Drive testing

RSRP, RSRQ and SINR: Read Them Together in Drive Tests

Evaluating LTE performance by signal level alone leads to false conclusions. Correlating RSRP, RSRQ and SINR during drive tests reveals the exact source of RF degradation.

Written by Mikaël Cauvez · Published 2024-03-29 · Reviewed before release

Why Single-Metric RF Analysis Fails in LTE

Field engineers evaluating LTE coverage often encounter areas where mobile equipment reports strong signal reception, yet data throughput collapses or voice calls drop. In 2G networks, analyzing received signal level (RxLev) and carrier-to-interference ratio (C/I) was often sufficient to determine link health. In LTE, evaluating signal level without evaluating channel quality and interference metrics leads to incomplete diagnoses.

LTE link performance is determined by the interaction of three distinct measurements defined by 3GPP technical specifications: Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal-to-Interference-plus-Noise Ratio (SINR). When conducting an RSRP RSRQ SINR drive test, reading these three values as a composite diagnostic signature lets you isolate whether an issue stems from raw path loss, neighboring cell interference, heavy traffic loading, or overshoot coverage.

Standard Metric Definitions and Relationships

According to 3GPP TS 36.214, the core physical layer measurements are standardized as follows:

RSRP (Reference Signal Received Power): The linear average over the power contributions of the resource elements that carry cell-specific reference signals (CRS) within the considered measurement frequency bandwidth. It measures pure signal strength from a specific cell without noise or neighbor interference.
RSSI (Carrier Received Signal Strength Indicator): The total received wideband power, including serving cell power, non-serving cell power, adjacent channel interference, thermal noise, and active subcarrier load across the measurement bandwidth.
RSRQ (Reference Signal Received Quality): Defined by the formula RSRQ = (N * RSRP) / RSSI, where N is the number of resource blocks across the RSSI measurement bandwidth. RSRQ reflects the ratio of dedicated reference signal power to total wideband power.
SINR (Signal-to-Interference-plus-Noise Ratio): The ratio of the desired reference signal power to the combined power of interference from other cells and background thermal noise. While not strictly standardized by 3GPP as a core reporting metric in the same manner as RSRP and RSRQ, it is computed by baseband chipsets and is essential for modulation and coding scheme (MCS) selection.

Diagnostic Matrix: Reading the Four Primary Signal Combinations

During a drive test, real-time logging tools capture fluctuations across all three values. Comparing the relative state of RSRP, RSRQ, and SINR isolates physical layer anomalies quickly.

RSRP	RSRQ	SINR	Primary Root Cause	Recommended Action
High (> -85 dBm)	High (> -10 dB)	High (> 15 dB)	Optimal RF conditions; cell near baseline capacity.	Validate peak throughput and latency.
High (> -85 dBm)	Low (< -14 dB)	Low (< 0 dB)	Pilot pollution, dominant co-channel interferer, or high sector load.	Audit antenna mechanical and electrical down-tilts; check cell neighbor list and PCI planning.
Low (< -110 dBm)	Low (< -15 dB)	Low (< 3 dB)	Coverage hole; thermal noise floor dominates total power.	Verify site transmission power; evaluate propagation path or add fill-in coverage.
Low (< -105 dBm)	High (> -10 dB)	Moderate (> 10 dB)	Isolated coverage edge without active co-channel interferers.	Normal behavior at cell edge in clean spectrum; check link budget margins.

To verify that antenna mechanical adjustments match theoretical design across suspect sectors, technicians can use the GSM Azimuth Checker during site audits.

Diagnosing Inter-Cell Interference Versus Traffic Loading

A common field challenge is distinguishing between heavy cell traffic load and physical inter-cell interference. Both conditions drive RSSI up, which lowers RSRQ.

To differentiate them during an active drive test, examine SINR alongside RSRQ:

High RSRP, Low RSRQ, Normal-to-High SINR: This pattern indicates high channel utilization without destructive co-channel interference. The serving cell (and possibly synchronized neighbors) is transmitting on a high percentage of resource elements due to active user payload, increasing wideband RSSI while the reference signal quality remains clear of direct collision.
High RSRP, Low RSRQ, Low SINR: This pattern signals direct RF interference. Dominant signals from co-channel neighbor cells are colliding with the serving cell reference signals. This frequently occurs when multiple cells have overlapping coverage footprints with equal signal strength (pilot pollution) or when an overshoot sector propagates far beyond its planned boundary.

Engineers can run pre-drive simulation models using the GSM Coverage Planner to identify potential overshoot sectors before verifying them along the drive route.

Step-by-Step Drive Test Troubleshooting Sequence

When poor throughput or dropped sessions are observed along the drive route, execute this systematic diagnostic routine:

Record Serving and Neighbor Cell Info: Capture the physical cell identity (PCI), serving channel (EARFCN), RSRP, RSRQ, and SINR concurrently using dedicated logging software such as GSM Drive Test.
Assess RSRP Level: If RSRP is below -115 dBm, link budget exhaustion is the dominant issue. Check line-of-sight conditions, building penetration loss, and feeder attenuation before troubleshooting interference.
Evaluate SINR in Strong Signal Areas: If RSRP is above -90 dBm but SINR drops below 0 dB, inspect the top three neighbor PCIs. If one or more neighbor cells show RSRP within 3 dB to 5 dB of the serving cell, you are dealing with dominant server contention.
Inspect RSRQ under Clean SINR: If SINR is above 12 dB but RSRQ is below -14 dB, inspect eNodeB scheduler statistics for resource block utilization. The cell is likely handling high data traffic rather than suffering from RF degradation.
Check for Modulo-3 PCI Collisions: If SINR is unexpectedly poor despite low traffic, verify that neighboring cells do not share the same PCI Modulo 3 value (PCI mod 3). Matching mod-3 values cause cell-specific reference signals to directly overlap in the frequency domain, causing severe reference signal degradation.

Practical Measurement Limitations in the Field

Field measurements are subject to practical constraints that can distort logged values:

Vehicle Attenuation: Vehicle chassis and tinted glass typically introduce 3 dB to 10 dB of signal attenuation when using internal test handsets without external roof-mounted antennas.
Fast Fading and Speed: At higher driving speeds, Rayleigh fading causes rapid short-term signal fluctuations. RSRP reporting relies on filtered measurement intervals defined by 3GPP (such as Layer 3 filtering parameters); rapid drive speeds across tight clutter can cause delayed handover triggers.
Handset Chipset Differences: Different baseband modem vendors implement internal SINR calculation and channel estimation filters differently. Logged SINR values can vary slightly between test devices in the same physical location.

Frequently asked questions

What is considered an acceptable RSRQ level during a drive test?

In an unloaded network, typical RSRQ values range from -3 dB to -9 dB. In a fully loaded network or in areas with moderate interference, values between -10 dB and -15 dB are standard. RSRQ values worse than -16 dB generally indicate severe interference, heavy load, or poor coverage.

Can SINR be high when RSRP is very low?

Yes. In an isolated rural cell edge with no co-channel neighbors, RSRP might drop to -110 dBm, but because the RF noise floor is quiet and there are no interfering cells, SINR can remain above 10 dB to 15 dB.

Why does RSRQ drop when network traffic increases?

RSRQ is calculated using total wideband RSSI in the denominator. As data traffic increases, the base station transmits on more subcarriers, increasing total RSSI and driving down the RSRQ calculation even if signal quality remains stable.

Sources and further reading

Technical parameters can vary by network, equipment and software release. Verify changes against current vendor documentation and your operator's procedures.