Overview

This guide provides a basic overview of how mobile signal is measured and the different factors that may influence the measurements. This can be useful for determining why mobile signal could be poor in certain areas or on your own equipment.

Measuring Signal Strength

Signal strength values are defined by a few different measurements which vary even more for different service modes. These measurements are as follows:

• RSSI
• RSRP
• RSRQ
• RSCP
• SINR
• EC/IO

You can find out more regarding each of the measure on their seperate pages linked above.

Factors Affecting Signal Strength

There are many different factors that influence signal strength and quality, including but not limited to:

• Tower load
• Proximity to the cellular tower
• Signal going through a cellular repeater
• Competing signals
• Physical barriers (mountains, buildings, trains, etc.)
• Weather

Therefore, measurements like Signal Strength (RSSI) and Signal Quality (EC/IO) do not incorporate all of the relevant factors to describe the quality of the connection. For example, you may have an excellent RSSI value of -51 dBm, but the Tower Load (the number of mobile users) in your area is very high. In this case, even though you have a great Signal Strength value, you may not achieve maximum mobile data speed.

Disclaimers:

• Both Signal Strength and Signal Quality must be considered for successful cellular data connection
• Measured or reported values vary by modem, carrier, and network environment
• There is no black/white answer to what constitutes a successful connection
• Although signal strength may appear to be adequate, throughput speeds may vary due to dependencies on cellular tower loads

2G (GSM)

2G (GSM) Signal strength is defined by only one value: RSSI – Received Signal Strength Indicator; RSSI is a negative value, and the closer to 0, the stronger the signal.

RSSI Signal Strength Chart:

3G (WCDMA, TDSCDMA, CDMA, EVDO, CDMA-EVDO)

For 3G service mode, there are three relevant measurements:

• RSSI - Received Signal Strength Indicator. RSSI is a negative value, and the closer to 0, the stronger the signal
• EC/IO - indicates the downlink carrier-to-interference ratio (signal quality).EC/IO is a negative dBm value. Values closer to 0 are stronger signals
• RSCP - indicates the Received Signal Code Power

The RSSI standard values for 3G are basically the same as 2G

RSSI Signal Strength Chart:

EC/IO Signal Strength Chart:

RSCP Signal Strength Chart:

4G (LTE)

For 4G service mode, there are four relevant measurements:

• RSSI - Received Signal Strength Indicator. RSSI is a negative value, and the closer to 0, the stronger the signal
• RSRP - the Reference Signal Received Power is the power of the LTE Reference Signals spread over the full bandwidth and narrowband
• RSRQ - Reference Signal Received Quality is a C/I type of measurement and it indicates the quality of the received reference signal (similar to EC/IO)
• SINR - Signal to Interference plus Noise Ratio (A minimum of -20 dB SINR is needed to detect RSRP/RSRQ). Indicates the throughput capacity of the channel. As the name implies, SINR is the strength of the signal divided by the strength of any interference

RSRP Signal Strength Chart:

RSRQ Signal Strength Chart:

SINR Signal Strength Chart:

RSSI for LTE is a calculated from several other signal related measurements: RSSI = wideband power = noise + serving cell power + interference power. For example, a 4G LTE modem might report an RSSI of -68 dBm, but:

RSRP = -102 dBm

RSRQ = -16 dB

SINR = -1.8 dB

In this case, the signal quality is actually very poor. This could be due to the device being some distance away from the LTE transmitter. It’s also possible that something is interfering with the signal, such as a building or other obstructions between the device and the tower.

RSSI Signal Strength Chart: