An architecture is presented that is a user-centered model for collaborative mobile learning. A paper prototype was first implemented to determine an optimum interface layout for mobile interaction between users via PDAs for the domain of reading-comprehension using Question-Answer Relationship (QAR). A prototype was then constructed using the results of the paper prototype test, the Java 2 Mobile Environment (J2ME), and the Java Wireless Toolkit 2.1. Unlike other systems, the interface developed provides collaborative interaction in mobile learning tasks by allowing textual or voice input.

Optimally fault-tolerant partial-connection multiple-bus networks and their fault-tolerant routing algorithms are presented in this paper. The proposed networks are scalable and provide flexibility in the choice of network parameters determining construction cost, system performance, and fault tolerance, given a fixed number of processors. In this design, when performance begins to fall due to contention, the simple addition of a bus can improve performance without adding costly processors or changing the whole topology, as required for other multiple-bus designs. Also, in situations requiring high reliability, for a fixed number of processors, excellent fault tolerance can be obtained.

A general class of optimal fault-tolerant partial-connection multiple-bus networks and their self-routing algorithms has been developed (Huan-yu Tu, 1999). By conducting a large number of network simulations, using self-similar traffic we compare the performance of these networks with those of traditional single-bus networks and complete-connection multiple-bus networks. Our simulation results show that given a fixed number of processors, these partial-connection networks have improved performance over single-bus systems, perform comparably to the more costly complete-connection multiple-bus systems, and have flexibility in setting the performance level and fault-tolerance level. Moreover, we demonstrate that, in certain of these networks, if the system load increases resulting in decreased performance, this can be handled by adding buses to the system rather than completely changing the topology. Thus, for very little additional cost and no change of topology or routing algorithm, increased loads are handled.

A regular communication architecture for large distributed systems is presented. The system topology consists of n = rm nodes, r ≥2, m ≥ 2, with internode connectivity of (r − 1) m. The system is fault tolerant of (r − 1)m −1 node failures for m ≥ 3.