Data Synchronization in Mobile Computing

Data synchronization is a method of establishing consistency among data from a data source to the target data storage and vice versa. In data synchronization, we have to keep multiple copies of a dataset in coherence with one another to maintain the data integrity.

Data synchronization provides the continuous harmonization of the data over time. This is the basic fundamental concept used in a wide variety of applications, including file synchronization and mobile device synchronization, e.g., PDAs. It is also used in encryption for synchronizing Public Key Servers.

The requirement of Data Synchronization

Data synchronization is important and required in mobile computing because it checks the differences between two data containers or data sources and data receivers to restrict the unnecessary transfer of data that already resides in both data sources. The data synchronization process typically updates both data sources by transferring only additions, changes, and deletions. The following are the reasons why data synchronization is required in Mobile computing:

• Data synchronization is required between the mobile devices and their service provider.
• It is also required between the device and personal area computer and nearby wireless access points (in Wi-Fi connection) and other nearby devices.
• It is used to establish consistency among data from a data source to the target data storage and vice versa.

Example of Data Synchronization

Let's see a simple example of data synchronization:

Suppose we have added a new popular ringtone to one of the servers of a mobile service provider, so here, data synchronization means that all the service provider servers get identical sets of ringtones. All the devices connected to the server should be updated about the availability of the new data. The ringtone databases available to all the mobile phones include a copy of the title of that tone.

Types of Data Synchronization in Mobile Computing

Following is a list of different types of data synchronization techniques used in mobile computing:

• Two-way data synchronization (partial or full copies of data)
• Server-alerted synchronization
• One-way server-initiated synchronization
• The client-initiated refresh synchronization
• Client-initiated synchronization
• Refresh from the client for backup and update synchronization
• Slow (full data copy and thorough) synchronization

Two-way data synchronization (partial or full copies of data)

The Two-way data synchronization is done between mobile-devices and personal area computers. For example, whenever any of them from the list of contacts and data of personal information manager is modified, the two ways data synchronization is used to make them consistent.

The Server-alerted synchronization

In server-alerted synchronization, the server alerts the client whenever the data is modified or added. After getting the alert message, the client synchronizes the modified or new data by pull the request. For example, data is modified on the device after getting the alert new email.

One-way server-initiated synchronization

In one-way server-initiated synchronization, the server initiates synchronization after getting any modification and sends the copies of modified data to the client. For example, when a new email arrives at a server or when the device connects to the server and pushes the mail, it initiates the synchronization.

The client-initiated refresh synchronization.

In client-initiated refresh synchronization, the client initiates synchronization with the server to refresh its existing copies of data and refresh the configuration parameters saved at the server. For example, a computer or mobile device initiates refreshing of the stocked contacts and personal information data either at periodic intervals or when it connects to the server. When the device configuration changes or a new device connects to a server, the configuration parameters sent earlier refresh at the server.

Client-initiated synchronization

In client-initiated refresh synchronization, the client initiates synchronization with the server to refresh its existing copies of data and refresh the configuration parameters saved at the server. For example, a computer or mobile device initiates refreshing of the stocked contacts and personal information data either at periodic intervals or when it connects to the server. When the device configuration changes or a new device connects to a server, the configuration parameters sent earlier refresh at the server.

Client-initiated synchronization

In client-initiated synchronization, the client initiates synchronization when the data is available at the server or periodic intervals when it connects to the server. For example, a client mobile device initiates synchronization of the mails or new ring tones or music files when it gets availability at the server either or at periodic intervals when it connects to the server.

Refresh from the client for backup and update synchronization

In this synchronization, the client initiates synchronization and sends backup to the server for updating its data.

Slow (full data copy and thorough) synchronization

In slow synchronization, the client and server data are compared and then synchronized as per conflict resolution rules. This synchronization usually takes place in the idle state of the device and not immediately after connecting to the server. That's why it is called slow synchronization.