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Understanding LTE with MATLAB by Houman Zarrinkoub

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Chapter 4

Modulation and Coding

The LTE (Long Term Evolution) downlink PHY (Physical Layer) chain can be viewed as the combination of processing applied to the Downlink Shared Channel (DLSCH) and Physical Downlink Shared Channel (PDSCH). DLSCH processing is also known as Downlink Transport Channel (TrCH) processing. It includes steps involving Cyclic Redundancy Check (CRC) code attachment, data subblock processing, channel coding based on turbo coders, rate matching, Hybrid Automatic Repeat Request (HARQ) processing, and the reconstruction of codewords. The codewords are inputs for the PDSCH processing, which involves scrambling, modulation, multi-antenna Multiple Input Multiple Output (MIMO) processing, time–frequency resource mapping, and Orthogonal Frequency Division Multiplexing (OFDM) transmission. We have subdivided the components of this two-step DLSCH and PDSCH processing chain into three segments, which are discussed in the next three chapters.

In this chapter, we examine the modulation and coding schemes used in the LTE standard. These include all the combined DLSCH and PDSCH processing steps, excluding the MIMO and OFDM operations. Discussion regarding OFDM and MIMO is presented in the next two chapters. First, we will examine the first couple of operations performed in PDSCH processing, including scrambling and modulation. Then we will examine TrCH processing, comprising a series of operations that map logical channels and user bit payload to codewords, which are passed ...

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