A wireless network refers to a telecommunications network that interconnects between nodes that are implemented without the use of wires. Wireless networks have experienced unprecedented growth over the past few decades, and they are expected to continue to evolve in the future. Seamless mobility and coverage ensure that various types of wireless connections can be made anytime, anywhere. In this chapter, we introduce some basic types of wireless networks and provide the reader with some necessary background on the state-of-the-art developments.

Wireless networks use electromagnetic waves, such as radio waves, for carrying the information. Therefore, their performance is greatly affected by the randomly fluctuating wireless channels. To develop an understanding of channels, in Section 2.1 we will study the radio frequency band first, then the existing wireless channel models used for different network scenarios, and finally the interference channel.

There exist many wireless standards, and we describe them according to the order of coverage area, starting with cellular wireless networks. In Section 2.2.1, we provide an overview of the key elements and technologies of the third-generation (3G) wireless cellular network standards. WiMax, based on the IEEE 802.16 standard for the wireless metropolitan area network, is discussed in Section 2.2.2. In Section 2.2.3, we study a wireless local area network (WLAN or WiFi), which is a network in which a mobile user can connect to a local area network through a wireless connection.