IJCSI International Journal of Computer Science Issues, Vol. 10, Issue 4, No 1, July 2013 ISSN (Print): 1694-0814 | ISSN (Online): 1694-0784 www.IJCSI.org 112 A Model for Optimizing Data Caching of Dual Mode Handheld Devices Mohamed Grida 1 , Hasnaa Soliman 2 and Mohamed Hassan 2 1 Industrial Engineering Department, Faculty of Engineering, Zagazig University Zagazig, Egypt 2 Information System Departments, Faculty of Computers and Informatics, Zagazig University Zagazig, Egypt Abstract Handheld apparatus are widely used especially when equipped with an automatic data capturing solutions. They are usually connected to the main database server using either an economic fixed location mode or a more expensive mobile mode. In order to quantify the gap of the two modes, a metric called mobility coefficient is introduced. Then, a mathematical model is developed to optimize the handheld data caching. This model considers several factors affect the cache performance such as the data item size, its access frequency, its update rate, the cache size, and the caching cost. Finally, a series of simulation experiments are conducted in order to validate of the proposed model under various system configurations. Keywords: Handheld performance, Caching optimization, dual mode gadget. 1. Introduction With the rapid evolution in mobile computing and wireless technologies, more smart handheld devices (such as laptops, palmtops, and personal digital assistants (PDAs)) are supported and used all over the world, and they become a significant part of everyday life and work. These devices were defined as small, mobile, and battery- powered computing devices, which have no mass storage system and all persistent data have to be kept in a limited battery-buffer RAM [1] [2][3][4]. The main motivation for using these devices is their ability to reduce data entry errors while increasing the data entry rate [1] [4]. At the same time, current handheld devices support various ways for communication with the mass data storage devices such as serial cables or Universal Serial Bus (USB) for direct connection, short range wireless connections such as Bluetooth, IrDA and Wi-Fi (IEEE 802.11) and cellular networks for long distances through GPRS or 3G [3] [5]. Handheld devices can be connected with the mass data storage devices (such as the database server) through two main modes, which are economic base mode (for connectivity inside the organization) and costly mobile mode (for connectivity outside the organization).Within the base mode, handheld can be connected to the database server through serial cables, USB, Bluetooth, or Wi-Fi by which they can obtain bulky amount of data with low cost, high bandwidth and little power consumption. On the other hand, within the mobile mode, a handheld can be connected to the database server through cellular network via GPRS or 3G technologies, which are costly and provide limited bandwidth [6] [7][8][9][10][11][12] [13]. In order to overcome the bandwidth and the cost limitation of the mobile mode, data caching at the handheld local memory is considered as an effective solution to overcome these limitations and to reduce the network traffic [14] [6][15][8][7][16][17] [13]. Due to the limited storage capacity and processing power of the handheld devices, it will be impossible to hold all the accessed data items at the handheld local memory. Consequently, a model for optimizing the handheld data caching is needed by which a user can determine which database items can be cached at handheld local memory in the base mode. This model should aim to reduce the total cost and traffic between the handheld device and the database server. In the next sections, an overview of related and previous researches on caching area will be presented. After that, a model for optimizing the handheld data caching will be developed based on a brief description of the handheld system architecture. Finally, the performance of the proposed scheme will be examined before concluding and highlighting future work possibilities. 2. Literature survey Through the past few years, cache optimality has been addressed by number of researchers to decide which data items should be kept in or evicted from the cache. In this section, a brief overview of the caching replacement schemas will be introduced along with the factors affecting the cache performance. Most of previously described cache replacement policies were represented as a function of the different factors such as access frequency, update rate and so on. Copyright (c) 2013 International Journal of Computer Science Issues. All Rights Reserved.