Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

222 ApplicationsCSI, etc.ACK/NACKHARQ infoeNodeB(base station)Transport blocksUE(mobile terminal)Transport blocksACK/NACKHARQ infoHARQCRCCRCErrorindicationHARQRedundancyversionCoding + Rate matchingDecodingRedundancyversionMAC schedulerModulationschemeResource/powerassignmentAntennamappingInterleavingModulationResource mappingAntenna mappingDeinterleavingDemodulationResource demappingAntenna demappingFigure 5-5Block diagram of the LTE downlinkchannels, OFDM guarantees high flexibility in resource allocation and scheduling in thefrequency domain. The block diagram of the LTE downlink is shown in Figure 5-5.Data packets from the higher layers, referred to as transport blocks, are delivered to thephysical layer at the base station (eNodeB). Up to two transport blocks can be processedin parallel in the physical layer. The functions of the individual blocks illustrated inFigure 5-5 are explained in the following sub-sections for the base station. The mobileterminal, referred to as user equipment (UE), includes the respective counterparts.5.2.5.1 Coding and ModulationCyclic Redundancy Check (CRC)The CRC is inserted into each transport block to detect at the receiver side (UE) thepresence of residual transmission errors.Channel Coding, Rate Matching, and HARQTurbo coding of rate 1/3 is used for channel coding. It uses the same rate 1/2, memory 3,Turbo codes as WCDMA/HSPA as constituent codes to generate the overall code rate1/3. Figure 5-6 illustrates the LTE Turbo encoder with the two constituent encoders.Compared to WCDMA/HSPA, the interleaver between both constituent codes has beenchanged in order to better support parallelization in the decoding without contention. Rate