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Construction of Virtual Backbone with Multiple Factors Constraints in Wireless Ad-hoc Network.
Abstract
Connected Dominating Set (CDS) has been a well known approach for constructing a virtual backbone to alleviate the broadcasting storm in wireless ad-hoc networks. Current research has focused on minimizing the CDS size, since computing a minimum size CDS is NP-hard. However, little work on CDS with multiple factors constraints has been found in literature. In this work, we investigate the trade-offs among multiple factors in CDS construction, such as fault tolerance, size, diameter and running time. To our best knowledge, no existing research has considered these important factors together in a single model, so that we introduce the multi-factors model studying a joint optimization problem in which the objective is to optimize the CDS size, network latency or running time while keeping the fault tolerance. Building on this model, we provide the approximation algorithms with constant ratios. In addition, we present improvement techniques, inspired by the computational geometry and probability, that systematically reduce running time or size of CDS. Simulation results show that our algorithms can gain good trade-offs among these factors, which coincide with theoretical analysis.
... In [6] a constant-ratio approximation algorithm for MCDS problem in unit ball graphs is proposed £rst and then introduced and analyzed the edge-weighted bottleneck CDS problem, which seeks a minimum edge weight in a graph such that the corresponding bottleneck subgraph has a CDS of size k. The work in [39] investigate the tradeoffs among multiple factors in CDS construction, such as fault tolerance, size, diameter and running time. They introduced multi-factors model studying a joint optimization problem in which the objective is to optimize the CDS size, network latency or running time while keeping the fault tolerance. ...
Connected dominating set (CDS) problem in unit disk graph has signi£cant impact on an ef£cient design of routing pro-tocols in wireless sensor networks, where the searching space for a route is reduced to nodes in the set. A set is dominating if all the nodes in the system are either in the set or neighbors of nodes in the set. In this paper, a simple and ef£cient heuristic method is proposed for £nding a minimum connected dominating set (MCDS) in ad hoc wireless networks based on the new parameter support of vertices. With this parameter the proposed heuristic approach effectively £nds the MCDS of a graph. Extensive computational experiments show that the proposed approach outperforms the recently proposed heuristics found in the literature for the MCDS.
In the constructing algorithms of sensor networks MIS (maximum independent set), the parallel-algorithm would construct a CDS (connected dominating set) with uncertain upper-limit size and edge nodes. In this case, based upon serial MIS constructing algorithm, a weight and timing based triggering CDS constructing algorithm was presented. The presented algorithm need not construct spanning tree, thus reduces the computation delay and communication overhead. Meanwhile, the nodes orderly join the MIS one after another in the algorithm, thus it greatly reduces the number of edge nodes, and builds a CDS with certain upper-limit.
In a broadcasting task, source node wants to send the same message to all the other nodes in the network. Existing solutions range from connected dominating set CDS based on static networks to blind flooding for moderate mobility and hyper-flooding for highly mobile and frequently partitioned networks. Existing protocols for all scenarios are based on some threshold parameters e.g. speed, which may be expensive to gather to locally select between these three solution approaches. Here, we describe a new seamless broadcasting from static to mobile protocol, which adjusts itself to any mobility scenario without using any mobility or density-related parameter. Unlike existing methods for highly mobile scenarios, in the proposed method, two nodes do not transmit every time they discover each other as new neighbours. Each node maintains a list of two hop neighbours by periodically exchanging ‘hello’ messages, and decides whether or not it is in CDS. Upon receiving the first copy of message intended for broadcasting, it selects a waiting timeout and constructs two lists of neighbours: neighbours that received the same message and neighbours that did not receive it. Nodes not in CDS select longer timeouts than nodes in CDS. These lists are updated upon receiving further copies of the same packet. When timeout expires, node retransmits if the list of neighbours in need of message is non-empty. ‘Hello’ messages received while waiting, or after timeout expiration may revise all lists and CDS status and consequently the need to retransmit. This provides a seamless transition of protocol behaviour from static to highly mobile scenarios, which is applicable to a variety of multi-hop wireless networks.
Advanced Metering Infrastructures (AMI) facilitate efficient and reliable exchange of electricity information between the homes and utilities. Their unique characteristics (e.g., connecting millions of smart meters; accessing customers’ private information), however, make them a lucrative target for adversaries. For example, an attacker might try to compromise the head-end of an AMI and send “remote disconnect commands” to the smart meters, disconnecting a large number of customers. To implement message authentication and protect message integrity and confidentiality, a number of cryptographic keys are being utilized. A “command key”, for example, signs messages that are sent from the head-end to the meters. Such keys, however, introduce their own set of problems if they ever get compromised. A stolen command key would allow an adversary to continuously send malicious commands to the meters. Hence, the compromised keys must be revoked and replaced as quickly as possible. This paper proposes an efficient and reliable key distribution framework for the AMI mesh networks based on the connected dominating set approach. The keys are replaced with minimal latency through our “hexagon-tile coloring scheme”, which allows the maximum number of keys to be transmitted in parallel, free of collision.
Virtual backbone is helpful to reduce computation and communication overhead in wireless networks. Based upon serial Maximum Independent Set (MIS) constructing algorithms, this paper presents a weight and timing based triggering Connected Dominating Set (CDS) constructing algorithm. In the algorithm, the nodes orderly join the MIS one after another, thus it greatly reduces the number of edge nodes, and builds a CDS with certain upper-limit. The algorithm is also designed to reduce the communication complexity, and helps to reduce the node's power consumptions.
This study focuses on the mechanisms responsible for enhanced oil
recovery (EOR) from fractured carbonate reservoirs by surfactant
solutions, and methods to screen for effective chemical formulations
quickly. One key to this EOR process is the surfactant solution
reversing the wettability of the carbonate surfaces from less
water-wet to more water-wet conditions. This effect allows the
aqueous phase to imbibe into the matrix spontaneously and expel
oil bypassed by a waterflood.
This study used different naphthenic acids (NA) dissolved in
decane as a model oil to render calcite surfaces less water-wet.
Because pure compounds are used, trends in wetting behavior can
be related to NA molecular structure as measured by solid adsorption;
contact angle; and a novel, simple flotation test with calcite
powder. Experiments with different surfactants and NA-treated
calcite powder provide information about mechanisms responsible
for sought-after reversal to a more water-wet state. Results indicate
this flotation test is a useful rapid screening tool to identify better
EOR surfactants for carbonates.
The study considers the application of surfactants for EOR
from carbonate reservoirs. This technology provides a new opportunity
for EOR, especially for fractured carbonate, where waterflood
response typically is poor and the matrix is a high oil-saturation
target.
Energy conservation is an important concern in wireless networks. Many algorithms for constructing a broadcast tree with minimum energy consumption and other goals have been developed. However, no previous research work considers the total energy consumption and transmission delays of the broadcast tree simultaneously. In this paper, based on an (alpha, beta){hbox{-}}{rm tree}, a novel concept to wireless networks, we define a new Strongly connected Broadcast Arborescence with bounded Transmission delay (SBAT) problem and design the Strongly connected Broadcast Arborescence (SBA) algorithm with linear running time to construct a strongly connected broadcast tree with bounded total power, while satisfying the constraint that the transmission delays between the source and the other hosts are also bounded. We also propose the distributed version of the SBA algorithm. The theoretical analysis and simulation results show that the SBA algorithm gives a proper solution to the SBAT problem.
In this paper, we study the connected dominating set (CDS) problem in disk graphs. The CDS problem has a significant impact on an efficient design of routing protocols in wireless networks. This problem has been studied extensively in unit disk graphs, in which each node has the same transmission range. However, in wireless ad hoc networks, the transmission ranges of all nodes are not necessary equal. In this paper, we introduce the CDS problem in disk graphs and present a constant approximation algorithm which can be implemented as a distributed algorithm.
This work investigates and analyzes recent research trends and presents experimental guidelines on MANETs. More than 1,300 MANET related papers in IEEE/ IEE Electronic Library (IEL Online) from 1998 to 2003 were collected and surveyed. The research trends, qualitative analysis and simulation guidelines from fifteen major MANET issues are investigated to assist the user in conducting MANET research. Based on recent six year trends we found that some issues such as routing and power management attracted much attention. We also found that some issues have potential study value, such as IP addressing and fault tolerance. In the qualitative analysis, we found that some factors such as scalability, stability, and reliability attracted much attention in major MANET issues. The essential simulation metrics for various MANET issues are identified and listed for experimental guidelines. The analysis results demonstrate the utilization trends for various MANET simulators.