Generalized Two-Dimensional Index Modulation in the Code-Spatial Domain for LPWAN

2026-04-23

AI Summary

This work addresses the challenges of low data rates, poor reliability, and insufficient energy efficiency in LPWAN systems under stringent hardware constraints by proposing a generalized code index modulation transceiver architecture. For the first time, it establishes a unified two-dimensional index modulation framework that jointly exploits code and spatial domains. By integrating spatial modulation (SM), space–time block coding (STBC), and code index modulation (CIM) with CPM-based spreading, Chirp, and Zadoff–Chu sequences, three novel schemes—SM-CIM, STBC-SM-CIM, and ESTBC-SM-CIM—are developed. Theoretical closed-form expressions for average bit error rate are derived, and simulations demonstrate that the proposed approaches significantly outperform existing benchmarks in terms of data rate, energy efficiency, and transmission reliability.

Technology Category

• Cognitive Modeling & Cognitive Systems: Neural Spike Coding
• Machine Learning: Large Multimodal Models (LMMs)
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

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.

Problem

• LPWAN
• IoT
• energy efficiency
• data rate
• hardware constraints

Innovation

• Index Modulation
• Code-Spatial Domain
• Low-Power Wide-Area Networks
• Two-Dimensional Coding
• Energy Efficiency