bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of an all‐digital multilevel modulator and its application to variable‐capacity transmission
Authors: Okada Takashi , Aikawa Satoru 
Published: July 2007

AbstractWith the advent of the radio relay system and multilevel modulation, the multicarrier system and variable capacity transmission system are proposed to realize excellent performance in the fading channel. Accordingly, it is desired to realize a highly functioned MODEM which can cope with those systems in a flexible way.On the other hand, intensive studies have been made on digital signal processing in the modulation and demodulation in the field of data modem. However, these methods consider the low‐rate system of less than 100 Kbaud and are difficult to apply directly to the system where the transmission rate of 10 Mbaud or above is required.For the foregoing reasons, this paper considers the realization of the all‐digital modulator which can realize the high‐capacity transmission of over 10 Mbaud for the multilevel modulation system, such as 256 QAM.This paper discusses the design of the digital filter with excellent intersymbol interference. The condition for the carrier frequency for a given clock rate is presented. Then a variable multilevel modulator with a simple correction circuit is proposed which can be applied to the variable‐capacity transmission system.Finally, the proposed circuit is constructed and it is confirmed that an excellent modulation performance is obtained without adjustment in various multilevel modulation systems.
Mac reconfiguration mechanism for a dual‐ring lan
Authors: Nakayashiki Susumu , Kashios Jiro , Harakawa Takeshi 
Published: July 2007

AbstractIn a reconfiguration mechanism for improving the RAS of a ring LAN, it is necessary to guarantee the proper functioning of communication functions up to the medium access control (MAC) layer. This paper proposes a reconfiguration mechanism for distributed‐control dual ring LANs which maximizes the size of the ring while maintaining MAC layer communication functions by automatic ring merging and wrapback. Each station bases its actions on the state of the two input links. When a link fails, the failed segment is isolated by ring wrap‐back and the ring operates in wrapback mode. When multiple failures occur, the ring is wrapped back further into a smaller ring or several rings until the MAC layer functions are recovered. On the other hand, when the MAC layer functions of the failed segment are recovered, wrapback is released and the failed segment is merged into the active ring. With this reconfiguration mechanism, the largest ring possible to maintain MAC layer functions is formed automatically regardless of failures, powering up or down, etc. This mechanism is represented using finite state machine (FSM) diagrams. The recovery times from multiple failures are evaluated using the specifications of the international LAN standard (ISO 8802‐5). This reconfiguration mechanism has been approved as the IEEE standard (recommended practice) for a dual‐ring reconfiguration mechanism, and its effectiveness has been proven by field trials.
Deterministic tree‐type algorithm with reservation mechanism
Authors: Kawano Hiroyuki , Hasegawa Toshiharu , Nishio Shojiro 
Published: July 2007

AbstractThe tree‐type algorithm has been proposed and investigated widely as a random multiple‐access communication protocol. It is a distributed algorithm but shows a stable throughput performance. Several proposals have been made, including Tsybakov's, for the tree‐type algorithm with a reservation mechanism to improve further the throughput performance.This paper proposes new TREE‐DTA with reservation mechanism, which is based on the block access method and employs the deterministic Q‐ary tree‐type algorithm operating on the terminal addresses as the retransmission algorithm. The feature of the reservation mechanism proposed in this paper is that the realization is easy, compared to various other methods that have been proposed.To evaluate the performance of TREE‐DTA with reservation mechanism, a mathematical model is used to derive the approximate expression for the relation between the throughput and the average delay. Furthermore, the performances of TREE‐DTA with reservation mechanism are examined by a simulation experiment. The robustness to the system error and the application of the priority scheme are discussed.
Performance of a controlled capacity digital radio system with diversity reception
Authors: Lee Hee‐Jin , Komaki Shozo , Morinaga Norihiko 
Published: July 2007

AbstractThis paper analyzes the effect of diversity on reducing fading in the controlled capacity digital radio systems. As a result, it is clarified that an improvement of one to three times in the traffic throughput can be obtained if diversity is combined with the controlled capacity system.Moreover, the performance of the diversity system is compared with the controlled capacity system when both are employed separately and it is made clear that the improvement effects of the controlled capacity system correspond to those of two‐ to four‐fold diversity in fixed‐capacity systems.
Contoured‐beam antenna using smoothly shaped dual‐reflectors for broadcasting satellites
Authors: Shogen Kazuyoshi , Nishida Hayato 
Published: July 2007

AbstractPreviously, the authors have proposed a design method of a shaped dual‐reflector contoured‐beam antenna with virtual multihorns with a view to applications to the broadcast satellite BS‐3. In such a design, there were discontinuities on the main reflector.In this paper, a method for eliminating these step discontinuities is studied for the dual‐reflectors. The current distribution on the main reflector corresponding to the desired radiation pattern is determined by optimization depending on the constraint gain of the far field. Note that the optimization method for the aperture phase distribution was known for a single smoothly shaped contoured‐beam antenna. Also, in this paper, an optimization method for the amplitude distribution is proposed anew. Further, by adding a restriction to the phase difference between the adjacent elements in the optimization of the phase distribution, the step discontinuity on the reflector is eliminated. By means of this method, an antenna made of a main reflector with an aperture diameter of 2.3 m is designed at 12 GHz which is the frequency of the downlink of the broadcast satellite.Most of Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa is covered by a radiation pattern with more than 40 dBi and other remote islands with more than 28 dBi. A one‐half scale model is fabricated and the radiation pattern is measured at 22 GHz. The results agree well with the numerical results. Also, the sidelobe and the cross‐polarization characteristics of this antenna sufficiently satisfy the technical standards in RR.AP 30.
Nonblocking atm switching networks for variable bit rate traffic
Authors: Sato Shohei , Akiyama Minoru 
Published: July 2007

AbstractAn asynchronous transfer mode (ATM) switching network handles not only traffic of various bandwidths, but multirate bursty traffic including constant bit rate and variable bit rate traffic as well. Consequently, to simplify the design and operation of the facility, it is desirable for the ATM network to be nonblocking at the connection level. The nonblocking issue when the network must handle variable bit rate traffic is related closely to the connection admission control (CAC) employed.While the nonblocking feature for a linear CAC function has been studied in the past, the relation between the switching network cell‐level quality and non‐blocking characteristic for a specific CAC premising variable bit rate traffic has not been analyzed.This paper examines a nonlinear CAC, evaluates the cell loss probability and statistical multiplex gain when it is applied and proposes the definition for a non‐blocking feature called “(p0, p, q) nonblocking.” Next, a cell distribution‐type, three‐stage ATM switching network is shown that ensures (p0, p, q) nonblocking for traffic including multicast connections without expanding the internal link capacity either in terms of space or speed.
Implementation of a communication sdl specification
Authors: Hasegawa Haruo , Tanaka Wataru 
Published: July 2007

AbstractThis paper describes a method of converting a specification and description language (SDL) specification into a program by introducing SDL/OS. The TRON‐specification OS is adopted as OS and C++ as a programming language to make the program portable. SDL/OS, which consists of libraries described in C++, is constructed on OS so that the program converted from SDL can run as it is. SDL/OS realizes the SDL functions easily by using the functions of TRON‐specification OS.Finally, this paper reports that this method is very effective in enhancement of software productivity by applying it to software development of real communication systems. Moreover, performance degradation can be compensated to some extent by introducing function calls in the same task.
Adaptive array antenna combined with tapped delay line using processing gain for direct‐sequence/spread‐spectrum multiple‐access system
Authors: Wang Hefeng , Kohno Ryuji , Imai Hideki 
Published: July 2007

AbstractAs countermeasures for co‐channel interference from simultaneously accessing users in the spread spectrum multiple access (SSMA), co‐channel interference cancellers using the adaptive digital filters, and array antennas and their combinations have been proposed. However, in these systems, it is necessary to generate a reference signal with a large correlation with the desired wave in receiver so that their coefficients can be updated adaptively. In the SSMA, a method has been proposed in which the reference signal generated by respreading of the demodulated data is used for the updating of the weight coefficient of the array antenna. However, as the input interference and the noise power increase, the convergence of the array antenna becomes difficult. Also, in the conventional method, most of the discussions have been limited to an array antenna in which one weight coefficient corresponds to an array element. However, as the interference signal bandwidth increases, the wideband interference signals cannot sufficiently be removed from the antenna output.In this paper, from the viewpoint of improving the co‐channel interference elimination capability of the array antenna in the space domain, the reduction of the noise component and the co‐channel interference in the error signal for the array antenna updating is considered and an updating method for an adaptive array antenna using the spread spectrum processing gain is proposed. Further, from the viewpoint of increasing the co‐channel interference elimination capability of the array antenna in the time domain, a receiving system using a TDL (tapped delay line) adaptive array antenna is proposed to increase the frequency characteristics of the bandstop filter for a wideband spread spectrum signal.Finally, by means of a computer simulation, the basic characteristics of the updating method and the performance of the receiving system are evaluated. It is shown that good characteristics can be obtained under an environment with co‐channel interference and noise power higher than in the conventional system.
A method of moving area‐detection technique in a muse decoder
Authors: Izumi Yoshinori , Gohshi Seiichi , Ninomiya Yuichi 
Published: July 2007

AbstractSubsampling is used widely in a bandwidth compression of video signals because it simply decreases the sampling rate with less artifacts. The compression efficiency and a final picture quality of a video compression based on a subsampling normally are improved by applying a motion adaptive technique. Such a technique switches processing between the static picture area and moving picture area depending on the movement. This switching is controlled as the result of detecting the moving picture area, a technique called “moving area detection.”In moving area detection used by a frame‐offset subsampling system such as a MUSE decoder, the frame difference cannot be obtained because the sampled value is omitted by subsampling, thereby causing erroneous detection or detection failure.In this paper, the improvement of the moving area detection method used in a MUSE decoder, which is the analog transmission system for Hi‐Vision signals, is described as an example of moving area detection of a subsampling system. The improvement of moving area detection is confirmed by an LSI MUSE decoder. The frequency characteristics of a moving area detection circuit also are discussed. Consequently, the frequency characteristics of moving area detection necessary for a MUSE decoder are obtained.
Broadband cylindrical‐cavity directional filter
Authors: Isota Yoji , Miyazaki Moriyasu , Ishida Osami 
Published: July 2007

AbstractThe diplexing bandwidth of a cylindrical‐cavity directional filter is restricted of coupling of the coupling hole, which is installed in order to excite a circular polarization on the common walls of the input and output rectangular waveguides and in the adjacent cylindrical cavity.This paper proposes a method of increasing the coupling of circular polarization by means of an iris‐loaded cross‐coupling hole (consisting of an iris mounted on the crossed‐coupling hole of a rectangular waveguide). The results of analysis of the magnetic field distribution and the magnetic field intensity in a rectangular waveguide loaded with an iris are described.It shown that the iris‐loaded cross‐coupling hole is effective in exciting a circular polarization and increasing coupling. The results of a trial fabrication of a directional filter using this type of coupling hole are presented. In the case of a three‐stage maximally flat K band filter, a passband relative bandwidth of 2.7 percent was obtained. This bandwidth is three times as great as in conventional filters. Hence, the range of application of the cylindrical cavity directional filter has been extended.
Measurement of angle of arrival by small circular array antenna for aircraft
Authors: Shirakawa Masayuki , Fukuda Yutaka , Ozeki Shigeru 
Published: July 2007

AbstractFor an airborne collision avoidance system, it is necessary to measure the directions of other aircraft in the vicinity with high accuracy. As one of the methods for such a purpose, a method was studied in which a small circular array and Butler matrix are combined. In such a case, the mutual coupling between the elements increases. However, by adjusting the phases appropriately, it is found possible to maintain a phase relationship in the same way as in the case without mutual coupling. Also, an angular measurement method was proposed in which the outputs of the Butler matrix are combined at the output stage. It was found that the accuracy is close to the one obtained in the maximum likelihood estimator while the circuit is simple.
Virtual path bandwidth control method for ATM networks: Batch modification method
Authors: Shioda Shigeo , Uose Hisao 
Published: July 2007

AbstractTraffic generated by B‐ISDN services is difficult to predict because the fluctuations in normal traffic patterns are large. As a result, it is difficult to provide network equipment to avoid traffic unbalance. The advantage of using asynchronous transfer mode (ATM) in B‐ISDN networks is that path bandwidth control facilities can be used to dampen the unbalance in traffic.This paper proposes a new algorithm, based on the batch modification method, for controlling traffic fluctuations. The batch modification method is used to control path bandwidth from a centralized control center. The virtual path bandwidth is calculated using optimization calculations based on information from the entire network. Hence, it is necessary to develop an algorithm to perform the optimization calculations. The algorithm uses the worst case blocking probability and the total amount of traffic. The algorithm is verified with numerical examples that compare traffic patterns in a model network.
FM‐FDM optical CATV system employing demand access technology
Authors: Maeda Mikio , Oyamada Kimiyuki , Ishikawa Tadasu , Fujisawa Syuichi 
Published: July 2007

AbstractA demand‐access optical CATV system using FM frequency multiplexing is developed. This system allows us to transmit 40 video signals including MUSE high vision signals over 40 km on a single‐mode fiber trunk‐line and can transmit arbitrary four video signals to subscribers at 10 km on subscribers' single‐mode optical fibers. The feature of the present system is the possibility to fabricate an inexpensive hub by using a newly developed channel selector which combines single heterodyne and RF switch and also to make use of a cheap conventional DBS tuner at the subscribers' receiving terminal. For a trunkline, an optical modulation depth has to be carefully determined by considering an inter‐modulation distortion. The present paper describes the degradation in effective CN ratio due to a white noise produced by the FM modulated third‐order distortion and shows an optimum optical modulation depth for a given transmitting distance. Also, a system design is discussed for certain distances of a trunkline and a subscriber line. One can estimate using the present design the CN ratio at a subscriber terminal. The present system can provide the video quality of 4.5 (CN ratio 17.5 dB) for high vision.
Digital loop‐preset synthesizer (dlps) for high‐speed frequency switching
Authors: Tarusawa Yoshiaki , Yamao Yasushi , Saito Shigeki 
Published: July 2007

AbstractAs a method for constructing a new PLL frequency synthesizer allowing high‐speed switching of oscillating frequencies and low power consumption, which has not been existent in the past, a digital loop‐preset frequency synthesizer (DLPS) is proposed. A synthesizer of this construction is applicable to mobile communications wireless equipment for which it has become especially important to make power consumption low.The DLPS is constructed from the PLL synthesizer circuit and the digital loop‐presetting (DLP) circuit that presets the frequency control voltage and loop phase of the PLL. A method of determining the frequency control voltage by fuzzy prediction is proposed for high‐accuracy presetting. A method of design based on the forementioned construction and analyses of DLPSs having this construction are presented.Next, DLPSs of the bandwidth of 25 MHz and the frequency step 25 kHz at the 800‐MHz band and 1.5‐GHz band have been trial constructed and these synthesizers are shown to switch the frequency at less than 1 ms, which is two places shorter than the frequency‐switching time of the conventional‐type PLL synthesizers.
Multipath suppression performance of an adaptive array antenna with a systolic array processor
Authors: Ohmiya Manabu , Kawabata Tatsuya , Ogawa Yasutaka , Itoh Kiyohiko 
Published: July 2007

AbstractThis paper describes an adaptive array antenna using a signal processing system which is implemented by a systolic array processor (SAP), SAP‐AA. Computer simulations show the behavior of the SAP‐AA against multipath fading. The SAP realizes a parallel pipelined processing by regularly placing many SAP cells with identical functions and structures so that it achieves the high throughput rate in the data processing. Also, the SAP has many desirable features for very large‐scale integration (VLSI) system design and enables miniaturization, weight reduction, and mass production of the processing equipment.In this paper, first, the SAP‐AA is described which realizes the least squares (LS) algorithm based on the QR decomposition for the input data matrix using the Givens rotations. In addition, the fundamental performances of the SAP‐AA are studied including both the transient response and the steady‐state behavior in multipath signal environments. To date, there has been no report which treats the multipath signal suppression performance of the SAP‐AA. Finally, it is concluded from the discussion that the SAP‐AA is effective for unwanted signal suppression in a multipath signal environment.
A gram‐schmidt SLC controlling the number of auxiliary antennas to preserve desired signals
Authors: Harasawa Yasuhiro , Kirimoto Tetsuo 
Published: July 2007

AbstractIn the SLC (sidelobe canceler) which automatically suppresses the interference signals received by the side‐lobe of the main antenna, there is a problem of suppression of the desired signal in addition to the interference signal if the desired signal power in the auxiliary antenna is larger than the receiver noise power and if the number of received interference signal is smaller than that of the auxiliary antennas.In this paper, an SLC is proposed in which the number of auxiliary antennas is adjusted automatically to be equal to that of the interference signals so that the problem of suppression of the desired signal is prevented. It is assumed here that both the desired signal and the interference signals have narrow band widths.In this SLC, with a view to adjusting the number of auxiliary antennas and the weights at the same time, the Gram‐Schmidt SLC (GS‐SLC) is used so that a sudden change of the input‐output signal power ratio of the Gram‐Schmidt processor is detected and the number of auxiliary antennas are made to coincide with that of the received interference signals. By way of a computer simulation, the fundamental characteristics of the present GS‐SLC are evaluated. It is confirmed that the desired signal preservation property is improved in comparison with the conventional SLC.
Envelope‐controlled digital modulation improving power efficiency of transmitter amplification—application to trellis‐coded 8 psk for mobile radio
Authors: Tomisato Shigeru , Suzuki Hiroshi 
Published: July 2007

AbstractTrellis‐coded modulation (TCM) has good spectrum properties and excellent bit error rate (BER) performance. This paper presents the envelope control (EC) method which improves the transmitter power amplification efficiency of TCM for mobile radio. Applying EC to TCM leads to two new modulation schemes: smoothed envelope trellis‐coded 8 PSK (SE‐TC8PSK) and constant envelope TC8PSK (CE‐TC8PSK). Modulation and demodulation techniques for SE‐TC8PSK and CE‐TC8PSK are created. The spectrum properties, BER performance, and power‐conversion efficiency of SE‐TC8PSK and CE‐TC8PSK are calculated by computer simulations and compared with those of TC8PSK. EC greatly improves the power‐conversion efficiency at the cost of degrading the spectrum properties and BER performance of both schemes.