Feature differences between 5G core and EPC

This post will look at the key feature differences between 5G core and EPC highlighting the new and exciting features available in the 5G core.

The following table provides the list of feature differences between EPC and 5GC that are useful for an end user.

Table 1: Features useful to end users

Sl.No	Feature	Availability in EPC	Availability in 5GC
1	One UE connecting to multiple network slices.	No	Yes
2	One UE connecting to one network slice.	Yes - through eDECOR	Yes
3	Support for Ethernet type PDN / PDU session.	As of this posting not available	Yes Note: There is a ongoing Release 16 study to support full fledged LAN over 5G. The requirements from SA1 based on ongoing study are in TR 22.821
4	Support for uplink branching point / classifier to divert select IP flows of a PDN to specific local network.	No (though SIPTO at a whole PDN level is available - branching of specific flows within a PDN is not available)	Yes
5	Local Area Data Network - Support for Mobile Edge Computing.	Partial - LIPA and SIPTO below the RAN	Yes
6	Multi-homed IPv6.	No	Yes
7	Mobile Originated Communication Only mode (MICO) that allows IoT devices that only send uplink data followed by immediate downlink data to initiate radio bearer setup only by the UE.	No	Yes
8	Enhanced security and privacy including encryption of IMSI using home operator (HPLMN) provided certificates.	No	Yes
9	Same authentication framework and authentication mechanism irrespective of access network (3GPP access and non 3GPP access like WLAN, Fixed network etc)	No	Yes
10	Application influence on traffic steering	PCRF providing traffic steering rules to PCEF is possible to divert traffic via TSSF / TDF. But application directly influencing the 3GPP network is not possible.	Yes
11	Ability of network to control allowed and non-allowed areas of a UE to initiate communication and dynamic update of those areas in the UE by the network.	Only forbidden tracking area (TA) list management is possible.	Yes. Network can page the UE while in non allowed area to update the service area list via a configuration update.
12	Ability of RAN to make the UE use RRC Inactive state while in core network connected state, thus providing signaling savings and energy efficiency to UE, based on core network provided RRC Inactive asistance information.	No	Yes.

The following table provides the list of feature differences between EPC and 5GC that have an impact on the operational aspects of the network for the operators.

Table 2: Features impacting operational aspects for the operators

Sl.No	Feature	Availability in EPC	Availability in 5GC
1	Any node communicating with any node directly through APIs (Service Based Architecture).	No	Yes
2	Selection of a service (API endpoint) to communicate instead of a node by contacting a service repository (NRF).	No	Yes
3	Policy layer influencing mobility policy	No	Yes
4	Standard interface towards network data analytics.	No	Yes

Once 5G phase 1 standards is completed in 3GPP SA2 more detailed analysis of each feature will follow.

What does the agreed accelerated plan for 5G standardization by 3GPP mean for core network evolution?

3GPP agreed an accelerated plan for 5G deployment in the RAN plenary meeting at Dubrovnik, Croatia between 6th and 9th March, 2017. The agreed plan is documented in RP-170741.zip. Stage 3 completion of non stand alone (NSA) mode 5G NR connecting to EPC will be done by Dec 2017 and the ASN.1 completion will be by March 2018 making the standards in a state for 5G-NR to be deployed by end of 2018.

What does this imply for the core network evolution and deployment for 5G?

• By 2018, 5G will be deployed as a non standalone radio enhancement, acting as a secondary cell to E-UTRAN eNBs as specified under option 3 of TR 38.801 under section 7.2 (given below)

• As the purpose of this accelerated time plan is to deploy high bandwidth services (for eMBB) by 2018, using option 3 implies that all 5G traffic from the 5G gNB has to be backhauled to eNB and the S1-U link from eNB to EPC shall have a huge backhaul capacity.
• Though with option 3A, this need to backhaul 5G traffic via eNB is not there, option 3A implies SCG bearer solution is deployed with dual connectivity, which means the core network has to create multiple bearers, with the eNB (acting as MeNB) moving the high bandwidth service bearers towards the gNB. For internet traffic, typically we dont see multiple bearers created. So practically speaking, its hard to see option 3A kind of deployment being used for increased bandwidth and capacity for internet services. Option 3A would rather be used for specialised services that would require multiple bearers (e.g RCS, low latency edge hosted services).
• If option 3 is used for capacity enhancement for internet traffic, then a huge investment in increasing the capacity of the S1U backhaul needs to be done.
• This increased investment in backhaul towards the EPC would make the operators run 5G services using EPC for a longer duration (to justify the investment). 
• Deployment of nexgen core (NG Core) would be rather slow.
• In the meantime, one might see 3GPP working in future to define more of the services of NG Core in EPC also - so that roll out of 5G services can happen with EPC itself. Already control user plane separation (CUPS) is supported in EPC. This would enable hosting the user plane node closer to RAN for edge hosted services. eDECOR allows support for basic network slicing in EPC. All these indicate a potentially longer run for EPC (atleast for few more years) before NG core deployments happen.