Orthogonal time frequency space (OTFS) modulation is a recently proposed delay-Doppler (DD) domain communication scheme, which has shown promising performance in general wireless communications, especially over high-mobility channels. In this paper, we investigate DD domain Tomlinson-Harashima precoding (THP) for downlink multiuser multiple-input and multiple-output OTFS (MU-MIMO-OTFS) transmissions. Instead of directly applying THP based on the huge equivalent channel matrix, we propose a simple implementation of THP that does not require any matrix decomposition or inversion. Such a simple implementation is enabled by the DD domain channel property, i.e., different resolvable paths do not share the same delay and Doppler shifts, which makes it possible to pre-cancel all the DD domain interference in a symbol-by-symbol manner. We also study the achievable rate performance for the proposed scheme by leveraging the information-theoretical equivalent models. In particular, we show that the proposed scheme can achieve a near optimal performance in the high signal-to-noise ratio (SNR) regime. More importantly, scaling laws for achievable rates with respect to number of antennas and users are derived, which indicate that the achievable rate increases logarithmically with the number of antennas and linearly with the number of users. Our numerical results align well with our findings and also demonstrate a significant improvement compared to existing MU-MIMO schemes on OTFS and orthogonal frequency-division multiplexing (OFDM).
翻译:orthomonal 时间频率空间调制( OTFS) 是最近提议的一种延迟- Doppler (DD) 域域通信方案, 它在一般无线通信中表现良好, 特别是在高流动性的频道上。 在本文中, 我们对多用户多输入和多输出 OTFS (MU-MIMO-OTFS) 传输的DD域域托林松- 哈拉岛预编码(THP) 进行了调查。 我们建议, 而不是直接应用基于巨大的等同频道矩阵的THP, 简单地实施不需要任何矩阵变异或变异的 THP 域通信方案。 这种简单的执行由 DT 域域域频道属性属性( 即不同的可解码路径不具有相同的延迟和多普勒尔的预编码( THPTHP ) 进行。 我们提议的方案可以使用信息- 理论等同模式直接应用 THP, 而不是使用信息- 等同的模型, 我们提议的方案可以实现一个接近最优化的性性性性性性性性性能性能的运行性运行, 和直径直径比值的用户的轨道比 。