les (see Figure 9-30 for the structure of the UL-PUSC tile). The uplink sub- channelization procedure can be described as follows, and has been depicted in Figure 9-31: 1. All usable sub-carriers are divided into UL-PUSC tiles over the legacy system uplink bandwidth. As an example, shown in Figure 9-31, in the 10 MHz bandwidth, there are 840 sub-carriers and thereby there are 210 UL-PUSC tiles. 2. The UL-PUSC subchannelization procedure (i.e., physical to logical resource mapping) as defined in reference [1] is performed. Given the previous example, there are 35 UL-PUSC subchannels where each UL-PUSC subchannel consists of six UL-PUSC tiles. 3. The available subchannels in the new frequency zone are identified through subchannel bitmap information broadcast by the AAI_SCD MAC management message. 4. All UL-PUSC tiles of specified subchannels from step 3 are extended in the time-domain from three OFDM symbols to Nsym OFDM symbols where Nsym = 6 or 9, depending on the subframe type. The time extension is done by concatenating two or three contiguous UL-PUSC tiles to form a new UL-PUSC tile. 5. Based on the number of subchannels obtained in step 3 with the symbol-extended tiles of step 4, the DRUs for the new subchannels are formed. 6. Steps 4 and 5 are repeated for the remaining OFDM symbols of each uplink subframe. Note that the tile permutation is performed over the extent of an uplink subframe. 7. Renumber the distributed LRU index in reverse order of UL-PUSC subchannel index. The tile indexing is the same as the legacy indexing method. CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) Tile 1 3 OFDM Tile 2 Symbols Tile 3 Tile 4 Tile 5 Tile 6 New PUSC Tile 1 New PUSC Tile 2 6 OFDM Symbols New PUSC Tile 3 New PUSC Tile 4 New PUSC Tile 5 New PUSC Tile 6 UL Subframe UL Subframe UL Subframe Uplink Portion of the TDD Radio Frame FIGURE 9-30 An illustration of uplink subchannelization when supporting legacy TDD system [2] 9.9 PILOT STRUCTURE AND CHANNEL ESTIMATION The transmission of pilot sub-carriers in the downlink