BHCC vs BHCA: Understanding Call Completion and Call Attempts

This page explains the difference between BHCC (Busy Hour Call Completions) and BHCA (Busy Hour Call Attempts). The busy hour is typically the specific time period when a telephone network experiences its maximum or peak load.

BHCC (Busy Hour Call Completions)

BHCC refers to the capacity of a Private Branch Exchange (PBX) to successfully establish calls between users.

For telephone trunks with 0% blocking, BHCC is related to BHCA as follows:

BHCC = BHCA * ASR

Where:

• ASR = Attempt Seizure Ratio or Answer Seizure Ratio

ASR represents the probability of a call finding a free traffic channel and subsequently being completed. It’s essentially a measure of how many attempted calls actually go through.

It is usually measured after the complete operations.

It is typically taken between 0.65 to 0.8.

BHCA (Busy Hour Call Attempts)

The time period during which the maximum number of call attempts are made is referred to as BHCA. BHCC is measured as the calls carried out in busy hour.

• BHCC is usually less than BHCA.
• BHCC does not consider unsuccessful calls. It only counts the calls that were successfully completed.

Key Differences Summarized

In short:

• BHCA: The total number of call attempts during the busy hour, regardless of whether they were successful or not.
• BHCC: The total number of calls successfully completed during the busy hour.

Therefore, BHCA will always be equal or greater than BHCC, as BHCC only accounts for successful calls. The ratio between the two (expressed as the ASR) gives an indication of network performance and call completion rates.