Showing papers in "IEICE Transactions on Communications in 2014"

Propagation channel models for next-generation wireless communications systems

Abstract: SUMMARY As new systems and applications are introduced for nextgeneration wireless systems, the propagation channels in which they operate need to be characterized. This paper discusses propagation channels for four types of next-generation systems: (i) distributed Multiple-Input Multiple-Output (MIMO) and Cooperative MultiPoint (CoMP) systems, which require the characterization of correlation between channels from a mobile station to different base stations or access points; (ii) device-todevice communications, where propagation channels are characterized by strong mobility at both link ends (e.g., in vehicle-to-vehicle communications), and/or significant impact of moving shadowing objects; (iii) fulldimensional MIMO, where antenna arrays extend in both the horizontal and vertical dimension, so that azimuthal and elevation dispersion characteristics of the channel become relevant, and (iv) millimeter wave Wireless Local Area Network (WLAN) and cellular communication systems, where the high carrier frequency leads to a change (compared to microwave communications) concerning which propagation processes are dominant. For each of these areas, we give an overview of measurements and models for key channel properties. A discussion of open issues and possible future

Image Sensor Based Visible Light Communication and Its Application to Pose, Position, and Range Estimations

Abstract: SUMMARY This study introduces an image sensor based visible light communication (VLC) and its application to pose, position, and range estimations. There are two types of visible-light receiver: a photodiode and an image sensor. A photodiode is usually used as a reception device of VLC, and an image sensor consisting of a large number of pixels can also be used as a VLC reception device. A photodiode detects the signal intensity of incoming light, while an image sensor not only detects the incoming signal intensity but also an accurate angle of arrival of light emitted from a visible light transmitter such as a white LED light. After angles of arrival of light are detected by an image sensor, positioning and data reception can be performed. The ability of an image sensor to detect an accurate angle of arrival will provide attractive applications of VLC such as pose, position calculation, and range estimation. Furthermore, because the image sensor has the ability to spatially separate sources, outdoor positioning even with strong

On achieving high survivability in virtualized data centers

Abstract: ©2013 IEICE Rabbani, M G, Zhani, M F, & Boutaba, R (2014) On Achieving High Survivability in Virtualized Data Centers IEICE Transactions on Communications, E97B(1), 10–18 https://doiorg/101587/transcomE97B10

A Survey on OpenFlow Technologies

Abstract: SUMMARY The paper presents a survey on OpenFlow related technologies that have been proposed as a means for researchers, network service creators, and others to easily design, test, and deploy their innovative ideas in experimental or production networks to accelerate research activities on network technologies. Rather than having programmability within each network node, separated OpenFlow controllers provide network control through pluggable software modules; thus, it is easy to develop new network control functions in executable form and test them in production networks. The emergence of OpenFlow has started various research activities. The paper surveys these activities and their results.

White Space Communication Systems: An Overview of Regulation, Standardization and Trial

Abstract: This paper summarizes the current status of regulations, standardization efforts and trials around the world regarding white space (WS) communications, especially television band WS (TVWS). After defining WS communication systems configurations and function and the categories of white space database, the TVWS regulations in United States, United Kingdom, and Japan are summarized. Then regarding status of standardization for TVWS devices, IEEE 802 and IEEE 1900 standards are summarized. Finally ongoing pilot projects and trials of WS communications in the world are summarized, and trends and future direction of research on WS communication systems are summarized. key words: white space, IEEE, cognitive radio, database, standardization

Spectrum Usage in Cognitive Radio Networks: From Field Measurements to Empirical Models

Abstract: Cognitive Radio (CR) is aimed at increasing the e ffi ciency of spectrum utilization by allowing unlicensed users to access, in an op- portunistic and non-interfering manner, some licensed bands temporarily and / or spatially unoccupied by the licensed users. The analysis of CR sys- tems usually requires the spectral activity of the licensed system to be rep- resented and characterized in a simple and tractable, yet accurate manner, which is accomplished by means of spectrum models. In order to guarantee the realism and accuracy of such models, the use of empirical spectrum oc- cupancy data is essential. In this context, this paper explains the complete process of spectrum modeling, from the realization of field measurements to the obtainment of the final validated model, and highlights the main rel- evant aspects to be taken into account when developing spectrum usage models for their application in the context of the CR technology

Anatomy of a Digital Coherent Receiver

Abstract: Digital coherent receivers have gained significant attention in the last decade. The reason for this is that coherent detection, along with digital signal processing (DSP) allows for substantial increase of the channel capacity by employing advanced detection techniques. In this paper, we first review coherent detection technique employed in the receiver as well as the required receiver structure. Subsequently, we describe the core part of the receiver — DSP algorithms — that are used for data processing. We cover all basic elements of a conventional coherent receiver DSP chain: deskew, orthonormaliation, chromatic dispersion compensation/nonlinear compensation, resampling and timing recovery, polarization demultiplexing and equalization, frequency and phase recovery, digital demodulation. We also describe novel subsystems of a digital coherent receiver: modulation format recognition and impairment mitigation via expectation maximization, which may gain popularity with increasing importance of autonomous networks. key words: digital coherent receiver, coherent detection

Network Management Challenges in Software-Defined Networks

Abstract: Software-Defined Networking currently appears to be a major evolution towards network programmability. In this paper, we first analyze the network management capabilities of OpenFlow in order to identify the main challenges that are raised for SDN management. We address current deficiencies of SDN management and suggest solutions that incur research directions to be carried out for the management of enhanced SDN.

Targeting Morbidity in Unreached Communities Using Portable Health Clinic System

Abstract: This study looks at how an e-Health System can reduce morbidity (poor health) in unreached communities. The e-Health system combines affordable sensors and Body Area Networking technology with mobile health concepts and is called a Portable Health Clinic. The health clinic is portable because all the medical devices fit inside a briefcase and are carried to unreached communities by a healthcare assistants. Patient morbidity is diagnosed using software stratification algorithm and categorized according to triage color-coding scheme within the briefcase. Morbid patients are connected to remote doctor in a telemedicine call center using the mobile network coverage. Electronic Health Records (EHR) are used for the medical consultancy and e-Prescription is generated. The effectiveness of the portable health clinic system to target morbidity was tested on 8690 patients in rural and urban areas of Bangladesh during September 2012 to January 2013. There were two phases to the experiment: the first phase identified the intensity of morbidity and the second phase reexamined the morbid patients, two months later. The experiment results show a decrease in patients to identify as morbid among those who participated in telemedicine process. key words: Portable Health Clinic, e-Health, Electronic Health Records (EHR), Telemedicine, e-Prescription, Clinical Decision Support System (CDSS)

Power Line Communications: Understanding the Channel for Physical Layer Evolution Based on Filter Bank Modulation

Abstract: This paper provides an overview of power line communication (PLC) applications, challenges and possible evolution. Emphasis is put on two relevant aspects: a) channel characterization and modeling, b) filter bank modulation for spectral efficient transmission. The main characteristics of both the indoor channel (in-home, in-ship, in-car) and the outdoor low voltage and medium voltage channels are reported and compared. A simple approach to statistically model the channel frequency response (CFR) is described and it is based on the generation of a vector of correlated random variables. To overcome the channel distortions, it is shown that filter bank modulation can provide robust performance. In particular, it is shown that the sub-channel spectral containment of filtered multitone modulation (FMT) can provide high notching capability and spectral efficiency. Reduced complexity can be obtained with a cyclic filter bank modulation approach that we refer to as cyclic block FMT modulation (CB-FMT) which still provides higher spectral flexibility/efficiency than OFDM. key words: power line communications, power line channel, channel model, filter bank modulation

Analysis of TV White Space Availability in Japan

Abstract: This paper analyzes TV white space (TVWS) availability in Japan by estimating the amount and distribution of TVWSs across Japan and comparing them with those across the USA. While TVWS regulation is still under discussion in Japan, the expected availability is likely to be more encouraging than that in the USA. Japanese metropolitan areas tend to have more available channels than those in the USA. Including the Tokyo metropolitan area which is the most populated area in Japan, 84.3% of areas (66.7% of the population) may expect greater than 100-MHz TVWSs. The Tokyo metropolitan area is also relatively unaffected by restricted use of the adjacent channel or increase in separation distance.

SPICE Behavioral Modeling of RF Current Injection in Wire Bundles

Abstract: In this work, a measurement-based procedure aimed at deriving a behavioral model of Bulk Current Injection (BCI) probes clamped onto multi-wire cable bundles is proposed. The procedure utilizes the measurement data obtained by mounting the probe onto the calibration jig for model-parameters extraction, and 2D electromagnetic simulations to adapt such parameters to the specific characteristics of the cable bundle under analysis. Outcome of the analysis is a behavioral model which can be easily implemented into the SPICE environment. Without loss of generality, the proposed model is here used to predict the radio-frequency noise stressing the terminal units of a two-wire harness. Model accuracy in predicting the common and differential mode voltages induced by BCI at the line terminals is assessed by EM modeling and simulation of the involved injection setup by the commercial software CST Microwave Studio. key words: Bulk Current Injection (BCI), conducted immunity, behavioral modeling, SPICE simulation

DOA Estimation for Multi-Band Signal Sources Using Compressed Sensing Techniques with Khatri-Rao Processing

Abstract: SUMMARY Much attention has recently been paid to direction of arrival (DOA) estimation using compressed sensing (CS) techniques, which are sparse signal reconstruction methods. In our previous study, we developed a method for estimating the DOAs of multi-band signals that uses CS processing and that is based on the assumption that incident signals have the same complex amplitudes in all the bands. That method has a higher probability of correct estimation than a single-band DOA estimation method using CS. In this paper, we propose novel DOA estimation methods for multi-band signals with frequency characteristics using the Khatri-Rao product. First, we formulate a method that can estimate DOAs of multiband signals whose phases alone have frequency dependence. Second, we extend the scheme in such a way that we can estimate DOAs of multi-band signals whose amplitudes and phases both depend on frequency. Finally, we evaluate the performance of the proposed methods through computer simulations and reveal the improvement in estimation performance.

Broadband Access in Complex Environments: LTE on Railway

Abstract: This paper assesses the main challenges associated with the propagation and channel modeling of broadband radio systems in a complex environment of high speed and metropolitan railways. These challenges comprise practical simulation, modeling interferences, radio planning, test trials and performance evaluation in different railway scenarios using Long Term Evolution (LTE) as test case. This approach requires several steps; the first is the use of a radio propagation simulator based on ray-tracing techniques to accurately predict propagation. Besides the radio propagation simulator, a complete test bed has been constructed to assess LTE performance, channel propagation conditions and interference with other systems in real-world environments by means of standard-compliant LTE transmissions. Such measurement results allowed us to evaluate the propagation and performance of broadband signals and to test the suitability of LTE radio technology for complex railway scenarios.

Quantification and Verification of Whole-Body-Average SARs in Small Animals Exposed to Electromagnetic Fields inside Reverberation Chamber

Abstract: This paper aims to achieve a high-quality exposure level quantification of whole-body average-specific absorption rates (WBASARs) for small animals in a medium-size reverberation chamber (RC). A two-step method, which incorporates the finite-difference time-domain (FDTD) numerical solutions with electric field measurements in an RCtype exposure system, has been used as an evaluation method to determine the whole-body exposure level in small animals. However, there is little data that quantitatively demonstrate the validity and accuracy of this method in an RC up to now. In order to clarify the validity of the twostep method, we compare the physical quantities in terms of electric field strength and WBA-SARs by using a direct numerical assessment method known as the method of moments (MoM) with ten homogenous gel phantoms placed in an RC with 2 GHz exposure. The comparison results show that the relative errors between the two-step method and the MoM approach are approximately below 10%, which reveals the validity and usefulness of the two-step technique. Finally, we perform a dosimetric analysis of the WBA-SARs for anatomical mouse models with the two-step method and determine the input power related to our developed RC-exposure system to achieve a target exposure level in small animals. key words: specific absorption rate (SAR), reverberation-chamber (RC), exposure system, finite-difference time-domain (FDTD) method, method of moments (MoM)

A Spatial Fading Emulator for Evaluation of MIMO Antennas in a Cluster Environment

Abstract: This paper presents a spatial fading emulator for evaluating handset MIMO antennas in a cluster environment. The proposed emulator is based on Clarke’s model and has the ability to control RF signals directly in spatial domain to generate an accurate radio propagation channel model, which includes both uniform and non-uniform angular power spectra (APS) in the horizontal plane. Characteristics of a propagation channel such as fading correlations, eigenvalues and MIMO channel capacities of handset antennas located in the vicinity of the emulator’s ring can be evaluated. The measured results show that the fading emulator with 31 antenna probes is sufficient to evaluate fading correlation and MIMO channel capacity of handset antenna in the case of a narrow APS with the standard deviation of more than 20 degrees. key words: fading emulator, cluster, angular power spectrum, OTA, handset antenna, MIMO, channel capacity

The Role of Photonics in Future Computing and Data Centers

Abstract: This paper covers new architectures, technologies, and performance benchmarking together with prospects for high productivity and high performance computing enabled by photonics. The exponential and sustained increases in computing and data center needs are driving the demands for exascale computing in the future. Power-efficient and parallel computing with balanced system design is essential for reaching that goal as should support ∼billion total concurrencies and ∼billion core interconnections with ∼exabyte/second bisection bandwidth. Photonic interconnects offer a disruptive technology solution that fundamentally changes the computing architectural design considerations. Optics provide ultrahigh throughput, massive parallelism, minimal access latencies, and low power dissipation that remains independent of capacity and distance. In addition to the energy efficiency and many of the fundamental physical problems, optics will bring high productivity computing where programmers can ignore locality between billions of processors and memory where data resides. Repeaterless interconnection links across the entire computing system and all-to-all massively parallel interconnection switch will significantly transform not only the hardware aspects of computing but the way people program and harness the computing capability. This impacts programmability and productivity of computing. Benchmarking and optimization of the configuration of the computing system is very important. Practical and scalable deployment of photonic interconnected computing systems are likely to be aided by emergence of athermal silicon photonics and hybrid integration technologies. key words: computing, data centers, optical interconnects, silicon photonics

S-Parameter Method and Its Application for Antenna Measurements

Abstract: SUMMARY This paper focuses on the S-parameter method that is a basic method for measuring the input impedance of balanced-fed antennas. The basic concept of the method is summarized using the two-port network, and it is shown that the method can be enhanced to the unbalanced antennas using a formulation based on incident and reflected waves. The compensation method that eliminates the influence of a measurement jig and the application of the S-parameter method for the measurement of a radiation pattern with reduced unbalanced currents are explained. Further, application of the method for measuring the reflection and coupling coefficients of multiple antennas is introduced. The measured results of the input impedance of a dipole antenna, radiation patterns of a helical antenna on a small housing, and S-parameters of multiple antennas on a small housing are examined, and the measured results obtained with the S-parameter method are verified.

Channel Prediction Techniques for a Multi-User MIMO System in Time-Varying Environments

Abstract: Although multi-user multiple-input multiple-output (MIMO) systems provide high data rate transmission, they may suffer from interference. Block diagonalization and eigenbeam-space division multiplexing (E-SDM) can suppress interference. The transmitter needs to determine beamforming weights from channel state information (CSI) to use these techniques. However, MIMO channels change in time-varying environments during the time intervals between when transmission parameters are determined and actual MIMO transmission occurs. The outdated CSI causes interference and seriously degrades the quality of transmission. Channel prediction schemes have been developed to mitigate the effects of outdated CSI. We evaluated the accuracy of prediction of autoregressive (AR)-model-based prediction and Lagrange extrapolation in the presence of channel estimation error. We found that Lagrange extrapolation was easy to implement and that it provided performance comparable to that obtained with the AR-model-based technique. key words: channel prediction, multi-user MIMO system, block diagonalization, eigenbeam-space division multiplexing, time-varying environments, AR model, lagrange extrapolation