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

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

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

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3GPP Long Term Evolution (LTE) 229Channel Coding, Rate Matching, <strong>and</strong> HARQTurbo coding of rate 1/3 is used for channel coding. The same code construction as forthe downlink is used. The selected rate for rate matching depends on the actual availableresources. The HARQ block applies incremental redundancy <strong>and</strong> triggers the rate matchingprocedure.InterleavingThe interleaver applies cell-specific scrambling to increase the robustness against inter-cellinterference.ModulationThe modulation schemes applied in LTE are QPSK, 16-QAM, <strong>and</strong> 64-QAM. The MACscheduler determines the actual modulation scheme.5.2.6.2 Resource MappingTriggered by the MAC scheduler via the uplink transmission control, the resource mappingassigns data symbols to the resource blocks by exploiting, for example, channel qualityinformation at the transmitter. The uplink frame structure is the same for FDD <strong>and</strong> TDD<strong>and</strong> is shown in Figure 5-13.One radio frame has the duration of 10 ms <strong>and</strong> consists of 10 sub-frames. In TDD, onesub-frame is either allocated to the downlink or uplink. One sub-frame has the durationof 1 ms <strong>and</strong> is build of two slots. A slot has a fixed length of 0.5 ms <strong>and</strong> includes eitherseven DFT-spread <strong>OFDM</strong> (DFTS-<strong>OFDM</strong>) symbols with a normal cyclic prefix length or10 msRadio frame (= 20 slots): 1 2 3 4 201 msSub-frame (= 2 slots):1 20.5 msSlot (= 6 or 7 DFTS-<strong>OFDM</strong> symbols): 1 2 3 6 or 7T CP66.7 µsDFTS-<strong>OFDM</strong> symbol:CPFigure 5-13LTE uplink frame structure

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