140126207
Energy Efficient Broadcast Routing in Static Ad Hoc Wireless Networks
In this paper, we discuss energy efficient broadcast in ad hoc wireless networks. The problem of our concern is: given an ad hoc wireless network, find a broadcast tree such that the energy cost of the broadcast tree is minimized. Each node in the network is assumed to have a fixed level of transmission power. We first prove that the problem is NP-hard and propose three heuristic algorithms, namely, shortest path tree heuristic, greedy heuristic, and node weighted Steiner tree-based heuristic, which are centralized algorithms. The approximation ratio of the node weighted Steiner tree-based heuristic is proven to be (1 + 2 ln(n - 1)). Extensive simulations have been conducted and the results have demonstrated the efficiency of the proposed algorithms.
11860267
On optimal placement of relay nodes for reliable connectivity in wireless sensor networks
The paper addresses the relay node placement problem in two-tiered wireless sensor networks. Given a set of sensor nodes in Euclidean plane, our objective is to place minimum number of relay nodes to forward data packets from sensor nodes to the sink, such that: 1) the network is connected, 2) the network is 2-connected. For case one, we propose a (6+ε)-approximation algorithm for any ε > 0 with polynomial running time when ε is fixed. For case two, we propose two approximation algorithms with (24+ε) and (6/T+12+ε), respectively, where T is the ratio of the number of relay nodes placed in case one to the number of sensors. We further extend the results to the cases where communication radiuses of sensor nodes and relay nodes are different from each other.
6771108
Fault-Tolerant Relay Node Placement in Wireless Sensor Networks
The paper addresses the relay node placement problem in two-tiered wireless sensor networks. Given a set of sensor nodes in an Euclidean plane, our objective is to place minimum number of relay nodes to forward data packets from sensor nodes to the sink, such that: 1 the network is connected, 2 the network is 2-connected. For case one, we propose a 6+e-approximation algorithm for any e>0 with polynomial running time when e is fixed. For case two, we propose two approximation algorithms with 24+e and 6/T+12+e, respectively, where T is the ratio of the number of relay nodes placed in case one to the number of sensors.
14550653
QoS Topology Control with Minimal Total Energy Cost in Ad Hoc Wireless Networks
This paper discusses the energy efficient QoS topology control problem in ad hoc wireless networks. Given a set of nodes in a plane, end-to-end traffic demands and delay bounds between node pairs, the problem is to find a network topology that can meet the QoS requirements and the total transmission power of nodes is minimized. We consider two cases of the problem: 1) the traffic demands are not splittable, and 2) the traffic demands are splittable. The first case is formulated as an integer linear programming problem. The latter case is formulated as a mixed integer linear programming problem. A greedy algorithm and an approximation algorithm with ratio n are proposed to solve the problem, where n is the number of nodes. Extensive simulations are conducted to evaluate the performance of proposed algorithms.
13122574
Bandwidth guaranteed call admission in TDMA/CDMA ad hoc wireless networks
This paper first studied the timeslot assignment problem in time division multiple access/code division multiple access (TDMA/CDMA) wireless ad hoc networks. Given a path P, we prove that a timeslot assignment providing one unit of bandwidth on P can be found in O(|P|) time if such an assignment exists. The results have been extended to the case that P can provide two units of bandwidth. Based on the timeslot assignment for the special cases, an efficient slot assignment algorithm with O(|P|^2k) is proposed for general cases, where k is the number of slots in a TDMA frame. Then, the timeslot assignment algorithm is integrated into a quality of service (QoS) call admission scheme for QoS call requests. Extensive simulations are conducted and the results have demonstrated the superior performance of our method.
893749
A Distributed and Efficient Flooding Scheme Using 1-Hop Information in Mobile Ad Hoc Networks
Flooding is one of the most fundamental operations in mobile ad hoc networks. Traditional implementation of flooding suffers from the problems of excessive redundancy of messages, resource contention, and signal collision. This causes high protocol overhead and interference with the existing traffic in the networks. Some efficient flooding algorithms were proposed to avoid these problems. However, these algorithms either perform poorly in reducing redundant transmissions or require each node to maintain 2-hop (or more) neighbors information. In the paper, we study the sufficient and necessary condition of 100 percent deliverability for flooding schemes that are based on only 1-hop neighbors information. We further propose an efficient flooding algorithm that achieves the local optimality in two senses: 1) the number of forwarding nodes in each step is minimal and 2) the time complexity for computing forwarding nodes is the lowest, which is O(nlogn), where n is the number of neighbors of a node. Extensive simulations have been conducted and simulation results have shown the excellent performance of our algorithm
13024009
Building effective defect-prediction models in practice
Defective software modules cause software failures, increase development and maintenance costs, and decrease customer satisfaction. Effective defect prediction models can help developers focus quality assurance activities on defect-prone modules and thus improve software quality by using resources more efficiently. These models often use static measures obtained from source code, mainly size, coupling, cohesion, inheritance, and complexity measures, which have been associated with risk factors, such as defects and changes.
8038499
Workshop Report
This is a report on a workshop held at Cornell University on Ma rch 30 – April 1, 2015. The workshop was held to honor Prof. Donald Farley on the occasio n of his 80th birthday (belatedly) and also to consider the future of radio and space physics. Ab out 60 scientists representing institutions in North America, South America, and Europe attende d. Participants included some of the most senior scientists in the field, mid-career scientists, early-career scientists, and students. Along with radio scientists, the workshop was attended by NASA inv estigators, theorists, modelers, and a representative from NSF. The focus of the workshop was the state of the AGS facilities. The first day of the workshop was retrospective in nature, and the second day considered cont emporary research being performed with the facilities. The third day focused on discussions about t he future. The discussions were vigorous and broad and extended to the vitality of not just the facilit ies but to geospace and heliospheric science generally. A recurring theme of the workshop was the fact that incoheren t scatter remains, by far, the most accurate and precise technique for studying the upper atmos phere, the standard by which other experimental techniques, ground-based and in situ, are valid ated and calibrated. Incoherent scatter experiments yield unambiguous estimates of the most import ant state parameters in the upper atmosphere with fine spatio-temporal resolution and offer the possibility of measurements with longterm continuity. Only sounding rockets make measurements w ith superior resolution, but sounding rockets are most often launched nearby incoherent scatter r dars since the latter provide critical experimental context. The incisive nature of incoherent scatter radar measuremen ts will be crucial for resolving fundamental problems in geospace physics. For example, the E region/ lower thermosphere is a complicated region of geospace that remains poorly understood . This is the region where turbulence transitions to laminar flow, where molecular oxygen is disso ciated, where ionization becomes abundant, where ions are unmagnetized whereas electrons are mag netized, and where strong neutral shears exist and electric currents flow. The dynamo fields whi ch drive the ionosphere are generated here and modulated by neutral waves in a complicated way whic h couples the upper atmosphere to the lower atmosphere. Neutral atmospheric waves break he re, but which waves penetrate and where the energy goes is unclear. Sporadic ionization layer s which have grave influence on radio propagation exist here, but their generation mechanism and the influence of the underlying neutral dynamics is not understood. Ground-based remote sensing us i our best experimental tool will be vital in elucidating the processes at work here. Much of the discussion concerned the dichotomy between basi c and applied research at the facilities, the two axes that define Pasteur’s quadrant. Examp les of basic research presented at the workshop included observations of heretofore unseen waves nd turbulence in the lower thermosphere made using broadband measurements of the full incohe rent scatter spectrum at Arecibo and HF interferometry at Jicamarca, observations of extraordi narily high-altitude irregularities over Jicamarca, and methods for inferring high-definition convect ion and current patterns with the PFISR. Applied research with the facilities includes long-durati on, 24-7 observations of basic state parameters used to drive global space-weather models.
17436749
Feature Transformation and Multivariate Decision Tree Induction
Univariate decision trees (UDT's) have inherent problems of replication, repetition, and fragmentation. Multivariate decision trees (MDT's) have been proposed to overcome some of the problems. Close examination of the conventional ways of building MDT's, however, reveals that the fragmentation problem still persists. A novel approach is suggested to minimize the fragmentation problem by separating hyperplane search from decision tree building. This is achieved by feature transformation. Let the initial feature vector be x, the new feature vector after feature transformation T is y, i.e., y = T(x). We can obtain an MDTb y (1) building a UDT on y; and (2) replacing new features y at each node with the combinations of initial features x. We elaborate on the advantages of this approach, the details of T, and why it is expected to perform well. Experiments are conducted in order to confirm the analysis, and results are compared to those of C4.5, OC1, and CART.
62639812
Traffic grooming in WDM/SONET BLSR rings with multiple line speeds
WDM/SONET provides a natural migration path to support traffic growth. In WDM/SONET, each wavelength is a separate SONET ring and each ring can be set to one of several line speeds. The line speed should be high if there is enough traffic to realize the economy of scale, otherwise, it should be low to reduce the cost. Despite of the advantages, there are no general tools and methodologies available to help network designers enjoy the benefits of multiple line speeds. For the first time, we propose a comprehensive approach to solve the traffic grooming problem, which includes both novel, complete ILP formulations that can be used to solve small size problems exactly and an efficient heuristic algorithm that can be used to solve large problems quickly. Using the tools we developed, we study the trade-offs of shortest path routing, study the cost benefits of traffic switching, compare UPSR and BLSR, and show that multiple line speeds can significantly reduce cost
267445
Biological Nomenclatures: A Source of Lexical Knowledge and Ambiguity
There has been increased work in developing automated systems that involve natural language processing (NLP) to recognize and extract genomic information from the literature. Recognition and identification of biological entities is a critical step in this process. NLP systems generally rely on nomenclatures and ontological specifications as resources for determining the names of the entities, assigning semantic categories that are consistent with the corresponding ontology, and assignment of identifiers that map to well-defined entities within a particular nomenclature. Although nomenclatures and ontologies are valuable for text processing systems, they were developed to aid researchers and are heterogeneous in structure and semantics. A uniform resource that is automatically generated from diverse resources, and that is designed for NLP purposes would be a useful tool for the field, and would further database interoperability. This paper presents work towards this goal. We have automatically created lexical resources from four model organism nomenclature systems (mouse, fly, worm, and yeast), and have studied performance of the resources within an existing NLP system, GENIES. Using nomenclatures is not straightforward because issues concerning ambiguity, synonymy, and name variations are quite challenging. In this paper we focus mainly on ambiguity. We determined that the number of ambiguous gene names within the individual nomenclatures, across the four nomenclatures, and with general English ranged from 0%-10.18%, 1.187%-20.30%, and 0%-2.49% respectively. When actually processing text, we found the rate of ambiguous occurrences (not counting ambiguities stemming from English words) to range from 2.4%-32.9% depending on the organisms considered.