5G Networks differs between SA and NON-SA
Signal flow in 5G networks differs between Standalone (SA) and Non-Standalone
(NSA) architectures due to the underlying network infrastructure and core
network dependencies. Below is an explanation of the signal flow in both
architectures:
1. 5G Standalone (SA) Network Signal Flow
In 5G SA, the network uses a
5G Core (5GC) and does not rely on 4G LTE
infrastructure. The signal flow is end-to-end 5G.
Key Components:
UE (User Equipment): The 5G-capable device.
gNB (5G New Radio Base Station): The 5G radio access node. 5GC (5G Core):
Includes AMF (Access and Mobility Management Function), SMF (Session Management
Function), UPF (User Plane Function), etc.
Signal Flow:
Initial Access and Random Access:
The UE sends a random access preamble to the gNB to establish a connection. The
gNB responds with a Random Access Response (RAR).
RRC Connection Setup:
The UE sends an RRC Connection Request to the gNB. The gNB responds with an RRC
Connection Setup message.
Authentication and Security:
The gNB forwards the UE's authentication request to the AMF in the 5GC. The AMF
interacts with the AUSF (Authentication Server Function) and UDM (Unified Data
Management) for authentication and key generation. Security keys are established
between the UE and the gNB.
Registration and Session Establishment:
The UE registers with the 5GC via the AMF. The SMF establishes a PDU (Packet
Data Unit) session with the UPF for user data routing.
Data Transmission:
User data flows between the UE and the gNB over the air interface. The gNB
forwards the data to the UPF in the 5GC for routing to the external data network
(e.g., the internet)
2. 5G Non-Standalone (NSA) Network Signal Flow
In 5G NSA, the network relies on the 4G LTE core (EPC) for control signaling
while using 5G NR for data transmission. This is also known as EN-DC (E-UTRA-NR
Dual Connectivity).
Key Components:
UE (User Equipment): A 5G-capable device that supports dual connectivity.
eNB (4G LTE Base Station): Handles control signaling.
gNB (5G NR Base Station): Handles user data transmission.
EPC (Evolved Packet Core): The 4G core network.
Signal Flow:
Initial Access and Random Access:
The UE connects to the 4G eNB first, as it is the anchor for control signaling.
The UE sends a random access preamble to the eNB.
RRC Connection Setup:
The UE establishes an RRC connection with the eNB.
Authentication and Security:
The eNB forwards the UE's authentication request to the MME (Mobility Management
Entity) in the EPC. Authentication and key generation are handled by the HSS
(Home Subscriber Server).
Dual Connectivity Setup:
The eNB determines that the UE can use 5G NR for data transmission and initiates
EN-DC. The eNB coordinates with the gNB to set up a secondary cell group (SCG)
for 5G NR.
Data Transmission:
Control signaling (e.g., mobility management) continues to flow through the eNB
and EPC. User data is split between the eNB (4G LTE) and gNB (5G NR) for higher
throughput.
Handover and Mobility:
Mobility management is handled by the eNB and MME. If the UE moves out of 5G
coverage, the gNB is released, and data transmission continues over 4G LTE.
Key Differences in Signal Flow:
Aspect5G SA5G NSA
Core Network5G Core (5GC)4G EPC
Control SignalingHandled by 5GC (AMF, SMF, etc.)Handled by 4G EPC (MME,
eNB)
Data PathEnd-to-end 5G (gNB to UPF)Split between 4G eNB and 5G gNB
Dependency on 4GNoneRelies on 4G for control signaling
LatencyLower (direct 5G core)Slightly higher (due to 4G involvement)
Deployment ComplexityHigher (requires new 5GC)Lower (leverages existing
4G EPC)
Summary
5G SA provides a pure 5G experience with end-to-end 5G signaling and data
flow. 5G NSA is a transitional architecture that leverages existing 4G
infrastructure for control signaling while using 5G NR for enhanced data
throughput. Both architectures have their use cases, with SA being the
long-term goal for full 5G capabilities and NSA serving as a stepping stone
for early 5G deployments.
Both architectures have their use cases, with SA being the long-term goal for full 5G capabilities and NSA serving as a stepping stone for early 5G deployments.
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