What is CDR?
Call Drop Rate (CDR)
measures the percentage of, usually mobile, calls that terminate unexpectedly due to network issues (e.g., poor signal, handover failure) rather than user action, calculated as:
Dropped CallsTotal Calls×100the fraction with numerator Dropped Calls and denominator Total Calls end-fraction cross 100
Dropped CallsTotal Calls×100
. A benchmark CDR of
≤1%is less than or equal to 1 %
≤1%
is generally considered good, with operators aiming for 0.1%–2%.
Key Details on Call Drop Rate (CDR)
-
- Definition: Percentage of calls that are prematurely disconnected by the network before the user hangs up.
- Formula:
Number of Dropped CallsTotal Number of Calls×100the fraction with numerator Number of Dropped Calls and denominator Total Number of Calls end-fraction cross 100
Number of Dropped CallsTotal Number of Calls×100
.
- Causes: Common reasons include poor signal quality, radio frequency interference, congestion, and failed handovers between cells.
- Performance Metrics: While 0.1%–2% is typical, some standards suggest a target of
≤1%is less than or equal to 1 %
≤1%
.
- Impact: High CDR directly causes customer dissatisfaction, increased churn, and lower revenue.
- Technology-Specifics: In 4G/LTE, this is closely related to “retainability” (RRC + eRAB drop rate).
Causes of High Call Drop Rate
-
- Radio Coverage Issues: Weak signal, interference, or no coverage.
- Network Overload: Excessive traffic leading to congestion.
- Handover Failures: Technical issues when moving between base stations.
- Equipment Failures: Faulty hardware, such as feeders, connectors, or repeaters.
How to Improve CDR
- Optimization: Adjusting handover margins and re-selection parameters.
- Network Upgrades: Expanding capacity to handle higher call volumes.
- Site Maintenance: Checking for hardware issues, such as water leaks in feeders or faulty amplifiers.
- Parameter Tuning: Optimizing timers and counters (e.g.,
N310cap N sub 310
𝑁310
and
T310cap T sub 310𝑇310
in LTE).