ODMA-Based Cell-Free Unsourced Random Access with Successive Interference Cancellation

2025-01-17

AI Summary

To address the challenge of passive random access in massive IoT scenarios lacking fixed base stations, this paper proposes a cell-free network architecture based on orthogonal multiple access (ODMA). The architecture employs distributed access points (APs) coordinated with a central processing unit (CPU) to implement a hierarchical signal processing framework: APs perform distributed channel estimation and initial decoding, followed by successive interference cancellation (SIC) for successfully decoded messages; the CPU conducts joint multi-AP decoding and final detection. This work is the first to integrate ODMA with the cell-free paradigm for passive random access and introduces a novel two-stage SIC mechanism leveraging AP–CPU collaboration. Experimental results demonstrate that the system supports concurrent access by up to 1,400 users, achieves significant improvements in energy efficiency, and reduces bit error rate by more than two orders of magnitude.

Technology Category

• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Cognitive Modeling & Cognitive Systems: Agent Architectures
• Search and Optimization: Distributed Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Large-scale security measurements

Abstract

We consider the unsourced random access problem with multiple receivers and propose a cell-free type solution for that. In our proposed scheme, the active users transmit their signals to the access points (APs) distributed in a geographical area and connected to a central processing unit (CPU). The transmitted signals are composed of a pilot and polar codeword, where the polar codeword bits occupy a small fraction of the data part of the transmission frame. The receiver operations of pilot detection and channel and symbol estimation take place at the APs, while the actual message bits are detected at the CPU by combining the symbol estimates from the APs forwarded over the fronthaul. The effect of the successfully decoded messages is then subtracted at the APs. Numerical examples illustrate that the proposed scheme can support up to 1400 users with a high energy efficiency, and the distributed structure decreases the error probability by more than two orders of magnitude.

Problem

• Ad-hoc networking
• Massive device connectivity
• Randomized network access

Innovation

• ODMA-based random access scheme
• Signal seeking and hierarchical interference cancellation
• Distributed signal processing and special coding techniques