Introduction

Introduction To Mobile Technology

In a mobile network, signals are transmitted through radio waves (Stetz, 1999). Since there are only limited numbers of radio waves available to allow millions of people to communicate simultaneously, the region covered by a mobile network is divided into a number of small areas called cells. Within each cell, the mobile devices communicate with the base station through radio waves. Each base station is connected to a public switched telephone network (PSTN) or wireless service provider. The same frequencies of radio waves can be re-used in different cells. The size of a cell depends on the number of users within the cell. The more the users are within each cell, the smaller the cell size. The size of a cell can vary from 100m in diameter in a highly concentrated urban area to 30km in a rural area. In such a way, millions of users can contact each other simultaneously in the world.

In its short history, the mobile network system has improved significantly. It has progressed from an analog cell phone system to a high speed digital cellular system integrated with the high speed broadband Internet service.

The first generation (1G) mobile technology is an analog wireless cell phone system introduced in the 1980’s (Harte & Bowler, 2003). Within each cell, 1G mobile technology such as Advanced Mobile Phone System (AMPS) developed by Bell Labs allows 56 users to use their cell phones simultaneously. The radius of a cell can range from 2km to 20km. The data transmission rate is 10Kbps. In today’s standard, the transmission rate is a bit too low. In addition to the low transmission rate and the limited number of users that can use the mobile network simultaneously, the analog technology has some other significant weaknesses. It is easily interfered by noise and has no protection against eavesdropping. Due to these weaknesses, the 1G mobile technology has very limited use in mobile learning.

The second generation (2G) is the digital cellular system introduced in the 1990’s (Harte & Bowler, 2003). Compared with the 1G mobile technology, the 2G mobile technology has improved significantly. It allows each radio wave to be dynamically shared by a number of users. Therefore, 2G can support more users operating simultaneously within a cell by using the radio waves more efficiently. Digital signals can be easily compressed to reduce network traffic. In addition, the digital mobile network provides encryption, and error detection and correction functionalities to improve the security and quality of data transmission. The 2G mobile technology has a data transmission rate ranging from 9.6Kbps to 1.2288Mbps. In addition to the cell phone service, the 2G mobile network includes data services such as text messaging. Currently, the 1G system has mostly been replaced by the 2G mobile technology. The 2G technology can meet some basic mobile learning needs. In fact, most of the early mobile learning reports are based on the 2G technology. Although the 2G technology can carry out some basic mobile learning tasks, it is not able to handle the rich multimedia course content posted on the Web.

Specified by the 3rd Generation Partnership Project (3GPP), the third generation (3G) mobile technology has made some significant improvement over the 2G technology by combining the cellular service with the Internet service (Harte & Bowler, 2003). The first 3G mobile network was released by Japan in 2001 for commercial use. Today, the 3G technology is available worldwide for commercial use. The early releases of the 3G technology included Universal Mobile Telephone Service (UMTS) which is implemented over the existing GSM (Global System for Mobile Communications) networks and CDMA2000 which is implemented over the existing CDMA networks. Later, the much improved UTMS-TDD was released. The 3G technology has been further improved by introducing the High Speed Packet Access (HSPA) family and the Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16e standard.