Understanding Dropped Call Rate (DCR) in GSM Networks

Dropped Call Rate (DCR) is a crucial performance metric in GSM networks. It represents the percentage of calls that are unintentionally terminated by the network while the call is still active. A high DCR significantly impacts user experience, indicating instability in maintaining ongoing calls.

Let’s delve into DCR in the context of GSM.

Definition of Dropped Call Rate (DCR)

DCR is defined as the percentage of calls that are unexpectedly disconnected after being successfully established. Importantly, it doesn’t include calls intentionally ended by the user.

The formula for calculating DCR is as follows:

For example, if 100 calls are initiated and 5 of them are dropped unexpectedly, the DCR would be 5%.

Causes of Dropped Calls in GSM

Dropped calls can result from various network issues:

• Weak Signal Strength: In areas with poor coverage, the received signal strength (RSSI) may fall below an acceptable threshold, causing call termination.

• Interference: Cross-channel or adjacent-channel interference from nearby cells or other devices can disrupt communication.

• Handover Failures: GSM networks rely on handovers to seamlessly transfer calls from one cell to another as users move. A failed handover due to congestion or poor coordination can result in a dropped call.

• Network Congestion: High traffic on a cell can lead to resource shortages, causing calls to be dropped to free up network capacity.

• Equipment Malfunctions: Faults in base station equipment, transceivers, or controllers can lead to signal disruptions and call drops.

• Power or Battery Issues on Mobile Devices: Low battery or device malfunction can sometimes lead to call termination, though this is less common in network calculations.

Importance of DCR in GSM Networks

• Quality of Service (QoS): DCR is a critical Quality of Service (QoS) metric that directly reflects user satisfaction. A lower DCR indicates a more stable and reliable network.

• Network Optimization: High DCR values alert operators to areas that may need more coverage, reduced interference, or additional capacity. For example, analyzing DCR data helps identify cells with poor signal strength, faulty equipment, or congestion issues.

• Compliance with Industry Standards: Telecommunications regulators and industry standards often set specific DCR thresholds to ensure operators provide consistent and reliable service. Failure to meet these standards can lead to penalties or customer dissatisfaction.

Typical Acceptable DCR Range in GSM

Industry standards typically recommend a DCR of below 2% to 3% for urban and suburban areas. ITU (International Telecommunication Union) recommendations suggest a DCR of less than 2% in most cases.

Achieving a low DCR is more challenging in rural areas, where coverage gaps or fewer base stations may lead to higher DCR values.

DCR Reduction Techniques in GSM Networks

• Improving Signal Coverage: Adding more base stations or deploying microcells in coverage gap areas to ensure strong signal levels.

• Enhanced Handover Management: Optimizing handover algorithms to reduce failed handovers, especially at cell boundaries.

• Interference Reduction: Minimizing interference through frequency planning and using adaptive power control mechanisms.

• Congestion Management: Adding capacity, offloading traffic, or optimizing network resources in high traffic cells to prevent congestion-induced drops.

• Equipment Maintenance: Regular monitoring and maintenance of base stations and network infrastructure to prevent equipment-related call drops.

Conclusion

In summary, DCR is an essential GSM parameter that measures the network’s reliability in maintaining calls. By monitoring and managing DCR, operators can enhance network stability, meet regulatory standards, and improve the overall quality of user experience.