Configure your budget
This model estimates round-trip service latency from device to application and back.
Example data table
| Scenario | Payload UL / DL | µ | Bandwidth | HARQ | Total latency | Notes |
|---|---|---|---|---|---|---|
| Robot control | 64 / 64 bytes | 3 | 40 MHz | 0 | ≈ 2.84 ms | Tight budget with edge application placement. |
| Cloud gaming | 1200 / 1200 bytes | 1 | 100 MHz | 1 | ≈ 14.34 ms | Application and HARQ dominate the round trip. |
| Campus AGV | 128 / 128 bytes | 2 | 60 MHz | 0 | ≈ 5.33 ms | Good fit for private deployments and MEC. |
| IoT telemetry | 256 / 256 bytes | 0 | 20 MHz | 1 | ≈ 32.73 ms | Core delay and queueing matter more here. |
Formula used
1) Slot duration
Slot Duration (ms) = 1 / 2^µ
2) Estimated user-plane rate
Rate (Mbps) = Bandwidth (MHz) × Spectral Efficiency (bps/Hz)
3) Over-the-air transmission time
Air Time (ms) = Payload Bits / (Rate Mbps × 1000)
4) Scheduling latency
Scheduling Delay (ms) = Scheduling Slots × Slot Duration
5) HARQ penalty
HARQ Penalty (ms) = Retransmissions × HARQ RTT
6) End-to-end round-trip latency
Total = UE Proc + UL Scheduling + UL Air Time + gNB Proc + Backhaul + Core + App + Security + Queueing + HARQ + DL Scheduling + DL Air Time + Jitter Margin
This calculator is a planning model. It simplifies real scheduler behavior, radio conditions, packet duplication, and implementation-specific protocol overheads.
How to use this calculator
- Select a preset close to your service type.
- Set the target round-trip latency budget in milliseconds.
- Choose NR numerology and the effective scheduled bandwidth.
- Enter uplink and downlink payload sizes separately.
- Add realistic UL and DL spectral efficiency assumptions.
- Estimate scheduling, processing, transport, core, and server delays.
- Include HARQ retransmissions and jitter margin when needed.
- Press the calculate button and review totals, headroom, and the graph.
- Export the result summary as CSV or PDF for documentation.
Frequently asked questions
1. What does this calculator estimate?
It estimates round-trip service latency across the device, radio scheduler, air interface, transport, core, application, retransmission, and margin components.
2. Why is numerology important?
Numerology changes slot duration. Higher µ shortens slots, which can reduce scheduling delay and improve responsiveness for demanding low-latency services.
3. Is this a measured latency value?
No. It is a budgeting model for design and comparison. Field measurements may differ because of radio conditions, congestion, implementation choices, and traffic patterns.
4. Why separate UL and DL payload sizes?
Request and response packets are often different. Modeling both directions improves realism, especially for control loops, gaming, and cloud-assisted workloads.
5. What does HARQ penalty represent?
It approximates added time from retransmissions after decoding failure. More retransmissions usually improve reliability but increase latency.
6. Should I include app server delay?
Yes. Application logic, edge processing, database lookups, and rendering can consume meaningful time and often dominate the user experience.
7. When is queueing delay significant?
Queueing matters during bursty traffic, oversubscription, shared transport links, or overloaded application tiers. It can quickly erase radio-layer gains.
8. How should I choose spectral efficiency?
Use conservative values from your link budget, CQI history, or lab tests. Planning with optimistic efficiency often understates air-time delay.