Grant-Free Radio Access for Short-Packet Communications over 5G Networks

TL;DR

This paper proposes a grant-free, asynchronous radio access protocol for 5G short-packet communications that reduces delay and energy consumption by leveraging packet replicas and advanced signal processing.

Contribution

It introduces a novel asynchronous grant-free protocol that exploits timing, frequency offsets, and packet replicas for improved reliability and energy efficiency in 5G networks.

Findings

The scheme achieves long battery lifetime for low-complexity devices.

Performance depends on traffic load, with asynchronous outperforming synchronous access in certain regions.

Closed-form expressions for reliability and battery life are derived.

Abstract

Radio access management plays a vital role in delay and energy consumption of connected devices. The radio access in existing cellular networks is unable to efficiently support massive connectivity, due to its signaling overhead. In this paper, we investigate an asynchronous grant-free narrowband data transmission protocol that aims to provide low energy consumption and delay, by relaxing the synchronization/reservation requirement at the cost of sending several packet copies at the transmitter side and more complex signal processing at the receiver side. Specifically, the timing and frequency offsets, as well as sending of multiple replicas of the same packet, are exploited as form of diversities at the receiver-side to trigger successive interference cancellation. The proposed scheme is investigated by deriving closed-form expressions for key performance indicators, including reliability and battery-lifetime. The performance evaluation indicates that the scheme can be tuned to realize long battery lifetime radio access for low-complexity devices. The obtained results indicate existence of traffic load regions, where synchronous access outperforms asynchronous access and vice versa.