When NR TDD spectrum is not yet available, spectrum sharing enables pooling of radio resources in both UL and DL directions according to instant needs and pre-defined policies between LTE and NR (5G), below the working principle :
- NR signals are transmitted over unused LTE resource
- With LTE, all the channels are statically assigned in the time-frequency, the NR physical layer is extremely flexible for reference signals, data and control channels
- Only 5G devices are made aware of DSS
- Existing LTE devices remain unaffected (i.e. LTE protocols in connected or idle mode)
- LTE PDSCH and NR PDSCH can coexist by using different set of RBs
What are the key UE features used for DSS ?
- SSB allocation on MBSFN subframes (supported by UEs above Rel8)
=> to handle NR Synchronisation Signals (SS Block) collision with configuration LTE Signals
2. LTE CRS rate matching or symbol/RB rate matching => to map around LTE signals PBCH/PSS/SSS,PDCCH region, etc. and avoid NR transmissions colliding with them
