Wireless Networks

Wireless network technology is one of the hottest topics in mobile computing. Everyone has an opinion on the state of the third-generation (3G) wireless networks, the effect of Bluetooth for personal networks, and which wireless local area network technology will dominate the market. Even though not all mobile applications require wireless connectivity, there is no doubt that wireless technology is one of the main driving forces behind mobile computing.

This post provides an overview of the four main categories of wireless networks: wireless personal area networks (WPANs), wireless local area networks (WLANs), wireless wide area networks (WWANs), and satellite networks. For each category we summarize the prevalent technologies and discuss what the future holds. By reading this post you will gain an understanding of which wireless network protocols are being used and for what types of applications. This knowledge will be valuable as you continue through the book to learn more about the design and development of mobile and wireless applications.

Overview of Wireless Networks
Wireless networks serve many purposes. In some cases they are used as cable replacements, while in other cases they are used to provide access to corporate data from remote locations. Much of the industry hype surrounds third-generation wide area networks that provide broadband wireless connectivity to users on a national basis. These networks are now commercially available (in larger urban centers) in most first-world regions. At the same time, breakthroughs in short-range networks are also generating excitement. As users carry around multiple devices, a need arises for an easy, effective way for them to communicate; and what is easier than wireless?

For the purpose of our discussion, wireless networks will be divided into two broad segments: short-range and long-range. Short-range wireless pertains to networks that are confined to a limited area. This applies to local area networks (LANs), such as corporate buildings, school campuses, manufacturing plants or homes, as well as to personal area networks (PANs) where portable computers within close proximity to one another need to communicate. These networks typically operate over unlicensed spectrum reserved for industrial, scientific, medical (ISM) usage. The available frequencies differ from country to country. The most common frequency band is at 2.4 GHz, which is available across most of the globe. Other bands at 5 GHz and 40 GHz are also often used. The availability of these frequencies allows users to operate wireless networks without obtaining a license, and without charge.

Long-range networks continue where LANs end. Connectivity is typically provided by companies that sell the wireless connectivity as a service. These networks span large areas such as a metropolitan area, a state or province, or an entire country. The goal of long-range networks is to provide wireless coverage globally. The most common longrange network is wireless wide area network (WWAN). When true global coverage is required, satellite networks are also available.