| dc.description.abstract | This research investigates cross-layer design in multi-hop wireless networks with
random access. Due to the complexity of the problem, we study cross-layer design
with a simple slotted ALOHA medium access control (MAC) protocol without considering any network dynamics. Firstly, we study the optimal joint configuration of routing and MAC parameters in slotted ALOHA based wireless networks under a signal to interference plus noise ratio based physical interference model. We formulate a
joint routing and MAC (JRM) optimization problem under a saturation assumption
to determine the optimal max-min throughput of the flows and the optimal configuration of routing and MAC parameters. The JRM optimization problem is a complex
non-convex problem. We solve it by an iterated optimal search (IOS) technique and
validate our model via simulation. Via numerical and simulation results, we show
that JRM design provides a significant throughput gain over a default configuration
in a slotted ALOHA based wireless network.
Next, we study the optimal joint configuration of routing, MAC, and network
coding in wireless mesh networks using an XOR-like network coding without opportunistic listening. We reformulate the JRM optimization problem to include the
simple network coding and obtain a more complex non-convex problem. Similar to
the JRM problem, we solve it by the IOS technique and validate our model via simulation. Numerical and simulation results for different networks illustrate that (i) the jointly optimized configuration provides a remarkable throughput gain with respect
to a default configuration in a slotted ALOHA system with network coding and (ii)
the throughput gain obtained by the simple network coding is significant, especially
at low transmission power, i.e., the gain obtained by jointly optimizing routing, MAC,
and network coding is significant even when compared to an optimized network without network coding. We then show that, in a mesh network, a significant fraction of
the throughput gain for network coding can be obtained by limiting network coding
to nodes directly adjacent to the gateway.
Next, we propose simple heuristics to configure slotted ALOHA based wireless
networks without and with network coding. These heuristics are extensively evaluated
via simulation and found to be very efficient. We also formulate problems to jointly
configure not only the routing and MAC parameters but also the transmission rate
parameters in multi-rate slotted ALOHA systems without and with network coding.
We compare the performance of multi-rate and single rate systems via numerical
results.
We model the energy consumption in terms of slotted ALOHA system parameters.
We found out that the energy consumption for various cross-layer systems, i.e., single
rate and multi-rate slotted ALOHA systems without and with network coding, are
very close. | en |
