 frequency diversity or frequency scheduling gain depending on the user mobility and channel conditions. The comparison between the new and legacy subchannelization schemes is shown in Figure 9-20. The one-dimensional resource blocks in IEEE 802.16m simplify the addressing of user allocations in the assignment MAPs, and allow efficient addressing and indexing schemes such as binary tree-structured resource indexing. Furthermore, localized and distributed resource units can be simultaneously assigned to a user in the same time zone. Regardless of the type of legacy subchannelization and permutation scheme in the DL or UL, there 9.8 Subchannelization and permutation UL-PUSC Tile Subchannelization DL-PUSC Slot Even-Numbered Subchannel Offset OFDM Symbol Cluster Odd-Numbered OFDM Symbol Cluster Symbol Offset Number of DL-PUSC Subchannelization Subchannels Number of Symbols DL/UL Subframe DL/UL Subframe DL/UL Subframe Data Region Parameters in the Legacy System Physical/Logical Resource Blocks in IEEE 802.16m FIGURE A comparison 9-20 of the subchannelization schemes in IEEE 802.16m and the legacy system [1,2] sub-carriers and a number of pilot sub-carriers and in 8 each pilot subchannel sub-carriers; or the slot UL-PUSC (e.g., the it slot can are 48 data slot contains 4 clusters, 48 data and sub-carriers, 24 pilot sub-carriers, etc.). From over the the total latter number example, of sub- PUSC contains 6 tiles, 48 data sub-carriers, ratio of pilot sub-carriers additional Layer 1 overhead be noted in that a resource the pilot block/subchannel) density (i.e., the is excessively high, resulting in carriers and lowering the throughput. CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) 9.8.1 Downlink Subchannelization and Permutation The available frequency resources over a downlink subframe are divided into a number of frequency partitions, where each partition consists of a set of physical resource units over the available number of OFDM symbols in the subframe. Each frequency partition can include localized and/or dis