Tu Number of Subframes per Frame Number of OFDM Symbols per Frame Idle Time (us) 45.71 45.71 45.71 Number of OFDM Symbols per Frame TTG + RTG (us) 142.853 212.8 142.853 142.853 Symbol Time Ts (us) 114.286 114.286 114.286 Tg = 1/4 Tu Number of Subframes per Frame Number of OFDM Symbols per Frame Idle Time (us) 85.694 85.694 85.694 Number of OFDM Symbols per Frame TTG + RTG (us) 199.98 199.98 199.98 Number of Guard Sub-carriers Right Number of Used Sub-Carriers Number of Physical Resource Units in a Subframe. CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) a 6 MHz channel bandwidth, the parameters of 10 MHz are used and the edge sub-carriers are dropped to fit the spectrum block). 9.5 IEEE 802.16M DUPLEX MODES The term duplex refers to bi-directional communication between two devices. When unpaired spec- trum or alternatively the same RF carrier is used for downlink and uplink communications, the transmit/receive functions are time-multiplexed. The Time Division Duplex (TDD) is a duplex scheme where uplink and downlink transmissions occur at different times but may share the same frequency. In other words, the downlink and uplink transmissions are multiplexed in time and are not concurrent. When paired spectrum or alternatively two RF carriers are used for downlink and uplink communications, the transmit/receive functions are frequency-multiplexed. The Frequency Division Duplex (FDD) is a duplex scheme in which uplink and downlink transmissions occur simultaneously using different frequencies. The downlink and uplink frequencies are separated by a sufficiently large frequency separation. IEEE 802. 16m supports TDD and FDD schemes with maximal commonality in baseband processing. In order to reduce the implementation complexity and cost of FDD terminals, and to further increase the reuse of baseband functional elements, a Half-Duplex FDD (H-FDD) operation is supported where the downlink and uplink transmissions are not simultaneous but occur in two different frequencies. As shown in Figure 9-14, classic H-FDD ope