Due to flexibility of the configuration, the RB-level rate-matching resources can be also used for forward compatibility of NR to avoid colli- sion with transmissions of future yet-to-be-defined NR releases. This allows unrestricted development of new physical layer signals and channels for currently unknown use cases. One of the common deployment options for NR system implies high carrier frequencies (e.g. 3.5GHz). Due to harsh propagation conditions at high frequency bands, the coverage of NR especially in uplink may be reduced compared with the coverage provided by existing LTE systems (see Figure 3.5.22). 3 5G System Overview UL LTE @ 1.9 GHz Figure 3.5.22 Deployment option for 5G UL NR@3.5 GHz Low band: High band: DL + UL frequency Figure 3.5.23 Frequency allocation for supplemental uplink. To allow NR deployments with the same coverage as LTE (and therefore site density, SO that the same cell sites can be used for NR), 5G NR defined a new band operation mode denoted as Supplementary Uplink. With Supplementary Uplink (SUL), a UE can use a low-frequency band (e.g. 1.9 GHz) for uplink transmission as supplementary to higher fre- quency downlink and uplink operation (see Figure 3.5.23). Due to the use of lower carrier frequencies in Supplementary Uplink, an uplink coverage can be significantly improved. References 3GPP Technical Specification (TS) 38.101-1 (2020). NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification (TS) 38.101-2 (2020). NR; User Equipment (UE) radio transmission and reception; Part 2: Range 2. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification (TS) 38.211 (2020). NR; Physical channels and modulation. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification (TS) 38.212 (2020). NR; Multiplexing and channel coding. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification (TS) 38.213 (