Introduction

WiMAX is not truly new; rather, it is unique because it was designed from the ground up to deliver maximum throughput to maximum distance while offering 99.999 percent reliability. To achieve this, the designers (IEEE 802.16 Working Group D) relied on proven technologies for the PHY including orthogonal frequency division multiplexing (OFDM), time division duplex (TDD), frequency division duplex (FDD), Quadrature Phase Shift Keying (QPSK), and Quadrature Amplitude Modulation (QAM), to name only a few. This chapter will provide a brief overview of the PHY and different variants (based on their PHY technologies and applications) of WiMAX, the technologies that make these variants work, and reasons why these technologies combine to make WiMAX a quantum leap over previous wireless technologies.

As the name implies, 802.16 (WiMAX) is an offshoot of IEEE 802, which applies to Ethernet, the technology that powers the Category 5 cable, which connects the vast majority of the world's computers. In Ethernet, the PHY is usually contained in a Category 5 cable. In short, WiMAX and the preceding standard 802.11 (Wi-Fi) are wireless forms of Ethernet. Therefore, much of the Open Systems Interconnection (OSI) Reference Model applies. Figure 2-1 details the OSI Reference Model as it relates to 802.11, and Figure 2-2 outlines the 802.16 PHY and Medium Access Control (MAC) layer.

As they are wireless versions of Ethernet, IEEE standards 802.11 and 802.16 employ a PHY and a MAC layer to accommodate the wireless medium. Figure 2-1 illustrates the IEEE 802.11 variations of the OSI...