Editorial - Educational Research ( 2022) Volume 13, Issue 5
Received: 08-Aug-2022, Manuscript No. ER-22-71436; Editor assigned: 10-Aug-2022, Pre QC No. ER-22-71436; Reviewed: 27-Aug-2022, QC No. ER-22-71436; Revised: 01-Sep-2022, Manuscript No. ER-22-71436; Published: 08-Sep-2022, DOI: 10.14303/2141-5161.2022.238
Wireless Sensor Network is one of the most exciting and growing branches of wireless communication. Our world is going toward autonomous, sustainable and environment conscious systems with technologies which can monitor the environment provide valuable and timely measurements. WSNs enable such drives in a non-intrusive manner yet with extended coverage of area thanks to their underlining distributed and miniature nature.
The ultimate goal and vision of WSNs field is to make sensor networks a fabric of social life. Minute sensors will be embedded in every conceivable manner to provide accurate timely information to sinks nodes. These nodes interested with the information will enable proactive response hence improving the user experience, quality of life as well as fortunes spent in industries and manufacturing
This paper approaches the theoretical study of Time Synchronization protocol in Wireless Sensor Network. Time synchronization is helpful in saving energy in WSN because it provides the possibility to set nodes into the sleeping mode. By Consuming the Energy Conservation which increases the life time of Sensor nodes.
Time synchronization is the indispensable part of the infrastructure in wireless sensor network. The efficient and precise operation of many applications in wireless sensor network requires synchronization time. In order to achieve network wide time synchronization, a synchronization protocol has been considered that is Tim-sync protocol for sensor network. The objective of this project is Conservation of energy and synchronization accuracy is achieved in the wireless sensor network (Swami e t a l . 2007).
Time Synchronization Protocols Based on PI Synchronization Algorithm
The Synchronization protocols for sensor networks based on the PI Sync algorithm. We first present a fully distributed time synchronization protocol, in which each sensor node considers only the logical clock values of its neighboring nodes to update the value and the rate of its logical clock. Then, flooding-based time synchronization protocols in which each sensor node synchronize to the clock of a reference node. All of the protocols that we propose have very little memory requirement and are lightweight in terms of computation since they require only a few arithmetic operations to update the logical clocks, independently of network size and topology. Moreover, the amount of information to be exchanged among the sensor nodes is quite small since sensor nodes only broadcast the value of their logical clocks (Locher e t .a, l . 2008)
PISync Protocol
In this Protocol, Each sensor node Synchronize to their direct neighbours. The pseudo-code of this approach is presented in Algorithm (Postscapes, 2012).
Each sensor node maintains two variables related to its logical clock: time estimate tu and oscillator frequency estimate Δu 2. Initially when the node is powered on, the time estimate is set to zero and the oscillator frequency estimate is set to 1/f, i.e. the nominal frequency, to progress the time estimate at the same speed of the hardware clock. Two other variables, sum and num are required to calculate the average synchronization error to the neighboring nodes. These variables are also initalized with zero (Lines 1-2). Whenever a synchronization message from any neighboring node is received (Line 4), the difference of the received time estimate ˆtv and the time estimate ˆt u of node u at the reception time, i.e. clock skew, is calculated .This value is added to the sum variable (Line 5) and The number of received clock values is incremented (Line 6).In order to inform its neighboring nodes, node Broadcasts its up-to-date time information approximately. Every B seconds, where B denotes the beacon period. Whenever the hardware clock is a multiple of B ˆf (Line 8), if the average clock skew sum/ num is greater than emax, i.e. the maximum difference that can be observed due to different clock speeds between subsequent synchronization message reception, then the clock skew is mainly due to the large off sets between the clocks. Otherwise, the frequency of the oscillator is required to be adjusted (Line 9). Finally, the time estimate ˆtu of node u is also updated (Line 10) (Ren etal 2008)
The variables sum and num are initialized (Line 11) and the clock value is broadcasted (Line 12) (Figure 1).
Figure 1. PISync Protocol.
It should be noted that AvgPISync operates in a completely blind fashion since it requires neither to know the sender node nor to store its time information. Hence, AvgPISync is quite robust to topological changes and it can even work efficiently in topologies with very high densities.
Flooding Based PISync Protocols
In Flooding PISync Protocol (FloodPISync), this synchronizes each sensor node to the clock of a reference node. In FloodPISync, a dynamically elected or a predefined reference node floods its stable time information into the network. Each sensor node collects this time information, updates its clock according to PISync algorithm and also broadcasts its clock value for its neighbouring nodes to achieve network-wide time synchronization. The pseudocode of FloodPISync is presented in Algorithm (Figure 2). Apart from the variables of the fully distributed version, each sensor node ualso maintains a sequence number sequ to store the largest sequence number received from the reference node. Initially when the node is powered on, the sequence number is also set to zero (Lines 1-2). The reception of a synchronization message carrying a greater sequence number than sequ indicates that the reference node has initiated a new synchronization round recently (Line 4). Hence, the received time information can be considered as a fresh estimate of the reference clock. Similar to the fully distributed version, the difference of the received time estimate ˆtv and the time estimate ˆtu of node u at the reception time is considered to update the oscillator frequency estimate ˆΔu. Similar to AvgPISync, this update is performed by setting the parameter β equal to unity (Schenato et al .,2007).
Figure 2. Flooding Based PISync Protocols.
The time estimate ˆtu of node u and the sequence number are also updated (Lines 6-7).
Approximately every B seconds, solely the reference node increments its sequence number and hence initiates a new flooding round. Since all of the sensor nodes broadcast their time estimates, time information of the reference node is propagated and network-wide synchronization is achieved (Lines 9-11) (Elson et al .,2002)
Time synchronization in all networks either wired or wireless is important. It allows for successful communication between nodes on the network. It is, however, particularly vital for wireless networks. Synchronization in wireless nodes allows for a Synchronization algorithm to be utilized over a multihop wireless network. Wireless time synchronization is used for many different purposes including location, proximity, energy efficiency, and mobility. In sensor networks when the nodes are deployed, their exact location is not known so time synchronization is used to determine their location. Time stamped messages will be transmitted among the nodes in order to determine their relative proximity to one another. Time synchronization is used to save energy; it will allow the nodes to sleep for a given time and then awaken periodically to receive a beacon signal. Many wireless nodes are battery powered, so energy efficient protocols are necessary. Lastly, having common timing between nodes will allow for the determination of the speed of a moving node.
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