Chapter 6: The Physical Layer of WiMAX

6.1 The 802.16 Physical Transmission Chains

The modulation and OFDM transmission aspects, described in the previous chapter, are the major building blocks of the WiMAX PHYsical Layer. In this chapter, some elements of the transmission chains of WiMAX are described for both OFDM and OFDMA PHYs.

6.1.1 The Global Chains

The PHY transmission chains of OFDM and OFDMA are illustrated in Figures 6.1 and 6.2. The blocks are the same with the small difference that OFDMA PHY includes a repetition block. The modulation is one of the four digital modulations described in the previous chapter: BPSK, QPSK, 16-QAM or 64-QAM. The modulated symbols are then transmitted on the OFDM orthogonal subcarriers. In the following, WiMAX channel coding building blocks are described.

Figure 6.1: OFDM PHY transmission chain

Figure 6.2: OFDMA PHY transmission chain

The building blocks of channel coding are described in Section 6.2. A possible FEC code is the Turbo Code. Turbo Code theory and the basic elements of its use in WiMAX can be found in Section 6.3. The Transmission Convergence Sublayer (TCS), which can be applied in OFDM PHY, is described in Section 6.4. Finally, the burst profiles of OFDM and OFDMA PHY, an important building block of IEEE 802.16 MAC layer, are described in Section 6.5.