Constructive Multiuser Interference in Symbol Level Precoding for the MISO Downlink Channel

TL;DR

This paper introduces a symbol-level precoding approach that exploits multiuser interference constructively in MISO downlink channels, improving signal quality and power efficiency by utilizing data and channel information.

Contribution

It proposes a novel interference exploitation method combining data and channel info for precoding, along with algorithms for power minimization and fairness enhancement.

Findings

Proposed schemes outperform existing techniques in simulations.

Constructive interference can be harnessed to improve SINR.

New relations between power minimization and fairness metrics are established.

Abstract

This paper investigates the problem of interference among the simultaneous multiuser transmissions in the downlink of multiple antennas systems. Using symbol level precoding, a new approach towards the multiuser interference is discussed along this paper. The concept of exploiting the interference between the spatial multiuser transmissions by jointly utilizing the data information (DI) and channel state information (CSI), in order to design symbol-level precoders, is proposed. In this direction, the interference among the data streams is transformed under certain conditions to useful signal that can improve the signal to interference noise ratio (SINR) of the downlink transmissions. We propose a maximum ratio transmission (MRT) based algorithm that jointly exploits DI and CSI to glean the benefits from constructive multiuser interference. Subsequently, a relation between the constructive interference downlink transmission and physical layer multicasting is established. In this context, novel constructive interference precoding techniques that tackle the transmit power minimization (min power) with individual SINR constraints at each user's receivers is proposed. Furthermore, fairness through maximizing the weighted minimum SINR (max min SINR) of the users is addressed by finding the link between the min power and max min SINR problems. Moreover, heuristic precoding techniques are proposed to tackle the weighted sum rate problem. Finally, extensive numerical results show that the proposed schemes outperform other state of the art techniques.