Impact of RSSI Imbalance on Network KPIs

RSSI imbalance has significant implications on various Key Performance Indicators (KPIs) that are critical to ensuring the quality of service (QoS) and user experience in wireless networks. These KPIs are directly impacted by variations in signal strength, especially when the imbalance is severe or persistent. Below are the key network KPIs affected by RSSI imbalance, along with specific impacts:

1. Call Drop Rate (CDR)

Impact of RSSI Imbalance:

• High RSSI Imbalance can result in call drops due to insufficient signal strength during handover or transitions between cells. If the signal strength in one sector drops below the threshold (typically around -100 dBm to -105 dBm), ongoing calls may be disconnected.
• Example: A sector with a signal drop from -85 dBm to -110 dBm can cause a call drop, especially during handover. A typical acceptable CDR is around 1-2%, but if RSSI imbalance is present, this can rise to 5-10% in affected areas.

2. Handover Success Rate (HSR)

Impact of RSSI Imbalance:

• Handover Failures are common in areas where the RSSI difference between neighboring cells or sectors exceeds the handover threshold. This leads to either early or late handovers, causing dropped calls or failed data sessions.
• Example: If the RSSI in the source cell is -90 dBm and the target cell is -105 dBm, the handover may fail due to insufficient signal strength in the target cell.
• Impact on HSR:Normal HSR: ~98-99%Imbalance-affected HSR: Can drop to 85-90% in worst-case scenarios.

3. Data Throughput (Downlink and Uplink)

Impact of RSSI Imbalance:

• Low RSSI can severely degrade data throughput, causing slower speeds and higher latency. In cases where RSSI imbalance occurs, the mobile device may be forced to switch to a lower modulation scheme (e.g., from 64-QAM to QPSK), which significantly reduces throughput.
• Example: An RSSI imbalance of 10-15 dB between two sectors can result in a 50-70% reduction in data throughput for users in the weaker sector.
• Impact on Throughput: Normal Data Throughput: 20-40 Mbps for 4G, 100-200 Mbps for 5G (depending on the location).Imbalance-affected Throughput: Can drop to 5-10 Mbps for users in the weaker signal areas.

4. Latency

Impact of RSSI Imbalance:

• Higher Latency occurs in areas with weak signal strength or high interference. This is primarily due to retransmissions, signal processing delays, and frequent handover attempts when the network struggles to maintain a stable connection.
• Example: In areas with high RSSI imbalance (e.g., sector with -110 dBm and neighboring sector with -80 dBm), users may experience increased ping times and delayed responses during real-time applications (gaming, video conferencing, etc.).
• Impact on Latency: Normal Latency (for good RSSI): 20-30 ms. Imbalance-affected Latency: Can rise to 60-100 ms or higher during heavy congestion or handover attempts.

**5. Signal-to-Interference-plus-Noise Ratio (SINR)

Impact of RSSI Imbalance:

• RSSI Imbalance is closely linked to variations in SINR, as poor signal strength leads to higher interference-to-noise ratios, which further degrade the quality of communication.
• Example: A drop in RSSI of 10-15 dB can cause a corresponding 10-20 dB decrease in SINR, resulting in lower data rates, dropped packets, and poor voice quality.
• Impact on SINR:Normal SINR: 15-30 dB in ideal conditions.Imbalance-affected SINR: Can drop to 0-5 dB in areas with significant interference or weak signals.

6. Availability and Accessibility

Impact of RSSI Imbalance:

• Network Availability refers to the ability of a mobile device to successfully connect to the network, while Accessibility refers to the ability to maintain that connection over time.
• RSSI Imbalance directly affects both metrics. Poor coverage or weak signal in specific sectors can cause mobile devices to fail to access the network, even though they are within the cell's coverage area.
• Example: An area with an RSSI imbalance (e.g., -110 dBm in one sector) can cause devices to fail to access the network entirely, leading to a reduced availability rate in that area.
• Impact on Availability/Accessibility:Normal Availability: ~99% (average).Imbalance-affected Availability: Can drop to 85-90% in regions with poor signal.

7. Dropped Data Sessions / Packet Loss Rate

Impact of RSSI Imbalance:

• Dropped Data Sessions and Packet Loss can occur when the signal strength fluctuates, especially in areas where there are large variations in RSSI across sectors or cells.
• Example: In a region where the signal fluctuates from -80 dBm to -100 dBm, data packets may be lost due to insufficient signal quality, leading to slower applications or dropped data sessions.
• Impact on Packet Loss Rate:Normal Packet Loss Rate: ~0.5-1% (optimal conditions).Imbalance-affected Packet Loss: Can increase to 5-10% or higher in affected sectors.

8. Network Congestion and User Experience (QoE)

Impact of RSSI Imbalance:

• Network Congestion often occurs in areas with poor signal strength as devices struggle to maintain connections, leading to higher demand on neighboring cells.
• Poor RSSI can also degrade the Quality of Experience (QoE) for users, leading to slower data speeds, poor voice quality, and a generally frustrating user experience.
• Example: During peak hours, a heavily congested sector with weak RSSI may see a 10-15% drop in QoE metrics, including slower browsing, video buffering, or lag in real-time apps.

9. Voice Quality (MOS - Mean Opinion Score)

Impact of RSSI Imbalance:

• Poor Voice Quality is a direct result of RSSI imbalance, especially in areas where handover is unstable, or the signal strength is inadequate for VoLTE or VoWiFi.
• Example: An imbalance in RSSI between sectors (e.g., -90 dBm vs. -110 dBm) can reduce the MOS (Mean Opinion Score), which typically ranges from 4.0 to 4.5 in optimal conditions, to below 3.0, indicating poor voice clarity and call interruptions.

10. Network Efficiency (Capacity Utilization)

Impact of RSSI Imbalance:

• RSSI Imbalance can cause inefficient network resource usage by concentrating traffic in weaker areas or neighboring cells that are not adequately optimized. This results in higher resource consumption, poor load balancing, and reduced overall capacity.
• Example: If a particular sector is underperforming due to RSSI imbalance, nearby cells may become overloaded, reducing the overall network efficiency by 10-20%.

Conclusion:

RSSI imbalance negatively impacts a wide range of network KPIs, from call drop rates to data throughput, latency, and overall user experience. The extent of the impact depends on the severity of the imbalance, with large discrepancies in signal strength (e.g., > 10 dB between neighboring cells or sectors) leading to significant degradation in QoS. Addressing RSSI imbalance through optimization of antenna alignments, transmission power, interference mitigation, and regular maintenance is crucial for maintaining optimal network performance and ensuring a seamless user experience.