We study an asynchronous transfer mode (ATM) multiplexer with selective cell discarding (SCD), and propose as a new traffic parameter the ratio of high and low priority cell streams when a cell stream multiplexed is classified by the cell loss priority (CLP) field in a cell header. By having loss priority control, it is possible to increase the multiplexing gain. For performance analysis we assume that an on-of T bursty traffic is described with several traffic parameters and the proposed priority ratio, and is approximately modeled by a Markov-modulated deterministic process (MMDP). Assuming that several independent and homogeneous on-off bursty traffics with priority discrimination are multiplexed, we present an analytical procedure for the cell loss probability of each priority level in statistical cell multiplexing with loss priority control, and use the performance results for connection admission control (CAC). Also, we consider the effect of the proposed priority ratio. Although loss priority control increases the statistical multiplexing gain, it is not appropriate for the on-off bursty traffic to change the value of the high-priority ratio in order to obtain a larger multiplexing gain, since the admissible load is determined by the loss probability of low priority traffic for most cases and the values of the ratio in a certain range slightly affect it.

In the original shared buffer memory switch, there exists inherent unfairness since multicast cells always own higher priority to be served such that unicast cells must endure longer delay time. We propose a multicasting balancing method to overcome this unfair phenomenon in which the service order for two kinds of cells is decided by a ratio of unicast queue length and multicast queue length for each output port. Performance results are provided to verify the effectiveness.

This paper proposes a novel phase ambiguity resolver with combining a very low power Viterbi decoder employing a scarce state transition scheme to realize cost effective receivers for the PCM sound broadcasting satellite service. The theoretical analyses on phase decision performance show that the proposed resolver achieves the symbol-by-symbol phase detection and decides correctly phases of the demodulated data even if the bit error probability of 710^-2. The resolver also reduces the phase decision time to below 1/1000 of that of the conventional resolver. Furthermore, experimental results of the power consumption estimate that the prototype Viterbi decoder consumes only 60mW at the data rate of 24.576Mbit/s.

This paper investigates the effect of crosstalk in multichannel coherent optical ASK systems. A closed-form signal-to-noise ratio (SNR) expression as a function of number of channels, channel separation, laser phase noise, intermediate frequency (IF) filter bandwidth expansion factor (α), system bit rate (R_b=1/T), and additive shot noise is presented. When the desired channel is between two channels in the electrical domain, the minimum permissible electrical domain channel spacing for a 1dB sensitivity penalty due to crosstalk is found to be 4.85R_b when α is optimum; and 8R_b when α=5 for νT=0.30 at BER=10^-9. A fairly good agreement is found between the results of this work and those of a previous study.

To connect among many radio base stations by using optical fiber bus link in microcellular system, subcarrier multiplexing (SCM) is excellent in simplicity and flexibility. But performance degradation due to optical beat noises is severe problem. To solve this problems, this paper proposes a new type of intercell connection bus fiber-optic link (ICBL) using time division multiplexing, called TDM-ICBL. This paper also analyzes transmission performance of TDM-ICBL theoretically and compares with SCM-ICBL. The analysis clarifies that while the number of RBSs connected to SCM-ICBL is severely restricted by beat noises, TDM-ICBL is more useful than SCM-ICBL when there are many number of connected RBSs.

We have proposed a connection-based optical wavelength division multiplexing network architecture. For the networks such as inter-office LANs, the guarantee of the bandwidths of connection-oriented calls is necessary. Notable features of the network are that multicast can be executed without copying the same data, and that time slots are rearrangeable to increase the throughput. The topology is passive star and a network controller (NWC) is connected to manage the time slot assignment. Each station's transmitting wavelength is fixed and is different from that of other stations. Each receiver changes the receiving wavelength slot by slot. Stations reserve time slots with permission of the NWC. Once a time slot is reserved the station can use the slot in every frame until the reservation is cancelled. This feature guarantees the bandwidths of connection-oriented calls. Upon receiving a time slot request, the NWC searches for a not-in-use slot common to the source station's transmitter (Tx) and the destination station's receiver (Rx). If there is no common empty slot and both the Tx and the Rx have empty slots, the NWC rearranges the already allocated time slots to create a new common empty slot. Simulations were performed to estimate the blocking rates for various cases of call bandwidth including multi-bitrate (the case in which various bandwidth calls are generated in a network) and multicast call, the calculation load of the NWC when it assigns a time slot including rearrangement, and the success rate of rearrangement. It was found that the blocking rate with the rearrangement is greatly reduced (1/10) compared with the case without rearrangement of the same throughput when the number of slots in a frame is more than 120, the number of stations in the network is 60 and the blocking rate without the rearrangement is less than 10^-2. Over 100 Gbps throughput can be achieved when the number of slots in a frame is 120-240, the number of stations is 60, the bitrate of a transmitter is 2.5Gbps and the blocking rate is about 10^-2. The rearrangement is especially effective in the case of multi-bitrate in which the blocking rate can be reduced to 1/100 that of the case without rearrangement at some point. It is also shown that a slot assignment including rearrangement can be executed sufficiently quickly (5s). These results indicate that practical realization of this access control architecture is possible.

The use of existing metallic local line facilities is being studied for providing "video on demand (VOD)" services to residential subscribers across asymmetric digital subscriber lines (ADSL). ADSL carries a high-rate channel in the downstream direction from a central office (CO) to the subscriber, and a low-rate channel in both directions on an existing 2-wire pair. Audio and video signals are compressed by the moving picture experts group's standardized algorithms (MPEG 1 and MPEG 2), and delivered to the subscriber in the high-rate channel. Control (demand and response) signals are transceived in the low-rate channel. This paper presents the line length coverage of ADSL systems given the environment of NTT's local networks. The bit rates in the downstream and upstream directions are assumed to be 1.6-9.2Mbit/s and 24kbit/s, respectively. Two types of ADSL systems are considered: transceiving ADSL signals using the plain old telephone service (POTS) line or the basic rate access (BRA; 320 kbaud ping-pong transmission system) line on the same 2-wire pair. 16-QAM, 32-QAM and 64-QAM are compared as transmission schemes. Intra-system crosstalk interference (interference between identical transmission systems) and inter-system crosstalk interference (interference between different transmission systems) with the existing digital subscriber lines (DSL) are estimated. It is shown that the inter-system crosstalk interference with BRA is most stringent, and ADSL with 16-QAM yields the best performance in NTT's local networks. This paper concludes that realizing ADSL with 16-QAM can achieve channel capacities of up to 9.2Mbit/s for fiber-in-the-feeder (FITF) access systems, but the possibility of applying ADSL to direct access systems is remote except for a restricted short haul use. Some comparisons regarding American local networks are also described.

In this paper, we analyze the traffic data management requirements of the customers, describe the functions of the traffic database needed to satisfy their requirements, and propose a highly distributed database system which can efficiently implement these functions. Finally, we report the results of system performance evaluations.

In this paper, a description of the Hopfield/Tank model used for the telecommunication network routing problem is given at first. And then through the "static" (i.e. the eigenvalue and the eigenspace of the connection matrix) and the dynamic analysis of the model, it has been found that the model has the faster rate to converge to the optimal or sub-optimal solutions from an initial value. Therefore the quality of the final solutions can be guaranteed. The influence of the initial value to the final solutions is also concerned in this paper. The simulation results are given at the end of this paper.

This letter presents SAM, a multiplexer for ATM's circuit emulation services that can precisely control the cell clumping at the connection-level. Compared with a FIFO (First In First Out) multiplexer, it also improves the connection-level diffusion and CDV (Cell Delay Variation) performance. SAM can therefore significantly increase the number of connections accepted by CAC (Call Admission Control) procedures in the subsequent multiplexer.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. Wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. A large capacity photonic ATM switch architecture using WDM technology is proposed in this paper. The proposed switch is suitable for WDM optical ATM networks, that is, an input and an output of the switch are wavelength division multiplexed. The basic switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

We present both numerical and approximate calculations to estimate the total harmonic distortion of demodulated signal from the PLL which has an excess phase shift or some time delay in the loop. Values by the two calculation methods are in agreement with results of the appropriate experiment.

This paper proposes novel optical path accommodation design algorithms for networks wherein the number of wavelengths multiplexed into a fiber is restricted. This algorithm optimizes both optical path route and wavelength assignment in VWP/WP networks. It minimizes optical path cross-connect (OPXC) system scale in terms of incoming/outgoing fiber port numbers. A comparison in terms of required OPXC system scale between the WP and VWP schemes is demonstrated for the first time.

The influence of cochannel, adjacent channel and intermodulation constraints on the capacity of the frequency band in the dynamic channel allocation problem is estimated. Algorithms including a backtracking phase with partial reassignment of currently assigned requirements are proposed. Numerical examples show a strong possibility of a 20% capacity improvement compared to the conventional strategies.