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

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 fullduplex 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 zeroforcing and null-space transmit beamforming.

Degrees-of-Freedom of the MIMO Three-Way Channel With Node-Intermittency

“…Lemma 3 follows from (44), (47), (50), and symmetry of node 2 and 3. The achievability and converse results developed in Sections IV-B1 and IV-B2 establish the sum-DoF of the intermittent 3WC and prove Theorem 2.…”

“…In this subsection we present a non-adaptive transmission scheme based on ZF, IA and EC that provides an inner bound on sum-DoF and DoF region of 3WCs. Previous works [18], [19], [21], [47] developed similar ZF/IA-based schemes only to the limited extent necessary to analyze the sum-DoF of various 3WCs. We take EC as additional technique to mitigate intermittency and develop the resulting ZF/IA/ECbased scheme in full generality, i.e., for arbitrary numbers of antennas and flexible allocation of DoFs to the available transmission techniques ZF, IA and EC.…”

“…To this end, several bounds are reported in the literature, among them cut-set outer bounds [49] on pairs of DoFs (involving two messages either intended for or originating at a certain node), and tighter genie-aided outer bounds on triplets of DoFs (involving two messages either intended for or originating at a certain node, and one message exchanged between the remaining two nodes). The latter bounding technique is due to [18], [19] and was later taken up in [21], [47].…”

Revisiting Degrees of Freedom of Full-Duplex Systems with Opportunistic Transmission: An Improved User Scaling Law

“…Several inter-terminal interference cancellation schemes for a three-terminal full-duplex system were presented in [ 3 ]. In addition, the DoF of multi-antenna full-duplex systems was recently studied in [ 4 , 5 ]. However, there are some practical challenges as follows.…”