空间-码域分组索引调制：流体天线辅助系统设计与误码率性能分析

中文摘要 AI 辅助

流体天线系统（FASs）在紧凑孔径内提供可重构的空间资源。本文针对FA辅助收发机，引入了码域分组索引调制（CGIM）及其空间-码域扩展，称为SCGIM。CGIM将可用的正交扩频码划分为多个子集，并将信息联合映射到它们的同相和正交索引以及星座符号上。在Rx-FAS辅助的单输入多输出（SIMO）链路中，分组级解扩将正交码组分离以进行并行检测，而接收端口选择提供空间分集。SCGIM进一步将交织的Tx-FA端口子集与码子集关联，其中Tx-FAS在多发多收（MIMO）链路中传递空间索引信息，而Rx-FAS提供选择分集。对于SCGIM，我们开发了最大似然（ML）、分阶段贪婪（GD）和跨域索引消息传递（CD-IMPD）检测器。CD-IMPD在无环因子图上交换软信息，以考虑空间和码索引之间的耦合，仅需一次向内和一次向外的消息传递。对于CGIM，误码率（BER）由解扩域观测的联合决策区域推导，并在瑞利、Nakagami-m和加性高斯白噪声信道下，对Rx-FAS选择增益分布进行平均。对于SCGIM，使用选择增益密度比和指数倾斜二次型拉普拉斯变换，从全对联合界推导出平均BER近似。仿真结果验证了BER分析，并表明所提出的方案相比所考虑的IM方案实现了更低的BER和更高的吞吐量，而CD-IMPD以较低的检测复杂度实现了接近ML的BER性能。

英文摘要

Fluid antenna systems (FASs) provide reconfigurable spatial resources within compact apertures. In this paper, we introduce code-domain grouped index modulation (CGIM) and its spatial-code-domain extension, termed SCGIM, for FA-assisted transceivers. CGIM partitions the available orthogonal spreading codes into multiple subsets and jointly maps information onto their in-phase and quadrature indices and constellation symbols. In an Rx-FAS-assisted single-input multiple-output (SIMO) link, group-wise despreading separates the orthogonal code groups for parallel detection, while receive-port selection provides spatial diversity. SCGIM further associates interleaved Tx-FA port subsets with the code subsets, with the Tx-FAS conveying spatial-index information and the Rx-FAS providing selection diversity in a multiple-input multiple-output (MIMO) link. For SCGIM, we develop maximum-likelihood (ML), staged greedy (GD), and cross-domain index message-passing (CD-IMPD) detectors. CD-IMPD exchanges soft information over a cycle-free factor graph to account for the coupling between the spatial and code indices, requiring only one inward and one outward message pass. For CGIM, the BER is derived from the joint decision regions of the despread-domain observations and averaged over the Rx-FAS selected-gain distribution under Rayleigh, Nakagami-m, and additive white Gaussian noise channels. For SCGIM, an average-BER approximation is derived from a full-pair union bound using the selected-gain density ratio and exponentially tilted quadratic-form Laplace transforms. Simulation results validate the BER analysis and show that the proposed schemes achieve lower BER and higher throughput than the considered IM schemes, while CD-IMPD achieves near-ML BER performance with lower detection complexity.

发表机构

• National Mobile Communications Research Laboratory, Frontiers Science Center for Mobile Information Communication and Security, Southeast University（东南大学国家移动通信重点实验室、移动信息与安全前沿科学中心）
• Purple Mountain Laboratories（紫金山实验室）
• Nanyang Technological University（南洋理工大学）
• AUMOVIO-NTU Corporate Laboratory（奥莫维欧-南洋理工大学企业联合实验室）
• School of Electronic and Information Engineering, South China University of Technology（华南理工大学电子与信息工程学院）
• School of Communication Engineering, Hangzhou Dianzi University（杭州电子科技大学通信工程学院）
• Stevens Institute of Technology（史蒂文斯理工学院）

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