bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on performance improvement of CRV collision detection method
Authors: Hakamata Yoshiro , Oguchi Kimio 
Published: July 2007

AbstractThis paper considers the CRV collision detection method which detects the signal collision in the star configured optical local area network by detecting CRV, using the dipulse code and the partial response (1, ‐1) circuit. The result of theoretical investigation of the performance improvement also is presented.First, the reflection‐type partial response (1, ‐1) circuit using a delay line is considered, and the transmission characteristics are formulated for the case where the delay line has a loss. Based on the result of formulation, a method to prevent the increase of the CRV rate due to the loss of the delay line without signal collision is considered.The methods which are shown to be effective are the method to set the driving source impedance for the delay line at approximately 1.08 times the characteristic impedance of the delay line, and the method to employ a first‐order high‐pass filter with the 3‐dB cut‐off frequency at approximately 0.046 times the bit‐rate frequency fo.Then, as a method to increase the CRV rate due to the signal collision, a method is considered in which two CRV detectors are used with the decision levels at Δ‐ and Δ+, respectively. It is shown to be effective to lower the decision level as far as possible.Next, the use of two CRV detectors with the phase of the driving clock signal differing by π is considered, and it is shown that the end of signal collision can be detected in the CRV collision detection method by forming the logical sum of the two outputs.
Clamping circuit design for Multi‐Gbit/s baseband transmission systems
Authors: Hakamata Yoshiro , Takemoto Kenji 
Published: July 2007

AbstractThe transmission rate of several Gbit/s is required at present for the optical fiber baseband transmission system. From such a viewpoint, a clear design principle must be established for the transmission circuit, which operates at the Gbit/s band. This paper describes especially the result of studies on the design and experimental construction of the clamping circuit, which is indispensable in the capacitor‐coupled optical receiver. The elements to be employed in the clamping circuit for several Gbit/s transmission are different for the conventional transmission system of several hundred Mbit/s. The distortion of the transmitted waveform is enhanced in the Gbit/s band. Consequently, the operation of the clamping circuit is different.From such a viewpoint, the behavior of the clamping circuit in the Gbit/s band is clarified by the analysis. An experimental circuit is constructed using the Schottky‐barrier GaAs diode and the depression‐type GaAs MESFET, and the operation is verified. As a result, it is shown that the characteristics of the experimental circuit agree well with the result of calculation, and the proposed method is useful in practice as the circuit design for the case with a large waveform distortion.
Interrupted voice quality evaluation and adaptive delay control in a voice packet communication system
Authors: Tanaka Yoshiaki , Ueno Tomoyuki , Inoue Jungo , Akiyama Minoru 
Published: July 2007

AbstractIn voice packet communication, a fluctuation is produced in the delay time in the network. This makes the packet, which is originally continuous, discontinuous at the receiver, and results in an interruption. The interruption deteriorates the voice quality. Then it is necessary that a delay should be provided at the side of the receiver to absorb the interruption. If the delay for absorbing the fluctuation is too small, the delay cannot sufficiently be absorbed; and if it is too large, the total delay is increased. In either case, the quality of the voice or speech is deteriorated.From such a viewpoint, this paper discusses the absorption of the delay fluctuation of the voice packet. To set the delay for absorbing the fluctuation, the quality of the voice containing interruptions must be evaluated.First, an objective evaluation measure is presented which is well aligned to the subjective evaluation of the deterioration of the voice quality with interruption. A control method to ensure the voice quality above a certain level is presented, which examines the objective evaluation measure for the varying traffic in the network. The method adjusts adaptively the delay for absorbing the delay fluctuation so that the voice quality is kept above a certain reference value.
Impedance characteristics of the normal mode helical antenna with a nearby conduction plate
Authors: Cho Keizo , Yamada Yoshihide 
Published: July 2007

AbstractTo improve the efficiency of a small‐sized antenna, a normal mode helical antenna (NMHA) is promising with a high radiation resistance. However, its efficiency is subject to degradation due to a nearby human body or radio equipment. In this paper, we replaced the human body, etc., by a conductive plate as a basic problem to analyze the influence of the human body and calculated the impedance when NMHA is in proximity of a conductive plate. In our calculation method, the influence of the conductive plate was replaced by an electric image of NMHA. We obtained the current distribution of a two‐element NMHA array which was placed in parallel by the improved circuit theory method which is similar to the moment method. As a result, we found that the real part of the mutual impedance between the array was positive, negative or zero depending on the value of the structural parameters of the antenna. The radiation resistance with a nearby conductive plate was the real part of subtracting the mutual impedance from the input impedance of a NMHA in a free space. In the shapes for zero or negative the real part of mutual impedance, the radiation resistance was equal to or greater than that of the unit antenna so that the conductive plate could be utilized effectively. We showed that the NMHA is a combined model of a dipole antenna and a loop antenna. For shapes with zero mutual impedances, we found that the far radiated field components of the dipole and those of the loop antenna were equal to the structural parameters which were almost equal to 2π2a2=pλ (a: helical radius, andp: pitch).
Simple go‐back‐N ARQ scheme for satellite channels with double acknowledgements
Authors: Komatsu Masaharu 
Published: July 2007

AbstractThis paper discusses a simple go‐back‐N ARQ scheme in which the satellite is provided not only with the repeater function but also with the processing function. The satellite detects the error in the data block sent from the transmitter. It returns ACK/NACK to the transmitter and relays the correctly received data block to the receiver. The receiver detects the error in the received data block and returns ACK/NACK to the transmitter. The transmitter examines two acknowledgement signals returned from the satellite and the receiver, and transmits the data block based on the basic go‐back‐N ARQ protocol. This paper analyzes the scheme in which the hardware complexity of the satellite is minimized. It is shown that the throughput can be increased and the average transmission delay can be decreased.
Experiments on suppression of differential lobing using an integrated SLS antenna
Authors: Kaku Nobuyuki 
Published: July 2007

AbstractSince conventional secondary surveillance radar for air traffic control uses an antenna with wide beamwidth in the vertical plane, the deep lobing that appears makes aircraft detection very difficult. When the interrogating and SLS signals are transmitted from two different antennas, the period of lobing variation differs for both the signals and differential lobing is also observed. To prevent the problems caused by differential lobing, the integrated SLS antenna that was developed transmits the SLS signal from the same phase center as an interrogating antenna; moreover, the period of lobing variation in both cases becomes equal.Experiments were defined out to compare the suppression capability of differential lobing of the integrated SLS antenna with the previous methods. The results show that the mainbeam killing and the sidelobe punch‐through due to differential lobing have been clearly suppressed and aircraft detection capability has improved by 10 percent as compared to the conventional method.
12/14‐GHz bands double‐flare type triple‐mode horn
Authors: Ebisui Takashi , Ishida Osami 
Published: July 2007

AbstractThis paper describes double‐flare type, triple‐mode horns made of two sets of cascaded combinations of a circular waveguide and a flare with a mechanism to generate higher order modes. This horn is intended to be used in two frequency bands. At a lower frequency band, the horn works as a dual‐mode horn, while it operates as a triple‐mode horn at a higher frequency band. Desired electrical characteristics can be obtained in both frequency bands.In this paper, a design method of this triple‐mode horn is described first and the condition for minimizing the cross‐polarization components is presented. Next, the double‐flare type triple‐mode horn is described. It is shown that this condition is satisfied in two frequency bands. Various characteristics of the triple‐mode horn fabricated for 12/14 GHz designed on the basis of the present design procedure are presented. Excellent electrical characteristics are measured including the level of the cross‐polarization components of less than ‐29 dB with respect to the peak level of the co‐polarization component. The measured results are similar to the designed data.
Signaling protocol architecture for a digital mobile communications network
Authors: Nakajima Akihisa , Yamamoto Kouji , Utano Takanori , Suzuki Shigefusa 
Published: July 2007

AbstractThis paper proposes a signaling protocol which can be applied to high‐capacity digital mobile communications networks.First, a hierarchical network function model based on the Intelligent Network (IN) concept is described. In the model, the need for mobile transit switching capability and subscriber line signaling transfer capability is discussed.Second, interoffice signaling protocol and subscriber line signaling protocol are proposed. The interoffice signals consist of circuit‐related signals which are based on the SS No. 7 ISDN User Part (ISUP) and noncircuit‐related signals which apply SCCP and TCAP. The subscriber line layer‐3 signals are designed for expansion and radio frequency efficiency. The layer‐3 grouping function is applied for efficient use of radio frequency.Third, some examples of procedures using those signals and comparisons of signal number and signal volumes between the digital system and the present analog system are shown.
Progressive coding scheme for binary images
Authors: Endoh Toshiaki , Kato Hisaharu , Yamazaki Yasuhiro 
Published: July 2007

AbstractThe progressive coding scheme (PCS) has been proposed as the coding scheme for the binary image with the progressive build‐up function. However, a problem in PCS is that a simple subsampling is employed in the resolution conversion, and the image quality is not sufficiently high in the intermediate stage.This paper proposes a progressive coding scheme using block reduction (PCSB) as a new coding method for the binary image with progressive build‐up function, with emphasis on the image quality. It is shown first by a subjective evaluation experiment that the progressive build‐up display has a better image quality in the intermediate stage than in the conventional scheme. Then the result of examining the coding efficiency is described in detail.By a simulation experiment using CCITT test documents Nos. 1 through 8, it is shown that the coding efficiency is improved by approximately 17 percent at the final stage, compared to the MMR scheme. It is shown also that dither image can be encoded with a high efficiency. Finally, it is shown that the proposed scheme can be applied to the highly efficient image storage at the image database center, as well as to efficient transmission to the receiver terminals with various performances.
Implementation and evaluation of X.25 and X.32 on personal computers
Authors: Suzuki Kenji , Kato Toshihiko , Obana Sadao 
Published: July 2007

AbstractWith the increased use of personal computers (PCs) in communication environments have come the expectation of reliable communication protocols. This paper describes the implementation details of two very similar packet communication protocol interfaces on PCs. One is the X.25 interface for packet‐switched public data networks, and the other is the X.32 interface for public‐switched telephone networks. The implementation of these protocols is performed with consideration of the future introductions of OSI higher‐layer protocols.This paper describes also that the addition of the assigning mechanism of level 2 address to the Rec. X.32 enables powerful personal computer communication through public‐switched telephone networks. Furthermore, the results of the performance evaluation are described which show the high throughput of more than 90 percent on various speeds of the physical circuit.
Optical loss variation due to fiber handling at the jointing point on the subscriber loop
Authors: Tomita Shigeru , Sutoh Kouichi 
Published: July 2007

AbstractIn response to the need for construction of new customer lines, usually the construction takes place at the joints where in‐service lines are accommodated. It is very difficult to select and establish connection to a specific line without touching other in‐service lines, thereby imposing additional curvatures upon them. Therefore, the losses are increased because of fiber bending; and, in such construction works, there is the fear that the transmission‐loss variations exceed the tolerable threshold.To eliminate such fears, experiments on optical fiber handling are carried out and the factors which influence the transmission losses and the magnitude of such variations are clarified. Further, it is shown that by proper choice of the mode field diameter and the cut‐off wavelength, it is possible to limit the variations of the transmission losses. The guidelines in the design of optical receivers which can tolerate these variations also are given.
Frequency diversity effects in multicarrier digital radio systems
Authors: Ichikawa Hirofumi , Murase Takehiro 
Published: July 2007

AbstractFrequency diversity usually is employed in microwave radio systems, where protection channels with different frequencies are prepared and the transmitting data signal is switched to the protection channel to secure the channel reliability when the channel quality is deteriorated by the fading. In multicarrier radio systems, there can be various channel switching configurations, since the protection channel is composed of more than one primary carriers.This paper discusses the effects of the frequency diversity in various switching schemes in the multicarrier radio system. As the model for the theoretical analysis for the microwave fading, the three‐ray multipath fading model is assumed which is close to the actual transmission path. The frequency correlation coefficient and the joint probability for the received power distribution in different radio channels also are derived by a simulation calculation.The effects of the frequency diversity of various switching schemes in the multicarrier system are evaluated. The validity of the presented result is verified by the simultaneous measurement of more than one channel with different frequencies in the actual over‐water transmission path by the measurements of the frequency correlation coefficient and the joint probability distribution for the received power.
Performance of a digital FM demodulator using a fixed‐point arithmetic operation
Authors: Kondo Shoji , Nakamura Noboru , Takizawa Osamu 
Published: July 2007

AbstractPerformance of a DSP demodulator for FM broadcasting receiver is examined by computer simulation and system parameters suitable for obtaining demodulated signal quality (SNR) are clarified. The DSP demodulator is preceded by an m‐digit linear A‐D converter operating at the IF stage of the receiver. A relation between required values of n, the register length of the processor, and m is investigated under the condition that a demodulated signal SNR of 60 dB and 55 dB for monophonic and stereophonic signals, respectively, is ensured. Moreover, only a slight increment of C/Ni (C is input carrier power; Ni is thermal noise power at the receiver input) is necessary to recover degradation due to quantization noise and mathematical rounding‐off errors. Simulation results show that demodulation can be performed with a margin by using parameters n = 16 with m = 7 and 10 under the condition of C/Ni = 23.5 dB and 40.5 dB for monophonic and stereophonic signals, respectively. However, an ideal analog receiver requires C/Ni of 23.2 and 40.0 dB to obtain the previously mentioned demodulated SNRs.
Design and sea trial results of a 48‐fiber submarine optical fiber cable
Authors: Yoshizawa Nobuyuki , Tada Hidenobu , Horiguch Tsuneo , Kurashima Toshio 
Published: July 2007

AbstractA new 48‐fiber submarine optical fiber cable and the technology for a multifiber joint box have been developed to provide compatibility with the number of fibers in land cables. Submarine optical fiber cables require durable construction to cross distances as long as tens of kilometers and to withstand high water pressure. In particular, they must be sufficiently waterproof to prevent moisture penetration into the fiber area in the event of cable damage.Simply increasing the number of fibers in a cable, however, degrades the forementioned characteristics, and the following technology has been developed to allow for fiber expansion without harmful effects.A new pressure‐resistant pipe configuration has been constructed which does not require an inner pressure‐resistant pipe and which can house the increased number of fibers, specifically, a 48‐fiber unit assembly containing four 12‐fiber units. A cable diameter equivalent to that of conventional 12‐fiber cables, a unit length of 30 km, and a loss due to laying of 2 mdB/km have been achieved.For the joint box, a mass fusion splicing technique has been developed in which four fibers are spliced at one time, thereby achieving an average fusion‐splicing loss of 0.13 dB for DSF fibers. This mass fusion splicing can be performed on a small scale in a short period of time on board a repair ship.The foregoing technology has enabled the construction of the first 48‐fiber submarine optical fiber cable in the world. In addition, as a result of strain distribution measurements performed during a sea trial using Brillouin OTDA, the residual elongation train in optical fibers due to new cable construction, laying, and recovery was found to be under 0.1 percent.
A multiple access scheme for radio access loop carrying multiple‐service traffic—virtual circuit multiple access (VCMA)
Authors: Kubota Fumito , Okada Kazunori 
Published: July 2007

AbstractThe integrated services digital network (ISDN), which is under construction at present, will enlarge the range of communication service by developing radio access systems, with the digital mobile communication systems as the core. The purpose of such a radio access system is to realize the communication capability, which is as flexible as that of the fixed system, while utilizing the features of the radio system. The following problems arise in the traditional access schemes, however, when multiple types of calls with various information characteristics and rates are to be handled. The immediate (circuit switching) system cannot contain efficiently the multiple type of traffic, while the waiting (packet switching) system may produce a delay with a long variation.This paper proposes a new scheme for radio channel access, aiming at a positive integration of the multiple type of traffic. In this scheme, the blank of information is compressed to construct a block (cell) with a constant length, and the physical channel is controlled to be assigned to each cell. The blank is inserted on the receiving side to ensure the time‐transparency. Then, the flexibility to various types of immediate and waiting calls, as well as the efficient operation of the channels, are realized.This paper describes also the concept of the scheme and fundamental composition. The channel capacity and the channel occupancy are evaluated by a computer simulation, and it is shown that the proposed scheme has the desirable property that the statistical multiplexing effect is utilized.
Wide‐angle radiation pattern improvement of a shaped offset tri‐reflector antenna by reducing higher‐order periodical reflector distortion
Authors: Karikomi Masahiro , Yamada Yoshihide , Kagoshima Ken‐Ichi 
Published: July 2007

AbstractThis paper describes the improvement of characteristics of an offset tri‐reflector antenna by introduction of reflector surface shaping, and the importance and allowance of suppression of the higher periodic components of the reflector surface distortion caused in the fabrication process. In an antenna with a good wide‐angle radiation pattern, degradation of the sidelobe characteristics due to the higher‐order periodical components of the surface distortion cannot be taken lightly.In this paper, the angle and the level of the side‐lobe peak due to the periodic aperture phase error are expressed in simple formulas. These formulas are combined with an approximate expression of the wide‐angle radiation pattern so that the allowance of the periodic reflector surface distortion is given. Next, a design and measured characteristics are described for a shaped offset tri‐reflector antenna with its aperture diameter of 3600 mm to be used at frequencies of 3.6 to 6.475 GHz. Two prototypes with difference values of surface accuracy are compared. By means of measured examples, it is pointed out that suppression of higher‐order periodic components of the surface distortion is important. By means of reflector shaping, a nonaxisymmetric aperture distortion is important. By means of reflector shaping, a nonaxisymmetric aperture distribution is realized so that the edge level in the horizontal cross section is made small. Further, by suppressing the higher‐order periodic components of the surface distortion, an offset tri‐reflector antenna with a good wide‐angle pattern and a good cross‐polarization characteristic was realized.
A local area radio network utilizing CSMA/CD scheme for its inter‐radio base station network
Authors: Serizawa Mutsumu , Sakakibara Katsumi 
Published: July 2007

AbstractThe cordless configuration of computer terminals and other systems is considered in various applications in recent years. Cordless terminals are expected to have the following advantages: the flexibility of the terminal user is enhanced; the geographical range of the service is enlarged; and the reconstruction of the local‐area network is made unnecessary when the office organization is to be modified.On the other hand, excellent communication quality is difficult to maintain in radio transmissions due to the effects of fading and shadowing. Moreover, the efficient use of limited frequency resources should be considered. Previous studies have already pointed out that the communication quality and the throughput are greatly improved by providing more than one base station for the random access radio channels in the radio communication system. In that case, however, the selection control of a packet received by more than one base station is not easy. No study on this problem has been made. This paper proposes an autonomous and distributed selection control of a packet received by more than one base station, on CSMA/CD LAN. The fundamental performances are analyzed and evaluated, and the usefulness of the system as an inter‐radio base station network in CSMA/CD LAN is indicated.