Asymmetric Degrees of Freedom of the Full-Duplex MIMO 3-Way Channel with Unicast and Broadcast Messages

TL;DR

This paper analyzes the asymmetric degrees of freedom in a full-duplex MIMO 3-way channel with unicast and broadcast messages, deriving bounds and optimal antenna configurations for maximizing system capacity.

Contribution

It provides the first comprehensive characterization of the asymmetric DoF in full-duplex MIMO 3-way channels with mixed message types, including optimal antenna configurations and achievable schemes.

Findings

Derived upper bounds on total DoF for both message configurations.

Identified optimal transmit and receive antenna allocations at each node.

Constructed achievable schemes based on zero-forcing and null-space beamforming.

Abstract

In this paper, we characterize the asymmetric total degrees of freedom (DoF) of a multiple-input multiple-output (MIMO) 3-way channel. Each node has a separate-antenna full-duplex MIMO transceiver with a different number of antennas, where each antenna can be configured for either signal transmission or reception. We study this system under two message configurations; the first configuration is when each node has two unicast messages to be delivered to the two other nodes, while the second configuration is when each node has two unicast messages as well as one broadcast message to be delivered to the two other nodes. For each configuration, we first derive upper bounds on the total DoF of the system. Cut-set bounds in conjunction with genie-aided bounds are derived to characterize the achievable total DoF. Afterwards, we analytically derive the optimal number of transmit and receive antennas at each node to maximize the total DoF of the system, subject to the total number of antennas at each node. Finally, the achievable schemes for each configuration are constructed. The proposed schemes are mainly based on zero-forcing and null-space transmit beamforming.