Low-power wide-area networks (LPWANs) are crucial for large-scale Internet of Things (IoT) applications, yet they face increasing demands for higher data rates, improved reliability, and enhanced energy efficiency under stringent hardware constraints. To address these challenges, this paper introduces a generalized code-index modulation (CIM) transceiver that employs multiple-antenna index modulation (IM). The transmitter integrates spatial modulation (SM), space-time block coding (STBC), and CIM into a unified two-dimensional (2D) coding structure, where the spreading sequences -- realized via continuous phase modulation with spread spectrum (CPM-SS), chirp spread spectrum, or Zadoff-Chu sequences -- serve as spreading codes. Three specific schemes are proposed: SM-CIM, STBC-SM-CIM, and an enhanced STBC-SM-CIM (ESTBC-SM-CIM), designed to jointly improve data rate and energy efficiency. Closed-form expressions for the average bit error probability are derived, and system performance is analyzed in terms of data rate, energy efficiency, and computational complexity. Simulation results show that the proposed designs consistently outperform benchmark schemes, demonstrating their potential for enabling high-data-rate, energy-efficient LPWAN and IoT communications.

翻译：低功耗广域网（LPWAN）是大规模物联网应用的关键基础设施，但在严苛硬件约束下，面临着日益增长的更高数据速率、更强可靠性及更高能效需求。针对上述挑战，本文提出一种采用多天线索引调制的广义码索引调制收发机。该发射机将空间调制、空时分组码与码索引调制统一为二维编码结构，其中由连续相位调制扩频、线性调频扩频或Zadoff-Chu序列实现的扩频序列用作扩频码。本文提出三种具体方案：SM-CIM、STBC-SM-CIM及增强型STBC-SM-CIM（ESTBC-SM-CIM），旨在协同提升数据速率与能效。推导了平均误比特率闭式表达式，并从数据速率、能效和计算复杂度三方面分析系统性能。仿真结果表明，所提设计方案始终优于基准方案，展现出实现高数据速率、高能效LPWAN及物联网通信的潜力。