procedure and, in general, related to LTE multiantenna schemes-are provided in Section 3.3. Resource element mapping. Modulation symbols for each antenna will be mapped to specific resource elements in the time-frequency resource grid. OFDM signal generation. The last step in the physical processing chain is the generation of time-domain signals for each antenna, which is addressed in detail in the next section. In addition to the functionalities previously described, HARQ with soft com- bining is jointly used with CRC and channel coding to allow the terminal to request retransmissions of erroneously received transport blocks. When a (re) transmission fails, incremental redundancy is used to enable the combination of successively received radio blocks until the full block is correctly decoded. Previous functionalities may be dynamically configured, depending on the type of physical channel being processed. As an example, the downlink control chan- nels (physical downlink control channel-PDCCH) are convolutionally encoded and use a transmit diversity configuration in the antenna mapping functionality. However, for downlink data channels (i.e., physical downlink shared channel- PDSCH-or physical multicast channel-PMCH), turbo coding is applied and other multiantenna schemes such as spatial multiplexing may be employed. LTE supports up to four transmit antennas. © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology To radio From modulation N-Point Resource Element M-Point Cyclic Prefix & interface mapping Mapping Pulse Shaping Up-conversion OFDMA SC-FDMA Figure 3.7 Processing sequence in the transmission modem (uplink and downlink). Also, some of the physical layer functionalities are adapted to the higher layer (e.g., scheduling) decisions in order to perform link adaptation or channel-aware scheduling. The modulation and coding scheme, resource allocation, and multian- tenna-related information are employed to configure the corresponding function- alities. Therefore, a c