Wireless communication relies on a plethora of metrics to assess the strength and quality of signals. This article expands upon the complexities of Received Signal Strength Indicator (RSSI), Reference Signal Received Quality (RSRQ), Reference Signal Received Power (RSRP), and Signal-to-Interference-plus-Noise Ratio (SINR). Together, these metrics offer a comprehensive perspective on wireless connectivity, including both signal strength and quality.
RSSI
Received Signal Strength Indicator (RSSI) serves as a basic measure of signal strength. It represents the relative strength of a signal as it is received by a device. It is a relative value often expressed on a scale from 0 to -99, where higher values indicate a stronger signal. However, RSSI does not provide a complete understanding of signal quality, as it does not consider factors like interference, noise, or reliability.
To better understand what RSSI entails, imagine being at a rock concert, trying to converse with a friend across the stage amidst a sea of loud music and shouting. The concept of RSSI can be likened to this scenario, where achieving clarity in communication is akin to establishing a reliable wireless connection.
Imagine your friend trying to speak to you in a crowded, noisy environment. The clarity of the message depends on various factors, and the same holds true for RSSI in wireless communication:
- Signal Obstruction: Just as a column at a concert might obscure your friend’s voice, signal obstructions, such as walls or physical barriers, can weaken wireless signals. This results in a lower RSSI reading.
- Interference: At a concert, the shouting crowd creates interference. Similarly, wireless signals can be hampered by competing signals, electronic devices, or even natural phenomena like atmospheric conditions.
- Distance: In our analogy, moving closer to your friend improved communication. Similarly, the distance between the transmitter and receiver significantly affects RSSI. The farther you are from the source, the weaker the signal strength.
- Multipath Propagation: Reflections and diffraction of signals can cause multiple versions of the same signal to reach the receiver, leading to signal cancellation and a lower RSSI reading.
Signal Attenuation: As sound can get quieter as you move away from the stage at a concert, wireless signals weaken with distance, known as signal attenuation.
RSSI, much like trying to converse amidst a noisy crowd, is influenced by environmental factors. These include signal obstructions, interference, distance, multipath propagation, and signal attenuation. These elements can obscure the true quality of the wireless connection and create challenges in ensuring a robust link.
Just as you would adapt in the noisy concert scenario to improve communication, there are strategies for enhancing RSSI:
- Signal Amplification: Your friend raising their voice is akin to increasing the transmit power of the wireless device, which can boost RSSI.
- Signal Path Optimization: Moving your position to eliminate obstructions between you and your friend at the concert mirrors the optimization of the signal path in wireless communication. This could involve repositioning antennas or devices for better line-of-sight.
- Proximity: Having your friend move closer to speak directly into your ear corresponds to reducing the distance between the transmitter and receiver, which strengthens the signal.
- Interference Mitigation: Similar to covering one ear to reduce noise, eliminating or shielding sources of interference can enhance the clarity of the wireless signal.
RSRP
RSRP plays a pivotal role in assessing the quality of cellular connections and is indispensable for optimizing network performance.
Reference Signal Received Power (RSRP) is a vital metric used in wireless communication, particularly in cellular networks. It quantifies the strength of the received signal from the serving cell’s base station. Essentially, it measures how strong the connection is between your device (e.g., smartphone) and the primary cell tower you’re connected to.
RSRP is typically expressed in decibels (dBm). Typical working values of RSRP are in the range from -130 dBm (distant from site) to -50 dBm (very close to site), where more negative values indicate weaker signal strength and less negative values reflect stronger signal strength.
In simple terms, a higher RSRP value means a more robust connection to the cell tower.
Why RSRP Matters:
- Network Optimization: RSRP is a fundamental tool for network operators to assess the quality and coverage of their cellular network. By monitoring RSRP values across different locations, they can pinpoint areas with weak signals and optimize their infrastructure to enhance coverage.
- Handover Decision: In a cellular network, your device can switch between different cell towers as you move. RSRP helps your device and the network make informed decisions about when and how to hand over the connection to another cell. This ensures a seamless user experience as you travel.
- Signal Quality: A strong RSRP value indicates a solid connection, which generally translates to faster data speeds, better call quality, and a more reliable connection for tasks like streaming, browsing, and online gaming.
- Signal Strength Indication: On many mobile devices, you can check the signal strength through the signal bars or dots on the screen. These visual indicators often use RSRP to give you a rough idea of the signal quality.
Factors Affecting RSRP
Several factors can influence the RSRP values you experience:
- Proximity to Cell Tower: The closer you are to the cell tower, the stronger the RSRP. Conversely, as you move away from the tower, RSRP weakens.
- Obstructions: Physical obstructions like buildings, trees, and hills can block or scatter signals, leading to lower RSRP values in certain locations.
- Interference: Interference from other electronic devices, buildings, or neighbouring cells.
- Terrain and Geography: RSRP can vary in hilly or mountainous terrain, with valleys potentially having weaker signals compared to hilltops.
Improving RSRP
If you’re experiencing poor RSRP values, there are some steps you can take to potentially improve your signal:
- Move Closer to the Cell Tower: Whenever possible, positioning yourself nearer to the cell tower can significantly boost your RSRP.
- Limit Obstructions: Reducing physical obstructions, such as moving to a window or an open area, can help improve signal strength.
- Signal Boosters: Signal boosters or repeaters can amplify the signal and enhance RSRP, especially in areas with weak coverage.
RSIP
Reference Signal Interference Power (RSIP) is a critical metric in the realm of wireless communication, particularly in cellular networks. RSIP quantifies the level of interference from neighbouring cell towers or signals that affect the received signal quality at a particular location. Essentially, it measures the unwanted noise and interference in a specific area, which can have a significant impact on the reliability and speed of wireless communication.
RSIP values can range from around -140 dBm to -44 dBm, where more negative values indicate higher levels of interference, meaning a noisier environment for wireless signals.
Factors Influencing RSIP
Several factors can affect RSIP values, leading to varying levels of interference in different locations:
- Proximity to Neighbouring Cells: RSIP tends to be higher in areas where multiple cell towers or signals overlap. The presence of competing signals from neighbouring cells increases RSIP.
- Obstructions: Physical obstructions such as buildings, trees, and even weather conditions like rain can scatter signals and contribute to higher RSIP values.
- Frequency Congestion: In areas with dense populations or high data usage, the frequency spectrum can become congested, leading to increased interference and elevated RSIP levels.
Improving RSIP
- Network Optimization: For network operators, optimizing the network layout and infrastructure to reduce signal overlap and interference can lead to lower RSIP values and improved connectivity.
RSRQ
Reference Signal Received Quality (RSRQ) is a key parameter in wireless communication systems, particularly in the context of cellular networks like 4G LTE and 5G. RSRQ quantifies the quality of the received reference signal from the serving cell’s base station (cell tower). This metric measures the signal’s strength, similar to Reference Signal Received Power (RSRP), but it goes a step further by assessing the level of interference and noise in the received signal.
Typical working values of RSRQ are in the range from -3 dB (low/no interference) to -18 dB (high load/high interference), higher values indicate a more favourable RSRQ and better signal quality.
RSRQ tends to drop off rapidly at the cell edge or as the serving cell load increases, which can make designing an appropriate level difficult. Typically, RSRQ down to −11 dB can be strongly influenced by serving or inter‐cell interference, with no indication as to which is the cause. Below -11 dB inter-cell, external interference or thermal noise become dominant.
In essence, RSRQ serves as a crucial indicator for the reliability and efficiency of wireless connections.
The Importance of RSRQ
- Signal Quality Assessment: RSRQ offers a comprehensive view of signal quality, incorporating both the signal strength (RSRP) and the level of interference from neighbouring cells. A higher RSRQ value signifies a stronger, cleaner signal, leading to improved call quality, data transfer rates, and overall connectivity.
- Network Optimization: RSRQ data is invaluable to network operators for optimizing their cellular networks. By monitoring RSRQ values across different locations, operators can identify areas with significant interference, address issues, and enhance network performance.
- Handover Decisions: In cellular networks, devices continuously switch between different cell towers as users move. RSRQ assists in determining when and how to transition the connection to another cell tower, ensuring seamless mobility and uninterrupted service.
- Cell Selection: RSRQ helps mobile devices select the best available cell for connection. Devices can choose cells with higher RSRQ values to ensure a stronger and more stable connection.
SINR
Signal-to-Interference-plus-Noise Ratio (SINR) is a fundamental metric in wireless communication. The measurement indicates the RF channel quality.
It assesses the quality of a wireless signal by considering three primary factors:
- Signal Power (S): The power of the desired signal.
- Interference Power (I): The presence of unwanted signals or noise that can distort the desired signal. Interference can originate from other devices, nearby cell towers, or sources that are not part of the intended communication.
- Noise Power (N): The intrinsic background noise that exists in all wireless communication systems.
SINR is the ratio between the received power and the interference (plus noise).
It is expressed in decibels (dB) and is a logarithmic measure that provides a clear picture of signal quality. Higher SINR values indicate a stronger, less noisy, and less interfered signal, resulting in better signal quality.
The Importance of SINR
- Signal Quality Assessment: SINR serves as a comprehensive indicator of the quality of wireless communication. It considers both the strength of the desired signal and the influence of interference and noise. A higher SINR value corresponds to a better quality connection, which means clearer calls, faster data speeds, and a more reliable internet experience.
- Network Optimization: For network operators, SINR data is invaluable for optimizing network performance. By monitoring SINR values across different locations, operators can identify areas with subpar signal quality, manage interference, and improve network coverage.
- Device Selection and Handover: In cellular networks, SINR helps mobile devices select the best cell for connection. Devices prioritize cells with higher SINR values for more reliable communication. Additionally, it plays a crucial role in seamless handovers between different cells as a device moves, ensuring uninterrupted service.
Factors Influencing SINR
Several factors can impact SINR values and signal quality:
- Signal Strength (S): A strong signal power (S) contributes to higher SINR values and better signal quality.
- Interference (I): The presence of strong interference from other devices, cell towers, or nearby signals can reduce SINR and degrade signal quality.
- Noise (N): Higher levels of background noise (N) can diminish SINR values and worsen signal quality.
- Distance to Signal Source: The proximity to the signal source (e.g., a cell tower or Wi-Fi router) plays a vital role in SINR. As you move away from the source, the signal strength diminishes, leading to lower SINR values.
The 3GPP and SINR Calculation
The 3GPP, the organization responsible for defining the standards for mobile communication systems, indeed specifies key parameters and standards for cellular networks like 4G LTE and 5G. However, it does not prescribe a specific method for calculating SINR. Instead, the calculation of SINR can vary and is often left to the discretion of phone manufacturers (UE manufacturers). This flexibility allows different manufacturers to use their algorithms and approaches to calculate SINR based on the capabilities of their devices.
The SINR defines the throughput, coverage, and capacity of the network, and ultimately the user experience.
SINR improvements can be achieved by reducing network load, optimizing performance antenna tilts and pans, reducing or removing overshooting cells, and optimizing Tx power levels.
Good, Bad and Fair Measured values of RSRP, RSRQ, SINR
First, good, bad or fair is subjective, and this is why I keep these definitions in the table below. Secondly measurements like RSRP does not help to determine why we have low throughput, for instance. These measurements alone might not explain certain KPIs, but can give you an idea of the radio environment:
CQI and Modulation Scheme
Channel Quality Indicator (CQI) directly impacts the modulation scheme used in wireless communication systems, particularly in the context of 4G LTE and 5G networks.
CQI is a critical parameter that provides real-time feedback on the quality of the wireless channel between the user equipment (UE) and the base station, typically referred to as the eNodeB in LTE or gNodeB in 5G networks. One of the key functions of CQI is its role in determining the modulation scheme that the UE will use for data transmission.
In wireless communication, modulation refers to the process of encoding information onto a carrier signal for transmission. Different modulation schemes offer varying levels of data rate and robustness, with more advanced modulation schemes capable of carrying more data but requiring a higher signal quality. CQI acts as an indicator to the network about the quality of the channel, which in turn guides the choice of modulation scheme for data transmission.
Mapping CQI to Modulation Schemes
CQI values are typically mapped to different modulation schemes based on their level of signal quality. The mapping of CQI to modulation schemes ensures efficient use of the available channel capacity while maintaining data reliability. Here’s a general mapping scheme:
- CQI below 6: When CQI falls below 6, it signifies that the channel quality is relatively poor. In such cases, the network will choose the most robust modulation scheme, which is Quadrature Phase Shift Keying (QPSK). QPSK is known for its robustness against noise and interference but offers lower data rates compared to more advanced modulation schemes.
- CQI between 6 and 10: CQI values in this range indicate a moderate level of channel quality. In this scenario, the network can use a more data-efficient modulation scheme, such as 16 Quadrature Amplitude Modulation (16QAM). 16QAM offers higher data rates compared to QPSK but is more susceptible to interference.
- CQI above 10: When CQI values are above 10, it indicates a relatively high-quality channel. In this case, the network can employ more advanced and data-intensive modulation schemes, including 64 Quadrature Amplitude Modulation (64QAM) and even 256 Quadrature Amplitude Modulation (256QAM). These schemes offer the highest data rates but require a very high signal quality and are more sensitive to interference.
The Importance of Dynamic Adaptation
The dynamic nature of CQI and its mapping to modulation schemes is crucial for ensuring efficient and reliable data transmission. As wireless conditions change, CQI values are continuously updated, allowing the network to adapt and optimize the modulation scheme in real-time. This dynamic adaptation ensures that the network maximizes data rates while maintaining data reliability, even in challenging and dynamic wireless environments.
LinkedIn: 