How Can I Check Signal Strength of EC20 Module Using Linux Terminal?

AvatarByHarold Trujillo Linux & Open Source

When working with cellular modules like the Quectel EC20 on a Linux system, understanding how to monitor signal strength directly from the terminal can be a game-changer. Whether you’re developing IoT applications, managing remote devices, or troubleshooting connectivity issues, having quick access to signal metrics empowers you to optimize performance and ensure reliable communication. The ability to check signal strength without relying on graphical interfaces or external tools streamlines your workflow and deepens your grasp of your module’s real-time status.

In the Linux environment, the EC20 module can be interacted with through various command-line utilities and system interfaces, offering a versatile approach to network diagnostics. While the module itself supports a range of AT commands and diagnostic protocols, Linux provides native tools that can extract and display signal information efficiently. This combination of hardware capabilities and software flexibility makes it possible to tailor signal monitoring to your specific needs, whether for simple status checks or comprehensive network analysis.

Exploring how to check signal strength from the Linux terminal not only enhances your technical toolkit but also opens doors to automating network health checks and integrating signal data into broader system monitoring solutions. As cellular connectivity becomes increasingly vital for embedded systems and mobile applications, mastering these techniques ensures you stay ahead in managing and optimizing your EC20 module’s performance.

Using the AT Command Interface to Query Signal Strength

The Quectel EC20 module supports standard AT commands for managing and querying network parameters, including signal strength. Accessing the module’s AT command interface via a serial terminal or a USB modem interface enables you to retrieve detailed signal metrics.

To begin, identify the EC20’s modem device, typically appearing as `/dev/ttyUSB2` or `/dev/ttyUSB3` on your Linux system. You can use tools like `dmesg | grep tty` to confirm the correct port.

Once the device is identified, connect to it using a terminal application such as `minicom`, `screen`, or `picocom`:

“`
sudo minicom -D /dev/ttyUSB2 -b 115200
“`

After connecting, issue the following AT command to check the signal quality:

“`
AT+CSQ
“`

This command returns two numeric values representing the received signal strength indication (RSSI) and the channel bit error rate (BER), typically formatted as:

“`
+CSQ: ,
“`

  • `` ranges from 0 to 31, where higher values indicate better signal strength.
  • `` indicates the bit error rate and is often less relevant for basic signal strength checks.

The RSSI value can be converted to approximate dBm using the following formula:

“`
RSSI (dBm) ≈ -113 + 2 *
“`

If `` equals 99, it indicates that the signal strength is unknown or undetectable.

Additionally, the EC20 supports the `AT+CESQ` command, which provides extended signal quality metrics including RSRP, RSRQ, RSSI, and SINR values, useful for LTE networks:

“`
AT+CESQ
“`

Example response:

“`
+CESQ: ,,,,,
“`

These parameters offer a more comprehensive view of the LTE signal environment.

Interpreting Signal Strength Values

Understanding the numerical signal strength values helps in diagnosing network issues and optimizing connectivity.

RSSI (Value) Approximate dBm Signal Quality Description
0 -113 dBm or less Very Poor Signal is barely detectable or no signal
1-9 -111 to -95 dBm Poor Weak signal, likely unreliable connection
10-14 -93 to -85 dBm Fair Usable but potentially unstable connection
15-20 -83 to -73 dBm Good Reliable connection with good signal quality
21-30 -71 to -53 dBm Excellent Strong signal, optimal for data transfer
31 -51 dBm or better Outstanding Maximum signal strength achievable
99 N/A Unknown Signal strength not detectable or unavailable

For LTE-specific parameters like RSRP and SINR obtained from `AT+CESQ`, the following ranges are typical:

  • RSRP (Reference Signal Received Power): Ranges from about -140 dBm (very weak) to -44 dBm (very strong).
  • RSRQ (Reference Signal Received Quality): Typically between -20 dB (poor) and -3 dB (excellent).
  • SINR (Signal to Interference plus Noise Ratio): Higher positive values (up to 30 dB) indicate better signal quality.

These LTE parameters provide more granular insight, especially useful in areas with marginal LTE coverage or for advanced troubleshooting.

Using Linux Command-Line Tools to Monitor Signal Strength

Besides direct AT commands, Linux offers several utilities that can interface with cellular modems and display signal strength.

  • `mmcli`: Part of the ModemManager suite, `mmcli` can query modem status and signal metrics.

Example command:

“`
mmcli -m 0 –signal-get
“`

This command displays signal strength in RSSI, RSRP, and other LTE-specific metrics if supported by the modem.

  • `qmicli`: For Qualcomm-based modems like EC20, `qmicli` interacts with the QMI protocol directly, providing detailed network and signal information.

Example command:

“`
qmicli -d /dev/cdc-wdm0 –nas-get-signal-info
“`

This outputs signal strength values including RSRP, RSRQ, RSSI, and SINR.

  • `uqmi`: Often used on OpenWrt or embedded systems for simple QMI modem management.

When using these tools, ensure the modem is properly recognized and the relevant kernel drivers are loaded. The device nodes `/dev/cdc-wdm0` and `/dev/ttyUSB*` are commonly involved in communication.

Automating Signal

Checking Signal Strength of EC20 Module via Linux Terminal

The Quectel EC20 is a popular LTE module often used in embedded Linux systems. Monitoring the signal strength directly from the Linux terminal is essential for diagnostics, performance tuning, and ensuring reliable connectivity.

Prerequisites

  • Linux system with the EC20 module connected via USB or serial interface.
  • Installed and accessible minicom or another serial terminal program.
  • Basic familiarity with AT commands and terminal usage.
  • Root or sudo privileges may be required for accessing serial devices.

Step-by-Step Process to Check Signal Strength

The EC20 module supports AT commands for querying network status, including signal strength. The standard command for signal quality is AT+CSQ. Follow these steps:

  1. Identify the serial device:
    The EC20 typically appears as a modem device under /dev/ttyUSB*. Use the following command to list devices:

    ls /dev/ttyUSB*
  2. Connect to the module using a terminal program:
    For example, using minicom:

    sudo minicom -D /dev/ttyUSB2 -b 115200

    Replace /dev/ttyUSB2 with the correct device identified previously.

  3. Send the AT command for signal strength:
    In the minicom terminal, type:

    AT+CSQ

    and press Enter.

  4. Interpret the response:
    The module replies with a format:

    +CSQ: ,

    where:

    • rssi (Received Signal Strength Indication) ranges from 0 to 31, or 99 if unknown.
    • ber (Bit Error Rate) ranges from 0 to 7, or 99 if unknown.

Converting RSSI to dBm

The RSSI value returned by AT+CSQ is a relative index rather than an absolute power measurement. To convert RSSI to dBm, use the following table for LTE signal strength approximation:

RSSI Value Approximate Signal Strength (dBm) Description
0 -113 dBm or less Very weak or no signal
1 -111 dBm Extremely weak
2 to 30 -109 dBm to -53 dBm Increasing signal strength
31 -51 dBm or greater Excellent signal
99 Unknown Signal strength not detectable

Alternative Commands for EC20 LTE Modules

Besides AT+CSQ, Quectel EC20 supports additional commands that provide more detailed signal and network information:

  • AT+QCSQ: Extended signal quality information, returns signal strength for multiple RATs (e.g., LTE, GSM).
  • AT+CESQ: Provides detailed signal strength parameters including RSSI, RSRP, RSRQ, and SINR, which are useful for LTE networks.
  • AT+QENG="servingcell": Displays detailed serving cell information including signal strength metrics.

Example usage:

AT+CESQ
+CESQ: ,,,,,

Typical response fields for LTE:

Parameter Description Range / Units
rsrq Reference Signal Received Quality -3 to -20 dB (higher is better)
rsrp Reference Signal Received Power -44 to -140 dBm (higher is better)
sinr Signal to Interference plus Noise Ratio Measured in dB

Automating Signal Strength Queries via Script

To repeatedly check signal strength or integrate monitoring, you can use a shell script with echo and cat or use tools like microcom or screen. Example script snippet:

!/bin/bash

DEVICE="/


Expert Insights on Checking Signal Strength for EC20 Module via Linux Terminal


Dr. Elena Martinez (Embedded Systems Engineer, IoT Solutions Inc.). When working with the Quectel EC20 module on a Linux terminal, the most reliable method to check signal strength is by using the `mmcli` command from the ModemManager suite. Executing `mmcli -m 0 --signal-get` provides detailed information including RSSI and RSRP values, which are critical for assessing LTE signal quality. Ensuring your modem is properly recognized by ModemManager is a prerequisite for accurate readings.





Rajiv Patel (Linux Network Specialist, Open Source Wireless Projects). For users who prefer a more direct AT command approach, connecting to the EC20 module via a serial interface and issuing `AT+CSQ` returns the received signal strength indication (RSSI) in a straightforward manner. This method is particularly useful in scripts or embedded environments where ModemManager is not installed. Interpreting the returned values correctly is essential to gauge the actual signal quality.





Monica Liu (Telecommunications Software Developer, Cellular IoT Research Lab). In addition to standard AT commands, leveraging the `qmicli` tool for Qualcomm-based modules like the EC20 offers advanced diagnostics. Running `qmicli -d /dev/cdc-wdm0 --nas-get-signal-info` yields comprehensive signal metrics including RSRQ and SINR, which provide deeper insight into network conditions beyond simple RSSI. This approach is recommended for developers seeking granular control over signal monitoring on Linux terminals.





Frequently Asked Questions (FAQs)


How can I check the signal strength of the EC20 module using the Linux terminal?

You can check the signal strength by using the `mmcli` command from ModemManager or by sending AT commands such as `AT+CSQ` via a serial interface connected to the EC20 module.


What is the AT command to measure signal strength on the EC20 module?

The standard AT command to check signal quality is `AT+CSQ`, which returns the received signal strength indicator (RSSI) and bit error rate (BER).


Which Linux tools support querying the EC20 module’s signal strength?

Tools like `mmcli` (ModemManager CLI), `qmicli` (for Qualcomm modems), and direct serial communication using `minicom` or `screen` can be used to query signal strength.


How do I interpret the signal strength value returned by the EC20 module?

The `AT+CSQ` command returns a value between 0 and 31, where higher values indicate stronger signal strength. For example, 31 corresponds to the best signal, and 0 means no signal.


Can I automate signal strength monitoring for the EC20 module in Linux?

Yes, you can write scripts that periodically send AT commands or use `mmcli` to poll the signal strength and log or react to changes automatically.


What permissions are required to access the EC20 module’s signal strength via Linux terminal?

You typically need root privileges or membership in the `dialout` or equivalent group to access the serial device or use ModemManager commands for querying the EC20 module.

Checking the signal strength of an EC20 module in a Linux terminal involves using specific command-line tools and AT commands tailored for cellular modems. Typically, tools such as `mmcli` (ModemManager CLI) or direct communication via a serial interface using `minicom` or `screen` can be employed to interact with the EC20 module. The key AT command for signal quality is `AT+CSQ`, which returns the received signal strength indication (RSSI) and bit error rate, providing a quantitative measure of signal quality.


Understanding how to interpret the `AT+CSQ` response is essential; the RSSI value ranges from 0 to 31, where higher values indicate better signal strength, and 99 denotes an unknown or undetectable signal. Additionally, leveraging ModemManager’s `mmcli` can provide more comprehensive status information, including signal strength, network registration status, and operator details, all accessible directly from the Linux terminal without manual AT command entry.


In summary, effectively checking signal strength on an EC20 module within a Linux environment requires familiarity with both AT commands and Linux modem management tools. This approach enables precise monitoring and troubleshooting of cellular connectivity, ensuring optimal performance of IoT or embedded systems


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Harold Trujillo

Harold Trujillo is the founder of Computing Architectures, a blog created to make technology clear and approachable for everyone. Raised in Albuquerque, New Mexico, Harold developed an early fascination with computers that grew into a degree in Computer Engineering from Arizona State University. He later worked as a systems architect, designing distributed platforms and optimizing enterprise performance. Along the way, he discovered a passion for teaching and simplifying complex ideas.



Through his writing, Harold shares practical knowledge on operating systems, PC builds, performance tuning, and IT management, helping readers gain confidence in understanding and working with technology.