Mobile Intelligence

9.1 INTRODUCTION

Mobile computing geared by wireless communication technologies is one of the explosive growth areas. Most wireless communication systems have the characteristics of asymmetry that the bandwidth of the downlink channel is higher than that of the uplink channel. Also, wireless channel has error-prone characteristics caused by various link error sources such as frequent disconnections [7]. Under mobile computing, mobile clients with limited battery lifetime can get their desired information anytime and anywhere like stock information, and so on. Also, by the advances in high-speed wireless networks and portable devices and location-identification techniques such as GPS, location-dependent information services (LDIS) are enabled [22, 28].

There are two approaches to satisfy the needs of mobile clients for their desired information under mobile computing environments mentioned above. One possible way to support various queries of a huge number of mobile clients is on-demand approach in which an information server takes care of queries from mobile clients [1]. In this approach, each client sends its query that requests its desired data items, then the information server returns results of the query via a one-to-one wireless communication. This may cause scalability problem in which the server is overheated by a huge number of mobile clients. Figure 9.1 shows an example of the on-demand approach. Each mobile client requests the stock price of its interesting company to ...