Background: Time synchronization between the sensor nodes to reduce average end to end
delay with the increase in number of sensor nodes in a network for critical and real time data monitoring
can be achieved by precisely predicting their wakeup/sleep timings and are of prime importance
as described in recent patents. The idea evolves as a reduction in duty cycle and precise time scheduling
of active/sleep cycles of the sensors to reduce the probability of collisions between data and control
packets which prolongs the network lifetime and reduces the average end to end delay. The multihop
transmissions are not always attractive in underwater communication due to high losses. The
proposed Slotted Cyclic Quorum with Influence nodes (SCQI) medium access control protocol is
capable of continuous monitoring of critical underwater events in a very effective manner in multihop
transmission networks. This work is an attempt to mitigate multihop hidden terminal and to reduce
the probability of collisions between data and control packets.
Methods: The mathematical model for the path loss due to attenuation of electromagnetic wave propagation
in the sea water is explained. The three path reflection model evaluating reflection loss from
the air-water and water-sand interfaces as a function of distance between sensors and water depth is
introduced. It is assumed that the sensors are properly anchored to limit their movement due to waves
within the permissible limits to follow the proposed cyclic quorum based medium access control protocol.
The fundamentals of cyclic quorum with a slotted scheme along with the influence nodes are
elaborated. This paper attempts to utilize electromagnetic waves at resonance frequency of 2.4 GHz
for underwater communication. The main advantages of using electromagnetic waves instead of
acoustic waves are that it reduces the latency due to faster propagation speed and give a high data rate
due to high frequency of the wave at the cost of reduction in communication range.
Results: The results verify that the implementation of cyclic quorum based medium access control
(CQ) protocol, slotted cyclic quorum based medium access control (SCQ) protocol and slotted cyclic
quorum based medium access control with influence nodes (SCQI) protocol has significantly reduced
the average end to end delay with the increase in number of sensor nodes and also prolongs the network
lifetime making it appropriate for critical and real time data monitoring.
Conclusion: This work proves the suitability of electromagnetic waves as an effective alternative for
underwater wireless communication. The main objective is to optimize the network lifetime and to
reduce the average end to end delay by implementing cyclic quorum based medium access control
protocol in underwater wireless sensor networks and to draw the attention of researchers in this area.
Keywords: Underwater wireless sensor network (UWSN), slotted cyclic quorum, influence nodes, underwater electromagnetic
wave communication, 2.4 GHz, multihop hidden terminal, collisions.
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