Quadrant-Constrained Constellation Design for Efficient ICI Self-Mitigation in OFDM Systems

Abstract

Orthogonal frequency division multiplexing (OFDM) is widely adopted in modern wireless communications, yet its performance is highly sensitive to carrier frequency offsets (CFOs), which destroy subcarrier orthogonality and introduce intercarrier interference (ICI). Although conventional ICI self-cancellation techniques can mitigate this impairment, they typically suffer from a significant spectral-efficiency loss due to redundant symbol transmission. To address this limitation, this paper proposes a quadrant-constrained constellation design for efficient ICI mitigation in OFDM systems. The key idea is to impose a geometric constraint on adjacent subcarriers such that their constellation points lie in opposite quadrants, thereby introducing controlled correlations that enable partial ICI suppression while maintaining higher spectral efficiency. A joint maximum-likelihood detection strategy with tailored soft-decision demodulation is further developed to support soft decoding. Simulation results demonstrate that the proposed scheme achieves improved error performance compared with conventional self-cancellation approaches under moderate CFO conditions.