k channel coding and HARQ performance in IEEE 802. 16m and IEEE 802.16-2009 [87] One of the techniques that has been utilized in the IEEE 802. 16m channel coding and HARQ-IR transmission and is constellation rearrangement. The effect of constellation rearrangement on the coding HARQ performance at link-level has been evaluated and is shown in Figures 9-56 and 9-57, for downlink method and uplink, respectively. We can see from the figures that the constellation can slightly improve the HARQ-IR performance. In these link-level simulations, rearrangement ITU PedB 3 km/h channel model (Rayleigh fading), SISO antenna configuration, data frame size of 512 bits CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) 1st Transmission (IEEE 802.16-2009) 1st Transmission (IEEE 802.16m) 2nd Transmission (IEEE 802.16-2009) 2nd Transmission (IEEE 802.16m) 3rd Transmission (IEEE 802.16-2009) 3rd Transmission (IEEE 802.16m) 4th Transmission (IEEE 802.16-2009) 4th Transmission (IEEE 802.16m) 101 3 SNR (dB) FIGURE 9-53 A comparison of the downlink channel coding and HARQ performance in IEEE 802.16m and IEEE 802.16- 2009 [87] inclusive of the 16-bit CRC in the downlink and 912 bits with 16-bit CRC in the uplink, 64 QAM modulation in the downlink and 16 QAM modulation in the uplink, one LRU in the downlink and five LRUs in the uplink (96 sub-carriers per LRU), a maximum of four HARQ re-transmissions, and max- log MAP detection have been assumed. Furthermore, a CTC encoder rate of 1/3 has been used for both the new and the legacy transmission chains. The effect of constellation rearrangement is more pronounced in the HARQ re-transmissions. 9.13 SYNCHRONIZATION CHANNEL Advanced Preamble (A-Preamble) or alternatively the synchronization channel is a downlink physical channel which provides a periodic reference signal for system discovery (IEEE 802.16m system beacon), timing and frequency acquisition, frame synchronization, RSSI and path loss measurements, channel estimation, and base station identification. The IEEE 802. 16m supports a hi