ary to fulfill the IMT-Advanced requirements and to allow future enhancements of the radio air interface. The main criteria in the design of the new physical layer were to increase the application throughput and capacity, reduce access latency, support higher user mobility, minimize intra-cell and inter-cell interference, improve reliability of control and data channel coverage (especially at the cell edge), and reduce the complexity and signaling overhead. The overall performance evaluations provided in Chapter 12 suggest that the above goals have been fulfilled. 9.1 Overview of IEEE 802.1 16M physical layer processing Packets Packets Reports Service Flow Service Flow Classification Declassification Header Compression Header Decompression Payload Selection and ARQ and ARQ and Sequencing Packet Segmentation Packet Reassembly PDU Formation and PDU Retrieval and Priority Handling Multiplexing De-multiplexing Encryption Dercryption Retransmission Control Redundancy Redundancy Versioh Version Channel Coding Channel Decoding Modulation Scheme Data Modulation Data Demodulation MIMO Mode Selection MIMO Encoding MIMO Decoding Resource/Power Resource Mapping Resource Demapping Assignment Antenna Mapping Antenna Mapping Antenna Demapping FIGURE 9-2 Physical layer processing in the downlink and uplink CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) In the next sections of this chapter and Chapter 10, we describe in detail the functional blocks and protocols of the physical layer and their interactions, based on the order in which the information is processed, as shown in Figure 9-2. 9.2 CHARACTERISTICS OF WIRELESS CHANNELS In a wireless communication system, a signal can travel from the transmitter to the receiver over multiple paths. This phenomenon is referred to as multipath propagation where signal attenuation varies on different paths. This effect, also known as multipath fading, can cause stochastic fluctu- ations in the received signal's magnitude, phase, and angle of arrival. The propagation over different paths