. The sequence used for the primary synchronization signal is generated from a frequency-domain Zadoff-Chu sequence (see © 2009 by Taylor & Francis Group, LLC Long Term Evolution: GPP LTE Radio and Cellular Technology Frame (10 ms) Subframe #0: Subframe #5 Reference signals PDCCH, PCFICH, PHICH Primary synchronization signals (P-SCH) PDSCH, PMCH Secondary synchronization signals (S-SCH) Figure 3.4 Downlink radio frame structure. Section 3.4 for further details) and transported over the primary synchro- nization channel (P-SCH). Secondary synchronization signals are used to acquire the full cell iden- tity. They are generated from the concatenation of two 31-length binary sequences. Secondary synchronization signals are allocated on the second- ary synchronization channel (S-SCH). Synchronization signals are transmitted on the 72 center subcarriers (around the DC subcarrier) within the same predefined slots, in the last two OFDM sym- bols in the first slot of subframes 0 and 5 (twice per 10 ms). Figure 3.4 shows the time allocation of both the synchronization and reference signals within the down- link radio frame. 3.1.4 Physical Channels LTE supports a wide set of physical channels that are responsible for carrying infor- mation from higher layers (both user data and control information). The complete set of downlink/uplink physical channels, together with a brief explanation of their purpose, is listed in Table 3.1. A simplified diagram showing the location of the physical channels and signals in the radio frame is provided in Figure 3.4 (down- link) and Figure 3.5 (uplink). For each physical channel, specific procedures are defined for channel coding, scrambling, modulation mapping, antenna mapping, and resource element map- ping. A general structure of the whole downlink processing sequence is illustrated in Figure 3.6. This sequence is determined by the following processes: Cyclic redundancy check (CRC). The first step in the processing sequence is the CRC attachment. A CRC code is calculated and appended to 