VoLTE Capacity Calculator
Size VoLTE load: Erlangs, concurrent QCI-1 bearers, busy-hour call attempts and the bearer bandwidth required.
About VoLTE Capacity Calculator
One Erlang is one call continuously in progress, so the Erlang total is also the average concurrent call count and therefore the number of QCI-1 dedicated bearers in use. Dividing the call-seconds by the average duration recovers the attempt rate that the signalling plane has to absorb. QCI-1 bearers are admission-controlled per cell and licensed per session in the core, so both the concurrent count and the attempt rate gate how many voice users a network can actually carry.
Formula
VoLTE Capacity
Erlangs = VoLTE subscribers × busy-hour Erlangs per subscriber; BHCA = Erlangs × 3600 ÷ AHT; bandwidth = concurrent calls × bearer rate.
- Erlangs
- Average number of calls in progress during the busy hour
- AHT
- Average hold time per call
Worked example
With the default values below, VoLTE Capacity Calculator returns Concurrent VoLTE Calls of 20,000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Subscribers on the networkaccepts 1–100,000,000 subscribers
- 1,000,000 subscribers
- VoLTE penetrationaccepts 1–100 %
- 80 %
- Busy-hour traffic per subscriberaccepts 0.001–0.5 Erlangs
- 0.025 Erlangs
- Average call durationaccepts 10–3,600 seconds
- 110 seconds
- Voice bearer rate on the wireone of AMR-NB 12.65k — 31.2 kbps, AMR-WB 12.65k — 34.4 kbps, AMR-WB 23.85k — 46.4 kbps, EVS-WB 13.2k — 35.2 kbps
- AMR-WB 23.85k — 46.4 kbps
Results
- Concurrent VoLTE Calls
- 20,000
- Busy-Hour Traffic
- 20,000 Erlangs
- Busy-Hour Call Attempts
- 654,545 calls/hour
- Voice Bearer Bandwidth per Direction
- 928.00 Mbps
Step by step
- 1Values used
- 2VoLTE Capacity
- 3Concurrent VoLTE Calls= 20,000
- 4Busy-Hour Traffic= 20,000 Erlangs
- 5Busy-Hour Call Attempts= 654,545 calls/hour
- 6Voice Bearer Bandwidth per Direction= 928.00 Mbps
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is VoLTE Capacity calculated?
Erlangs = VoLTE subscribers × busy-hour Erlangs per subscriber; BHCA = Erlangs × 3600 ÷ AHT; bandwidth = concurrent calls × bearer rate. One Erlang is one call continuously in progress, so the Erlang total is also the average concurrent call count and therefore the number of QCI-1 dedicated bearers in use. Dividing the call-seconds by the average duration recovers the attempt rate that the signalling plane has to absorb.
Why does VoLTE Capacity matter?
QCI-1 bearers are admission-controlled per cell and licensed per session in the core, so both the concurrent count and the attempt rate gate how many voice users a network can actually carry.
What values do I need to enter?
This calculator takes 5 inputs: Subscribers on the network, VoLTE penetration, Busy-hour traffic per subscriber, Average call duration, Voice bearer rate on the wire. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.