Merge pull request #250569 from James-Green-Microsoft/4g-s1-handover

Add support for 4G S1 handover

Author: prmerger-automator[bot]

articles/private-5g-core/private-mobile-network-design-requirements.md

@@ -126,7 +126,7 @@ If you are affected by this issue, it is strongly recommended to configure the R
 
 The UEs must be able to communicate with the RAN from any location at the site. This means that the signals must propagate effectively in the environment, including accounting for obstructions and equipment, to support UEs moving around the site (for example, between indoor and outdoor areas).
 
-You should perform a site survey with your RAN partner and the enterprise to make sure that the coverage is adequate. Make sure that you understand the RAN units’ capabilities in different environments and any limits (for example, on the number of attached UEs that a single unit can support). If your UEs are going to move around the site, you should also confirm that the RAN supports X2 (4G) or Xn (5G) handover, which allows for the UE to transition seamlessly between the coverage provided by two RAN units. Note that UEs cannot use these handover techniques to roam between a private enterprise network and the public cellular network offered by a telecommunications operator.
+You should perform a site survey with your RAN partner and the enterprise to make sure that the coverage is adequate. Make sure that you understand the RAN units’ capabilities in different environments and any limits (for example, on the number of attached UEs that a single unit can support). If your UEs are going to move around the site, you should also confirm that the RAN supports X2 (4G) or Xn (5G) handover, which allows for the UE to transition seamlessly between the coverage provided by two RAN units. If the RAN doesn't support X2 (4G) or Xn (5G), then RAN must support S1 (4G) and N2 (5G) for UE mobility. Note that UEs cannot use these handover techniques to roam between a private enterprise network and the public cellular network offered by a telecommunications operator.
 
 ### SIMs
 

articles/private-5g-core/statement-of-compliance.md

@@ -43,6 +43,7 @@ All packet core network functions are compliant with Release 15 of the 3GPP spec
 
 - TS 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access: 
   - 5.5.1.1 X2-based handover.
+  - 5.5.1.2 S1-based handover.
 
 ### Policy and charging control (PCC) framework