Mobile Query and Processing in Mobile Database Environment

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Bala Srinivasan1

David Taniar2

School of Computer Science and Software Engineering, Monash University, Australia {Agustinus.Borgy.Waluyo, Bala.Srinivasan} 2 School of Business Systems, Monash University, Australia

Abstract Mobile database is a new context of database application in wireless environment. It introduces unique type of queries, and query-processing strategies that are different to traditional databases. We classify mobile database query into two categories, especially context-awareness query and adhoc query. Context-awareness query is further classified into location dependent, context dependent, and hybrid query. As for the query processing, we define three strategies namely mobile client, on air, and server strategy. Mobile client and on air strategy relates to caching strategy and broadcast strategy respectively. Finally, we include some challenges in mobile databases.

1. Introduction
Recent advances in wireless technology have led to mobile computing, a new dimension in data communication and processing. Many predict a new emerging, gigantic market with millions of mobile users carrying small, battery-powered terminal equipped with wireless connection [1,2,10]. The mobile computing environment provides database applications with useful aspects of wireless technology, which is known as mobile databases. This advance technology has created a new age of nomadic database users. Basically, these users are simply accessing a database through a network. However, the network is now applied in wireless environment, and has several novel properties, which include user’s locations are constantly changing, the likelihood of losing connections is much greater than in a traditional network, and asymmetric communication environment in which the wireless bandwidth for uplink communication is smaller than downlink communication [11]. In general, mobile user communicates with a Mobile Base Station (MBS) to carry out any activities such as transaction and information retrieval. MBS has a wireless interface to establish communication with mobile client and it serves a large number of mobile users in a specific region called cell. In mobile environment architecture, each MBS is connected to a fixed network as illustrated in Figure 1(a). Mobile units or mobile clients in each cell can connect to the fixed network via wireless radio, wireless Local Area Network (LAN), wireless cellular, or satellite. Each of the wireless networks provides a different bandwidth capacity. However, the wireless bandwidth is too small as compared to the fixed network such as ATM (Asynchronous Transfer Mode) can provide speed up to 155Mbps [7].


Wireless Network
Mobile Base Station

Mobile Base Station

Wireless Network

High speed Wired Network
Fixed Host

Fixed Host



Mobile Client


Query Processing Strategy

Data Repository

Query Result


Mobile Base Station

Mobile Base Station

Query Taxonomy

= Mobile Client = Wireless Network


(a) Mobile Environment Architecture

(b) Query Application in Mobile Environment

Figure 1. Mobile Environment Architecture and Query Processing

Figure 1(b) depicts the query processing in mobile databases. Mobile client initiates a query, and retrieve the data from data repository. The data repository is available in the fixed network. The query is transmitted through wireless channel, and the result is obtained using certain query processing strategies. As can be seen in Figure 1b, a sign of number 1, and 2, which is attached in query taxonomy, and query processing strategy respectively, correspond to the main content of this paper. Driven by differences between wired and wireless environment results in differences of type of queries, query processing mechanisms as well as...
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