摘要:

AbstractThis paper studies the system performance of a zone‐structured packet radio network with mobile terminals to which the slotted ALOHA protocol is applied. Conventional performance analyses of the zone‐structured packet radio network have not considered the effect of terminal mobile speed. Here, a model is developed for such a zone‐structured network where a Markov model is used as the mobility model of a terminal and analytical techniques to evaluate static and dynamic performance of the system are presented. Numerical results and their intuitive interpretations are discussed to examine the effect of zone overlapping, mobile speed

ISSN:8756-6621    

DOI:10.1002/ecja.4410770201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is known that the beyond‐line‐of‐sight radio communication channel can be set probabilistically by a column of ionized particles generated when a meteor penetrates into the atmosphere. Numerous transmission control procedures have been reported for an efficient data transmission with this communication channel. Since this communication channel appears independently between two points, it is possible to transmit identical messages from several different locations to one station, thereby improving the receiving probability of a specific message. Because of this characteristic, the transmission time can be reduced by relay transmission of the message by the station successful in receiving the message to other stations. However, to date, little has been reported on relay systems of this type.The present paper proposes a relay system called the unconditional diffusion repeating broadcast scheme and analyzes its characteristics. In this system, the station successful in receiving a message unconditionally broadcasts it. In the case of typical numerical examples studied here, it is shown that the broadcasting time in which the probability of stations without reception is less than 1 percent can be reduced to about two‐thirds when the number of receiving stations is 2. For more than two receiving stations, the reduction is even greater while the improvement effect is saturated when the number of stations is about 20. The situation worsens for more than 30 s

ISSN:8756-6621    

DOI:10.1002/ecja.4410770202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractNumerous methods have been employed to analyze the traffic characteristics of an asynchronous transfer mode (ATM) communication system when multiplexed bursty traffic is applied to a single server. Some of the well‐known methods include solving a state equation numerically, approximating the arrival process by Markov modulated Poisson process (MMPP), and a fluid‐flow approximation method.This paper proposes a new approximating analysis technique employing fluid‐flow approximation that requires very small computational quantity. It also focuses on a queue where constant bit‐rate cell traffic and multiplexedN‐independent bursty cell traffic are applied to a finite buffer single server.The characteristics of cell generation during a cell‐overload period and a cell‐underload period are studied to derive a virtual queueing system. If the burst length and the burst interval of the original queue are distributed exponentially, it will be shown that this virtual queue is aGI/GI/1 queue.Finally, a method of calculating the cell loss probability by approximating this virtual queue is presented and it is shown that the results agree with the results of simulations and exis

ISSN:8756-6621    

DOI:10.1002/ecja.4410770203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper evaluates the performance of the two‐way message transmission system on the meteor burst channel developed and tested by the authors. First, the usual channel model is simplified and then the system is analyzed. It is shown through simulations that the errors introduced by the new channel model and by the approximated analysis method are negligible and the proposed method can be used to design and evaluate the system.The performance of the system having packets with subblocks is compared to that of one with usual packets. It is shown that, by using packets with subblocks, robustness of the system performance against changes of channel parameters as well as a shorter time needed to transmit a message can be obtained. The method of performance evaluation shown in this paper has adequate generality and is also applicable to many other meteor burst communication (MBC) system

ISSN:8756-6621    

DOI:10.1002/ecja.4410770204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the area of mobile communications, there has been increasing demand and development for new technologies and services such as digitization and personalization. With this as background, this paper studies the use of adaptive antenna technology for mobile communication.In the area of mobile communications, the adaptive antenna technology has been studied with a view to reducing the fading for reception by the mobile station. In the case of microcells and indoor communication for which an expanded use is anticipated, arrivals of multiple waves from various directions are expected even for the base station so that the application of the adaptive antennas to the base stations is effective.In the case of high‐speed data transmission such as wireless local wireless networks (LAN), further reduction of fading and interference is required. Also, the frequency sharing among different radio services is an area in which the adaptive antenna is useful.Introductions of dynamic control of the systems are expected for mobile communications in time, space, and frequency domains. The adaptive antenna is effective for control in space. The dynamic zone configuration will be a new application area in which, depending on the distributions of the users, the zone shape is varie

ISSN:8756-6621    

DOI:10.1002/ecja.4410770205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper proposes an application of a Kalman filter for an adaptive array antenna. This method has an advantage in that the control gain can automatically be adaptable to the variation of the arriving signal and the convergence speed is high. The convergence condition to optimum weight coefficients is analyzed in the case where a Kalman filter is used for the control of the weight coefficients. By means of a simulation for a four‐element array antenna, it is confirmed that the directivity control error is small and the convergence is swift. The effect of the initial value of the unknown weight coefficient vectorW(0) and the initial valueP(0) of the estimated error covariance matrix on the convergence characteristics is studied. By means of the simulation, the range of allowable values is indicated. IfW(0) andP(0) are chosen appropriately, the maximum error for the directivity control can be restricted to less than 1.5 degree

ISSN:8756-6621    

DOI:10.1002/ecja.4410770206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOne effective technique for reducing multipath fading in mobile communications is introduction of directional diversity with the help of adaptive arrays. This technique requires direction of arrival (DOA) estimation of coherent signals and relative time delay estimation. Eigenvector analysis or maximum likelihood localization is an efficient technique to estimate DOA. However, for coherent signals, spatial smoothing preprocessing is required and information about the number of signals is needed.This paper proposes to use spatial autoregressive modeling and final prediction error (FPE) to estimate the number of coherent signals. Since FPE drastically decreases withpwhen the length of prediction filterpis less than the number of coherent signalskand FPE converges to a constant value determined byC/Nwhenpis greater thank, the number of coherent signals can be estimated. Moreover, by appropriately defining the FPE threshold, the number of dominant coherent signals can be estimated under theC/Nconcept. Numerical experiment indicates that this technique can estimate the number of signals and DOA with sufficient accuracy. Further, by appropriately defining the FPE threshold, the number of dominant coherent signals can be estimated.

ISSN:8756-6621    

DOI:10.1002/ecja.4410770207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe efficacy of applying quantized soft decision data to unique word (UW) detection, which plays an important role in frame synchronization in digital radio transmission systems, is discussed considering hardware implementation. This UW detection method represents the received signal vector using representative points within a multidimensional space and measures the Euclidean distance from the vector point corresponding to the UW pattern.Probability calculations are employed for obtaining theoretically UW detection characteristics such as missed detection and false detection, assuming that white Gaussian noise is added to the signal during transmission. These various characteristics are then compared quantitatively with the characteristics obtained by the conventional UW detection method using hard decision data. In addition, the UW detection characteristics obtained experimentally using hardware are presented. As a result of the quantitative evaluations, it has been clarified that the application of soft decision data is effective in reducing the UW length required for objectives of the UW detection performance associated with frame synchronization characteristics.

ISSN:8756-6621    

DOI:10.1002/ecja.4410770208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTo improve the present conventional management system for further expansion of line facilities, a new system which has an automated, real‐time updating capability of system data has been proposed. The design principle and the result of SC2‐ (in‐house single wire) and MT‐type (outside, single∼multiwires) optical connectors with ID modules, which are the key components for this proposed system are presented in this paper. For the design of those connectors, the requirement for the ID module memory device is clarified and a serial‐type electrically‐erasable programmable ROM (EEPROM) is demonstrated to be the most suitable as a memory element.For further designing an integrated structure with connectors to avoid the degradation of the operationality, the packaging is discussed. As a result, the SIP‐type ID modules are located at one side of a connector. To minimize the contact‐loss fluctuation, the design for the structural and mechanical characteristics is discussed where a lateral force or electrode insertion force required to attain a desirable electrical resistance is evaluated. A prototype connector has been fabricated, which exhibits a contact loss change of ‐0.01 dB (SC2) and +0.02 dB (MT) and also a dynamic loss fluctuation level of less than 0.1 dB at the time of a connector insertion. Further, a contact resistance of less than 4 mμ (target: less than 40 mω), the package density of 1.5 to 1.8, and the connector loading time of 1.0 to 1.08 were obtained, which are comparable to

ISSN:8756-6621    

DOI:10.1002/ecja.4410770209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper advocates the nonparametric approach and shows its application to asynchronous transfer mode (ATM) network dimensioning. The conventional dimensioning procedure, which is used in conventional dedicated and low‐speed networks, can cause the following problems in ATM networks and intelligent networks:(1) The need for a complicated arrival process model to describe high burstiness. As a result, elaborate modeling is necessary for each new service, which reduces flexibility in introducing new services.(2) The need for traffic measurement of higher moments of interarrival times. However, traffic measurement mechanisms cannot meet this requirement.(3) It is impossible to verify the arrival process model. The nonparametric approach dispenses with parametric modeling of arrival processes and derives performance measures directly from traffic measurement, thereby resolving the forementioned problems. This approach can be applied when the peak and average cell rates in ATM networks are known and provides an accurate measure of the cell loss rat

ISSN:8756-6621    

DOI:10.1002/ecja.4410770210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY