2 research outputs found
Degrees of Freedom of the Rank-deficient Interference Channel with Feedback
We investigate the total degrees of freedom (DoF) of the K-user
rank-deficient interference channel with feedback. For the two-user case, we
characterize the total DoF by developing an achievable scheme and deriving a
matching upper bound. For the three-user case, we develop a new achievable
scheme which employs interference alignment to efficiently utilize the
dimension of the received signal space. In addition, we derive an upper bound
for the general K-user case and show the tightness of the bound when the number
of antennas at each node is sufficiently large. As a consequence of these
results, we show that feedback can increase the DoF when the number of antennas
at each node is large enough as compared to the ranks of channel matrices. This
finding is in contrast to the full-rank interference channel where feedback
provides no DoF gain. The gain comes from using feedback to provide alternative
signal paths, thereby effectively increasing the ranks of desired channel
matrices.Comment: The material in this paper will be presented in part at the IEEE
International Symposium on Information Theory (ISIT) 2013 and was in part
submitted to the Allerton Conference on Communication, Control, and Computing
201
The DoF of the 3-user () MIMO Interference Channel
The \emph{degrees of freedom} (DoF) of the 3-user multiple-input
multiple-output (MIMO) interference channel (IC) with full channel state
information (CSI) and constant channel coefficients are characterized when
linear filters are employed and antennas are deployed at the
transmitters and receivers, respectively. The point of departure of this paper
is the work of Wang et al, which conjectured but not proved the DoF for the
configuration tackled in this work. In this work we prove the optimal DoF by
means of a transmission scheme based on asymmetric complex signaling (ACS)
together with symbol extensions in time and interference alignment (IA)
concepts. The paper deals with the cases, providing the transmit and
receive filters and the tools needed for proving the achievability of the DoF
for other values of .Comment: 31 pages, 3 figures, submitted to the IEEE Transactions on
Communication