 Layer and Protocols 3.4.10 Channel Coding Channel coding is needed in mobile systems to provide more reliable connection for data and control in the presence of fading and interference. The channel coding in 3G and in LTE was Turbo coding for data channels, while 5G uses a different solution: Low Density Parity Check (LDPC) for data channels and Polar coding for control channels. LDPC, Turbo, and Polar have similar link performance for data-intensive applications, while LDPC has a clear advantage over Turbo and over Polar for implementation complexity. These implementation aspects are important when the peak data rate in 5G increases even beyond 10 Gbps. Table 3.6 shows the benchmarking of coding solutions in terms of area efficiency and energy efficiency. LDPC shows the highest efficiency in term of Gbps per silicon area, and LDPC also shows highest energy efficiency in terms of bits per nanojoule. LDPC has most efficient implementations due to parallelized architec- ture and flexibility of code design, and can satisfy new radio access requirements. Polar coding was proposed in 3GPP for 5G, but Polar coding is less efficient than LDPC for high data rates. As a compromise, Polar coding was selected to be used for the control channels. 3.4.11 Pipeline Processing and Front-Loaded Reference Signals The 5G physical layer includes a concept called pipeline processing that aims to min- imize both decoding latency and UE power consumption. The LTE subframe has the control part followed by the reference signals and data. The LTE UE must receive the complete subframe before decoding can be started. 5G has the Demodulation Refer- ence Signal (DMRS) in the beginning of the subframe followed by data symbols that can be decoded one by one. This approach is called front-loaded DMRS, and the target is to minimize decoding latency. Pipeline processing enables faster and continuous decod- ing. Pipeline processing also enables a faster UE sleep mode if no data are transmitted to that UE. The concept of pipeline processing is illu