摘要:

AbstractThe protocol in the open system interconnection (OSI) basic reference model is specified as a system with a multilayer structure. The performance of the network is related closely to the network configuration and the protocol parameters. The authors have been attempting to evaluate the transmission efficiency of the network using the multilayered protocol, with the transmission speed, the window size, and the transmission delay as the parameters.It is assumed in the studies that the acknowledgement is returned at the end of each window. On the other hand, it is seen that the throughput of the network in the high‐speed transmission is affected greatly by the acknowledgement method. This paper notes this point and evaluates the relation between the acknowledgement method and the transmission efficiency. To achieve the desired transmission speed, the conditions for the window size, the acknowledgement method, and the protocol processing time are presente

ISSN:8756-6621    

DOI:10.1002/ecja.4410770901

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper considers a function to improve the efficiency of the operation administration and maintenance (OAM) of the virtual path (VP) in the ATM network. A VP test method is proposed which can test the connectivity and performance at new VP establishment and locate the fault point at VP failure. The implementation of the method is discussed. The feature of proposed method is that the number of error bits, the number of lost cells, and the number of misdelivered cells can be measured by transmitting and receiving the test OAM cell in any test section of VP.In this paper, the purpose and requirements for the VP test system are described first. Then the mechanisms in the proposed system and the allocation of test functions are considered. A transmission performance measurement algorithm is proposed for the test OAM receiver so that the bit error, the cell loss, and the cell misdelivery can accurately be counted. The structure of the VP test OAM cell to realize the proposed algorithm is presented. Finally, the system parameters of the proposed method are evaluated quantitatively.

ISSN:8756-6621    

DOI:10.1002/ecja.4410770902

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

年代:1994

数据来源: WILEY

摘要:

AbstractAs the broadband integrated services digital network (B‐ISDN) become more available for home use, it is expected that the demand for broadcast services, e.g., video distribution from a center to end terminals, will increase. Thus, in the local switching system, the number of output subscriber lines is much larger than the number of input trunk lines. Therefore, an asymmetric broadcast ATM switching network is needed for this service. However, most of the switching networks already proposed are symmetric.In this paper, an asymmetric switching network is realized by partitioning the output and by using existing symmetric switching networks. Furthermore, the size of symmetric switching networks which are used as parts is reduced by placing concentrators in the front. This decreases the total amount of hardware. Since excessive concentration invites cell loss, the relation between the hardware‐reduction effect and the cell‐loss characteristic also is st

ISSN:8756-6621    

DOI:10.1002/ecja.4410770903

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

年代:1994

数据来源: WILEY

摘要:

AbstractEfficient handover during both mobile telephone and portable telephone communication is a technology essential in implementing ideal mobile communications. However, there exists the possibility of a transmission data slip during the process of circuit switching, which has become a problem in communication using terminal machines such as data modems and FAX machines connected to mobile telephones and portable telephones.In this paper, a transmission data slip accompanying route changes inside digital exchanges in a handover during telephone communications is assumed; it is shown on the basis of this assumption that a lag in synchronism occurs in the receiver terminal equipment.Then a sync lag of the receiver terminal modem during handover has been confirmed by tests using actual analog cellular phones and a transmission data slip has been shown on the basis of the results of the tests. In this paper, a synchronism control method minimising the sync lag has been studied. The efficacy of this method has been confirmed as a result of applying the method to a mobile telephone FAX modem.

ISSN:8756-6621    

DOI:10.1002/ecja.4410770904

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn the conventional adaptive discrete cosine transform (ADCT) using the fixed length code, it is known that the source coding performance can be improved greatly by the combined use of the M‐transform (MT). This method is called ADCT‐MT. The purpose of this paper is to evaluate the effect of the combined use of MT from the viewpoint of the channel coding performance. In the conventional ADCT, as well as in the scene adaptive coding (SAC) using the variable length code, the damage in the reconstructed image due to the channel error often is manifested as the local block distortion. In ADCT‐MT, the damage is diffused and distributed uniformly by the inverse MT over a large number of blocks, making the damage less noticeable.A subjective evaluation experiment is conducted (five‐step score) assuming the binary symmetrical channel. A simple error‐correcting code is applied to the coding data of the additional information and DCT dc component. When the bit‐error rate is 10−3, the average score is approximately 3.5 for ADCT and 1.2 for SAC, while it is above 4.5 in ADCT‐MT. Thus, in ADCT‐MT, the damage is

ISSN:8756-6621    

DOI:10.1002/ecja.4410770905

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn the 21st century, 10∼30 Mbps video services will be the main traffic services of B‐ISDN. Therefore, bandwidth control is effective for dividing a 150‐Mbps line into the call bandwidths. A shared buffer‐type ATM switch with this function can be achieved by queueing call by call and by reading out cells from the queues according to the bandwidth control table sequence. When the traffic is random with utilization of 0.9, the switch with 128∼512 queues on the 4000‐cell shared buffer has sufficiently small cell loss characteristics.Multiqueueing technology is provided by embedded RAMs which point to the first addresses and last addresses of the queues. Queue length control, which limits each queue length, for multiqueueing is provided by the embedded RAMs. A one‐board switch with 128 queues on a 4000‐cell shared buff

ISSN:8756-6621    

DOI:10.1002/ecja.4410770906

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

年代:1994

数据来源: WILEY

摘要:

AbstractA multicast error control scheme which takes advantage of both MDS codes and GMD decoding is proposed and analyzed. The proposed scheme is characterized as follows:1. The sender does not retransmit data frames. The frames to be retransmitted consist of the redundant symbols obtained by encoding the previously transmitted data frames.2. Each receiver stores erroneous frames not greater than the prearranged number and decodes them all of a lump using the retransmitted frames of the fixed number.Numerical results show that the proposed scheme yields higher throughput not only for the case where the bit error rate is very large but also for the case where the number of VSATs is very large.

ISSN:8756-6621    

DOI:10.1002/ecja.4410770907

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper considers the decision feedback transversal‐combining (TC) diversity reception system in the digital mobile communication, and describes experimentally the interference cancelling characteristics of decision feedback equalizer‐type (DFE) TC diversity reception through laboratory tests. Three kinds of interference signals are considered: the intersymbol interference (ISI), the cochannel interference (CCI), and the adjacent channel interference (ACI). The exponentially weighted RLS, which executes the least‐square method in realtime, is employed in the adaptive control of the combining coefficients.It is shown first that the method for equalization and diversity combining can be classified into the TC and the metric combining (MC), among which TC has the linear interference cancelling effect. By 40 kbit/s quadri‐phase‐shift keying (QPSK) transmission experiments under Rayleigh fading condition, the following properties of TC are shown compared to MC: (1) In ISI, dominant condition in double path model, the average BER performance for averageEb/N0values over 20 dB; (2) For CCI, dominant condition BER performance of TC is better than that of MC by 5 dB in average CIR at average BE

ISSN:8756-6621    

DOI:10.1002/ecja.4410770908

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

年代:1994

数据来源: WILEY

摘要:

AbstractA ranging and positioning system using a geostationary satellite has been developed and its performance has been evaluated using an aircraft. This system can be applied to oceanic air traffic control and can be used at a ground station to determine positions of aircraft. An experimental system consists of a geostationary satellite, a ground station, an aircraft, and a pseudo‐satellite, which is installed inside the ground station and used as the substitute for another geostationary satellite. TheEngineering Test Satellite V (ETS‐V)of Japan was used in the experiment.It is known that the positioning error increases as a user approaches the equator in a positioning system using two geostationary satellites. This fact has been confirmed in this paper by experiment. It has also been shown that positioning errors can be decreased by using relative positioning in which the position of the ground station is used as a reference station. The use of old orbit elements increases the error of the predicted position of the geostationary satellite and therefore increases the positioning error of the aircraft. This has also been confirmed in the experiment. Furthermore, it has been shown that, in relative positioning, positioning errors do not increase much even with old orbit elements and the epoch of orbit elements does not have much influence on positioning err

ISSN:8756-6621    

DOI:10.1002/ecja.4410770909

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

年代:1994

数据来源: WILEY

摘要:

AbstractWhen metallic telecommunication lines carrying digital signals are laid adjacent to ac supply lines in an office or a house, then the noise generated by the ac supply lines is induced on the telecommunication lines and the quality of transmission may be degraded. To calculate the induced voltage generated directly between the cores of a telecommunication line requires accurate values of the coupling admittance or coupling impedance between the two lines corresponding to the cable construction and the problem becomes very complicated.This paper proposes a simple method of estimating the voltage induced between the cores of a telecommunication line when the telecommunication line is laid adjacent to an ac supply line. The amount of coupling from the primary circuit with an open‐circuited terminal and with a short‐circuited terminal to the secondary circuit is measured. Using this value, the characteristics of the induced voltage corresponding to an arbitrary value of terminal impedance of the primary or secondary circuit simply are estimated. The validity of the estimation method was confirmed by experime

ISSN:8756-6621    

DOI:10.1002/ecja.4410770910

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

年代:1994

数据来源: WILEY