DSS Part-3

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DSS:
Other NR UE features that are considered important for an efficient operation of spectrum sharing are:
  • PDCCH in symbol 2
  • Rate matching pattern to map around LTE PSS/SSS and PBCH
  • TRS in symbol 6 and 10
  • Flexible CSI-RS placement
  • Alternative PDSCH DM-RS pattern when LTE CRS rate matching is configured
  • 7.5 kHz UL shift
DSS will help a mobile operator to flexibly allocate existing spectrum across low-, mid- and high- frequency bands, by dynamically switching between 4G LTE and 5G NR coverage based on traffic demand.Mobile operators can hold DSS to deliver the best possible performance and coverage for a mix of 4G and 5G devices.

How LTE overhead can be avoided?

5G capacity is impacted by LTE Cell Reference Signals (CRSs),PDCCH, PSS, SSS, PBCH and MBSFN subframes overheads as well as NR PDSCH DMRS and NR corset.There is less impact from the 5G control channels on LTE as 5G does not use any CRS.UE can support DSS in either RB level and RE level. Using the RATE  matching technique network can avoid LTE overhead.

Features enabling Dynamic Spectrum Sharing (DSS) were introduced to enable LTE and NR in the same spectrum. With DSS, NR in LTE bands can efficiently share the same channel and dynamically allocate available resources to NR and LTE on need basis.

Can the operator implement DSS with 5G deployment option-3a?

As we know, Option 3a has the drawback of not supporting the transfer of application data across the X2 interface. The coverage provided by the gNodeB (higher band) may be smaller than the coverage provided by the eNodeB (low band). 

 A UE may move out of the coverage of the gNodeB making it necessary to switch all data transfer to the eNodeB. But in DSS case both LTE and NR (eNB and gNB) use same bandwidth so Coverage level issue are not there.

Can the operator implement DSS with 5G deployment option-4a?

The 5G gNodeB provides control plane connectivity towards the Core Network and acts as the Master Node (MN). The Next Generation eNodeB (ng-eNodeB) has control plane connectivity across the Xn interface and acts as the Secondary Node (SN). 

 These Configurations require the ng-eNodeB to support the Xn interface rather than the X2 interface. same like above option3a, if MN and SN both use different Band it may case coverage issue but in the DSS case both MN and SN use same band so there is no coverage related issues.

Can operator implement DSS with 5G deployment option-7a?

the Next Generation eNodeB (ng-eNodeB) provides control plane connectivity towards the Core Network and acts as the Master Node (MN). The gNodeB has control plane connectivity across the Xn interface and acts as the Secondary Node (SN). These configurations require the ng-eNodeB to support the NG-C, NG-U and Xn interfaces. They are similar to options 3a but the 4G Core Network is, changed to the 5G Core Network and the X2 interfaces become Xn interfaces. Same like option3a, both MN and SN have use same bandwidth so there is no coverage related problem seen.


Can DSS implement in FR2?

No, as we know LTE support below Sub-6 GHz frequency, hence practically it is not possible.


In the next section, we will learn more about DSS and its basic and advance level stuff. So keep reading……. And Stay tune……………
Pinal Dobariya………..



Reference:
3GPP TS 38.331
3GPP TS 38.221
3GPP TS 36.331
https://www.researchgate.net/publication/330188547_RF_Self-interference_Cancellation_for_Full-duplex_Communication_by_Using_Photonic_Technique
https://www.researchgate.net/publication/269306294_Adaptive_transmission-reception-sensing_strategy_for_cognitive_radios_with_full-duplex_capabilities
RP-191042, Enhancements for dynamic spectrum sharing in Rel-16, Ericsson, RAN #84, 3-6 June 2019

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