Data-Over-Cable Service Interface Specifications v1.1 (DOCSIS v1.1), developed for data transmissions over Hybrid Fiber Coaxial (HFC) networks, defines five upstream services for supporting per-flow Quality of Services (QoS). The cable modem termination system (CMTS) must periodically grant upstream transmission opportunities to the QoS flows based on their QoS parameters. However, packets may violate QoS requirements when several flows demand the same interval for transmission. This study proposes a two-phase, i.e., the scheduling sequence determination phase and the minislot assignment phase, minislot scheduling algorithm to reduce the QoS violation rate. In the scheduling sequence determination phase, the flow whose packets are most unlikely to violate QoS is scheduled first. Then, in the minislot assignment phase, the scheduler allocates to a flow the available interval where the likelihood of packet violation is minimum. Simulation results demonstrate that our scheduling algorithm can reduce the QoS violation rate by 80-35% over that of the first-come-first-serve-random-selection algorithm. It increases the utilization by 25% as well. The two-phase minislot scheduling algorithm can work within the DOCSIS v1.1 framework.

In this paper, we propose a new scheduling algorithm to achieve fault tolerance in multiprocessor systems. This algorithm first partitions a parallel program into subsets of tasks, based on the notion of height of a task graph. For each subset, the algorithm then duplicates and schedules the tasks in the subset successively. We prove that schedules obtained by the proposed algorithm can tolerate a single processor failure and show that the computational complexity of the algorithm is O(|V|4) where V is the set of nodes of a task graph. We conduct simulations by applying the algorithm to two kinds of practical task graphs (Gaussian elimination and LU-decomposition). The results of this experiment show that fault tolerance can be achieved at the cost of small degree of time redundancy, and that performance in the case of a processor failure is improved compared to a previous algorithm.

We propose the problem of how to transmit an information-theoretically secure bit using random deals of cards among players in hierarchical groups and a computationally unlimited eavesdropper. A player in the highest group wants to send players in lower groups a secret bit which is secure from the eavesdropper and some other players. We formalize this problem and design protocols for constructing secret key exchange spanning trees on hierarchical groups. For each protocol we give sufficient conditions to successfully construct a secret key exchange spanning tree for the hand sizes of the players and the eavesdropper.

When a failure or upset occurring in a controller computer induces a task failure durable for a substantial period, system dynamics apparently deviates from its desirable sample paths, and loses its stability in an extreme case for the period to exceed the hard deadline in a real-time control system. In the paper, we propose an algorithm to combine the deadlines of all elementary tasks (derived formerly by our work) executed in several operation modes with multi-sampling periods. This results in computing the hard deadline of the entire system through modifying task-state equations to capture the effects of task failures and inter-correlations among tasks.

Dynamical theory of cellular automata on groups is developed. Main results are non-Euclidean extensions of Sato and Honda's results on the dynamics of Euclidean cellular automata. The notion of the period of a configuration is redefined in a more group theoretical way. The notion of a co-finite configuration substitutes the notion of a periodic configuration, where the new term is given to it to reflect and emphasize the importance of finiteness involved. With these extended or substituted notions, the relations among period preservablity, injectivity, and Poisson stability of parallel maps are established. Residually finite groups are shown to give a nice topological property that co-finite configurations are dense in the configuration space.

Heavy-ion-induced soft errors (single event upset) in submicron silicon-on-insulator (SOI) MOSFETs under space environmental conditions are studied over the temperature range of 100-400 K using three-dimensional device simulator with full-temperature models. The temperature dependence of the drain collected charge is examined in detail when a heavy-ion strikes the gate center perpendicularly. At very low temperatures, SOI MOSFETs have very high immunity to the heavy-ion-induced soft errors. In particular, alpha-particle-induced soft errors hardly occur at temperatures below 200 K. As the temperature increases, the collected charge shows a marked rate of increase. The problem of single event upset in SOI MOSFETs becomes more serious with increasing working temperature. This is because the induced bipolar mechanism is a main factor to cause charge collection in SOI MOSFETs and the bipolar current increases exponentially with increasing temperature. At room and high temperatures, the drain collected charge is strongly dependent on channel length and SOI film thickness.