Energy-aware wireless multi-hop networks

Abstract

Summary
Wireless networks have provided us a variety of services which facilitate communication
between people beyond the physical boundaries. Mobile telephony, mobile Internet
access and high-de nition video calls are examples of services supported by modern
networks nowadays. Beyond this, advances in wireless communication coupled with
enhancements in processing capabilities of electronic devices have resulted in the
emergence of devices which have high communication and processing capabilities. Small
devices that we carry or miniaturized devices embedded in our surroundings can execute
sophisticated communication protocols. This allows them to form distributed networks
in which nodes communicate with each other to collaboratively o er services without
the need for pre-established expensive infrastructures. Such networks are known
as wireless multi-hop networks, where instead of powerful base stations, multi-hop
communication connects all the devices that are outside the transmission range of each
other. Each device may act as a router which relays packets on behalf of other devices.
Ad hoc communication between laptops in a conference hall, multi-hop communication
between personal devices at home, and collaborative communication between sensors
distributed over a large area are example scenarios of multi-hop communication in
wireless networks.
This dissertation addresses the design of energy-aware wireless multi-hop networks,
where energy is the key element in the design and analysis. Wireless multi-hop networks
must be energy-aware for two reasons. First, devices in these networks usually run on
batteries. Thus, reducing energy consumption can save scarce battery energy of devices
and extend the autonomy of systems that are composed of. Second, vast deployment of
these easy-to-establish networks can excessively increase energy consumption in the ICT
sector. Energy-e cient and energy-aware communication protocols and mechanisms
not only extend operational lifetime of devices but also reduce environmental impacts
of these networks. The novelty of this dissertation is the proposal of a suite of
new protocols which together form a platform for energy-aware and energy-e cient
communication in wireless multi-hop networks. The proposed platform scans di erent
layers of the communication stack taking into account cross-layer dependency between
them from an energy-e ciency point of view. The energy e ciency across OSI
Reference Architecture layers is addressed. Notably, the physical layer (Layer 1) to
the transport layer (Layer 4) is covered. For the physical layer, we propose cooperative
signal transmission techniques based on MIMO (Multi-Input Multi-Output) technology
to reduce the transmission power of nodes without sacri cing link reliability. For the
data link layer, we propose a network topology control algorithm which speci es a
neighbor discovery policy to keep the maximum transmission power of nodes as low as
required for network connectivity. For the network layer, we propose routing schemes
for nding the most energy-e cient routes between any two nodes of the network taking
into account the impact of the transmission control of the transport layer. Furthermore,
we enhance these routing schemes with the capability to balance the tra c according to
the available battery energy of nodes. We also analyze the expected duration that two
nodes in a wireless multi-hop network with a random topology can communicate with
each other (from transport layer point of view) through intermediate nodes between
them. The proposed schemes in this dissertation together make the communication
stack in wireless multi-hop networks more and more energy-e cient leading to green
wireless multi-hop networks. This work is of a fundamental and theoretical nature
supported by simulations. It could be continued by experimental studies using a
testbed.