Optimal controlled flooding search in a large wireless network
In this paper we consider the problem of searching for a node or an object (i.e., piece of data, file, etc.) in a large wireless network. We consider the class of controlled flooding search strategies where query/search packets are broadcast and propagated in the network until a preset TTL (time-to-live) value carried in the packet expires. Every unsuccessful search attempt results in an increased TTL value (i.e., larger search area) and the same process is repeated. We derive search strategies that minimize the search cost in the worst-case, via a performance measure in the form of the competitive ratio between the average search cost of a strategy and that of an omniscient observer. This ratio is shown in prior work to be lower bounded by 4 among all deterministic search strategies. In this paper we show that by using randomized strategies this ratio is lower bounded by e. We derive an optimal strategy that achieves this lower bound, and discuss its performance under other performance criteria.

title: Sound mobility models
abstract: Simulation has become an indispensable tool in the construction and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. Unfortunately, the vast majority of mobility models---including all those in which nodal speed and distance or destination are chosen independently---suffer from decay; average speed decreases until converging to some long-term average. Such decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process.This paper shows via analysis that such decay is inevitable in a wide variety of mobility models, including the most common in use today. We derive a general framework for describing this decay, and apply it to a number of practical cases. Furthermore, this framework allows us to transform any given mobility model into a stationary one: choose initial speeds from the steady-state distribution, and subsequent speeds from the original. This transformation provides sound models for simulation, eliminating variations in average nodal speed.

title: On the optimality of an index policy for bandwidth allocation with delayed state observation and differentiated services
abstract: In this paper we study the optimality of an index policy for a bandwidth allocation problem, where a single server is allocated among N queues in a slotted system based on the queue backlog information. Due to the physical nature of the system this information is delayed, in that when the allocation decision is made, the server only has the backlog information from an earlier time. This results in imperfect and partial state observation. Queues have Bernoulli arrival processes with different probabilities of arrival, as well as different buffering/holding costs to differentiate heterogeneous classes of traffic/service. The objective is to minimize the expected total discounted holding cost over a finite or infinite horizon. We introduce an index policy with indices defined as functions of the state of a queue. We first show that when the state of the system is away from the boundary, i.e., no empty queues, the index policy is optimal. When there are empty queues, we show that under sufficient separation of the indices the index policy is still optimal. We show by example that if the separation does not hold, the index policy is not necessarily optimal. We then formulate the optimal bandwidth allocation as a restless bandit problem and show under what conditions the index policy calculated using Whittle's heuristics, which in general is only asymptotically optimal, is optimal for the finite case

title: A general framework to construct stationary mobility models for the simulation of mobile networks
abstract: Simulation has become an indispensable tool in the design and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. In this paper, we show that a large class of mobility models - including all those in which nodal speed and distance or destination are chosen independently - have a transient period in which the average node speed decreases until converging to some long-term average. This speed decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process. In this paper, we derive a general framework for describing this decay and apply it to a number of cases. Furthermore, this framework allows us to transform a given mobility model into a stationary one by initializing the simulation using the steady-state speed distribution and using the original speed distribution subsequently. This transformation completely eliminates the transient period and the decay in average node speed and, thus, provides sound models for the simulation of mobile systems.

title: AMRoute: Ad Hoc Multicast Routing Protocol
abstract: The Ad hoc Multicast Routing protocol (AMRoute) presents a novel approach for robust IP Multicast in mobile ad hoc networks by exploiting user-multicast trees and dynamic logical cores. It creates a bidirectional, shared tree for data distribution using only group senders and receivers as tree nodes. Unicast tunnels are used as tree links to connect neighbors on the user-multicast tree. Thus, AMRoute does not need to be supported by network nodes that are not interested/capable of multicast, and group state cost is incurred only by group senders and receivers. Also, the use of tunnels as tree links implies that tree structure does not need to change even in case of a dynamic network topology, which reduces the signaling traffic and packet loss. Thus AMRoute does not need to track network dynamics; the underlying unicast protocol is solely responsible for this function. AMRoute does not require a specific unicast routing protocol; therefore, it can operate seamlessly over separate domains with different unicast protocols. Certain tree nodes are designated by AMRoute as logical cores, and are responsible for initiating and managing the signaling component of AMRoute, such as detection of group members and tree setup. Logical cores differ significantly from those in CBT and PIM-SM, since they are not a central point for data distribution and can migrate dynamically among member nodes. Simulation results (using ns-2) demonstrate that AMRoute signaling traffic remains at relatively low level for typical group sizes. The results also indicate that group members receive a high proportion of data multicast by senders, even in the case of a highly dynamic network.

title: Controlled Flooding Search with Delay Constraints
abstract: In this paper we consider the problem of query and search in a network, e.g., searching for a specific node or a piece of data. We limit our attention to the class of TTL (time-to-live) based controlled flooding search strategies where query/search packets are broadcast and relayed in the network until a preset TTL value carried in the packet expires. Every unsuccessful search attempt results in an increased TTL value (i.e., larger search area) and the same process is repeated. Every search attempt also incurs a cost (in terms of packet transmissions and receptions) and a delay (time till timeout or till the target is found). The primary goal is to derive search strategies (i.e., sequences of TTL values) that minimize a worstcase cost measure subject to a worst-case delay constraint. We present a constrained optimization framework and derive a class of optimal strategies, shown to be randomized strategies, and obtain their performance as a function of the delay constraint. We also use these results to discuss the trade-off between search cost and delay within the context of flooding search.

title: Combinatorial constructions for optimal supersaturated designs
abstract: Combinatorial designs have long had substantial application in the statistical design of experiments, and in the theory of error-correcting codes. Applications in experimental and theoretical computer science, communications, cryptography and networking have also emerged in recent years. In this paper, we focus on a new application of combinatorial design theory in experimental design theory. E ( f NOD ) criterion is used as a measure of non-orthogonality of U-type designs, and a lower bound of E ( f NOD ) which can serve as a benchmark of design optimality is obtained. A U-type design is E ( f NOD )-optimal if its E ( f NOD ) value achieves the lower bound. In most cases, E ( f NOD )-optimal U-type designs are supersaturated. We show that a kind of E ( f NOD )-optimal designs are equivalent to uniformly resolvable designs. Based on this equivalence, several new infinite classes for the existence of E ( f NOD )-optimal designs are then obtained.

title: An Evaluation of the Use of Problem-Based Learning Software By Middle School Students
abstract: Research has shown the potential of a problem-based approach to enhance students' learning. The interactive nature of hypermedia technology and its ability to deliver information in different media formats can provide unique capabilities for implementing problem-based learning (PBL) environments. Yet, we know little about the types of tools that are effective in supporting students' learning in a hypermedia supported PBL environment. The purpose of this study was to investigate both the use of tools and design features in a piece of PBL software and their effectiveness on middle school students' learning. The findings of this study show that students who were exposed to the PBL environment increased their achievement scores from pre to posttest more than those students who learned the same content in the traditional classroom. Students' reading ability was found to be a better predictor for their achievement in PBL than their math ability. However, the brief treatment of the study had only limited impact on students' attitude toward learning science. The findings of the study and their implications are discussed in detail.

title: A High Population, Fault Tolerant Parallel Raytracer
abstract: We present hierarchical master-slave architecture for performing parallel raytracing algorithms that can support a large population of participating clients and at the same time maintain fault tolerance at the application level. Our design allows for scalability with minimal data redundancy and maximizes the utilization of each client involved in the raytracing process. Our results show that this three-layer system can survive any type or number of client failures, and any non-concurrent server failures, while maintaining a near linear increase in performance with the addition of each new processing client.

title: Deploying the Mobile-Agent Technology in Warehouse Management
abstract: Mobile agents, a relatively new paradigm for distributed software development, has become an accessible technology in recent years. The potential benefits of this paradigm, including the reduction of network bandwidth consumption and latency, promise to revolutionize distributed applications. 
 
This paper describes a proposed project to deploy the mobile agent technology in warehouse management.

title: The History and Status of Chinese Americans in Librarianship
abstract: This article reviews the brief history of Chinese Americans in the United States and their contributions to librarianship. Despite the hardships and challenges they faced, Chinese American librarians made great contributions to the building of East Asian libraries, to the cataloging of East Asian and Chinese collections, and to the development of library automation. They have advanced information technologies, promoted multicultural and diversity library services, and participated in library management and administration. Chinese Americans are active in library and information science education, in professional associations, in international librarianship, in national library and information services policy making and programming, and national policy making. Pioneers and key figures are identified with their accomplishments. The origin, purpose, programs, and activities of the Chinese American Librarians Association are also described.