Modulation and Coding

The Long Term Evolution (LTE) downlink PHY (Physical Layer) chain can be viewed as the combination of processing applied to the downlink shared channel (DLSCH), which includes steps such as those involving cyclic redundancy check (CRC), channel coding based on turbo coders and rate matching. In LTE, a transport block connects the MAC layer and the PHY, and contains a large amount of data bits, which are simultaneously transmitted. This chapter examines the modulation and coding schemes used in the LTE standard and transport channel (TrCH) processing. MATLAB functions can be used to study the effects of different modulation schemes and coding rates on the bit error rate (BER) performance with an additive white Gaussian noise (AWGN) channel model. LTE specification allows for an effective way of resolving the tradeoff between accuracy of a turbo decoder and the number of iterations of the turbo decoder by devising an early termination.