The Degrees of Freedom Region of the MIMO Interference Channel With Hybrid CSIT

Abstract

The degrees of freedom (DoF) region of the two-user MIMO (multiple-input multiple-output) interference channel is established under a new model termed as hybrid CSIT. In this model, one transmitter has delayed channel state information (CSI) and the other transmitter has instantaneous CSIT, of incoming channel matrices at the respective unpaired receivers, and neither transmitter has any knowledge of the incoming channel matrices of its respective paired receiver. The DoF region for hybrid CSIT, and consequently that of 2 × 2 × 3 5 CSIT models, is completely characterized, and a new achievable scheme based on a combination of transmit beamforming and retrospective interference alignment is developed. Conditions are obtained on the numbers of antennas at each of the four terminals such that the DoF region under hybrid CSIT is equal to that under (a) global and instantaneous CSIT and (b) global and delayed CSIT, with the remaining cases resulting in a DoF region with hybrid CSIT that lies somewhere in between the DoF regions under the instantaneous and delayed CSIT settings. Further synergistic benefits accruing from switching between the two hybrid CSIT models are also explored.

The Degrees of Freedom Region of Temporally Correlated MIMO Networks With Delayed CSIT

“…Specifically, the DoF region of MIMO networks (BC/IC) in this setting with general antenna configuration and general current CSIT qualities has been fully characterized, thanks to a simple yet unified framework employing interference quantization, block-Markov encoding and backward decoding techniques. Our DoF regions generalize a number of existing results under more specific CSIT settings, such as delayed CSIT [5][6][7], perfect CSIT [2,3], partial/hybrid/mixed CSIT [23][24][25].…”

“…It is worth noting that our results embrace the previously reported particular cases: the perfect CSIT setting [2,3] (i.e., current CSIT of perfect quality), the pure delayed CSIT setting [6,7] (i.e., current CSIT of zero quality), the partial/hybrid CSIT MIMO BC/IC case [23][24][25] (with perfect CSIT at one receiver and delayed CSIT at the other one), and the special MISO case [13][14][15] with N 1 = N 2 = 1, symmetric MIMO case [16], as well as the MISO case with asymmetric current CSIT qualities [18].…”

“…Remark III.3. Some previous reported results can be regarded as the special cases of our results: delayed CSIT case [6] for α 1 = α 2 = 0; perfect CSIT case [3] for α 1 = α 2 = 1, where the weighted sum DoF bounds (12d)-(12g) are inactive; hybrid CSIT (i.e., perfect CSIT for one channel and delayed CSIT for the other one) case [25] for α 1 = 1, α 2 = 0, where the bounds (12e) and (12f) are active.…”

On the degrees of freedom of the K-user time correlated broadcast channel with delayed CSIT

“…In [10], [11], the approach is adapted to two-user and three-user settings with multiple-antenna at the RXs, and to Interference Channels (ICs) and X-channels in [12]- [15], among others. In [16], the IC with TXs having unequal CSIT is also investigated.…”

The Degrees of Freedom of the Interference Channel With a Cognitive Relay Under Delayed Feedback

“…In [25], the authors presented a hybrid CSIT model where one transmitter has perfect and instantaneous knowledge of channel matrices corresponding to one user while the other transmitter has only delayed CSI corresponding to the other user, and derived the DoF region of the MIMO interference channel with hybrid CSIT. Moreover, the DoF regions of MIMO interference channel and broadcast channel without CSIT were derived in [26], and in addition to MIMO interference channel and broadcast channel, the DoF region of a cognitive radio channel without CSIT was reported in [27].…”