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"... This paper is motivated by a sensor network on a correlated field where nearby sensors share information, and can thus assist rather than interfere with one another. We consider a special class of two-user Gaussian interference channels (IFCs) where one of the two transmitters knows both the message ..."

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This paper is motivated by a sensor network on a correlated field where nearby sensors share information, and can thus assist rather than interfere with one another. We consider a special class of two-user Gaussian interference channels (IFCs) where one of the two transmitters knows both the messages to be conveyed to the two receivers. Both achievability and converse arguments are provided for a channel with Gaussian inputs and Gaussian noise when the interference is weaker than the direct link (a so called weak IFC). In general, this region serves as an outer bound on the capacity of weak IFCs with no shared knowledge between transmitters.

### 1Linear Degrees of Freedom of MIMO Broadcast Channels with Reconfigurable Antennas in the Absence of CSIT

"... The K-user multiple-input and multiple-output (MIMO) broadcast channel (BC) with no channel state information at the transmitter (CSIT) is considered, where each receiver is assumed to be equipped with reconfigurable antennas capable of choosing a subset of receiving modes from several preset modes. ..."

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The K-user multiple-input and multiple-output (MIMO) broadcast channel (BC) with no channel state information at the transmitter (CSIT) is considered, where each receiver is assumed to be equipped with reconfigurable antennas capable of choosing a subset of receiving modes from several preset modes. Under general antenna configurations, the sum linear degrees of freedom (LDoF) of the K-user MIMO BC with reconfigurable antennas is completely characterized, which corresponds to the maximum sum DoF achievable by linear coding strategies. The LDoF region is further characterized for a class of antenna configurations. Similar analysis is extended to the K-user MIMO interference channels with reconfigurable antennas and the sum LDoF is characterized for a class of antenna configurations. Index Terms Blind interference alignment, broadcast channels, degrees of freedom (DoF), multiple-input and multiple-output (MIMO), reconfigurable antennas. I.

### 1Diophantine Approach to Blind Interference Alignment of Homogeneous K-user 2 × 1 MISO Broadcast Channels

"... Although the sufficient condition for a blindly interference-aligned (BIA) 2-user 2 × 1 broadcast channel (BC) in homogeneous fading to achieve its maximal 4/3 DoF is well understood, its counterpart for the general K-user 2 × 1 MISO BC in homogeneous block fading to achieve the corresponding 2K2+K− ..."

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Although the sufficient condition for a blindly interference-aligned (BIA) 2-user 2 × 1 broadcast channel (BC) in homogeneous fading to achieve its maximal 4/3 DoF is well understood, its counterpart for the general K-user 2 × 1 MISO BC in homogeneous block fading to achieve the corresponding 2K2+K−1 (DoF) remains unsolved and is, thus, the focus of this paper. An interference channel is said BIA-feasible if it achieves its maximal DoF only via BIA. In this paper, we cast this general feasibility problem in the framework of finding integer solutions for a system of linear Diophantine equations. By assuming independent user links each of the same coherence time and by studying the solvability of the Diophantine system, we derive the sufficient and necessary conditions on the K users ’ fading block offsets to ensure the BIA feasibility of the K-user BC. If the K offsets are independent and uniformly distributed over a coherence block, we can further prove that 11 users are enough for one to find, with certainty of 95%, 3 users among them to form a BIA-feasible 3-user 2 × 1 BC.