Conference Paper

On the degrees-of-freedom of the MIMO interference channel

Lincoln Lab., MIT, Lexington, MA
DOI: 10.1109/CISS.2008.4558496 Conference: Information Sciences and Systems, 2008. CISS 2008. 42nd Annual Conference on
Source: IEEE Xplore

ABSTRACT The high signal-to-noise ratio capacity of the symmetric MIMO interference channel is characterized as a function of the interference-to-noise ratio. This work is a multiple antenna extension of the degrees of freedom expressions derived by Etkin et al. for the single antenna case. This characterization considers the case where the number of receive antennas is greater than or equal to the number of transmit antennas and shows the number of degrees of freedom available for communication as a function of log(INR)/log(SNR).

  • [Show abstract] [Hide abstract]
    ABSTRACT: The K-user multiple input multiple output (MIMO) Gaussian symmetric interference channel where each transmitter has M antennas and each receiver has N antennas is studied from a generalized degrees of freedom (GDOF) perspective. An inner bound on the GDOF is derived using a combination of techniques such as treating interference as noise, zero forcing (ZF) at the receivers, interference alignment (IA), and extending the Han-Kobayashi (HK) scheme to K users, as a function of the number of antennas and the log INR / log SNR level. Several interesting conclusions are drawn from the derived bounds. It is shown that when K >; N/M + 1, a combination of the HK and IA schemes performs the best among the schemes considered. When N/M <; K ≤ N/M + 1, the HK-scheme outperforms other schemes and is found to be GDOF optimal in many cases. In addition, when the SNR and INR are at the same level, ZF-receiving and the HK-scheme have the same GDOF performance.
    IEEE Transactions on Communications 01/2013; 61(1):187-196. DOI:10.1109/TCOMM.2012.120117.120117 · 1.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The generalized degrees of freedom (GDoF) region of the MIMO Gaussian interference channel is obtained for the general case with an arbitrary number of antennas at each node and where the SNR and interference-to-noise ratios (INRs) vary with arbitrary exponents to a nominal SNR. The GDoF region reveals various insights through the joint dependence of optimal interference management techniques at high SNR on the SNR exponents that determine the relative strengths of direct-link SNRs and cross-link INRs and the numbers of antennas at the four terminals. For instance, it permits an in-depth look at the issue of rate-splitting and partial decoding at high SNR and it reveals that, unlike in the SISO case, treating interference as noise is not GDoF optimal always even in the very weak interference regime. Moreover, while the DoF-optimal strategy that relies just on transmit/receive zero-forcing beam-forming and time-sharing is not GDoF optimal (and thus has an unbounded gap to capacity) the precise characterization of the very strong interference regime, where single-user DoF performance can be achieved simultaneously for both users, depends on the relative numbers of antennas at the four terminals and thus deviates from what it is in the SISO case. For asymmetric numbers of antennas at the four nodes the shape of the symmetric GDoF curve can be a “distorted W” curve to the extent that for certain MIMO ICs it is a “V” curve.
    Information Theory Proceedings (ISIT), 2011 IEEE International Symposium on; 01/2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper derives outer bounds on the sum rate of the K-user MIMO Gaussian interference channel (GIC). Three outer bounds are derived, under different assumptions of cooperation and providing side information to receivers. The novelty in the derivation lies in the careful selection of side information, which results in the cancellation of the negative differential entropy terms containing signal components, leading to a tractable outer bound. The overall outer bound is obtained by taking the minimum of the three outer bounds. The derived bounds are simplified for the MIMO Gaussian symmetric IC to obtain outer bounds on the generalized degrees of freedom (GDOF). The relative performance of the bounds yields insight into the performance limits of multiuser MIMO GICs and the relative merits of different schemes for interference management. These insights are confirmed by establishing the optimality of the bounds in specific cases using an inner bound on the GDOF derived by the authors in a previous work. It is also shown that many of the existing results on the GDOF of the GIC can be obtained as special cases of the bounds, e.g., by setting K=2 or the number of antennas at each user to 1.
    IEEE Transactions on Communications 01/2013; 61(1):176-186. DOI:10.1109/TCOMM.2012.010913.120132 · 1.98 Impact Factor