The Underwater Internet of Things system is designed to provide access to autonomous underwater tools: various sensors, actuators, AUV / ROV directly from the Internet. The system is designed to solve the problems of remote data collection and control of various underwater mechanisms, data transfer from autonomous underwater sensors without the need for pre-setting or coordination in the changing composition and position of agents.
The Underwater Internet of Things system is a set of specialized devices and a stack of network protocols, originally developed considering their use in hydroacoustic channel conditions: complex hydrological conditions, low information transfer rate, and low signal propagation rate in the medium, narrow available frequency band.
The basis of the system includes three types of devices:
The main problem faced by the developers of such projects is the occurrence of collisions of acoustic signals at the receiving point while using relatively high-speed (and calculated over short distances – up to hundreds of meters) methods of data transmission. A bet is made on complicating the routing methods, but practice shows that this approach is unjustified for the following reasons: in a real hydroacoustic channel, rapidly changing, where the probability of message delivery may be significantly less than one, data transmission through the repeater chain is extremely inefficient not only because of the ever-increasing with the number of repeaters the probability of error, but also because of unacceptable delay and overhead costs for routing.
In our Headen system is applied a completely different approach, which, thanks to the specialized protocol stack, ensures the complete absence of collisions on the receiver side and data transmission without intermediaries-repeaters. The control commands and the transfer of small amounts of data are carried out using fixed-length code parcels, the transfer of data from autonomous underwater nodes takes place only at the request of a surface two-medium access point, which, having information about the location (and therefore possible propagation delays) of the underwater nodes, polls them optimally using time and bandwidth. In addition, this system uses methods that initially provide data transmission over long distances (up to 8 km between the transmitter and receiver), which eliminates the need to use repeaters. The fixed length of messages allows you to maximize the system’s energy efficiency and, as a result, increase autonomy. Moreover, to the separation in time, the system uses the code division of subscribers at the physical level, which is an integral part of the specialized protocol stack.
Under this system, underwater sites are divided into three types:
So, in total, one access point can simultaneously serve up to 555 different nodes, in the water area with a radius of up to 8 kilometers.
All nodes support remote configuration of power saving modes in a wide range. At the same time, the mode is controlled by a modem, which, before going to sleep mode, signals this to the interface device, and on waking up, it also awakens the interface device connected to it.
Modems use modern highly reliable and noise-resistant digital hydroacoustic communication technology, which allows them to work steadily in a wide range of hydrological conditions and has proven itself well both in marine conditions and in extremely complex shallow water bodies.
High versatility of the system is complemented by passive positioning, which is provided by the following technical solutions:
The development of the system is supposed to be carried out in the following stages.
Stage 1. Implementation of basic functionality. Long basic positioning system + physical protocol. Planned completion dates – the beginning of 2018.
Stage 2. Implementation of a two-frequency system of interaction. Increasing the frequency of data exchange with nearby devices should lead to the unloading of the main low-frequency channel, as well as to a significant increase in the speed of information exchange. The planned deadlines for the implementation of the stage are 2018.
Stage 3. Implementation of two-medium buoys with phased antenna arrays. Ensuring the operation of the communication system and navigation all on one buoy. The planned deadlines for the implementation of the stage are 2019.