on the input sequence. Subblock interleaving and rate matching are used to adjust the number of coded bits to the actual number of the available resources using puncturing, shortening, and repetition. Finally, interleaving is applied in order to improve the performance of Polar codes in fading channels. Depending on the waveform, Release-15 NR supports the following modulation schemes: CP-OFDM: QPSK, 16QAM, 64QAM, 256QAM DFT-s-OFDM: /2-BPSK, QPSK, 16QAM, 64QAM, 256QAM. The constellation mapping used in 5G NR is the same as in LTE and is based on Gray coding. /2-BPSK modulation was added to support efficient uplink transmission in coverage-limited scenarios. Due its low PAPR, the use of /2-BPSK modulation in con- junction with pulse-shaping filters can achieve better efficiency for power amplifiers, thus improving the link budget of NR system in the uplink. 3.5.10 Co-Existence with LTE, Forward Compatibility and Uplink Coverage Enhancement NR supports several techniques that ensure efficient co-existence of the system with previ- ous technologies such as LTE/LTE-A. In particular, to ensure smooth migration from LTE to NR, simultaneous operation of NR and LTE on the same downlink carrier is supported. For that purpose, the physical channels and reference signals of the NR system are designed to avoid collision with the physical channels necessary for operation of the LTE system. For example, to avoid collision with LTE CRS signals, special patterns for DM-RS, SS/PBCH, and CSI-RS for tracking are supported. Moreover, PDSCH in NR can be also configured with mapping patterns to avoid transmission on the resource elements occupied by LTE CRS signals. The NR signals and physical channels are also designed to avoid overlapping transmission with other LTE signals such as PSS, SSS, and PBCH. In particular, config- urable RB-level rate-matching resources (or "blank resources") are defined to avoid PDSCH transmissions in the PRBs and OFDM symbols used by the corresponding LTE reference signals and channels (3GPP TS 38.214). 