In the world of 5G NR, before a UE (User Equipment) can even say “hello” to a cell, it needs the “secret handshake”, otherwise known as System Information (SI).
While the core components of SI remain consistent, the way they are delivered changes drastically depending on whether you are running in Standalone (SA) or Non-Standalone (NSA) mode.
Minimum SI (MSI): This is the Must-Have. It includes the Master Information Block (MIB) and Remaining Minimum SI (RMSI). Without this, an RRC connection is impossible.
Other SI (OSI): The “Nice-to-Have.” Optional info for specific use cases.
The Key Difference:
SA Mode: It’s a 5G-only show. Everything (MIB, RMSI, OSI) is delivered via 5G channels (PBCH and PDSCH).
NSA Mode: The delivery is divided into two parts. While the MIB (which contains dynamic, real-time data) still comes via 5G PBCH, the RMSI and OSI are often delivered via LTE Dedicated Signaling.
The NSA Advantage: In NSA mode, LTE acts as the ubiquitous (found everywhere) anchor. By delivering RMSI and OSI via an LTE RRC transparent container, the network ensures more reliable communication and broader coverage, providing the UE with necessary 5G information before it even attempts to camp on the NR cell.
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