761 research outputs found
MISO Networks with Imperfect CSIT: A Topological Rate-Splitting Approach
Recently, the Degrees-of-Freedom (DoF) region of multiple-input-single-output
(MISO) networks with imperfect channel state information at the transmitter
(CSIT) has attracted significant attentions. An achievable scheme is known as
rate-splitting (RS) that integrates common-message-multicasting and
private-message-unicasting. In this paper, focusing on the general -cell
MISO IC where the CSIT of each interference link has an arbitrary quality of
imperfectness, we firstly identify the DoF region achieved by RS. Secondly, we
introduce a novel scheme, so called Topological RS (TRS), whose novelties
compared to RS lie in a multi-layer structure and transmitting multiple common
messages to be decoded by groups of users rather than all users. The design of
TRS is motivated by a novel interpretation of the -cell IC with imperfect
CSIT as a weighted-sum of a series of partially connected networks. We show
that the DoF region achieved by TRS covers that achieved by RS. Also, we find
the maximal sum DoF achieved by TRS via hypergraph fractional packing, which
yields the best sum DoF so far. Lastly, for a realistic scenario where each
user is connected to three dominant transmitters, we identify the sufficient
condition where TRS strictly outperforms conventional schemes.Comment: submitted for publicatio
Achievable Sum DoF of the K-User MIMO Interference Channel with Delayed CSIT
This paper considers a -user multiple-input-multiple-output (MIMO)
interference channel (IC) where 1) the channel state information obtained by
the transmitters (CSIT) is completely outdated, and 2) the number of transmit
antennas at each transmitter, i.e., , is greater than the number of receive
antennas at each user, i.e., . The usefulness of the delayed CSIT was
firstly identified in a -phase Retrospective Interference Alignment (RIA)
scheme proposed by Maddah-Ali et al for the Multiple-Input-Single-Output
Broadcast Channel, but the extension to the MIMO IC is a non-trivial step as
each transmitter only has the message intended for the corresponding user.
Recently, Abdoli et al focused on a Single-Input-Single-Output IC and solved
such bottleneck by inventing a -phase RIA with distributed overheard
interference retransmission. In this paper, we propose two -phase RIA
schemes suitable for the MIMO IC by generalizing and integrating some key
features of both Abdoli's and Maddah-Ali's works. The two schemes jointly yield
the best known sum Degrees-of-Freedom (DoF) performance so far. For the case
, the achieved sum DoF is asymptotically given by
when
Rate Analysis of Two-Receiver MISO Broadcast Channel with Finite Rate Feedback: A Rate-Splitting Approach
To enhance the multiplexing gain of two-receiver Multiple-Input-Single-Output
Broadcast Channel with imperfect channel state information at the transmitter
(CSIT), a class of Rate-Splitting (RS) approaches has been proposed recently,
which divides one receiver's message into a common and a private part, and
superposes the common message on top of Zero-Forcing precoded private messages.
In this paper, with quantized CSIT, we study the ergodic sum rate of two
schemes, namely RS-S and RS-ST, where the common message(s) are transmitted via
a space and space-time design, respectively. Firstly, we upper-bound the sum
rate loss incurred by each scheme relative to Zero-Forcing Beamforming (ZFBF)
with perfect CSIT. Secondly, we show that, to maintain a constant sum rate
loss, RS-S scheme enables a feedback overhead reduction over ZFBF with
quantized CSIT. Such reduction scales logarithmically with the constant rate
loss at high Signal-to-Noise-Ratio (SNR). We also find that, compared to RS-S
scheme, RS-ST scheme offers a further feedback overhead reduction that scales
with the discrepancy between the feedback overhead employed by the two
receivers when there are alternating receiver-specific feedback qualities.
Finally, simulation results show that both schemes offer a significant SNR gain
over conventional single-user/multiuser mode switching when the feedback
overhead is fixed.Comment: accepted to IEEE Transactions on Communication
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