A Novel Random Access Algorithm for Very High Frequency Data Exchange (VDE)

Yi Jiang,Junsen Wang,Yang Zheng

doi:10.3390/jmse8020083

Yi Jiang, Junsen Wang + Show 1 more

Open Access

https://doi.org/10.3390/jmse8020083

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Abstract

VHF Data Exchange System (VDES) is considered as an important component of the future maritime communication system by the International Maritime Organization (IMO). On the basis of the existing Automatic Identification System (AIS), VDES adds the other two higher capacity subsystems: Application Specific Message (ASM) and VHF Data Exchange (VDE). The Random Access Channel (RACH) of VDE was first introduced in the International Telecommunication Union (ITU) Recommendation M.2092-0. As the slot planning principle of RACH in VDE is by interval, which is significantly different from the continuous slot map for access algorithms in AIS, the existing slot access algorithms cannot meet the requirements of VDE. The simulation results show that the VDE slot map can reduce the normalized throughput of the existing algorithm by 39%. A novel random access algorithm called Adaptive Traffic Load Contention Resolution Diversity Slotted ALOHA (ATL-CRDSA) is proposed in this paper. The algorithm combines the load control strategy and contention resolution scheme to overcome the challenges of the new RACH of VDE. Simulation results show that ATL-CRDSA has remarkable improvement on RACH, making it very efficient and providing low latency of the packets. The insights gained from this study may be of assistance to the Media Access Control (MAC) layer design for upcoming versions of VDES standard.

Highlights

Nowadays Automatic Identification System (AIS), as a maritime communication system, plays a significant role in avoiding ship collisions
This paper mainly focuses on the Random Access Channel (RACH) access algorithm of VHF Data Exchange (VDE)-TER
In the VDE application, the normalized throughput of the Contention Resolution Diversity Slotted ALOHA (CRDSA) decreases rapidly when a large number of mobile stations access RACH at the same time; it cannot meet the functional requirements of VDE

Summary

Introduction

Nowadays AIS, as a maritime communication system, plays a significant role in avoiding ship collisions. In the VDE application, the normalized throughput of the CRDSA decreases rapidly when a large number of mobile stations access RACH at the same time; it cannot meet the functional requirements of VDE. Considering the VDE network with a massive number of stations and the idea of load control in [17,18], a novel hybrid algorithm with high normalized throughput and load control strategy is proposed in this paper, which is called Adaptive Traffic Load Contention Resolution Diversity Slotted ALOHA (ATL-CRDSA). Through analyzing VDE functional requirements, we allocate each slot in the VDE frame and construct a new slot map It can provide reference for future research. (2) We propose a new slot access algorithm ATL-CRDSA for VDE, which can meet the system requirements in terms of normalized throughput, packet collision ratio, packet loss ratio and system stability. The main conclusions are summarized, and further research is put forward

Related Work

Traffic Load Control

ATL-CRDSA Throughput under Different Loads

Conclusions