1 research outputs found
On the Degrees of Freedom of the MISO Interference Broadcast Channel with Delayed CSIT
The Maddah-Ali and Tse (MAT) scheme is a linear precoding strategy that
exploits Interference Alignment and perfect, but delayed, channel state
information at the transmitters (delayed CSIT), improving the degrees of
freedom (DoF) that can be achieved for the broadcast channel (BC). Since its
appearance, many works have extended the concept of Retrospective Interference
Alignment (RIA) to other multi-user channel configurations. However, little is
known about the broadcast channel with multiple cells, i.e. the interference
broadcast channel (IBC). In this work, the DoF are studied for the -user
-cell multiple-input single-output (MISO) IBC with delayed CSIT (with
users per cell).
We show that the straightforward application of the MAT scheme over the IBC
fails because it requires all interference to be received from the same source.
Hence, in this case not all the interference can be cancelled, thus blocking
the decoding of the received messages. We call this phenomenon as
\textit{interference coupling}, forcing to use the MAT scheme by serving just
one cell at a time. In this work, we propose an extension, namely the uncoupled
MAT scheme (uMAT), exploiting multiple cells, uncoupling the interference, and
achieving the best known DoF inner bound for almost all settings.Comment: 17 pages, 5 figures, submitted to IEEE Transactions on Information
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