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

TL;DR

This paper introduces a cell-free unsourced random access scheme with successive interference cancellation, enabling support for up to 1400 users with high energy efficiency and significantly reduced error probability.

Contribution

It proposes a novel cell-free architecture with distributed processing and interference cancellation for unsourced random access, improving scalability and reliability.

Findings

Supports up to 1400 users with high energy efficiency

Reduces error probability by over two orders of magnitude

Demonstrates effectiveness through numerical simulations

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.