Introduction
Over the past few years, advances in the field of network based computing and applications on demand have led to an explosive growth of application models such as Mobile computing, Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link. The main concept involves [1]
• Mobile communication
• Mobile hardware
• Mobile software
Mobile communication
The mobile communication in this case, refers to the infrastructure put in place to guarantee that consistent and dependable communication goes on. These would include devices such as protocols, services, bandwidth, and portals necessary to facilitate and support the stated services. The data format is also additionally characterized at this stage. This guarantees there is no impact with other existing systems which offer the same service. Since the media is unguided and unbounded, the overlaying infrastructure is fundamentally radio wave-oriented. That is, the signals are carried over the air to intended devices that are fit for accepting and sending similar kinds of signals.[1]
Mobile hardware
Mobile hardware includes mobile devices or device components that get or get to the service of mobility. They would run from portable laptops, Smartphone’s, tablet Pc's, Personal Digital Assistants. These devices will have a receptor medium that is equipped for detecting and accepting signals. These devices are designed to work in full-duplex, whereby they are fit for sending and getting signals in the meantime. They don't need to hold up until one device has completed communicating for the other device to start communications. Aforementioned devices utilize a current and set up system to work on. By and large, it would be a wireless network.[1]
Mobile software
Mobile software is the real program that keeps running on the mobile hardware. It manages the characteristics and requirements of mobile applications. This is the engine of the mobile device. In different terms, it is the operating system of the appliance. It's the essential component that works the mobile device. Since portability is the primary component, this kind of computing guarantees that users are not tied or pinned to a single physical location, but are able to operate from anyplace. It incorporates all aspects of wireless communications.[1]
DATABASE MANAGEMENT ON MOBILE COMPUTING
A mobile database is a database which can be associated with by a mobile computing device over a mobile network. The client and server have wireless connections. A cache is kept up to hold frequent data and transactions so that they are not lost due to connection failure. A database is a structured way to organize information. With the advances in mobile technology and portable mobile devices, which include handheld mobile phones, their larger counterpart, personal device assistance and the laptop, are becoming increasingly useful tools for mobile users. Modern technologies have provided portable computers with wire-less interfaces that allow networked communication even while a user is mobile. Wireless networking greatly enhances the utility of a portable computing device. The mobile users can access information independent of their physical location through wireless connections.
1. STRUCTURE
• Mobile Unit (MU): portable computer equipped with a wireless interface.
• Base Station (BS): Fixed host augmented with wireless interface. It is also called Mobile Support Station (MSS). Mobile Units communicate with other units through those Base Stations of the cells in which they reside.
• Fixed Host (FH): computer without a wireless interface.
2. ISSUES
Data Management:
Today’s mobile applications require more than basic data synchronization. They require a complete arrangement of data management services, including solid data modelling, mobile and server-side support for schema deployment and version, rules-based data distribution, bi-directional data transfers that are quick and secure, mobile device-based database services, and tight transaction-level integration with multiple enterprise information sources. The asymmetric nature of the wireless communication link is another challenge for data management in wireless links to ensure low utilization and data access inactivity. [3]
Security:
Implementing security in a wireless environment is a troublesome undertaking because of the portability of the users and the network components and the fact that the medium is powerless to spying. Since mobile devices connect with various networks authentication of a mobile host is a difficult task and it is problematic. When I mobile device moves from one location to another the data that is sent to it is defenceless against theft and coping. This can be avoided by receiving different encryption techniques.
One of the most important issues in mobile computing related to security in databases is the trust between system components. Traditionally, database systems based their operation and their security on that of the underlying operating system. It is clearly that some such degree of trust is required for resource sharing between a mobile computer and a foreign environment for the mobile device to work legitimately in a foreign network.
Mobility:
The location of mobile units is an essential parameter when finding a mobile station that may hold the required data and while selecting information particularly for location dependent information services. However the search cost to locate mobile units is added to the cost of each communication including them. Two arrangements have been discussed in the literature [16] for the main problem. In one solution, each mobile unit has a home base station that keeps track of its location by receiving notifications of its movements. The second solution is based on restricted broadcast within the area of the mobile unit that wants to access.
Query Processing:
Query processing in mobile databases is a unique challenge since we have to consider the limited resource of the mobile system and the changing location of the mobile user. The queries issued in the mobile system are not quite the same as those issued by the fixed system because the location information adds power to the query but at the same time it also adds complexity to the query processing. The complete process of query processing can be divided into the three phase’s translation, optimization, and execution.
On the off chance that we have just restricted resources in the mobile device then we send the query to the server to be processed there and the results are returned back to the mobile device. In the second circumstance the query processing is started in the mobile device. After the semantic analysis of the query it is seen that the processing of the query will require lots of resources therefore the query is again sent to the server to be further processed. In the third circumstance the entire query is processed in the mobile device since the mobile device has enough resources to compute the query or it is disconnected from the network.
The constraints of the mobile computing will make approximate answers to queries more acceptable than in traditional database systems, since the alternative to an approximate answer may be no answer at all. Another aspect of query processing for mobile computing relates to the nature of queries themselves, parameters to a query may be expressed relative to the current location of the mobile computer from where the query is executed.
3. CHALLENGE
Limited storage:
Due to mobility and portability, the sizes of retention and hard ride are smaller than the ones in the wired network. The consequences of this are less stored/cached/replicated data, fewer installed applications, and more communication [5].
Power consumption:
The most unmistakable impediment of cell phone is force. These gadgets depend completely on battery power. Joined with the minimal size of numerous cell phones, this frequently implies strangely costly batteries must be utilized to acquire the fundamental battery life. [5]
Insufficient bandwidth:
Mobile access is for the most part slower than cable connections. Utilizing advances, for example, GPRS and EDGE, and more recently 3G networks, bandwidth has been expanded yet at the same time less contrasted with the wired network. Asymmetry issue is confronted when bandwidth in the downstream direction (1805–1880 MHz) is frequently much more prominent than bandwidth in the upstream direction (1710–1785 MHz). [5]
Conclusion
Mobile computing has proven a fertile area of work for researchers in the areas of database and data management. The inherent limitations of mobile computing systems present a challenge to the traditional problems of database management. As we can see, the amounts of research in this case have been staggering. However, some problems remain open for research.
Moreover, we have introduced the main features of the context, that in fact have a great influence on the performance of the mobile systems, focusing on the data management aspects. In summary we can conclude that mobile computing opens new expectations for data applications. However, mobile computing is not mature yet and many problems must be solved, so it is expected that new proposals will appear in the future.