On X-Channels with Feedback and Delayed CSI

Abstract

The sum degrees of freedom (DoF) of the two-user MIMO X-channel is characterized in the presence of output feedback and delayed channel state information (CSI). The number of antennas at each transmitters is assumed to be M and the number of antennas at each of the receivers is assumed to be N. It is shown that the sum DoF of the two-user MIMO X-channel is the same as the sum DoF of a two-user MIMO broadcast channel with 2M transmit antennas, and N antennas at each receiver. Hence, for this symmetric antenna configuration, there is no performance loss in the sum degrees of freedom due to the distributed nature of the transmitters. This result highlights the usefulness of feedback and delayed CSI for the MIMO X-channel. The K-user X-channel with single antenna at each transmitter and each receiver is also studied. In this network, each transmitter has a message intended for each receiver. For this network, it is shown that the sum DoF with partial output feedback alone is at least 2K/(K+1). This lower bound is strictly better than the best lower bound known for the case of delayed CSI assumption for all values of K.

Submitted to IEEE ISIT 2012 on Jan 22, 2012

References in corpus (3)

• On the Degrees of Freedom of $K$-User SISO Interference and X Channels with Delayed CSIT
• The Degrees of Freedom Regions of Two-User and Certain Three-User MIMO Broadcast Channels with Delayed CSIT
• The Degrees of Freedom Region and Interference Alignment for the MIMO Interference Channel with Delayed CSI

Cited by in corpus (5)

• Secure Degrees of Freedom of MIMO X-Channels with Output Feedback and Delayed CSIT
• Distributed Space-Time Interference Alignment with Moderately-Delayed CSIT
• Secure Degrees of Freedom of Wireless X Networks Using Artificial Noise Alignment
• Interference and X Networks with Noisy Cooperation and Feedback
• On the Degrees of Freedom of SISO X-networks with Synergistic Alternating Channel State Information at transmitters