in the South Korean market, driven by the rapid development of the WiBro standard (a sub-set of 802.16e, described in the Section "TTA WiBro, 320"). Commercial uptake has also been speeded by the use of licensed spectrum, and the granting in 2005 of operating licences to three telecom companies. The form factor for devices to deliver mobile Internet services reflects the need to combine telephony and PDA capabilities - a larger screen and QWERTY input to overcome the limitations experienced with WAP phones. Figure 3-25 shows two early WiBro phones developed by Samsung. Summary of Part I Chapters 2 and 3 have introduced the basic logical and physical architecture of wireless networks, the software and hardware elements that are the building blocks for the construction and operation of all wireless networks. Although all networks require protocols and standards operating at all layers in the OSI model in order to operate, it is primarily the protocols and mechanisms of the Data Link and PHY layers which distinguish wired from wireless networking because of their specific design to Wireless Network Physical Architecture Figure 3-25: Wireless MAN Enabled Phones (courtesy of Samsung Electronics) address the challenges of data transmission across the wireless medium. These protocols and mechanisms are explored in greater detail in Parts III to V, where the main wireless networking standards, such as 802.11 (WLAN), 802.15 (WPAN) and 802.16 (WMAN) are discussed. Chapter 3 has also provided an overview of the different types of devices available for wireless networking at these three operating scales - personal, local and metropolitan. Device convergence is a common feature at the personal-local and local-metropolitan interfaces, and devices are increasingly appearing with multi-mode radios, enabling a single device to participate in a variety of different wireless networks. This page intentionally left blank WIRELESS COMMUNICATION Introduction The OSI network model illustrates how data and protocol messages from the appl