The scarce and overpopulated radio spectrum is going to present a major barrier to
the growth and development of future wireless networks. As such, spectrum sharing seems
to be inevitable to accommodate the exploding demand for high data rate applications.
A major challenge to realizing the potential advantages of spectrum sharing is interference
management. This thesis deals with interference management techniques in noncooperative
networks. In specific, interference alignment is used as a powerful technique
for interference management. We use the degrees of freedom (DoF) as the figure of merit
to evaluate the performance improvement due to the interference management schemes.
This dissertation is organized in two parts. In the first part, we consider the K-user
multiple input multiple output (MIMO) Gaussian interference channel (IC) with M antennas
at each transmitter and N antennas at each receiver. This channel models the
interaction between K transmitter-receiver pairs sharing the same spectrum for data communication.
It is assumed that the channel coefficients are constant and are available at
all nodes prior to data transmission. A new cooperative upper-bound on the DoF of this
channel is developed which outperforms the known bounds. Also, a new achievable transmission
scheme is provided based on the idea of interference alignment. It is shown that
the achievable DoF meets the upper-bound when the number of users is greater than a
certain threshold, and thus it reveals the channel DoF.
In the second part, we consider communication over MIMO interference and X channels
in a fast fading environment. It is assumed that the transmitters obtain the channel state
information (CSI) after a finite delay which is greater than the coherence time of the channel.
In other words, the CSI at the transmitters becomes outdated prior to being exploited
for the current transmission. New transmission schemes are proposed which exploit the
knowledge of the past CSI at the transmitters to retrospectively align interference in the
subsequent channel uses. The proposed transmission schemes offer DoF gain compared to
having no CSI at transmitters. The achievable DoF results are the best known results for these channels. Simple cooperative upper-bounds are developed to prove the tightness of
our achievable results for some network configurations.
| Identifer | oai:union.ndltd.org:WATERLOO/oai:uwspace.uwaterloo.ca:10012/7401 |
| Date | January 2013 |
| Creators | Ghasemi, Akbar |
| Source Sets | University of Waterloo Electronic Theses Repository |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
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