摘要:

AbstractIn a conventional Trellis coded modulation (TCM), the error‐event probability is minimized by designing the Trellis code so as to achieve the maximum free Euclidean distance (ED). This paper proposes a new coding technique which improves the post‐decoding bit error rate without changing the ED‐structure of the conventional TCM code. This is achieved by channel coding with mapped signal sets having minimum Hamming distance (MHD) on information bits for error events generated at free ED.First, this mapping was obtained by calculating Hamming distances on information bits for error events generated at free ED for all code mappings by using a computer, which requires a large amount of calculation. We show that such codes for multiphase modulation are constructed by a simple coding method without this much calculation. Also, its effectiveness is confirmed by the simul

ISSN:8756-6621    

DOI:10.1002/ecja.4410731201

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

年代:1990

数据来源: WILEY

摘要:

AbstractISDN basic access interface provides transmission capability of two B channels and one D channel for various telecommunications services. The electrical characteristics of this interface are strictly regulated in CCITT recommendation I.430 to allow up to eight terminals to be connected in a bus wiring system. This paper describes a design method for achieving desired line interface characteristics, including output voltage with specified loads, transmitter output impedance at inactive state, receiver threshold voltage and cut‐off frequency of a low‐pass filter. The electrical characteristics of the line interface circuit based on the proposed design are measured by using practical bus wiring systems and are confirmed to satisfy recommendation I.

ISSN:8756-6621    

DOI:10.1002/ecja.4410731202

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

年代:1990

数据来源: WILEY

摘要:

AbstractWith the recent development of digital LSI integration, numerous studies have been made on the digital implementation of the phase‐locked loop (PLL). Among those, the binary quantized digital PLL, which is simple in circuit structure and the multilevel quantized digital PLL which is an extension of the forementioned type are considered interesting.This paper proposes a new type of sequential loop filter (SLF) for the multilevel quantized digital PLL by which the tracking range can be expanded. As in the case of the random‐walk filter, the general idea about SLF has been to control the output phase by smoothing the result of phase comparison. Consequently, when the input frequency of the phase information, mark ratio is low, it has been difficult to keep a wide tracking range for any extent of the frequency offset.In the proposed SLF(APCF) (adaptive phase‐control fitler), in contrast to the smoothing process, an adaptive search of the phase‐control interval is made by applying the steepest descent method to the result of phase comparison. In this paper, the algorithm of APCF is described first and the evaluative expressions of the performance are derived theoretically.Some evaluations are given to compare adaptive phase‐control filter with the conventional sequential loop filter by simulation. It is shown that the output jitter for the low mark‐ratio is small and the degradations such as the reduction of the tracking range are small even if the mark‐ratio

ISSN:8756-6621    

DOI:10.1002/ecja.4410731203

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

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper considers an access scheme to realize a packet switching function using the time‐division multiplexed frame which circulates on a ring‐type backbone LAN. A slotted token‐passing scheme is proposed which enables a long packet transmission by concatenating the time‐division slots available by dividing the frame. Its access control algorithm and the recovery mechanism from ring failure are shown, along with the numerical analysis of the mean transfer time of the proposed scheme by comparison with the token ring access scheme of ISO (ISO 8807/5). The communication performance is evaluated from the viewpoints of the number of stations, packet length, transmission rate, etc. As a result, it is demonstrated that the slotted token passing scheme proposed as the packet switching function for the time‐division multiplexed ring is effective for high‐speed LANs having heavy traffic loads with a large number of stations and a long transm

ISSN:8756-6621    

DOI:10.1002/ecja.4410731204

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

年代:1990

数据来源: WILEY

摘要:

AbstractTo design a highly efficient video codec, comparisons of available techniques from various viewpoints are necessary so that the coding scheme and parameters are chosen appropriately. In recently presented papers and equipment, many systems use motion‐compensated interframe prediction and DCT or VQ schemes for the prediction error coding. A loop filter often is adopted to improve coding efficiency.This paper compares DCT and VQ schemes in an interframe coding scheme, on an optimal blocksize for interfreme prediction error signal coding and on the effect of loop filtering from the viewpoints of coding efficiency and reproduced image quality. Simulations using actual image sequences show that the optimal block size is 4 × 4 or 8 × 8, that the loop filter improves significantly the coding efficiency and reproduced image quality, and that DCT and VQ schemes give nearly the same efficiency with an appropriate loop fil

ISSN:8756-6621    

DOI:10.1002/ecja.4410731205

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

年代:1990

数据来源: WILEY

摘要:

AbstractInitially, jitter characteristics of the multistage connection of optical repeater modules using the digital phase‐locked loop (DPLL) for the timing extraction are examined. Then some problems to be solved are pointed out from the results. Next, a system using new modules with a nonresponse period to improve the jitter characteristics of the module is proposed. It is shown that the nonresponse period is nearly equal to one divided period (TDO).The proposed scheme shows much better jitter suppression characteristics than some other systems, e.g., the clock frequency duplication system, the phase correcting‐restriction system and the system using a random walk filter.Finally, experimental jitter suppression characteristics of multistage connection of new modules with a nonresponse period of 0, 0,5TDOand 1.0TDO, respectively, are shown. These characteristics show a good agreement with simulated results. It is confirmed that the system using DPLL with a 1.0TDOnonresponse period shows the most satisfactory res

ISSN:8756-6621    

DOI:10.1002/ecja.4410731206

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new unidirectional LAN called SURVIVALNET, suitable to high‐speed integrated (HSI) LAN, is proposed. It has a function of controlling transmission by sensing a carrier not only on the outbound as in the case of DAMA but also on the inbound channel. Therefore, high channel utilization and short packet delay can be realized even if the network size becomes large.This paper describes first the principle of SURVIVALNET. Second, its channel utilization is discussed analytically under both light and maximum load and analyzed numerically under medium load using computer simulation. Finally, it is shown that the SURVIVALNET is applicable to HSI LA

ISSN:8756-6621    

DOI:10.1002/ecja.4410731207

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

年代:1990

数据来源: WILEY

摘要:

AbstractA method is presented in this paper to determine the FM modulation/demodulation limit by numerical calculation. This is the synchronization limit when a phase‐locked loop is used as an FM modulator or demodulator. It is shown that the same differential equation can be used both for modulation and demodulation to describe the behavior of the phase‐locked loop for the FM signal. An algorithm is shown which solves the derived equation, which is nonlinear in general, by the harmonic analysis, and derives the periodic solution with the same period as that of the modulating signal by a numerical calculation. The limit of existence for the stable periodic solution is the limit of synchronization.A method is presented which can determine the limit. A phase‐locked loop with a sinusoidal phase comparator and an adequate loop filter is considered as an example. The periodic solution is actually calculated and the FM modulation/demodulation limit is determined from the limit of stability. The obtained result can be accounted for qualitatively and agrees with the experimentally obtained r

ISSN:8756-6621    

DOI:10.1002/ecja.4410731208

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe time‐varying transmission characteristics, as in the case of the selective fading channel, are modeled. Based on the model, the optimum adaptive equalization is proposed considering the speed of variation. Proposals have already been made on this problem for the case of the baseband transmission.This paper extends the results to the case of band transmission and discusses several points which have not been covered in previous studies. First, the model is extended to the case where the overall system including the channel is the band transmission, and the adaptive equalization algorithm is derived using the complex Kalman filter. A simulation based on the model is executed.The tolerable range is determined for the frequency deviation between the carrier and the local oscillation considered as a cause of the deterioration of the performance, along with the variation of the transmission characteristics. To suppress the effect of the decision error in the decision feedback equalization, the training procedure periodically is combined and the effect of the method is analyzed.Finally, the effect of the deviation between the model parameter of the channel characteristics and the equalizer is examined, the tolerable range is determined, and the usefulness of the algorithm is demonstrate

ISSN:8756-6621    

DOI:10.1002/ecja.4410731209

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe multipath channel between a satellite and an aircraft is modeled as direct wave + mirror reflected interference wave + scattered interference wave + receiver thermal noise. The symbol error rate in the channel is analyzed theoretically by strict and approximate methods for the case where the multiphase phase‐modulated wave is received by delayed detection (MDPSK) and for the case where the pilot wave is added and synchronous detection is made (MCPSK). As a result, it is seen that MDPSK is better when the direct wave‐to‐noise power ratio is less than 20 dB and MCPSK is better when it is larger than

ISSN:8756-6621    

DOI:10.1002/ecja.4410731210

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

年代:1990

数据来源: WILEY