Received Signal Strength Indicator (RSSI) is a measurement of the power level at which a wireless device is receiving a radio signal. Put simply, it tells you how strong the signal is at the point of reception, not at the source, but at the end of the journey, after it has travelled through the air and encountered whatever interference, distance, or obstruction lay in between.
RSSI is typically expressed as a negative number in decibel-milliwatts (dBm). A value closer to zero indicates a stronger signal. So, -50 dBm is considerably better than -90 dBm. The exact thresholds that constitute “good” or “poor” vary by technology and use case, but the underlying principle is consistent: the weaker the received signal, the higher the risk of degraded performance.
Why RSSI matters for voice quality
RSSI is one of the foundational indicators used to assess wireless link quality, and its relationship to voice performance is direct. A weak signal doesn’t just mean slower data, for real-time voice communications, it translates into exactly the kinds of impairments that make calls difficult or impossible: increased packet loss, higher jitter, garbled audio, and dropped connections.
That said, RSSI alone doesn’t tell the full story. A strong RSSI reading doesn’t guarantee a clean call if interference is high or if the signal-to-noise ratio is poor. This is why RSSI is most useful when treated as one input among several; a starting point for investigation rather than a definitive verdict on call quality. Understanding what RSSI is telling you, and what it isn’t, is key to using it effectively in a monitoring and diagnostics context.
RSSI in telecom networks
In mobile and wireless telecom environments, RSSI is a staple metric. It appears across Wi-Fi, LTE, 5G, and legacy 2G/3G technologies, used by network engineers to map coverage, identify weak spots, and diagnose connectivity issues at the cell or access point level.
For voice services specifically, whether that’s VoLTE on a mobile network, Voice over Wi-Fi (VoWiFi), or enterprise VoIP over wireless, RSSI plays a meaningful role in understanding why a call degrades. An engineer troubleshooting a complaint about choppy audio on a mobile handset will often look at RSSI as an early diagnostic indicator: is this a coverage issue, a handover issue, or something deeper in the network?
The complexity in telecom is that RSSI captures just one dimension of the radio environment. Interference from adjacent cells, channel congestion, and multipath propagation can all affect call quality even when RSSI looks acceptable. This is why effective voice monitoring needs to correlate RSSI with media-layer metrics, such as jitter, packet loss, MOS, to build a complete picture.
RSSI in air traffic control
In air traffic control, RSSI takes on a role that goes well beyond routine network management. ATC voice communications rely on VHF and UHF radio links between ground stations and aircraft, links that are inherently susceptible to the physical realities of radio propagation: distance, terrain, atmospheric conditions, and interference from other transmitters.
RSSI monitoring in ATC environments is used to verify that ground-to-air radio coverage is sufficient and consistent across a sector. When an aircraft moves through a sector, the received signal strength at the ground station will naturally vary. What matters is whether it stays above the threshold required for intelligible, reliable communication. Because in ATC, a degraded or broken transmission isn’t just a nuisance, it’s a safety event.
Modern IP-based ATC voice systems, built to standards like EUROCAFE ED-137, generate rich telemetry data including signal strength measurements from radio stations and associated equipment. Monitoring these values continuously, and correlating them with audio quality metrics, is essential for ANSPs who need to maintain the highest standards of communication reliability. ATC monitoring solutions should be designed to surface exactly these kinds of signal-layer insights alongside perceptual quality data, giving operations teams the visibility to act before a weak signal becomes a communication failure.
RSSI and the gap between signal and quality
One of the most common misconceptions about RSSI is that a “good enough” signal level guarantees good call quality. In reality, the relationship between signal strength and perceived audio quality is non-linear and context-dependent. Near the edges of acceptable RSSI ranges, small drops in signal level can cause disproportionate degradation in voice quality, particularly for codecs that are sensitive to packet loss.
This is why the most effective monitoring frameworks treat RSSI as a leading indicator: something that prompts investigation rather than a standalone measure of service health. The real benchmark is always what the end user – or in ATC, the controller or pilot – actually hears.