4G embracing of network slicing concept

4G steps towards moving into world of network slicing with different options to utilize the opportunities which cloud/ virtualization market unleashing. Final destination to 5G architecture, where the network slicing is build-in with NSSF introduction in 3GPP.

CUPS – Control User Place Separation of 4G network. This attempts to separate the Control and User Place at SGW/ PGW to achieve better control and resource requirements for network deployments.

(e)DÉCOR – (enhanced) Dedicated Core Network allocation

DÉCOR – R13 (No UE Changes, UE Usage Type parameter in Subscription Data … /// describes UE usage characteristics that enables the selection of a specific Dedicated Core Network (DCN).… MME uses it to map to DCN value.

DCN selection at ENodeB

Messages where it can be contained

ULR (MME-> HSS) / IDR (HSS -> MME) / Reset (HSS -> MME)

Authentication Information Answer (AIA – S6A)

29272 – S6A spec - If the MME or SGSN supports the Dedicated Core Networks functionality, and the MME or SGSN needs to retrieve the UE Usage Type from the HSS, it shall set the "Send UE Usage Type" flag in the AIR-Flags AVP in the AIR command.

If the HSS supports the Dedicated Core Networks functionality, and the MME or SGSN has set the "Send UE Usage Type" flag in the AIR-Flags AVP in the AIR command, the HSS shall include the UE-Usage-Type AVP in the AIA response command, if it is available in the subscription data of the user.

Support of Dedicated Core Networks/// This feature is applicable to the ULR/ULA and IDR/IDA command pairs over the S6a and S6d interfaces.

If the MME/SGSN does not indicate support of this feature in the ULR command, the HSS shall not send DCN-related subscription data (e.g., UE Usage Type) in ULA, and shall not send subsequent IDR commands when such subscription data are updated.

Enhancements

MME - To keep the UE-Usage-Type mapping to DCN value, and MME instance, further the DCN value to instances of MME/ SGW/ PGW mapping. These 2 mappings requires at all MME's. The first mapping used by source MME to find the target MME, second mapping done at target MME to find the right instances of SGW/ PGW to map the user session.

HSS – Pre subscription new parameter – UE Usage Type (integer 0-255)

This approach has NO UE changes, but the overall approach add 5 Signaling messages from the eNB -> Default MME -> HSS -> Def MME -> eNB -> Selected MME ... in-case MME change, or if first MME stays unchanged, then effectively no change in # of signaling messages. If MME changes, new MME performs the authentication procedure again.

eDECOR – R14

DCN selection at mobile device

A new optional subscription information parameter ("UE Usage Type") is defined for the HSS subscriber profile and is used by the serving network to select which of its CNs shall serve the UE. For the MME, the MME Group Identity (MMEGI)(s) identifies a DCN within the PLMN. For SGSNs, a group identifier(s) identifies a DCN within the PLMN. That is, the group of SGSNs that belong to a DCN within a PLMN. This identifier can have the same format as a Network Resource Identifier (NRI) value that does not identify a specific SGSN node in the serving area, or; “SGSN Group ID” provided by an SGSN to the RAN which triggers the NAS Node Selection Function (NNSF) procedure to select an SGSN from the group of SGSNs corresponding to the Null-NRI/SGSN Group ID.

The UE will use two parameters to assist DCN Selection

DCN Selection Assistance Parameter *** UE to provide DCN value, received earlier by the Network (?? procedure) and stored per PLMN in the UE. Each value (Operator-specific) can map to a certain DCN. For example 1: MBB DCN - 2: CIoT DCN.
NAS Type Parameter*** assigned by the UE and it indicates the NAS Protocol variant the UE uses. Similar to DCN Selection parameter, One scalar value may indicate specific NAS type used for NB-IOT or MBB, etc.

UE includes the DCN Selection Parameter together with the NAS Type parameter in the RRC message (RRC Connection Setup Complete). MME shares the NAS-Type supported and DCN selection assistance information by MME during S1-Setup Request message with eNodeB.

eNodeB uses both DCN assistance and NAS-Type information to decide on DCN network (MME/ SGW/ PGW) to connect the subscriber.

Reference articles
https://www.linkedin.com/pulse/edecor-getting-closer-network-slicing-karim-rabie/
file:///C:/Users/nqgupta/Downloads/FM56(18)016_Network%20sharing%20and%20slicing%20for%20Railway.pdf
https://www.linkedin.com/pulse/network-slicing-why-would-you-slice-karim-rabie/
https://www.comparlo.com/question/what-is-the-difference-between-decor-and-edecor/
https://www.nttdocomo.co.jp/english/binary/pdf/corporate/technology/rd/technical_journal/bn/vol17_4/vol17_4_009en.pdf

Specs
3GPP TS 23.707 - Architecture enhancements for dedicated core networks; Stage 2
3GPP TS 23.711 - Enhancements of Dedicated Core Networks selection mechanism