RE: ppt on underwater wireless communications
||UNDERWATER WIRELESS COMMUNICATION
1UNDERWATER WIRELESS.doc (Size: 415 KB / Downloads: 19)
Underwater wireless communication is a flourishing research area in the field of wireless communications. This paper presents the overall framework of the necessity of underwater wireless systems, characteristics of an acoustic channel, hardware and working of acoustic modems, sensor networks and different communication architectures involved in the sensor networks. Applications till date, like oceanographic data collection,AUVs(autonomous underwater vehicles),underwater radio etc.., future challenges like effective transmission of video and audio signals by real time monitoring have been emphasized with a view to overcome the present limitations.
The signals that are used to carry digital information through an underwater channel are not radio signals as electromagnetic waves propogate over short distances. Instead acoustic waves are used which can propogate over long distances. Over the past decades, cabled submersibles were used to discover the remains of titanic and hydrothermal vents due to the burden and cost of heavy cables that must be used to establish a high-speed communication between the remote end and the surface. To overcome such impediments, underwater wireless communication has come into existence.
When no data is being transmitted, the modem stays in sleep mode thereby it periodically wakes
Up to receive possible data being transmitted by far end modem. This results in low power consumption.
DATA TRANSMISSION IN MODEM:
Suppose the bottom modem tries to send data to surface modem, it receives data from its link while it is in sleep mode and then it switches to the transmit mode and begins to transmit. As the surface modem wakes up and detects data from bottom modem, it switches from sleep mode to receive mode.
UNDERWATER ACOUSTIC SENSOR NETWORKS:
Underwater networks consist of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area. Traditional approach for ocean bottom monitoring is to deploy underwater sensors that record data and then recover the instruments. By this method real time monitoring is not possible, failures occur. This can be overcome by connecting underwater instruments by means of wireless links.
• Sensor nodes float at different depths in order to observe a given phenomenon.
• The possible solution to achieve different depths would be to attach each UW-sensor node to a surface buoy, by means of wires.
• Multiple floating buoys may obstruct ships navigating on the surface.
They may also be easily detected and deactivated by enemies in military settings.
Due to the above reasons, each sensor is anchored to the ocean bottom and equipped with a floating buoy that can be inflated by a pump. The buoy pushes the sensor towards the ocean surface. The depth of the sensor can then be regulated by adjusting the length of the wire that connects the sensor to the anchor, by means of an electronically controlled engine that resides on the sensor.
This paper gives the overall view of the necessity of underwater wireless communication and its applications. Despite much development in this area of the underwater wireless communication, there is still an immense scope so more research as major part of the ocean bottom yet remains unexploded. Advanced versions of the existing applications and innovative inventions have become a must in this field. Therefore, the main objective is to imbibe knowledge about this emerging field and thereby encourage research and implementation of advanced technology to overcome the present limitations such as the environmental effects on the noise performance of acoustic systems as mentioned in this paper.