H logical channel. The downlink shared channel (DL-SCH) multiplexes the CCCH, DCCH, DTCH and BCCH logical channels. The BCCH logical channel includes the RRC messages relating to SIB system information. The MCCH and MTCH logical channels are mapped to the DL-SCH transport channel if the number of mobiles concerned by transmitted IP packets in broadcast mode is low. The multicast channel (MCH) multiplexes the MCCH and MTCH logical channels if the number of mobiles concerned by IP packets transmitted in broadcast mode is significant. 4.1.3.2. Uplink The random access channel (RACH) does not transport logical channels. It is used by the mobile for random access to the eNB entity. The RACH transport channel only carries a preamble to initialize the connection with the eNB entity. The uplink shared channel (UL-SCH) multiplexes the DCCH, CCCH and DTCH logical channels. 4.1.4. Physical layer 4.1.4.1. Transmission chain The transmission chain consists of two sub-sets: - for each direction of transmission, the first sub-set comprises the error detection code, the error correction code and the bit rate matching; - for the downlink direction, the second sub-set includes modulation, mapping on spatial layers, precoding, resource element mapping and inverse fast Fourier transform (IFFT) to generate the orthogonal frequency division multiple access (OFDMA) signal (Figure 4.3). Radio Interface Procedures Transport block Control information Error detection code Modulation Error correction code Mapping on spatial layers Precoding Rate matching Physical channel Mapping on resource elements OFDMA signal Figure 4.3. Transmission chain: downlink - for the uplink direction, the second sub-set includes modulation, mapping to resource elements and inverse Fourier transform IFFT. The generation of the single carrier frequency division multiple access (SC-FDMA) signal introduced a fast Fourier transform (FFT). The spatial layer mapping and precoding are implemented only for Release 10 (Figure 4.4). Transport block Control information Erro