Feasibility Conditions for Relay-Aided Interference Alignment in Partially Connected Networks

Abstract

In this paper, we investigate the feasibility conditions for relay-aided interference alignment in a class of partially connected networks. The considered scenario consists of several single-antenna communicating node pairs and multiple singleantenna amplify-and-forward relays. Some of the direct links between the source and the destination nodes may have zero gain. A two-hop transmission scheme is applied. The relays' scaling factors, along with the transmit and receive filters, are adapted to the channel to null the interference signals at every destination node. However, this would also null the desired useful signal at certain destinations if the number of relays is insufficient. To avoid this, the required number of relays is studied. We show that the required number of relays depends on the rank of the incidence matrix of a graph defined by the topology of the direct links.

Relay-aided interference alignment for multiple partially connected subnetworks

“…In constant multiple-input-multiple-output (MIMO) interference networks for instance, the number of antennas required at every user increases linearly with the total number of users [3]- [5]. In contrast to this, IA aided by half-duplex relays guarantees the achievement of 1/2 DoF per user even if each user only has a single antenna, but requires lots of relays or relay antennas depending on the network size [6]- [8]. The challenge we are facing is how to reduce the required number of relays or relay antennas in large networks.…”

“…In [9] and [10], partial connectivity has been exploited to reduce the number of required antennas at the nodes for IA in MIMO interference networks as compared to the fully connected case. However, to our knowledge, only few results are published for relay-aided IA in partially connected networks [1], [8].…”