RFLTE RSRP vs. RSRQ: Understanding the Key Differences
This page explains the difference between RSRP and RSRQ in LTE (Long Term Evolution) networks. We’ll cover the basics of each, how they are used, and the key distinctions between these important metrics.
Introduction to RSRP and RSRQ
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RSRP: Stands for Reference Signal Received Power. It’s essentially the LTE equivalent of CPICH RSCP (Received Signal Code Power) used in UMTS (3G) networks.
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RSRQ: Stands for Reference Signal Received Quality. Think of it as the LTE counterpart to CPICH Ec/Io, also used in UMTS.
Both RSRP and RSRQ are crucial parameters for several key network functions:
- Cell Selection: Choosing the best cell to initially connect to.
- Cell Reselection: Switching to a better cell while in idle mode.
- Handover: Seamlessly transferring a connection from one cell to another during a call or data session.
RSRP also plays a role in power control calculations by helping to estimate the path loss between the UE (User Equipment, i.e., your phone) and the eNodeB (base station).
LTE RSRP: Reference Signal Received Power
RSRP measures the average power received from a single reference signal resource element. Here’s a breakdown:
- It’s calculated only for the useful part of the OFDMA (Orthogonal Frequency Division Multiple Access) symbol, explicitly excluding the cyclic prefix (the guard interval).
- The average is taken using linear units (not dBm directly).
- The antenna connector of the UE (your phone) is used as the reference point for the measurement.
- The reference signal can be transmitted from one or both antennas at the base station; this is taken into account during RSRP measurement.
- System Information Block 3 (SIB3) broadcasts the maximum measurement bandwidth used during intra-frequency cell reselection. It also tells the UE whether to consider the second antenna for RSRP measurements. SIB-5 provides similar information.
Before being included in RRC (Radio Resource Control) messages, RSRP measurements are mapped to integer values ranging from 0 to 97. The table below shows the mapping:
| Reported RSRP integer value | Actual RSRP in dBm |
|---|---|
| 0 | RSRP < -140 |
| 1 | -140 <= RSRP < -139 |
| 2 | -139 <= RSRP < -138 |
| 3 | -138 <= RSRP < -137 |
| 4 | -137 <= RSRP < -136 |
| 5 | -136 <= RSRP < -135 |
| 6 | -135 <= RSRP < -134 |
| 7 | -134 <= RSRP < -133 |
| … | … |
| n | n-139 <= RSRP < n-140 |
| … | … |
| 87 | -54 <= RSRP < -53 |
| 88 | -53 <= RSRP < -52 |
| 89 | -52 <= RSRP < -51 |
| 90 | -51 <= RSRP < -50 |
| 91 | -50 <= RSRP < -49 |
| 92 | -49 <= RSRP < -48 |
| 93 | -48 <= RSRP < -47 |
| 94 | -47 <= RSRP < -46 |
| 95 | -46 <= RSRP < -45 |
| 96 | -45 <= RSRP < -44 |
| 97 | -44 <= RSRP |
RSRP Measurement Accuracy:
- Absolute Accuracy (Intra-frequency): Between +/-6 and +/-8 dB. This means the measured RSRP could be off by as much as 6-8 dB from the true value.
- Relative Accuracy (Between two intra-frequency points): Between +/-2 and +/-3 dB. When comparing RSRP values from two cells on the same frequency, the difference is more accurate.
- Absolute Accuracy (Inter-frequency): Between +/-6 and +/-8 dB.
- Relative Accuracy (Between one intra-frequency and another inter-frequency point): +/-6dB. Comparing RSRP between cells on different frequencies has lower accuracy.
LTE RSRQ: Reference Signal Received Quality
The formula for calculating LTE RSRQ is:
Where:
- RSRP is the Reference Signal Received Power (as defined above).
- RSSI is the Received Signal Strength Indicator. It’s calculated as a linear average of the total power measured across OFDMA symbols containing reference signals transmitted from the first antenna port (e.g., symbols 0 and 4 when MIMO is not used).
- N is the number of resource blocks over which RSSI is measured.
Key RSRQ Points:
- Like RSRP, RSRQ also uses the antenna connector of the UE as the reference point.
- RSRQ values (in dB) are mapped to integer numbers before being included in RRC messages. The mapping is shown in the table below:
| Reported RSRQ integer value | Actual RSRQ in dBm |
|---|---|
| 0 | RSRQ < -19.5 |
| 1 | -19.5 <= RSRQ < -19 |
| 2 | -19 <= RSRQ < -18.5 |
| 3 | -18.5 <= RSRQ < -18 |
| 4 | -18 <= RSRQ < -17.5 |
| 5 | -17.5 <= RSRQ < -17 |
| 6 | -17 <= RSRQ < -16.5 |
| 7 | -16.5 <= RSRQ < -16 |
| 8 | -16 <= RSRQ < -15.5 |
| 9 | -15.5 <= RSRQ < -15 |
| 10 | -15 <= RSRQ < -14.5 |
| 11 | -14.5 <= RSRQ < -14 |
| 12 | -14 <= RSRQ < -13.5 |
| 13 | -13.5 <= RSRQ < -13 |
| 14 | -13 <= RSRQ < -12.5 |
| 15 | -12.5 <= RSRQ < -12 |
| 16 | -12 <= RSRQ < -11.5 |
| 17 | -11.5 <= RSRQ < -11 |
| 18 | -11 <= RSRQ < -10.5 |
| 19 | -10.5 <= RSRQ < -10 |
| 20 | -10 <= RSRQ < -9.5 |
| 21 | -9.5 <= RSRQ < -9 |
| 22 | -9 <= RSRQ < -8.5 |
| 23 | -8.5 <= RSRQ < -8 |
| 24 | -8 <= RSRQ < -7.5 |
| 25 | -7.5 <= RSRQ < -7 |
| 26 | -7 <= RSRQ < -6.5 |
| 27 | -6.5 <= RSRQ < -6 |
| 28 | -6 <= RSRQ < -5.5 |
| 29 | -5.5 <= RSRQ < -5 |
| 30 | -5 <= RSRQ < -4.5 |
| 31 | -4.5 <= RSRQ < -4 |
| 32 | -4 <= RSRQ < -3.5 |
| 33 | -3.5 <= RSRQ < -3 |
| 34 | -3 <= RSRQ |
The maximum RSRQ value is based on the assumption that all Reference Signal Resource Elements are occupied (i.e., there’s no traffic). Since there are 2 RS REs (Resource Elements) per OFDMA symbol, the maximum RSRQ can be derived as follows:
RSRQ Measurement Accuracy:
- Absolute Accuracy (Intra-frequency): Between +/-2.5 and +/-3.5dB.
- Relative Accuracy (Intra-frequency): Not specified.
- Absolute Accuracy (Inter-frequency): Between +/-2.5 and +/-3.5dB.
- Relative Accuracy (Between intra and inter frequency): +/-3dB and +/-4dB.
RSRP vs. RSRQ: Key Differences Summarized
In simple terms:
- RSRP is a measure of signal strength. A higher (less negative) RSRP generally indicates a stronger signal.
- RSRQ is a measure of signal quality. It takes into account both the signal strength (RSRP) and the interference or noise level (RSSI). A higher RSRQ indicates a cleaner, less noisy signal.
While both are important, RSRQ provides a more complete picture of the overall signal conditions, especially when dealing with interference.
LTE RSRP and RSRQ Calculators and Formula
- Refer our RSRP & RSRQ Calculator
