In the present paper, a new coding scheme for infrared ASK communication systems--Pulse Sequence Modulation (PSM)--will be proposed, which uses a combination of pulse sequences so that it canattain zero-spectrum points at specific frequencies within the main-lobe region. The interference to the other IR systems was a problem of the conventional infrared ASK communication systems. The proposed PSM coding scheme reduces the interference by decreasing the emission at specific frequencies, and helps multiple IR communication systems co-exist without deteriorating coding efficiency.

In the present paper, a new coding scheme for infrared ASK communication systems--Pulse Sequence Modulation (PSM)--will be proposed, which uses a combination of pulse sequences so that it canattain zero-spectrum points at specific frequencies within the main-lobe region. The interference to the other IR systems was a problem of the conventional infrared ASK communication systems. The proposed PSM coding scheme reduces the interference by decreasing the emission at specific frequencies, and helps multiple IR communication systems co-exist without deteriorating coding efficiency.

For traffic control in high speed ATM Networks Usage Parameter Control (UPC) plays an important role. The existing UPC schemes have some limitations. It is difficult to implement policy which involves monitoring vioations while guaranteeing QoS for the compliant connections-particularly with respect to bursty traffic sources. This is due to the difficulty in measuring the Sustained Cell Rate (SCR) and Maximum Burst Size (MBS) parameters simultaneously. To ensure prompt action against policy-violations, speedy detection is an important requirement. But the existing UPC schemes do not have a satisfactory response time. In this paper, we propose a new scheme called Markovian State-Dependent UPC schemes (MSDU) to police SCR and MBS parameter violation simultaneously with a satisfactory response time. The MSDU scheme is performed by using two virtual queues: 1) a Markovian State Dependent Service queue and 2) a Fixed Service queue. The discrete time analysis of the MSDU is carried out for a bursty source which is a Markov-Modulated Bernoulli Process (MMBP). The improved effectiveness of the proposed MSDU is clarified by a numerical comparison with UPC based on standard Leaky Bucket scheme.

Communication costs have become a performance bottleneck in many applications, and are a big issue for high performance computing on massively parallel machines. This paper proposes a halo exchange method for unstructured sparse matrix vector products within the algebraic multigrid method, and evaluate it on a supercomputer with mesh/torus networks. In our numerical tests with a Poisson problem, the proposed method accelerates the linear solver more than 14 times with 23040 cores.

Recent progress in the optical transmission technology makes an ATM passive optical network (APON) a good candidate for access networks. APON based on tree topology requires efficient medium access control (MAC) to multiplex upstream data flows efficiently while not disturbing the original pattern. In this paper, we proposed a Window-based permit distribution scheme for the MAC protocol of APON. It derives the rate of generated cell during one spacing window by the unit called time segment, and spaces permits not to cluster the cells in upstream transmission. The purpose of the proposed scheme is to make the permit arrival rate close to the cell arrival rate, so, reduces the CDV even if under the various kinds of bursty traffic. In addition, the proposed scheme does not require the additional MAC overhead for cell arrival timing information. The result of simulation shows that the performance of proposed protocol is better than current protocols in terms of transfer delay and 1-point CDV.

Recent progress in the optical transmission technology makes an ATM passive optical network (APON) a good candidate for access networks. APON based on tree topology requires efficient medium access control (MAC) to multiplex upstream data flows efficiently while not disturbing the original pattern. In this paper, we proposed a Window-based permit distribution scheme for the MAC protocol of APON. It derives the rate of generated cell during one spacing window by the unit called time segment, and spaces permits not to cluster the cells in upstream transmission. The purpose of the proposed scheme is to make the permit arrival rate close to the cell arrival rate, so, reduces the CDV even if under the various kinds of bursty traffic. In addition, the proposed scheme does not require the additional MAC overhead for cell arrival timing information. The result of simulation shows that the performance of proposed protocol is better than current protocols in terms of transfer delay and 1-point CDV.

Major problems of traffic control in ATM networks include how to decide whether a network accepts a new call or not in real time and how to select the best set of Dual Leaky Bucket (DLB) parameter values. To solve these problems, it is necessary to determine the amount of network bandwidth required by the call. In this paper, we present an analysis based on bounding technique to derive an upper bound on bandwidth requirement when the call is characterized by a set of DLB parameters. Consequently, a new definition of the upper bound on bandwidth requirement and simple formulae used for computing the upper bound have been obtained. To clarify the advantages of the derived upper bound, we demonstrate its two applications, one to select the best set of DLB parameter values from candidates for minimizing the amount of bandwidth to be allocated to the call and the other to establish a Connection Admission Control (CAC) scheme. The upper bound-based CAC scheme is fast enough to process in real time due to its simplicity and provides a significant improvement of network utilization compared to the peak rate-based CAC scheme.