conducted to investigate the performance of this low energy LR-WPAN system. As a result, we have found that a device may consume up to 40% and 2% of its total operation time to perform channel scanning and transmission, respectively. Applying the proposed energy-efficient mechanism, the achievable reduction of channel scanning time and transmission time are 20% and 1% respectively. We have also observed that the average residual battery capacity can be most effectively preserved when the number of devices in the network reaches approximately 30.

This paper analyzes the performance of a realistic multi-PHY layer IEEE 802.15.4g Smart Utility Networks (SUN) design and proposes a coexistence approach for multi-PHY interference management. Technical details of the design such as network architecture, mechanism protocols, signal formats, device interfaces, regulatory requirements and channel characterization are implemented following the IEEE 802.15.4g SUN specification. The performance evaluation is conducted in a cross-layer computer simulation based on the MAC (medium access control) and multi-PHY technical specification in the standard with realistic application scenarios and channel characteristics. To manage the interference in the system, a Multi-PHY Management (MPM) protocol is proposed and evaluated. The MPM is adopted in the current IEEE 802.15.4g standard. As a result, the coexistence mechanism is observed to be able to improve the victim throughput performance up to 25%. It is also found that the throughput degradation in a non-beacon-enabled network is 50% worse than the degradation in a beacon-network.

This paper proposes an energy-efficient beaconless synchronization mechanism for SUN operating in the TVWS. From the aspects of fulfilling the pervasive yet stringent requirements of low-energy wireless meters and TVWS regulations, the proposed mechanism is able to prolong battery lifespan beyond the required level for wireless smart meters, and is compliant to the specific network architecture and communication protocols demanded by the TVWS rules. In the MAC layer, a novel design for low duty cycle beaconless synchronization/data exchange is specified. In the PHY layer, the transceiver and realistic channel models applicable to the IEEE 802.15.4g SUN is constructed. Actual data from chip vendors of the wireless meter industry are also included to facilitate a more practical investigation. All the above are combined for performance evaluation to quantify the energy-efficiency and error performance of the proposed mechanism. As a result, it is found that the proposed mechanism enables battery lifespan of more than 10 years in most typical cases. For the system to achieve a ten-year battery lifespan at data transmission interval of 15 minutes, it is recommended that the system duty factor to be controlled in the order of 10-4, and that transmitted data frames to be limited within the length of 50 octets.

This paper proposes a generic enhanced beaconless synchronization mechanism for industrial standard IEEE 802.15.4g Smart Utility Networks (SUN) in multiple regulatory domains globally. IEEE 802.15.4g has specified different regulatory domains for SUN applications, each with a distinctive set of channelization and corresponding operating parameters such as center frequency, channel width and channel spacing. This has added new challenges not limited to, but particularly in beaconless synchronization mechanism supporting low energy consumption demands in conventional IEEE 802.15.4 low rate wireless personal area networks (WPANs). This paper first provides the updates in the SUN technical specification, identifies the challenges due to the effort of addressing multi-regional governing regulatory demands and then proposes a generic solution to tackle the problem. This simple but straightforward approach is preferable in industrial applications with strict energy efficiency requirement. The proposed beaconless synchronization mechanism has outlined two metrics with conflicting interest, namely required time to achieve synchronization and effective bandwidth for data communication. As a result, it is found that as the input radio resource increases, the effective communication bandwidth increases exponentially, while the required time for synchronization increases only linearly.

This paper presents the analysis on communication range and interference range of the IEEE 802.15.4g Smart Utility Networks (SUN). Firstly, error performance analysis corresponding to different propagation environments based on realistic measurement is conducted. Secondly, the effective communication range of SUN devices in these propagation channels are presented and discussed. Thirdly, in the presence of an interfering SUN device, the interference range between the victim and interfering devices are also studied. As a result, we have found that the achievable communication range of SUN devices in the GHz-order bands, the higher-UHF bands and the lower-UHF bands are 33m, 65m and 104m respectively. The critical interferer-to-victim distance below which, causing intolerable degradation to the victim receiver, is found to be 20m for typical urban and 35m for hilly rural environment. Finally, the analysis results are compared with the requirements based on the survey on utility metering device deployment conditions.

This paper presents the performance analysis of a realistic Smart Utility Network (SUN) system with low duty signaling design. The main focus of this paper is to evaluate the performance of the SUN system based on the specifications in an on-going industrial standardization activity, the IEEE 802.15.4g. For this purpose, a theoretical framework is constructed to model the transceiver with low duty signals over a realistic SUN channel based on actual measurements. The theoretical framework provides the models of multiple access interference (MAI) and inter-symbol interference (ISI). To align the analysis with actual industrial requirements, the developed framework is substituted with parameters from the IEEE 802.15.4g specifications. As a result, it is found that the low duty system (i.e. 0.1%) is capable of supporting up to 100 users in a single network. Additionally, by reducing the duty factor (e.g. from 1% to 0.1%), a 2-digit performance improvement (e.g. bit error rate (BER)=10-5to BER=10-7) can be achieved as compared to the requirement of IEEE 802.15.4g specifications (i.e. BER ≈ 10-5).

In this paper, we propose a spacial time slot scheduling algorithm for relay operation to improve the throughput performance of millimeter-wave wireless personal area network (mmWave WPAN) systems which employ directional antenna. The upcoming mmWave WPAN is designed for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. Based on the fact that the significant path loss of millimeter-wave environments provides good space isolation, we have proposed a coexistence mechanism by sharing time slots for relay with direct transmission to guarantee throughput for the above data-rate-greedy applications. This paper is an extension that addresses spacial time slot scheduling for relay operation taking the effect of directional antenna into consideration. We model the throughput maximization with scheduling as an integer optimization and solve it by transforming the problem to a max-weight matching problem of a bipartite graph. We propose a scheduling algorithm based on the Kuhn-Munkres algorithm which can be used to solve the max weight matching problem. Simulation results show that there is up to 25% throughput improvement achieved compared with random scheduling method.

In this paper, we proposes the pro-active beamforming (BF) protocol realized in media access control (MAC) layer following IEEE 802.15.3c criteria for millimeter-wave 60GHz wireless personal area networks (60GHz WPANs). The pro-active BF may be used when the piconet controller (PNC) is the source of data to one or multiple devices (DEVs). It allows multiple DEVs to train their own receiver antennas for optimal reception from the PNC with lower overhead. The pro-active BF realizes part of BF operation in association process, extending the system's BF capability. It also enables DEVs to associate with PNC with directional antenna pattern, thus enlarges the coverage area of a piconet. Since it may train multiple users simultaneously based on the proposed multi-resolution codebooks, it significantly decreases the BF set-up time and mitigates the high path loss of 60GHz WPAN systems. Simulation results show that the proposed pro-active BF further reduce more than 20% of the BF set-up time comparing with on-demand BF in the multiple DEVs scenarios. It is completely compliant to IEEE 802.15.3c, and adopted by IEEE 802.15.3c as an important compliment to the on-demand BF to realize Giga-bit-per-second (Gbps) communication in WPAN Systems.

In this paper, we propose a feasible beamforming (BF) scheme realized in media access control (MAC) layer following the guidelines of the IEEE 802.15.3c criteria for millimeterwave 60 GHz wireless personal area networks (60 GHz WPANs). The proposed BF targets to minimize the BF set-up time and mitigates the high path loss of 60 GHz WPAN systems. It is based on designed multi-resolution codebooks, which generate three kinds of patterns of different half power beam widths (HPBWs): quasi-omni pattern, sector and beam. These three kinds of patterns are employed in the three stages of the BF protocol, namely device-to-device (DEV-to-DEV) linking, sector-level searching and beam-level searching. All the three stages can be completed within one superframe, which minimizes the potential interference to other systems during BF set-up period. In this paper, we show some example codebooks and provide the details of BF procedure. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. The proposed BF is a complete design, it re-uses commands specified in IEEE 802.15.3c, completely compliant to the standard; It has thus been adopted by IEEE 802.15.3c as an optional functionality to realize Giga-bit-per-second (Gbps) communication in WPAN Systems.

In this paper, we propose a deflection routing scheme for throughput improvement to realize Gbps millimeter-wave wireless personal area network (mmWave WPAN) system. The upcoming mmWave WPAN system is designed to support transmission of uncompressed high definition TV (HDTV), high speed wireless downloading and docking etc. These data-rate-greedy applications require Gbps-order throughput which can be met by the capability of mmWave PHY. However, because of the ad-hoc formed network topology, it is easily happening that the line-of-sight (LOS) path may be blocked, while the non-line-of-sight (NLOS) path is not sufficient to guarantee Gbps throughput due to signal degradation. In this paper, we propose a cross-layer deflection routing (DR) scheme to solve the issue. When the direct path is blocked, the source device finds a relay to form deflection route, send the data to the destination through this alternative route. To avoid throughput degradation due to the consumption of extra time for relay operation, the deflection route is designed to share time slots with other transmissions on direct path. Two routing algorithms are proposed, namely random fit DR (RFDR) and best fit DR (BFDR). They search appropriate relay and time slots that provides sufficient isolation of co-channel interference (CCI) between the transmissions on direct path and deflection route. Computer simulations show that, in realistic 60 GHz environment, Gbps-order system throughput is achieved under blocking condition. There is up to 35% system throughput improvement compared to the conventional relay scheme.

Abstract-The paper proposes a codebook design to support beamforming mechanism in a wide band millimeter-wave 60 GHz wireless personal area networks (60 GHz WPANs) in a realistic millimeter-wave environment. The codebooks are designed symmetrically in order to mitigate the possible beam shift due to the large differences of wave lengthes at different sub-bands of a wide band communication system. In order to provide a high data rate and high performance with minimum power consumption in 60 GHz systems, the codebooks are generated with 90 degree phase resolution without amplitude adjustment. The codebooks are designed for different numbers of antenna elements, supporting a multitude of antenna configurations. The paper provides codebook design mechanism, some example codebooks and some analysis on antenna gain loss due to phase shift errors of phase shifters. Simulation results shows that: (1) To keep the gain loss at the intersections of any two patterns inside the codebook lower than ldB, the number of patterns inside the codebook shall be at least 2 times of the number of antenna elements used for pattern generation; (2) The designed codebooks are robust to phase shift errors: the gain loss is lower than ldB with only 10% outage probability when standard deviation of phase shift errors at phase shifters is 0.5 [28.6 degree]. The proposed codebooks are a feasible design, they are the key basis of the beamforming protocol in 60 GHz WPANs (IEEE 802.15.3c).

In this paper, we propose a deflection routing scheme that improves effective throughput (defined as the successfully transmitted bits over the duration between two available sequential time slots) of millimeter-wave wireless personal area network (mmWave WPAN) systems. The upcoming mmWave WPAN is based on dynamic time division multiple access (TDMA) and designed to guarantee Gbps-order transmission capability for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. The decode-and-forward (DF) type of relay offers a simple solution to the issues of mmWave WPAN systems, such as limited coverage range and unexpected blockage. However, due to the required extra time, DF relay on the other hand decreases the effective throughput, and may not be sufficient to satisfy the requirement of the above data-rate-greedy applications. Inspired by the fact that the significant path loss of a millimeter-wave environment can provide good space isolation, we propose a deflection routing scheme to improve the effective throughput by sharing time slots for direct path with relay path. Based on the sub-exhaustive search, a routing algorithm, named as best fit deflection routing (BFDR), has been developed to find the relay path with the least interference that maximizes the system throughput. To reduce the computational complexity of the BFDR, we have also developed a sub-optimal algorithm named as random fit deflection routing (RFDR). The RFDR algorithm finds the sub-optimized relay path, where the interference may not be the least but is sufficiently low to guarantee the concurrent transmissions. Computer simulations show that, in realistic 60 GHz environments, the effective system throughput can be improved up to 28% under grid topology and 35% under random topology. RFDR achieves almost the same order of throughput improvement with only 10% of the computational complexity of BFDR.

In order to realize high speed, long range, reliable transmission in millimeter-wave 60 GHz wireless personal area networks (60 GHz WPANs), we propose a beamforming (BF) protocol realized in media access control (MAC) layer on top of multiple physical layer (PHY) designs. The proposed BF protocol targets to minimize the BF set-up time and to mitigate the high path loss of 60 GHz WPAN systems. It consists of 3 stages, namely the device (DEV) to DEV linking, sector-level searching and beam-level searching. The division of the stages facilitates significant reduction in setup time as compared to BF protocols with exhaustive searching mechanisms. The proposed BF protocol employs discrete phase-shifters, which significantly simplifies the structure of DEVs as compared to the conventional BF with phase-and-amplitude adjustment, at the expense of a gain degradation of less than 1 dB. The proposed BF protocol is a complete design and PHY-independent, it is applicable to different antenna configurations. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. Furthermore, based on the codebooks with four phases per element, around 15.1 dB gain is achieved by using eight antenna elements at both transmitter and receiver, thereby enabling 1.6 Gbps-data-streaming over a range of three meters. Due to the flexibility in supporting multiple PHY layer designs, the proposed protocol has been adopted by the IEEE 802.15.3c as an optional functionality to realize Gbps communication systems.

Because of the unknown position of devices in ad-hoc network, it is difficult for the MAC to discover other devices by using directional antenna. This device discovery procedure needs extra signaling and costs considerable time, especially if there are a lot of devices. In this paper, on top of IEEE 802.15.3 MAC, we introduce the ultra superframe concept and propose an on-demand device discovery mechanism that significantly reduces signaling overhead, therefore speeds up the device discovery process and increases channel efficiency. Computer simulations show that, assuming up to 64 uniformly distributed devices, this MAC enhancement accomplishes device discovery procedure within 200 ms while keeping channel efficiency over 70% under 60 GHz channel environment.

This paper proposes an air interface for ultra high-speed millimeter wave (60 GHz) systems which have been under standardization process at IEEE 802.15.3c: the proposed channel plan permits ease of portable device implementation employing the major crystal oscillator used in CDMA cellar phones. The proposed transmission modes offer much greater scalability, covering from several tens Mbps to over 4 Gbps. The proposed preamble employs Golay codes, providing sufficient robustness against wireless environment being subject to the characteristics of millimeter wave with reduced hardware complexity. Common mode is a novel technique to communicate with single carrier (SC) and OFDM camps with multi rates up to around 1.5 Gbps. This technique gives the proposed systems easy expandability from SC to OFDM or other SCs and vice versa.

To achieve ultra high speed (several gigabits/s) transmission over 60 GHz system efficiently, this paper proposes Automatic Device Discover (ADD) and frame aggregation. The computer simulation results show good feasibility of handling directional antenna for ultra high speed transmission and highly efficient transmission up to 87 percent over 4.094 Gbps PHY-SAP with 8PSK modulation.

This paper reports about fundamental transmission performance for ROF-RVC based mobile CATV system. We have proposed the concept of multiple services transmission for RVC system, where several services signals are integrated on the same radio frequency band by exploiting the broadband transmission capability of ROF system, and thereby achieves simple configuration of antenna module. As an attractive application form of such multiple services transmission, we have proposed mobile CATV system that is provided by the introduction of conventional CATV signal to such multiple services transmission on the ROF-RVC system. The mobile CATV system could realize both of one-way broadcasting and two-way data transmission applications under mobile environments, inherently providing the intelligent security control of the conventional CATV system. Thus, in this paper, we evaluate the fundamental transmission performances of such mobile CATV system, and discuss about the feasibility of the system.

The paper proposes a system configuration for a private mobile network that is constructed by several mobile terminals and needs no base station infrastructure, as in ad hoc networks. This configuration uses an autonomous packet routing algorithm that provides an intelligent wireless network structure. Our packet routing algorithm senses the preferred paths for packet transmission, which are dynamically generated among terminals according to traffic conditions. We discuss the entire system configuration where such a packet routing algorithm is suitably supported by the lower layer protocols, such as control sequence configuration, transmission frame format, and transmission schemes. We assume the VHF band transmission that is widely used for private systems and assume the slotted-ALOHA based packet transmission protocol. One of the most significant goals of our system is to achieve IP based service transmission on limited bandwidth. Essential logical channel signal introduction and effective slot format are investigated.

This paper proposes a concept of multimedia lane and station that use an ROF transmission technique for ITS road-to-vehicle communication. In the developing stages of ITS, its service infrastructure is expected to be limited to a relatively small portion of the road system due to incompleteness of ITS structure. The proposed ITS service structures make the most of this environment, by providing intermittent and non-real-time services by using high-bit-rate package transmission. Moreover, we propose an adaptive resource management scheme for radio on fibre (ROF) cells in order to improve the capacity of the multimedia lane system. Computer simulation confirmed that the proposed scheme is very effective in reducing the blocking rate and improving system capacity of the multimedia lane system.

This paper proposes an autonomous relay access algorithm that provides an intelligent wireless network structure for an inter-vehicle communication system. The proposed algorithm introduces a special classification among mobile terminals and assigns terminals to one of several terminal groups, which are adaptively and autonomously constructed according to traffic conditions. The proposed algorithm uses the terminal groups to conduct relay access transmission among terminals, and achieves a higher rate of successful inter-terminal transmission. Computer simulation confirms that the proposed algorithm can achieve a lower blocking probability than an algorithm without a relay access scheme.

The maximum transmission rate in public mobile data communication services such as PHS (Personal Handyphone System) is currently limited to 64 kbit/s in Japan, but a higher transmission rate will be needed in order to meet the requirements of mobile multimedia applications. We have therefore developed 384 kbit/s-PHS experimental system that uses the 64 kbit/s PHS data communication protocol (PIAFS) and the PPP multilink protocol. This paper presents the implementation and performance evaluation of the 384 kbit/s-PHS experimental system. The throughput performance of the system is evaluated using FTP under various radio propagation environments.