Understanding BHT (Busy Hour Traffic) and Blocking

This page explains the basics of BHT (Busy Hour Traffic) and blocking in a telephone network. It also includes an example calculation for both.

BHT (Busy Hour Traffic)

BHT represents the amount of telephone network traffic using the unit Erlangs. Think of it as a way to measure how busy the network is during its peak time.

To understand this, consider 1 Erlang as equivalent to 1 hour of calls. BHT is then the number of hours of telephone traffic a network trunk group handles during its busiest hour.

Example Calculation of BHT

Let’s say we want to calculate the BHT for a specific trunk group. We have the following information:

• Number of calls made: 400
• Average call duration: 180 seconds

We can use the following formula to calculate BHT:

BHT = (Average call duration in seconds * Calls per Hour) / 3600

Plugging in the values:

BHT = (180 * 400) / 3600

BHT = 20 Erlangs

So, in this example, the Busy Hour Traffic is 20 Erlangs.

Blocking

Blocking refers to calls that cannot be completed because there aren’t enough available telephone lines or network resources.

A blocking rate of 0.01 means that 1% of calls will be blocked. This is a critical metric used in telephone traffic engineering to ensure sufficient capacity. Service providers aim to keep blocking rates low to provide a good user experience.

Normally, the blocking rate is taken into consideration during telephone traffic engineering to make sure there is enough capacity on the network.