As a promising technique for high-mobility wireless communications, orthogonal time frequency space (OTFS) has been proved to enjoy excellent advantages with respect to traditional orthogonal frequency division multiplexing (OFDM). Although multiple studies have considered index modulation (IM) based OTFS (IM-OTFS) schemes to further improve system performance, a challenging and open problem is the development of effective IM schemes and efficient receivers for practical OTFS systems that must operate in the presence of channel delays and Doppler shifts. In this paper, we propose two novel block-wise IM schemes for OTFS systems, named delay-IM with OTFS (DeIM-OTFS) and Doppler-IM with OTFS (DoIM-OTFS), where a block of delay/Doppler resource bins are activated simultaneously. Based on a maximum likelihood (ML) detector, we analyze upper bounds on the average bit error rates for the proposed DeIM-OTFS and DoIM-OTFS schemes, and verify their performance advantages over the existing IM-OTFS systems. We also develop a multi-layer joint symbol and activation pattern detection (MLJSAPD) algorithm and a customized message passing detection (CMPD) algorithm for our proposed DeIMOTFS and DoIM-OTFS systems with low complexity. Simulation results demonstrate that our proposed MLJSAPD and CMPD algorithms can achieve desired performance with robustness to the imperfect channel state information (CSI).

翻译：作为一种有前景的高移动性无线通信技术，正交时频空间（OTFS）已被证明相比传统正交频分复用（OFDM）具有显著优势。尽管已有多项研究考虑基于索引调制的OTFS（IM-OTFS）方案以进一步提升系统性能，但如何针对必须工作在信道时延与多普勒频移环境下的实际OTFS系统，开发有效的索引调制方案及高效接收机仍是一个具有挑战性的开放问题。本文针对OTFS系统提出两种新型逐块索引调制方案，分别命名为基于时延索引调制的OTFS（DeIM-OTFS）和基于多普勒索引调制的OTFS（DoIM-OTFS），其中延迟/多普勒资源块被同时激活。基于最大似然（ML）检测器，我们分析了所提DeIM-OTFS与DoIM-OTFS方案的平均误比特率上界，并验证了其相比现有IM-OTFS系统的性能优势。同时，我们为所提出的DeIM-OTFS与DoIM-OTFS系统开发了低复杂度的多层联合符号与激活模式检测（MLJSAPD）算法和定制化消息传递检测（CMPD）算法。仿真结果表明，所提MLJSAPD与CMPD算法能够在对非理想信道状态信息（CSI）具有鲁棒性的前提下实现期望性能。