Page 653 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

654 CHAPTER 23 The Future of ROV Technology
Table 23.1 Pros and Cons of Various Underwater Communications Technologies
Pros Cons
Acoustic
Optical
RF
• Proven
• Up to 20 km range • High precision
• Very high bandwidth
• Low physical and power
footprint
• Tolerant of water depth, turbidity, suspended particles/aeration, acoustic noise, air/water interface, etc.
• Low latency
• High bandwidth
• Limiting conditions:

Background noise
Multipath

Reverberation
• Poor performance in shallow depths • Narrow bandwidth
• Latency
• May harm marine life
• Very poor transmission at air/water interface
• Turbidity and suspended particles obstruct transmission
• Alignment and focus require calibration
• Short range in water
• Air/water interface degrades
transmission
• Very limited range
• Low energy efficiency • Vulnerable to in-band
electromagnetic interference (EMI)
Source: Courtesy WFS Technologies.
completed to assure a safe return to manned platform operations. It may be much cheaper to keep a fleet of AUVs (assigned to the facility and on standby for such an operation) than a fleet of MSVs.
And should the operator want real-time data sent back on what the AUV is finding, instead of recovering the vehicle and downloading the data, an unmanned surface vehicle (USV) could follow the AUV and provide a communication link back to the operator. Acoustic communications, espe- cially when transmitting directly to the surface, are quite capable of providing such feedback to the operator. Also, by coupling a USV and an AUV, the AUV’s navigation can be updated when required because the USV knows its exact position through GPS.
Another communications technique, as discussed in the following sections, is the provision of a fiber-optic cable, with communication nodes, that follows the pipelines back to the control station on shore or onboard the floating production, storage, and offloading (FPSO) vessel. The AUV can dock with the node, download the data, recharge its batteries, and continue the operation.
As explained throughout this text, ROVs are capable of many things. From sensor delivery to tooling operations, the ROV is quickly reaching maturity. The mundane operations of IRM will be continually thrown off to the logic-driven vehicles with onboard power (AUVs). The continued “brick wall” for operation of the subsea field will be the mechanical ability to turn valves, pull