Near-Optimal Distributed Approximation of Minimum-Weight Connected Dominating Set

This paper presents a near-optimal distributed approximation algorithm for the minimum-weight connected dominating set (MCDS) problem. The presented algorithm finds an $O(\log n)$ approximation in $\tilde{O}(D+\sqrt{n})$ rounds, where $D$ is the network diameter and $n$ is the number of nodes. MCDS is a classical NP-hard problem and the achieved approximation factor $O(\log n)$ is known to be optimal up to a constant factor, unless P=NP. Furthermore, the $\tilde{O}(D+\sqrt{n})$ round complexity is known to be optimal modulo logarithmic factors (for any approximation), following [Das Sarma et al.---STOC'11].Comment: An extended abstract version of this result appears in the proceedings of 41st International Colloquium on Automata, Languages, and Programming (ICALP 2014

Considering Pigeons for Carrying Delay Tolerant Networking based Internet traffic in Developing Countries

There are many regions in the developing world that suffer from poor infrastructure and lack of connection to the Internet and Public Switched Telephone Networks (PSTN). Delay Tolerant Networking (DTN) is a technology that has been advocated for providing store-and-forward network connectivity in these regions over the past few years. DTN often relies on human mobility in one form or another to support transportation of DTN data. This presents a socio-technical problem related to organizing how the data should be transported. In some situations the demand for DTN traffic can exceed that which is possible to support with human mobility, so alternative mechanisms are needed. In this paper we propose using live carrier pigeons (columba livia) to transport DTN data. Carrier pigeons have been used for transporting packets of information for a long time, but have not yet been seriously considered for transporting DTN traffic. We provide arguements that this mode of DTN data transport provides promise, and should receive attention from research and development projects. We provide an overview of pigeon characteristics to analyze the feasibility of using them for data transport, and present simulations of a DTN network that utilizes pigeon transport in order to provide an initial investigation into expected performance characteristics

Improved Approximation Algorithm for Minimum-Weight (1,m)(1,m)--Connected Dominating Set

The classical minimum connected dominating set (MinCDS) problem aims to find a minimum-size subset of connected nodes in a network such that every other node has at least one neighbor in the subset. This problem is drawing considerable attention in the field of wireless sensor networks because connected dominating sets can serve as virtual backbones of such networks. Considering fault-tolerance, researchers developed the minimum $k$-connected $m$-fold CDS (Min$(k,m)$CDS) problem. Many studies have been conducted on MinCDSs, especially those in unit disk graphs. However, for the minimum-weight CDS (MinWCDS) problem in general graphs, algorithms with guaranteed approximation ratios are rare. Guha and Khuller designed a $(1.35+\varepsilon)\ln n$-approximation algorithm for MinWCDS, where $n$ is the number of nodes. In this paper, we improved the approximation ratio to $2H(\delta_{\max}+m-1)$ for MinW$(1,m)$CDS, where $\delta_{\max}$ is the maximum degree of the graph

Distributed construction of energy-efficient ad hoc wireless broadcast trees

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 71-72).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.We address the energy-efficient broadcasting problem in ad hoc wireless networks. First we show that finding the minimum energy broadcast tree is NP-complete and develop an approximation algorithm, which computes sub-optimal solutions in polynomial time. We present a distributed algorithm that computes all N possible broadcast trees simultaneously with O(N2) message complexity. We compare our algorithm's performance to the best known centralized algorithm, and show that it constructs trees consuming, on average, only 18% more energy. Finally, we introduce the multiple source broadcasting problem, and explore algorithms that address this problem.by Ashwinder S. Ahluwalia.M.Eng

Allocation Algorithms for Networks with Scarce Resources

Many fundamental algorithmic techniques have roots in applications to computer networks. We consider several problems that crop up in wireless ad hoc networks, sensor networks, P2P networks, and cluster networks. The common challenge here is to deal with certain bottleneck resources that are crucial for performance of the underlying system. Broadly, we deal with the following issues. Data: The primary goal in resource replication problems is to replicate data objects on server nodes with limited storage capacities, so that the latency of client nodes needing these objects is minimized. Previous work in this area is heuristic and without guarantees. We develop tight (or nearly) approximation algorithms for several problems including basic resource replication - where clients need all objects and server can store at most one object, subset resource replication - where clients require different subsets of objects and servers have limited non-uniform capacity, and related variants. Computational resources: To facilitate packing of jobs needing disparate amounts of computational resources in cluster networks, an important auxiliary problem to solve is that of container selection. The idea is to select a limited number of ``containers'' that represent a given pool of jobs while minimizing ``wastage'' of resources. Subsequently, containers representing jobs can be packed instead of jobs themselves. We study this problem in two settings: continuous - where there are no additional restrictions on chosen containers, and discrete - where we must choose containers from a given set. We show that the continuous variant is NP-hard and admits a polynomial time approximation scheme. Contrastingly, the discrete variant is shown to be NP-hard to approximate. Therefore, we seek bi-approximation algorithms for this case. Energy resources: Wireless ad hoc networks contain nodes with limited battery life and it is crucial to design energy efficient algorithms. We obtain tight approximation (up to constant factors) guarantees for partial and budgeted versions of the connected dominating set problem, which is regarded as a good model for a virtual backbone of a wireless ad hoc network. Further, we will discuss approximation algorithms for some problems involving target monitoring in sensor networks and message propagation in radio networks. We will end with a discussion on future work

PrESerD - Privacy ensured service discovery in mobile peer-to-peer environment

In mobile peer-to-peer networks many service discovery protocols have been proposed. Most of these protocols disregard the exposure of the participating peers\u27 privacy details, although they consider the security issues. In these methods, the participating peers must provide their identities, during the service discovery process, to be authorized to utilize the service. However, a peer might not be willing to reveal its identity until it identifies the service providing peer. So these peers face a problem; should the requesting peer or the service providing peer reveal the identity first, and hence, this is similar to the chicken-and-egg problem. The protocol presented in Private and Secure Service Discovery via Progressive and Probabilistic Exposure, solves this problem to some extent and works considerably to discover the services available in the user\u27s vicinity in a single-hop time sync peers only. In this paper, we propose a privacy-preserving model based on challenge/response idea to discover the services available in the mobile peer-to-peer network even when the moving user and the service provider are at a multi-hop distance away. The performance studies shows that our protocol does this in a communication efficient way with reduced false positives while preserving the privacy details of the user and service provider --Abstract, page iv