異質移動中基於OFDM正交時頻空間調變之干擾對齊

Abstract

隨著非地面網路技術的發展，低地球軌道 (LEO) 衛星提供了廣泛的連接潛力。然而，由於它們的快速移動，會在距離LEO衛星不同的用戶之間造成異構移動性，導致多用戶干擾消除的挑戰。此外，傳統的正交頻分複用 (OFDM) 調變易受都卜勒效應引起的載波間干擾 (ICI) 影響，從而破壞正交性和通信可靠性。在雙選擇性衰落通道中，具有異構速度的多用戶傳輸，傳統的干擾消除技術顯然不足以解決如此複雜的干擾問題。因此，它們所提供的自由度 (DoF) 增益是有限的。

為了解決這些挑戰，我們提出了一種將基於OFDM的正交時頻空間 (OTFS) 調變與盲干擾對齊 (BIA) 結合的調變方案。我們首先推導出修正的基於OFDM的OTFS調變，獲得了精確的具有延遲和都卜勒頻移的通道矩陣。在此精確調變的基礎上，我們利用用戶不同的同調時間，在干擾通道 (IC) 和廣播通道 (BC) 中實現多用戶干擾對齊，應對都卜勒效應和異構移動性。與傳統的干擾消除方法相比，我們的方法具有更少的限制，並提供更高的DoF增益。

In the future, with the development of non-terrestrial network technology, low-earth-orbit (LEO) satellites offer extensive connectivity potential. However, their rapid movement causes heterogeneous mobility between users at different distances from the LEO satellites, leading to challenges in multi-user interference cancellation. Additionally, conventional orthogonal frequency division multiplexing (OFDM) modulation is susceptible to inter-carrier interference (ICI) caused by the Doppler effect, which disrupts orthogonality and communication reliability. For multi-user transmission with heterogeneous speeds in doubly selective fading channels, traditional interference cancellation techniques are clearly insufficient to address such complex interference issues. Therefore, the degrees of freedom (DoF) gains they provide are limited.

To tackle these challenges, we propose a modulation scheme that combines orthogonal time frequency space (OTFS) based on OFDM with blind interference alignment (BIA). We first derived a corrected OFDM-based OTFS modulation, obtaining a precise channel matrix with delay and Doppler shift. Building upon accurate modulation, we achieve multi-user interference alignment in both interference channels (IC) and broadcast channels (BC) with Doppler effects and heterogeneous mobility by utilizing the different coherence times of users. Compared to traditional interference cancellation methods, our approach has fewer constraints and provides higher DoF gains.