Exploiting In-Slot Micro-Synchronism for S-ALOHA

TL;DR

This paper introduces an enhanced S-ALOHA system with in-slot micro-synchronism using time offsets, improving throughput and reducing access delay in IoT networks by enabling collision resolution and optimized backoff algorithms.

Contribution

It proposes a novel S-ALOHA system with time offsets and Bayesian-optimized backoff algorithms, significantly improving throughput and delay performance over traditional methods.

Findings

Adopting multiple time offsets surpasses traditional throughput limits.

Proposed backoff algorithms achieve near-optimal throughput.

System drastically reduces access delay in IoT scenarios.

Abstract

Proliferation of the urban Internet-of-Things (IoTs) for smart cities has fuelled massive amounts of data over wireless cellular networks. Random access (RA) system of wireless cellular networks, e.g., 5G New Radio (NR), based on S-ALOHA system should cope with ever-growing IoT traffic. This work proposes S-ALOHA system with time offsets (TOs), where one slot consists of K TOs and one packet transmission time. The length of the overall TOs is a fraction of a packet transmission time. In the system users (re)transmit to the boundary of a TO randomly selected. This enables the base station (BS) to inform the users of who transmits the first and the last packets in the slot with collision so that the two users can retransmit successfully in the following two slots respectively. Our throughput analysis compared to simulations shows that adopting even with three and four TOs surpasses the throughput limit of S-ALOHA system without TOs. Additionally, we propose two Bayesian-optimized backoff algorithms for S-ALOHA system with TOs, with which users can apply throughput-optimal (re)transmission probability or uniform backoff window even in unsaturated traffic scenarios. Numerical results demonstrate that the proposed backoff algorithms can achieve the throughput close to an ideal system and drastically reduce the access delay compared to S-ALOHA system.