In 5G NR, for the procedures such as handover to a stronger cells or adding a new Carrier Component (CC) in the case of Carrier Aggression, it is required to measure the serving cell and neighbor cell signal strength or signal quality matrix i.e. RSRP or RSRQ. This requirement enables the measurement process to be executed appropriately, maintaining the radio link quality.
In LTE, all eNodeBs continually transmits Cell-specific Reference Signal (CRS), so it is easy for the mobile device to measure the cell quality of neighboring cells. However in 5G NR, there is the concept of CRS has be removed to reduce the overhead and Reference Signal interference from other cells.
5G NR has introduced cell signal measurement by using SS/PBCH Block (SSB), which is composed of Synchronizations Signal (SS) and Physical Broadcast Channel (PBCH) having longer transmission periodicity than CRS.
The number of SSB in one burst depend on the Operating frequency. If Operating frequency (fc) is < 3GHz (FR1) the no. of SSB is 4, for fc = 3GHz to 6 GHz (FR1) no. of SSB is 8 and for fc >6 GHz mm-wave no. of SSB is be 64 within one burst.
1) Serving Cell Measurements:
- RSRP (Reference Signal Received Power): Measurement of the received power level of reference signals from the serving cell, indicating the signal strength of the serving cell.
- RSRQ (Reference Signal Received Quality): Measurement of the quality of the received signals by comparing the RSRP to the average received signal interference plus noise power.
- CQI (Channel Quality Indicator): Measurement of the downlink channel quality, indicating the appropriate modulation and coding scheme (MCS) for data transmission.
- PMI (Precoding Matrix Indicator): Measurement of the optimal precoding matrix to improve the beamforming performance in MIMO systems.
- Timing Advance Measurement: Measurement of the timing advance to estimate the distance between the UE and the serving cell.
2) Neighbor Cell Measurements:
- RSRP (Reference Signal Received Power): Measurement of the received power level of reference signals from neighboring cells, providing information about the signal strength of neighboring cells.
- RSRQ (Reference Signal Received Quality): Measurement of the quality of the received signals from neighboring cells, assisting in neighbor cell selection and handover decisions.
- Interference Measurements: Monitoring of interference levels from neighboring cells to assess the interference impact on the serving cell and optimize resource allocation.
- Cell Load Measurements: Monitoring of neighboring cell load and congestion to assist in cell selection and handover decisions based on load balancing considerations.