Web services are a unified framework that enables the exchange of information among distributed applications using existing World Wide Web communications technologies. Web services offer the benefit of simplifying the sharing of information among different applications that are operated via remote terminals. However, when multiple services exist that provide the same functionality, a mechanism for automatically selecting the most appropriate service from those on offer is necessary. Unfortunately, the majority of automatic selection mechanisms are designed to use a fixed set of indicators as the selection criteria and are therefore unable to adapt to the diverse demands of users. In this paper we propose a new mechanism for automatically performing such service selection that integrates a wide range of different indicators. Specifically, we assign attributes to each of the services that can be used as evaluation criteria; we then gather these attributes at the user's client. We can compute a rating for each service on the basis of the attributes that have been collected and select the service that is assigned the highest rating. In this paper we introduce the concept of an attribute database (an attribute repository ) and define a new communications protocol to enable the registration and searching of attributes in order to deal with variation in the attributes used by different services. In addition, using a simulation of a distributed applications environment, we perform evaluations and demonstrate that the proposed selection mechanism is able to reduce execution times as compared to a random selection mechanism. We also implement the proposed mechanism in an experimental environment and show that it can be used in practice for automatically selecting services on the basis of attribute values. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(8): 40–49, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecja.20284 Copyright © 2004 Wiley Periodicals, Inc.Copyright © 2007 Wiley Periodicals, Inc.
Recently, on-board distributed power systems consisting of bus converter and POL have usually been used for IT infrastructure equipment. However, even if each converter has stable operation, the bus voltage may oscillate and the system may be unstable, depending on the bus converter design; this has been a serious problem in recent years. Solution of the issue is highly desirable, and in order to improve the system stability various techniques have been discussed. This paper investigates the improvement of the system stability by the control method. The availability of full-regulated bus converter is especially examined. It is determined that the full-regulated method is the optimal control method for the bus converter because a full-regulated bus converter can reduce bus voltage oscillation and adjust to input voltage variations flexibly by regulation. A stability design process is proposed for an on-board distributed power system using a full-regulated bus converter. (C) 2007 Wiley Periodicals, Inc.
A system for lightning location from single station observations has been developed for localizing lightning (distance and direction) at rather short distances (several hundred kilometers). In this system, a vertical component of the electric field and two horizontal components of the magnetic field of the VLF wave of the sferics are observed. The sferics are usually observed as a pulse train. The first pulse is used for estimation of the direction. The second and subsequent pulses are multiple reflections between the ionosphere and the ground. The differences in arrival time of these reflected waves are determined by the propagation distance between the ground and the ionosphere. The reflection altitude of the ionosphere and the horizontal distance to the lightning location are estimated from the arrival time difference of more than two pulses. In this research, the electromagnetic pulses radiated from the lightning are first analyzed by the full wave method, considering the ionosphere, free space, and the ground, in order to evaluate the location estimation method. The lightning location is estimated by calculating the space discharge sferics waveform at the observation point. Observations were also carried out with the lightning location system for estimation of lightning locations. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(1): 25– 34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20329
Previously, the authors studied biological tissue equivalent phantoms able to simulate the electrical constants of the human body in the 3- to 6-GHz band in a single composition ratio. Therefore, in this paper, we examined how to study the antenna characteristics using the phantom when extended to a bandwidth including 900 MHz to 3 GHz and 6 to 10 GHz and performed a quantitative study focusing on the electrical constants of the phantom. The result clearly showed hardly any effect of divergence of the phantom's electrical constants from the target values on the antenna input impedance, radiation efficiency, and radiation directivity. Therefore, in the entire ultra-wideband (UWB), this phantom can be accurately evaluated through antenna characteristic measurements and is clearly effective. Furthermore, differences due to the divergence of the phantom's electrical constants from the target values in the entire UWB bandwidth (3 to 10 GHz) are within ±3% for the average local specific absorption rate (SAR) inside the phantom caused by the electromagnetic wave energy radiated from the antenna. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(5): 48–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20300
This study examines the practicality of M-quadrature amplitude modulation (M-QAM) where the number of signal points M is not a power of two. A practical problem is the complexity of the configuration because one symbol in an M-QAM signal does not correspond to an integer number of bits, and the symbol error does not simply convert to the bit error. Therefore, from the perspective of simplifying the configuration and minimizing bit error rate (BER) properties, multidimensional encoding (binary/M-ary conversion) for converting a binary sequence to correlated symbols is proposed and the theoretical formulas of the symbol error rate (SER) and the bit error rate (BER) are clarified. SER properties of 40QAM, 44QAM, 48QAM, 56QAM, and 60QAM fall between 32QAM and 64QAM. The configuration of a QAM scheme where the number of signal points becomes 3 × 2p−1 where p is an integer greater than or equal to 3 is shown, as are theoretical values for the SER properties of 12QAM and 24QAM in particular. Also shown are the theoretical values of the BER properties with and without differential encoding; these are verified with a computer simulation. A discussion based on these results concerns the effectiveness of M-QAM in the sense of expanding decision branches for adaptive modulation. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(2): 46–57, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20269
This paper discusses the modeling and broadband design of an indoor infrared wireless communication channel consisting of a nondirected diffusion system. The property of the nondirected diffuse link is analyzed by the ray tracing technique and the modified Monte Carlo method. The physical parameters are directly related to the impulse response of the link and are modeled by a gamma probability density function. The impulse response model and a simulation indicate that it is effective for the broadband link to narrow the radiation angle of the optical source and to expand the receiver field of view to match the ceiling area of the room. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(6): 9–19, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecja.20352
As broadband Internet access channels such as ADSL and FTTH become more widely used, network compression by power users becomes a problem. In order to deal with this problem, bandwidth control that assigns bandwidth among users in a fair manner is needed. In this paper, we studied the DRR method, which is known to allow fair bandwidth allocation and to be highly realizable. A new method that resolves the problem of realizability at high speeds in the range of gigabits and tens of gigabits typical of the DRR method is proposed. By this method, it is possible to realize fair allocation of bandwidth even if the channel speed is increased to several gigabits or several tens of gigabits. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(8): 50–56, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecja.20266 Copyright © 2004 Wiley Periodicals, Inc.Copyright © 2007 Wiley Periodicals, Inc.
In this paper, a new SDMA (Space Division Multiple Access) configuration is proposed in which the number of multitudes of SDMA can be increased by using dual polarization antennas at both the smart antenna base stations and the mobile terminals. In the proposed configuration, the smart antennas at the base stations constantly monitor the mutual correlations between the mobile terminals at the time of reception. Then, the polarization (vertical or horizontal) to be transmitted by each mobile terminal is determined in such a way that the mutual correlation between the mobile terminals connected at the same time is minimized. The mobile terminal used in the proposed system has a configuration in which the antennas with vertical and horizontal polarizations can be switched for transmission. Transmission is carried out with the polarization specified by the base station. The proposed configuration is expected not only to improve spatial division capability of SDMA by the smart antenna base station with vertical and horizontal polarizations but also to compensate the deterioration of the transmission quality along with the increase of multiplicity of SDMA by means of the switching configuration of the transmission polarization of the mobile terminal while the interference between the mobile terminals is taken into account. The proposed configuration can be applied to the uplinks in the TDD or FDD channels. By means of the numerical simulation, the basic characteristics of the proposed configuration are clarified in the case where the cross polarization discrimination (XPD) and the number of mobile terminals vary. In this way, it is demonstrated that the mobile terminal discrimination capability is improved over the conventional SDMA with the vertical polarization and the system is useful for increased multiplicity of SDMA. Further, the propagation characteristics (amplitude and phase) of the vertical and horizontal polarizations are obtained when the base station antenna and the mobile terminal antenna are placed on a steel tower and on a vehicle, respectively. The characteristics of the proposed configuration are presented where several mobile terminals exist. Usefulness of the proposed configuration in an actual environment for increased multiplicity of SDMA is presented. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(2): 33–45, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecja.20287
When communication signals are transmitted at high speed on balanced cable (UTP cable), signals may leak from the cable and affect the reception of wireless signals. To evaluate this effect, the radiated electromagnetic field from the balanced cable is measured by using a 4-port network at 300 MHz or less. Although this method has the advantage that it can be used to analyze line constants, it is not clear whether it can be applied in an analysis at a frequency greater than 300 MHz. In this paper, the authors investigate the applicability of this method at frequencies up to 1 GHz. As a result, they discuss a method of Using a 4-port network to represent telecommunication equipment for increasing precision and a balun for simulating this equipment and also discuss the dependency of this method on the number of subdivisions of one twist of the cable. From the results of actually evaluating the radiated electromagnetic field by using a 3-meter length of UTP cable, it was apparent that this analysis method using a 4-port network was effective for obtaining the trends exhibited by the characteristics of the radiated electromagnetic field at up to 1GHz by obtaining the 4-port network parameters of the terminal equipment parts and dividing one twist of the cable into 80 parts. (c) 2007 Wiley Periodicals, Inc.
GMPLS (Generalized Multi-Protocol Label Switching) is considered promising as the basic technology for forming the next-generation ISP (Internet Service Provider) backbone network. In an IP backbone network based on GMPLS, the optical layer and the packet layer are vertically integrated and operate in close collaboration. It is due to this collaborative operation of multiple layers that integrated network control such as path setting in the optical layer according to the IP traffic in the packet layer and fast recovery from faults is realized. However, there is a danger, due to the similarity of functions in the two layers or to mismatch of the parameters, that collaborative operation between layers may affect the stability of IP routing in the packet layer. This situation is mostly due to the fact that the time granularity in the change of path state in the optical layer is finer than that of the IP routing protocol processing in the packet layer. This paper discusses route stability in the packet layer during collaborative operation of layers. The situation is analyzed by simulation and a method of improving stability is proposed. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(11): 71–80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20332
This paper considers environment-adaptive content delivery in which an intermediary modifies the content between the content provider and the content user, and proposes a system in which the provider can securely control content modification by the intermediary in accordance with usage rules defined in the content. In order to have the intermediary follow the usage rules strictly, it is indispensable to provide a content protection technique in which tampering with content or usage rules by a third party is prevented while permitting content modification by intermediaries approved by the provider within the scope of the usage rules. The authors consider the hash-tree signature method in which data deletion by the intermediary is permitted, and propose a signature system with a place holder extension permitting data addition. A highly efficient realization of the proposed signature system based on the hash-sign-switch (HSS) method is presented. The effectiveness of the approach is shown by a quantitative evaluation using the implemented system. (c) 2007 Wiley Periodicals, Inc.
The multifractal nature of traffic volume is known to have significant influence to queuing behavior in network nodes. In the Internet, TCP traffic, which is the major traffic flowing through the Internet has been reported to have multifractal nature. To control the effect of the multifractal nature, the origin of the multifractal nature in TCP traffic needs to be explained. However, it is still unclear what part of TCP control mostly affects the multifractal nature. In this paper, we focus on TCP congestion control from the viewpoint of multifractal nature of generated traffic. We investigate “what component of TCP congestion control mechanism affects multifractal nature of generated traffic?” Our simulation results show that Retransmission Time-Out mechanism plays an important role for multifractal nature of TCP traffic. In addition, our results show that avoiding occurrence of Retransmission Time Out is the best approach to improve TCP performance, i.e., throughput degradation, LRD, and multifractal nature. Random Early Detection (RED), based on the fact that Retransmission Time Out should be avoided, to improve TCP performance are also reasonable from the viewpoint of LRD and multifractal nature. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(1): 68–76, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20277
A distributed array radar is a radar configuration to form a high-gain receive beam suited to an equivalent large-aperture antenna by arbitrarily distributing and positioning multiple small antennas and coherently synthesizing their received signals. When the placement intervals of the small antennas are sufficiently longer than the wavelength, the conventional beamformer generates many grating lobes and, therefore, ambiguity in the estimated direction of the target. This paper shows that robust Capon beamformer using the norm constraints is effective as a beamforming method that suppresses these grating lobes when using distributed array radar in search radar and prevents a decrease of the search efficiency caused by the reduction in beam width. In addition, an improvement based on diagonal loading is proposed for this algorithm in order to improve the search efficiency. Finally, we consider the parameter optimization and demonstrate the performance using numerical simulation examples. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(5): 33–47, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20325
In recent years the amount of software running on mobile phones has increased dramatically due to the start of data network connection services for mobile phones. As a result it has sometimes become necessary to repair defects in such products after they have been shipped to market. In this context, services have been launched that enable software to be updated after a terminal has been sold. The time taken for software to be updated is made up of the time taken to transmit the data to the handset via a mobile network or from a PC (which in turn depends on the amount of data being transmitted) and the time taken to overwrite the data on flash memory. A standard method for making the amount of data that needs to be transmitted to the handset small, is to only send delta data corresponding to those parts of the new version of the software that differ from the old version; it is generally necessary to make this delta as small as possible. Following a description of existing techniques for extracting deltas, in this paper we make multiple proposals regarding delta extraction schemes that are designed with the structure of mobile phone software particularly in mind with a view to making the delta data transmitted to the handset when updating software as small as possible; we then describe results of evaluations with actual mobile phones immediately prior to shipping. Both of the schemes that we propose are shown to allow a reduction of approximately 30 percent in the size of the delta when compared with standard delta representation mechanisms. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(7): 26–37, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecja.20348
This paper considers the sensor network based on IEEE 802.15.4, and proposes a method in which a probabilistic model of wireless propagation characteristics in a real environment is constructed, and the node position is estimated by maximum-likelihood estimation using the model. The performance of the proposed method is evaluated by simulation and position estimation experiments based on the probabilistic model obtained from the actual indoor measurement. It is shown that the proposed method is useful for indoor personnel location management. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 62–72, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20359
This paper investigates an intervehicle communication method as a safe driving support system for intersection collision avoidance warnings. In this kind of system, realization of highly reliable communications in the physical layer is an absolute requirement. As a result, we propose a new MIMO-STBC (Space-Time Block Coding) method based on intersection propagation channel characteristics. MIMO transmission characteristics are determined by the propagation channel characteristics. First, we use a ray-tracing method simulation to clarify the propagation channel conditions, and then model the intersection propagation channel. We use the characteristics of this propagation channel to propose a MIMO-STBC method that utilizes decision feedback channel estimation, and verify the effectiveness of the proposed method in computer simulations. (c) 2007 Wiley Periodicals, Inc.
In this paper, we improve On-Demand Multicast Routing Protocol (ODMRP), which is a multicast routing protocol for Mobile Ad hoc Network (MANET), and propose a new protocol decreasing the number of data forwarding without deteriorating communication reliability. The proposed protocol avoids unnecessary data forwarding by distinguishing each multicast source at every Forwarding Group (FG) Node used in ODMRP. Moreover, the proposed protocol utilizes Support Group (SG), which also distinguishes each multicast source, in order to retain substitute routes without any redundant data forwarding. Therefore, the proposed protocol can avoid deteriorating communication reliability. We evaluate the performance of ODMRP, ODMRP with SG, and the proposed protocol, and we show that the proposed protocol can decrease the number of data forwarding compared with the conventional protocols. We also show that the proposed protocol can restrain the deterioration of packet delivery ratio within allowable range except the case where the number of multicast sources and receivers is extremely large. Furthermore, we show that the proposed protocol can mitigate the deterioration of packet delivery ratio caused by traffic congestion in the case where the number of multicast sources is large. (c) 2007 Wiley Periodicals, Inc.
Because of the rapid development of mobile communications and ITS (intelligent transport systems), the electromagnetic wave propagation environment is becoming complex, and there is an increasing demand for techniques to estimate the direction of arrival with high resolution and to reduce the effect of interference waves. Among these, Cyclic MUSIC and Cyclic ESPRIT, in which the direction of the arriving wave can be estimated selectively by utilizing the periodic stationary property of the arriving wave, are attracting attention. The authors are proposing Cyclic ESPRIT based on the noise subspace (NS Cyclic ESPRIT) in order to remedy the performance degradation produced by the fact that the correlation matrix of the array input used in Cyclic ESPRIT is not a Hermitian matrix. However, when the number of snapshots is finite in the estimation of arrival direction by Cyclic MUSIC or Cyclic ESPRIT, the interference wave component remaining in the correlation matrix has an adverse effect on the accuracy of direction-of-arrival estimation. Consequently, adaptive spatial smoothing processing and generalized eigenvalue decomposition are introduced into NS Cyclic ESPRIT in this study, aiming at reduction of the remaining interference component and at performance improvement in direction-of-arrival estimation. A computer simulation verifies that the performance in direction-of-arrival estimation in NS Cyclic ESPRIT is improved. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(11): 95–104, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20304
FMCW (frequency-modulated continuous wave) radar is a radar system which can achieve high resolution by relatively low signal processing load. The authors have reported on clutter suppression by FMICW (FM interrupted CW) radar, where the transinission/reception of FMCW radar in pulse waveform is switched in order to assure transmission/reception isolation and to suppress undesired waves from short distances. This paper proposes the FM staggered PRI system, in which the pulse repetition interval (PRI) is randomized for each pulse in order to suppress the interference when FMICW radars are congested within the search distance. The target-signal in the FM staggered PRI system is formulated. Conditions such as the average PRI and the possible range of staggering are derived from requirements such as the maximum search distance. The output S/I is statistically evaluated by computer simulation, with the average PRI, the pulse width, the number of interference waves, and the input S/I (signal-to-interference ratio) as variables. The effectiveness of the FM staggered PRI system is demonstrated. (c) 2007 Wiley Periodicals, Inc.
The transmission characteristics of a fiber Fabry-Perot etalon formed by mirror-finishing both ends of an optical fiber are dependent on the external stress applied. A theoretical study and an experimental confirmation of a fiber Fabry-Perot etalon with a ferrule diameter of 2.5 mm and a resonator length of 4 mm are carried out to investigate variations of the transmission frequencies as a function of the stress. It is confirmed that there is a proportional relationship of 1.5 GHz/N and -0.1 GHz/N in the transmission frequency variations versus the stress in the axial and radial directions. Arbitrary transmission frequencies within FSR can be obtained by adjustment of the stress at values less than 17 N, so that the fiber Fabry-Perot etalon can be used as a tunable optical frequency filter. (C) 2007 Wiley Periodicals, Inc.
