3 research outputs found
Low Complexity Opportunistic Interference Alignment in -Transmitter MIMO Interference Channels
In this paper, we propose low complexity opportunistic methods for
interference alignment in -transmitter MIMO interference channels by
exploiting multiuser diversity. We do not assume availability of channel state
information (CSI) at the transmitters. Receivers are required to feed back
analog values indicating the extent to which the received interference
subspaces are aligned. The proposed opportunistic interference alignment (OIA)
achieves sum-rate comparable to conventional OIA schemes but with a
significantly reduced computational complexity.Comment: 8 pages, 8 figures, typos corrected, some clarifications added in
'Performance Comparison
On the Achievable DoF and User Scaling Law of Opportunistic Interference Alignment in 3-Transmitter MIMO Interference Channels
In this paper, we propose opportunistic interference alignment (OIA) schemes
for three-transmitter multiple-input multiple-output (MIMO) interference
channels (ICs). In the proposed OIA, each transmitter has its own user group
and selects a single user who has the most aligned interference signals. The
user dimensions provided by multiple users are exploited to align interfering
signals. Contrary to conventional IA, perfect channel state information of all
channel links is not required at the transmitter, and each user just feeds back
one scalar value to indicate how well the interfering channels are aligned. We
prove that each transmitter can achieve the same degrees of freedom (DoF) as
the interference free case via user selection in our system model that the
number of receive antennas is twice of the number of transmit antennas. Using
the geometric interpretation, we find the required user scaling to obtain an
arbitrary non-zero DoF. Two OIA schemes are proposed and compared with various
user selection schemes in terms of achievable rate/DoF and complexity.Comment: To appear in IEEE Transactions on Wireless Communication
Multiuser Diversity in Interfering Broadcast Channels: Achievable Degrees of Freedom and User Scaling Law
This paper investigates how multiuser dimensions can effectively be exploited
for target degrees of freedom (DoF) in interfering broadcast channels (IBC)
consisting of K-transmitters and their user groups. First, each transmitter is
assumed to have a single antenna and serve a singe user in its user group where
each user has receive antennas less than K. In this case, a K-transmitter
single-input multiple-output (SIMO) interference channel (IC) is constituted
after user selection. Without help of multiuser diversity, K-1 interfering
signals cannot be perfectly removed at each user since the number of receive
antennas is smaller than or equal to the number of interferers. Only with
proper user selection, non-zero DoF per transmitter is achievable as the number
of users increases. Through geometric interpretation of interfering channels,
we show that the multiuser dimensions have to be used first for reducing the
DoF loss caused by the interfering signals, and then have to be used for
increasing the DoF gain from its own signal. The sufficient number of users for
the target DoF is derived. We also discuss how the optimal strategy of
exploiting multiuser diversity can be realized by practical user selection
schemes. Finally, the single transmit antenna case is extended to the
multiple-input multiple-output (MIMO) IBC where each transmitter with multiple
antennas serves multiple users.Comment: To appear, IEEE Transactions on Wireless Communication