Signaling Load Calculator
Estimate busy-hour signaling load for LTE MME (S1-AP / Diameter) based on subscriber procedures and mobility patterns.
Technology
Active SIMs served by this MME node
Subs attaching/detaching in BH (typical: 2–5%)
Periodic + mobility TAU (typical: 2–5)
App wake-ups, paging responses (typical: 10–25)
Inter-cell handovers in BH (typical: 3–8)
Data session setup per BH (typical: 2–6)
| Procedure | msgs/s | |
|---|---|---|
| Attach / Detach (MME) | 58.3 | |
| TAU (Tracking Area Update) | 2500.0 | |
| Service Request | 8333.3 | |
| Handover (X2/S1) | 5555.6 | |
| PDN Session Activation | 3333.3 | |
| Total signaling load | 19780.5 |
Total msgs/second (MME)
All signaling procedures combined
HSS lookup rate (Diameter)
Auth + subscriber data fetch lookups
MME load index
Relative indicator — >5 suggests multi-node needed
Signaling Load Reference
Core network node capacity (MME in 4G, AMF in 5G) is measured in NAS messages per second. Each subscriber procedure generates multiple messages across multiple interfaces.
| Procedure | 4G Interface | 5G Interface | Approx. msgs |
|---|---|---|---|
| Attach / Register | S1-MME, S6a | NG-AP, N8, N11 | 14 |
| TAU / Reg Update | S1-MME, S6a | NG-AP, N8 | 6 |
| Service Request | S1-MME | NG-AP | 4 |
| Handover | S1-AP, X2-AP | NG-AP, Xn-AP | 8 |
| PDN / PDU Session | S11, S5 | N11, N4 | 6 |
To understand how subscriber load feeds into RAN, combine with the RRC capacity calculator.
Frequently Asked Questions
What is NAS signaling load in LTE and 5G?▾
NAS (Non-Access Stratum) signaling is the control-plane messaging between the UE and the core network (MME in 4G, AMF in 5G) for procedures such as Attach, TAU, Service Request, and Handover. Each procedure generates multiple messages across multiple interfaces. Signaling load is measured in messages per second (msg/s) or transactions per second (TPS) and is a key dimensioning parameter for core network node capacity.
What is the difference between MME (4G) and AMF (5G)?▾
The MME (Mobility Management Entity) is the 4G LTE core node responsible for UE authentication, mobility management, and session management control via the S1-MME and S6a interfaces. The AMF (Access and Mobility Management Function) is its 5G SA equivalent, handling registration, connection management, and mobility via NG-AP, N8, and N11 interfaces. The AMF is a microservice-based function in the 5G Service-Based Architecture, offering better scalability and redundancy than the monolithic MME.
Which NAS procedure generates the most signaling?▾
The Attach (4G) or Registration (5G) procedure generates the highest signaling load — approximately 14 messages per attach across S1-MME/NG-AP, S6a/N8, and S11/N11 interfaces. This includes authentication, security mode, subscriber data fetch from HSS/UDM, and PDN/PDU session setup. For this reason, frequent device detach-reattach cycles (poorly behaved IoT devices, SIM cycling) can cause disproportionate MME/AMF load even with modest subscriber counts.
What is BHCA and how does it affect core network dimensioning?▾
BHCA (Busy Hour Call Attempts) is the number of session setup attempts per hour during the peak traffic period. It drives the attach, service request, and PDN session signaling rates. A network with 1 million subscribers at 0.03 BHCA per subscriber generates 30 000 call attempts per hour — about 8.3 per second. Multiplied by 14 messages per Attach, this yields approximately 116 msg/s on the MME/AMF just from Attach procedures, before TAU, handover, and other procedures are added.