Reference signals: DMRS, CSI-RS, SRS, SSB

On-Demand Reference Signals in NR

One of the most significant design changes from LTE to NR is the elimination of always-on cell-specific reference signals. In LTE, CRS was transmitted continuously across every subframe regardless of traffic load, consuming overhead and causing interference. NR instead transmits reference signals only when and where they are needed. The Demodulation Reference Signal is UE-specific and accompanies every data transmission to enable coherent channel estimation. DMRS supports two configurations: Type 1 with up to 8 antenna ports and Type 2 with up to 12 ports for higher-order MIMO operation.