Symmetric two-user MIMO BC with evolving feedback

Abstract

Abstract-Extending recent findings on the two-user MISO broadcast channel (BC) with imperfect and delayed channel state information at the transmitter (CSIT), the work here explores the performance of the two user MIMO BC, in the presence of feedback with evolving quality and timeliness. Under standard assumptions, and in the presence of M antennas at the transmitter and N antennas per receiver, the work derives the DoF region, which is optimal for a large range of current and delayed CSIT quality. This region concisely captures the effect of having predicted, current and delayed-CSIT, as well as concisely captures the effect of the quality of CSIT offered at any time, about any channel realization. In addition to the progress towards describing the limits of using such imperfect and delayed feedback in MIMO settings, the work offers different insights that include the fact that DoF optimality, in the presence of an increased number of receiving antennas, can be achieved with reduced quality feedback.

Achievable DoF Regions of MIMO Networks With Imperfect CSIT

“…Moreover, the DoF region with perfect CSIT and no CSIT can be reached with α 1 =α 2 =1 and α 1 =0 (∀α 2 ∈[0,1]), respectively. When N 1 =N 2 , L 1 and L 2 in Proposition 1 boil down to the the sum DoF constraint in the symmetric antenna case [15].…”

“…Moreover, as mentioned in [5], this definition of the channel uncertainty can link to the cases where the CSIT error is due to channel quantization [23] and/or Doppler effect [4], [9], [10], [15], [19], [24]. In these cases, one has…”

“…For symmetric MIMO IC where each transmitter has the same number of antennas and each receiver has the same number of antennas, the optimality of the DoF region achieved by HK scheme was found in [13] when there is no CSIT and the number of transmit antennas is no greater than the number of receive antennas. When there is imperfect CSIT, the extension of the RS scheme designed for MISO BC to the MISO IC was reported in [14]; the generalizations to the symmetric MIMO BC and IC were reported in [15], [16], respectively. In the context of two-receiver MIMO BC and IC with arbitrary antenna configuration, the DoF region with no CSIT was fully characterized in [17] for BC and in [18] for IC, while the DoF region with a mixture of perfect delayed CSIT and imperfect current CSIT were found in [19], [20] for both BC and IC.…”

Throughput Region of Spatially Correlated Interference Packet Networks

“…Other results consider more realistic settings in which wireless links exhibit some sort of correlation. Temporal correlation has been studied in several papers [25]- [30] with the idea being that correlation across time allows transmitters to better estimate what will happen next, and to adjust their transmission strategies accordingly. There are also some results that consider spatial correlation in wireless networks.…”

Optimally bridging the gap from delayed to perfect CSIT in the K-user MISO BC

“…The above work was then improved to reach the maximal DoF in a two-user MISO scenario in [8], [9]. This approach has since been extended to imperfect delayed CSIT in [10], [11], to the broad setting of any-time any-quality feedback in [12], and to the two-user MIMO BC and IC in [13], [14]. In the K-user case, a general outer bound was provided in [15], and efforts to reach this bound can be found in [16].…”