Date of Submission

7-22-2010

Date of Award

7-22-2011

Institute Name (Publisher)

Indian Statistical Institute

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Subject Name

Computer Science

Department

Advance Computing and Microelectronics Unit (ACMU-Kolkata)

Supervisor

Das, Nabanita (ACMU-Kolkata; ISI)

Abstract (Summary of the Work)

Wireless ad hoc networking is an upcoming communication technology that makes exchange of information possible without any pre-existing infrastructure. Over the last decade it has grabbed tremendous interest in the research community due to its easy deployability and high flexibility, with numerous applications to social, industrial and personal uses. In this thesis, we designed effcient light weight distributed algorithms based on minimal local information to resolve the problems related to the initialization and topology configuration of wireless ad hoc networks with special emphasis on optimal utilization of limited resources. Once the ad hoc nodes with in-built radio transceivers are deployed the media access control (MAC) problem is to be resolved first for collision-free message exchange. Here, we studied the Time Division Multiple Access (TDMA) protocol for low-power and guaranteed access of the medium. For any arbitrary distribution of nodes, determining the minimum TDMA frame length is NP-hard. Moreover, scheduling a time slot to each node within the given frame length in a purely distributed fashion is much harder. A new upper bound is established on the TDMA frame length for any random distribution of nodes on a two-dimensional region. We proved the fact that this upper bound is of linear order of the maximum node degree. Distributed algorithms are presented for single and multiple slot assignments followed by a scheme for rearranging the slots to adapt with limited perturbations in the network topology. Next, we investigated the problem of constructing connected dominating set (CDS) as a routing backbone for infrastructure-less ad hoc networks. However, finding the minimum connected dominating set is an NP-hard problem. A distributed algorithm is proposed for computing a CDS which terminates in constant number of rounds and outperforms several well-known heuristics in terms of runtime and the quality of results. Similarly, for Bluetooth networks, we proposed a distributed energy effcient algorithm for constructing scatternet as a virtual routing backbone which reduces the number of piconets and bridges in the network. The algorithm imposes a novel synchronization technique, compatible with the original Bluetooth specication, that enables nodes to save signicant amount of energy during the procedure. It is observed that adjustments of transmission power at nodes play a crucial role in improving the network lifetime and reducing the effect of interference. The connectivity preserving optimal power assignment problem in an arbitrary network is NP-hard. We investigated the idea of node based transmission power control that maintains the connectivity among the nodes and builds up a network topology for energy-effcient communication. Two distributed algorithms are proposed for two distinct situations, one for mobility-prone networks, and the other for lifetimecritical networks with less mobile nodes. Therst algorithm completes transmission power assignment in two rounds of message passing only. The second algorithm takes as many rounds as the most effcient distributed minimum spanning tree algorithm, but it outperforms the latter in terms of node power levels. An interesting observation is to note that the power control reduces node degree, by releasing some links in the network, which in turn reduces the computational time of many algorithms addressed for ad hoc networks, where the time complexity depends on node degree. Finally, we studied an interesting problem of data gathering in multi-hop wireless sensor networks. Assuming a uniform traffic pattern, we presented a distributed greedy algorithm for extracting a rooted spanning tree to gather sensed data from individual sensors to the sink node to improve the network lifetime. The most important feature of the proposed distributed algorithms is that each node can execute those with a minimal knowledge about its two-hop neighbourhood which it can gather easily and rapidly using limited number (2 or 3) of communication rounds. We supplement our theoretical study of the distributed algorithms by extensive simulation studies. Comparison with earlier works showed that our algorithms perform better in terms of various appropriate performance metrics.Our study enabled us to build up an intricate knowledge about the interdependency of dierent cross-layer issues, like the media access control, routing backbone design, topology control and energy-effcient data routing in mobile ad hoc networks in general, with some studies on special cases of ad hoc networks, namely the Bluetooth networks and wireless sensor networks. Hence, we hope this work will throw new light on the initialization and self-coguration of these infrastructure-less ad hoc networks, and can help its design for various applications.

Comments

ProQuest Collection ID: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:28843323

Control Number

ISILib-TH336

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

DOI

http://dspace.isical.ac.in:8080/jspui/handle/10263/2146

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