A Tutorial on Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions

Abstract

Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area.

Reconfigurable Intelligent Surfaces for Smart Cities: Research Challenges and Opportunities

“…Following this approach, symbol-level precoding (SLP) accounts for the underlying MUI by shaping the transmitted waveforms so as to induce constructive interference (CI) at each user. SLP is a non-linear technique that employs CSI along with users' data to form the precoder [35], [36].…”

“…which models a transmit power minimization under the constraints of using feasible reflection coefficients belonging to F (general reflections, or continuous-phase shifters, or even discrete-phase shifters, as defined in Section III-B) and of enabling constructive interference at the receiver side according to the general SLP methodology detailed, for instance, in [35], [36]. More specifically, H θ (1) , .…”

Interference Exploitation 1-Bit Massive MIMO Precoding: A Partial Branch-and-Bound Solution With Near-Optimal Performance

“…CI is defined as the interference that leads to an increased distance to all the detection thresholds for a specific constellation point, as discussed in [42]- [44]. Closed-form CI precoding was firstly considered for PSK signaling in small-scale MIMO systems to improve the performance of the linear ZF precoding in [46]- [48].…”

Near-Optimal Interference Exploitation 1-Bit Massive MIMO Precoding Via Partial Branch-and-Bound

“…where α A k ≥ 0 and α B k ≥ 0 are the introduced scaling coefficients that jointly represent the effect of interference and 1-bit quantization on s k . Following [23], minimizing the SER is equivalent to pushing the noiseless received signal OB as deep as possible in the decision region and farther away from both of the decision boundaries, which is further equivalent to maximizing the minimum value of α A k , α B k . Accordingly, the 1-bit precoding design can be formulated as…”

“…CI is defined as the interference that pushes the received signals deeper in the decision region and farther away from the decision boundaries, which further improves the detection performance, though the MSE in this case will increase. This observation has been exploited in [23] and the references therein by symbol-level CI precoding to achieve an improved error rate performance in traditional multi-user MIMO scenarios. Inspired by this concept, [24]- [26] extended the idea of CI to 1-bit precoding designs, and the resulting performance is shown to be promising.…”