Abstract
The generalized degrees of freedom of the two-user symmetric multiple input multiple output interference channel are characterized as a function of the channel strength levels and the level of channel state information at the transmitters. In this symmetric setting, each transmitter is equipped with $M$ antennas, each receiver is equipped with $N$ antennas, and both cross links have the same strength parameter $\alpha $ and the same channel uncertainty parameter $\beta $ . The main challenge resides in the proof of the outer bound which is accomplished by a generalization of the aligned image sets approach.
Highlights
The pursuit of progressively refined capacity approximations over the past decade has produced numerous new insights into the fundamental limits of wireless networks
While degrees of freedom (DoF) studies are often the starting point, a generalized degrees of freedom (GDoF) characterization is the natural step forward along this path. It is a most significant step forward, because unlike the DoF metric which is not capable of making distinctions based on channel strength levels or partial channel state information at the transmitters (CSIT) levels, GDoF is sensitive to both channel strengths and channel uncertainty levels
Building upon these recent advances, in this work we explore the GDoF of the two user multiple input multiple output (MIMO) interference channel (IC)
Summary
The pursuit of progressively refined capacity approximations over the past decade has produced numerous new insights into the fundamental limits of wireless networks. To this end, we characterize the GDoF of the symmetric MIMO IC, where each transmitter is equipped with M antennas, each receiver is equipped with N antennas, and where each cross-channel has channel strength parameter α and CSIT level β, for arbitrary values of M, N, α, β. While the restrictive assumptions of symmetry are enforced to avoid an explosion in the number of parameters, the key ideas from this work should generalize to asymmetric settings as well This is the first application of the AIS argument to jointly deal with multiple spatial dimensions at both transmitters and receivers, in conjunction with different channel strengths and partial CSIT levels. We define x as the largest integer that is smaller than or equal to x when x > 0, the smallest integer that is larger than or equal to x when x < 0, and x itself when x is an integer
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