Subsea Communication - Implementing and Evaluating Protocols

Abstract

This thesis compares the performance, features, and practical implementation experience for subsea relevant protocols. Modbus TCP and Ethernet/IP are examples on mature communication protocols that can be used to exchange process data between topside and subsea. OPC UA is added as a suggestion to perform prospective data exchange between topside and subsea. The theoretical evaluation is performed for Modbus TCP, Ethernet/IP, and OPC UA. The evaluation reveals that Ethernet/IP is the only protocol that quantifies achievable performance indicators, Modbus TCP and OPC UA are not supposed to have performance indicators due its wide range of application. Also, the direct comparison of Modbus TCP and Ethernet/IP concludes that Ethernet/IP has better real-time properties, better multicast performance, and better support for features like time synchronization and safety protocol. CAN bus (SIIS level II) and IWIS are used for data exchange at sensor level, an introduction and evaluation of these two principles are performed. However, a direct comparison of the two were not considered relevant as they are engineered for two different purposes. The practical part of the thesis has consisted of implementing two different communication protocols that can be used for the same purpose. The first task was reading and interpreting the official Modbus TCP specification and implementing this for message exchange between two microcontrollers. The second task involved implementation of OPC UA on a microcomputer by use of a software development kit.