2,101 research outputs found
Congestion Control and Routing over Challenged Networks
This dissertation is a study on the design and analysis of novel, optimal
routing and rate control algorithms in wireless, mobile communication networks.
Congestion control and routing algorithms upto now have been designed and
optimized for wired or wireless mesh networks. In those networks, optimal
algorithms (optimal in the sense that either the throughput is maximized or
delay is minimized, or the network operation cost is minimized) can be
engineered based on the classic time scale decomposition assumption that the
dynamics of the network are either fast enough so that these algorithms
essentially see the average or slow enough that any changes can be tracked to
allow the algorithms to adapt over time. However, as technological advancements
enable integration of ever more mobile nodes into communication networks, any
rate control or routing algorithms based, for example, on averaging out the
capacity of the wireless mobile link or tracking the instantaneous capacity
will perform poorly. The common element in our solution to engineering
efficient routing and rate control algorithms for mobile wireless networks is
to make the wireless mobile links seem as if they are wired or wireless links
to all but few nodes that directly see the mobile links (either the mobiles or
nodes that can transmit to or receive from the mobiles) through an appropriate
use of queuing structures at these selected nodes. This approach allows us to
design end-to-end rate control or routing algorithms for wireless mobile
networks so that neither averaging nor instantaneous tracking is necessary
INTERMITTENTLY CONNECTED DELAY-TOLERANT WIRELESS SENSOR NETWORKS
Intermittently Connected Delay-Tolerant Wireless Sensor Networks (ICDT-WSNs), a branch of Wireless Sensor Networks (WSNs), have features of WSNs and the intermittent connectivity of Opportunistic Networks. The applications of ICDT-WSNs are increasing in recent years; however, the communication protocols suitable for this category of networks often fall short. Most of the existing communication protocols are designed for either WSNs or Opportunistic Networks with sufficient resources and tend to be inadequate for direct use in ICDT-WSNs.
In this dissertation, we study ICDT-WSNs from the perspective of the characteristics, chal- lenges and possible solutions. A high-level overview of ICDT-WSNs is given, followed by a study of existing work and our solutions to address the problems of routing, flow control, error control, and storage management. The proposed solutions utilize the utility level of nodes and the connectedness of a network. In addition to the protocols for information transmissions to specific destinations, we also propose efficient mechanisms for information dissemination to arbitrary destinations. The study shows that our proposed solutions can achieve better performance than other state of the art communication protocols without sacrificing energy efficiency
Multiple Random Walks to Uncover Short Paths in Power Law Networks
Consider the following routing problem in the context of a large scale
network , with particular interest paid to power law networks, although our
results do not assume a particular degree distribution. A small number of nodes
want to exchange messages and are looking for short paths on . These nodes
do not have access to the topology of but are allowed to crawl the network
within a limited budget. Only crawlers whose sample paths cross are allowed to
exchange topological information. In this work we study the use of random walks
(RWs) to crawl . We show that the ability of RWs to find short paths bears
no relation to the paths that they take. Instead, it relies on two properties
of RWs on power law networks: 1) RW's ability observe a sizable fraction of the
network edges; and 2) an almost certainty that two distinct RW sample paths
cross after a small percentage of the nodes have been visited. We show
promising simulation results on several real world networks
TCP-Aware Backpressure Routing and Scheduling
In this work, we explore the performance of backpressure routing and
scheduling for TCP flows over wireless networks. TCP and backpressure are not
compatible due to a mismatch between the congestion control mechanism of TCP
and the queue size based routing and scheduling of the backpressure framework.
We propose a TCP-aware backpressure routing and scheduling that takes into
account the behavior of TCP flows. TCP-aware backpressure (i) provides
throughput optimality guarantees in the Lyapunov optimization framework, (ii)
gracefully combines TCP and backpressure without making any changes to the TCP
protocol, (iii) improves the throughput of TCP flows significantly, and (iv)
provides fairness across competing TCP flows
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