Cellular Networks and Wireless Data ApplicationsIntroductionComputers and computer networks have changed the way in which we live, run our lives, communicate with each other and the way we work and produce what makes every commercial organisation function and reach success within its field, and in the same time, continue on the path of that success. The computers as stand-alone machines, or as separated ones, are nothing more than advanced computing machines, but what was required in reality is a way to link all the computers with each other and to allow users to have simultaneous access to databases and information; and this is why networks had to be created. Tanenbaum (2003, p.2) explains this fact by stating that “The merging of computers and communications has had a profound influence on the way computer systems are organized. The concept of the ‘computer centre' as a room with a large computer to which users bring their work for processing is now totally obsolete. The old model of a single computer serving all of the organization's computational needs has been replaced by one in which a large number of separate but interconnected computers do the job. These systems are called computer networks.” The main principle behind Computer networking is the communication between two or more computer systems. Computers within a network might be close to one another (such as the case with Bluetooth for example) or hundreds of kilometres away from each other (through the Internet). The first important step in this field came in 1984, when a completely digitalised, circuit-switched telephony system was introduced; this system was called ISDN; which stands for Integrated Services Digital Network for voice and non-voice data. After that, BellCore started developing the standard for the Synchronous Optical Network (SONET), and by the end of the 1980's, Local Area Networks (LAN) appeared as effective method of transferring data between a number of local computers, which led telephone companies replaces all its analogue multiplexing with digital multiplexing. But it is also essential to point out the element of the Internet; this international linked network, composed of servers and clients all over the world, encouraged the changes in both information technology and mobile computing, and this is why we find most of the indications, whenever we face a new product or application, referring to its characteristics in what concerns wireless connection, Bluetooth link, infrared, and much more. Raidl (2003, p.199) states that “mobile cellular networks are by far the most common of all public wireless communication systems. One of the basic principles is to re-use radio resources after a certain distance.” Walters and Kritzinger (2004) refer to the fact that mobile technology has turned to become one of the fastest, if not the fastest, growing field in the telecommunications industry. To give a clearer idea about the change brought to the world and to every one of us, we can refer to the comments of Furht and Ilyas (2003), as they state that “just a few years ago, the only way to access the Internet and the Web was by using wireline desktop and laptop computers. Today, however, users are traveling between corporate offices and customer sites, and there is a great need to access the Internet through wireless devices. The wireless revolution started with wireless phones and continued with Web phones and wireless handheld devices that can access the Internet” Types of networkComputer networks can vary according to the purpose for which they were created and depending on the area they are supposed to cover geographically. Computer networks can be one of the following: 1) LAN (Local Area Network) is “a small interconnection infrastructure that typically uses a shared transmission medium. Because of such factors as the volume of traffic, the level of security, and cost, the network structure in a local area network can be significantly different from that for a wide area network.” And “LAN is used for communications in a small community in which resources, such as printers, software, and servers, are shared. Each device connected to a LAN has a unique address. Two or more LANs of the same type can also be connected to forward data frames among multiple users of other local area networks” (Mir, 2007, p.102). 2) WAN (Wide Area Network) is “spans a large geographical area, often a country or continent. It contains a collection of machines intended for running user (i.e., application) programs” (Tanenbaum, 2003, p.19). 3) CAN (Campus Area Networks) “are the enterprise networks that serve number of related structure, as in a large company or a college campus.” Lehtinen, Gangemi, Gangemi Sr, and Russel, 2006, p.182).