Pattern Division Random Access (PDRA) for M2M Communications with Massive MIMO Systems

TL;DR

The paper tackles pilot contention in massive MIMO-enabled mMTC random access by introducing Pattern-Division Random Access (PDRA), which constructs pattern-domain pilots as a superposition of $L$ cyclically-shifted ZC sequences to expand the contention space from $N$ to ${\binom{N}{L}}$ without additional physical resources. It provides a rigorous analysis of the PDRA success probability under MF detection, deriving conditions under which pattern collisions do not preclude successful data recovery and showing that the SINR constraint reduces to a simple bound in the large-$M$ regime. Numerical results in both uncorrelated and spatially correlated channels validate the asymptotic analysis and demonstrate notable gains over conventional schemes, with performance improvements arising from reduced pilot collisions outweighing modest CSI degradation. The approach is extensible to quasi-orthogonal blocks and other resource domains (time/frequency), offering a practical path to scalable massive connectivity in beyond-5G networks.

Abstract

In this work, we introduce the pattern-domain pilot design paradigm based on a "superposition of orthogonal-building-blocks" with significantly larger contention space to enhance the massive machine-type communications (mMTC) random access (RA) performance in massive multiple-input multiple-output (MIMO) systems.Specifically, the pattern-domain pilot is constructed based on the superposition of $L$ cyclically-shifted Zadoff-Chu (ZC) sequences. The pattern-domain pilots exhibit zero correlation values between non-colliding patterns from the same root and low correlation values between patterns from different roots. The increased contention space, i.e., from N to $\binom{N}{L}$, where $\binom{N}{L}$ denotes the number of all L-combinations of a set N, and low correlation valueslead to a significantly lower pilot collision probability without compromising excessively on channel estimation performance for mMTC RA in massive MIMO systems.We present the framework and analysis of the RA success probability of the pattern-domain based scheme with massive MIMO systems.Numerical results demonstrate that the proposed pattern division random access (PDRA) scheme achieves an appreciable performance gain over the conventional one,while preserving the existing physical layer virtually unchanged. The extension of the "superposition of orthogonal-building-blocks" scheme to "superposition of quasi-orthogonal-building-blocks" is straightforward.

Figures (8)

• Figure 1: Random access transmission structure.
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Theorems & Definitions (1)

• Remark 1