3 research outputs found
Energy-efficiency versus delay tradeoff in wireless networks virtualization
This paper studies the issues on wireless networks virtualization in terms of two important performance metrics, i.e., energy efficiency (EE) and delay. Different from existing works on physical layer, we aim to achieve a good tradeoff between EE and delay in wireless networks virtualization using cross-layer stochastic optimization approach. In particular, we formulate a cross-layer problem using fractional programming and Lyapunov
optimization method. The EE and delay tradeoff solution is given explicitly by deriving their analytical bounds that are verified by simulation results
Communications in Mobile Wireless Networks: A Finite Time-Horizon Viewpoint
In mobile wireless networks (MWNs), short-term communications
carry two key features: 1) Different from communications over a
large time window where the performance is governed by the
long-term average effect, the short-term communications in MWNs
are sensitive to the instantaneous location and channel condition
caused by node mobility. 2) The short-term communications in MWNs
have the finite blocklength coding effect which means it is not
amenable to the well-known Shannon's capacity formulation.
To deal with the short-term communications in MWNs, this thesis
focuses on three main issues: how the node mobility affects the
instantaneous interference, how to reduce the uncertainty in the
locations of mobile users, and what is the maximal throughput of
a multi-user network over a short time-horizon.
First, we study interference prediction in MWNs by proposing and
using a general-order linear model for node mobility. The
proposed mobility model can well approximate node dynamics of
practical MWNs. Unlike previous studies on interference
statistics, we are able through this model to give a best
estimate of the time-varying interference at any time rather than
long-term average effects. In particular, we propose a compound
Gaussian point process functional (CGPPF) in a general framework
to obtain analytical results on the mean value and
moment-generating function of the interference prediction.
Second, to reduce the uncertainty in nodal locations, the
cooperative localization problem for mobile nodes is studied. In
contrast to previous works, which highly rely on the synchronized
time-slotted systems, this cooperative localization framework we
establish does not need any synchronization for the communication
links and measurement processes in the entire wireless network.
To solve the cooperative localization problem in a distributed
manner, we first propose the centralized localization algorithm
based on the global information, and use it as the benchmark.
Then, we rigorously prove when a localization estimation with
partial information has a small performance gap from the one with
global information. Finally, by applying this result at each
node, the distributed prior-cut algorithm is designed to solve
this asynchronous localization problem.
Finally, we study the throughput region of any MWN consisting of
multiple transmitter-receiver pairs where interference is treated
as noise. Unlike the infinite-horizon throughput region, which is
simply the convex hull of the throughput region of one time slot,
the finite-horizon throughput region is generally non-convex.
Instead of directly characterizing all achievable rate-tuples in
the finite-horizon throughput region, we propose a metric termed
the rate margin, which not only determines whether any given
rate-tuple is within the throughput region (i.e., achievable or
unachievable), but also tells the amount of scaling that can be
done to the given achievable (unachievable) rate-tuple such that
the resulting rate-tuple is still within (brought back into) the
throughput region.
This thesis advances our understanding in communications in MWNs
from a finite-time horizon viewpoint. It establishes new
frameworks for tracking the instantaneous behaviors, such as
interference and nodal location, of MWNs. It also reveals the
fundamental limits on short-term communications of a multi-user
mobile network, which sheds light on communications with low
latency