No description available.

No description available.

Checkpointing and rollback recovery are well-known techniques for coping with failures in distributed systems. Future generation Supercomputers will be message passing distributed systems consisting of millions of processors. As the number of processors grow, failure rate also grows. Thus, designing efficient checkpointing and recovery algorithms for coping with failures in such large systems is important for these systems to be fully utilized. We presented a novel communication-induced checkpointing algorithm which helps in reducing contention for accessing stable storage to store checkpoints. Under our algorithm, a process involved in a distributed computation can independently initiate consistent global checkpointing by saving its current state, called a tentative checkpoint. Other processes involved in the computation come to know about the consistent global checkpoint initiation through information piggy-backed with the application messages or limited control messages if necessary. When a process comes to know about a new consistent global checkpoint initiation, it takes a tentative checkpoint after processing the message. The tentative checkpoints taken can be flushed to stable storage when there is no contention for accessing stable storage. The tentative checkpoints together with the message logs stored in the stable storage form a consistent global checkpoint. Ad hoc networks consist of a set of nodes that can form a network for communication with each other without the aid of any infrastructure or human intervention. Nodes are energy-constrained and hence routing algorithm designed for these networks should take this into consideration. We proposed two routing protocols for mobile ad hoc networks which prevent nodes from broadcasting route requests unnecessarily during the route discovery phase and hence conserve energy and prevent contention in the network. One is called Triangle Based Routing (TBR) protocol. The other routing protocol we designed is called Routing Protocol with Selective Forwarding (RPSF). Both of the routing protocols greatly reduce the number of control packets which are needed to establish routes between pairs of source nodes and destination nodes. As a result, they reduce the energy consumed for route discovery. Moreover, these protocols reduce congestion and collision of packets due to limited number of nodes retransmitting the route requests.

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Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 292-303). / Microfiche. / xxxii, 303 leaves, bound ill. 29 cm

The objective of this thesis is to design bandwidth-efficient, low-complexity LDPC code based receivers that porovide good performance under static, phase varying channels. / Thesis (PhDTelecommunications)--University of South Australia, 2009

This thesis addresses the problem of decoding high rate convolutional codes directly without resorting to puncturing. High rate codes are necessary for applications which require high bandwidth efficiency, like high data rate communication systems and magnet recording systems. Convolutional ( rate k/n) codes, used as component codes for turbo codes, are preferred for their regular trellis structure and the resulting ease in decoding. However, the branch complexity of the (primal) code trellis increases exponentially with 'k' for k/(k+1) codes, making decoding on the code trellis quickly impractical with increasing code rate. 'Puncturing' is the method traditionally used for generating high rate codes, which keeps the decoding complexity nearly the same for a wide range of code rates, since the same 'mother' code decoder is used at the receiver, while only the puncturing and depuncturing pattern is altered for changes in code rate. However, 'puncturing' puts a constraint in the search for the best possible high rate code, thereby resulting in a performance penalty, particularly at high SNRs. / Thesis (PhD)--University of South Australia, 2008.

The objective of this thesis is to design bandwidth-efficient, low-complexity LDPC code based receivers that porovide good performance under static, phase varying channels. / Thesis (PhDTelecommunications)--University of South Australia, 2009

Thesis (M.S.)--Ohio University, November, 2001. / Title from PDF t.p.

Thesis (Ph. D.)--Ohio University, August, 1997. / Title from PDF t.p.