THESIS
2013
xii, 141 pages : illustrations ; 30 cm
Abstract
Spatial Time Division Multiple Access (STDMA) networks are immune from the hidden-and
exposed-terminal problems inherent in a multi-hop Carrier Sensing Multiple
Access/Collision Avoidance (CSMA/CA) network. In this thesis, we study three important
issues in the design of an STDMA wireless mesh network.
We first study slot assignment, routing and scheduling schemes for SISO and MIMO
wireless mesh networks respectively. Conventional algorithms are usually link-based and
scheduling in each slot is fixed and done for links. When the scheduled link is in deep fade or
has no traffic, the slot given to that link will be wasted. In this thesis, we present a node-based
scheme in which scheduling in each slot is done for nodes. Since a node has multiple links, it
allows the exploitatio...[
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Spatial Time Division Multiple Access (STDMA) networks are immune from the hidden-and
exposed-terminal problems inherent in a multi-hop Carrier Sensing Multiple
Access/Collision Avoidance (CSMA/CA) network. In this thesis, we study three important
issues in the design of an STDMA wireless mesh network.
We first study slot assignment, routing and scheduling schemes for SISO and MIMO
wireless mesh networks respectively. Conventional algorithms are usually link-based and
scheduling in each slot is fixed and done for links. When the scheduled link is in deep fade or
has no traffic, the slot given to that link will be wasted. In this thesis, we present a node-based
scheme in which scheduling in each slot is done for nodes. Since a node has multiple links, it
allows the exploitation of multi-user diversity. For SISO networks, the proposed scheme can
achieve a throughput gain between 35% and 70% for some typical topologies tested in our
study. For MIMO networks, the throughput gain is 33% to 45%.
As new network applications have arisen rapidly in recent years, it is becoming more
difficult to predict the exact traffic matrix of a network. The second topic we explore is how to
use oblivious routing techniques to handle traffic uncertainty in a wireless mesh network.
Oblivious routing intends to use one routing scheme to achieve a predicable performance for a
set of traffic matrices. Prior works on the design of oblivious routing and slot assignment fail to
exploit a key feature of a wireless network that can be used to tackle traffic uncertainty: link
capacities can be dynamically assigned as the traffic demand changes. Based on this insight, we
propose a new oblivious-routing framework for STDMA wireless mesh networks. Our
simulation results indicate that the oblivious ratios of the proposed node-based scheme can be
61% and 57% lower than that of the conventional link-based scheme for the tested grid and the
random topology respectively.
We also present a new approach for energy conservation routing, which is an important
design issue for battery-powered wireless mesh networks. We study the problem when traffic
demand uncertainties are present. Our new approach does not suffer from the two problems
prevalent in conventional oblivious routing designed for energy conservation networks: the
inaccuracy caused by the adoption of the protocol interference model and the instability caused
by the assumption of unbounded transmission power and data rate. Our approach intends to fix
these problems. We propose two energy conservation routing frameworks: one is node based
and the other link based. The node-based framework can explore the dynamic bandwidth sharing feature of a wireless network and leads to a higher throughput and longer network
lifetime. For the gateway traffic model, which is a common assumption for studying mesh
networks, the gains of a node based scheme in throughput and network lifetime over those of a
link-based scheme are 14% and 24% respectively. However, regarding to the mesh traffic
model, the two frameworks allow comparable network lifetime and system throughput.
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