What are LTE updates needed to support 5G Dual Connectivity?
November 24, 2019

At first, we need to identify the meaning of word EN–DC, It’s E-UTRAN New Radio Dual Connectivity. Simply it means the possibility of UE to get simultaneous data from LTE eNB and 5G gNB. 

In EN-DC, the radio access network is composed of eNBs (eNodeBs) as the master node and gNBs (gNodeBs) as the secondary node. The radio access network is connected to EPC (Evolved Packet Core). 

Source: 3GPP

For a successful deployment of EN-DC the 4G network needs to support dual connectivity between E-UTRAN (LTE) and NR.
This enhancement allows a device to consume radio resources provided by both 4G and 5G. Typically the 4G radio will be used to carry control signaling while NR and/or LTE will be used for user data. 

LTE Network Updates 

To support NSA, the 4G core network needs to do a small software upgrade to add or expand several parameters. There is no need
to make any modifications to the hardware.

5G EN-DC EPC Upgrade
  • MME
    • Support high bandwidth with extended QoS.
    • Support 5G subscription access control (DCNR bit, Secondary RAT).
    • Support reporting Secondary RAT traffic.
  • SGW/PGW
    • Support high bandwidth with extended QoS.
    • Support reporting Secondary RAT traffic.
  • HSS
    • AMBR maximum guaranteed bandwidth adds the maximum uplink/downlink bandwidth.
    • Extended-Max-Requested-BW-UL.
    • Extended-Max-Requested-BW-DL.
  • PCRF
    • A new QoS extended bandwidth AVP [Attribute-Value pairs] is added to the Gx interface.
    • Extended-Max-Requested-BW-DL and Extended-Max-Requested-BW-UL AVP.
    • Extended-GBR-DL and Extended-GBR-UL AVP.
    • Extended-APN-AMBR-DL and Extended-APN-AMBR-UL AVP.

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