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Diagnosing Cellular Connectivity Issues

Weak cellular signal strength or non-existent connectivity can lead to issues that may not immediately reveal themselves when working with the Notecard. If your Notecard takes a lengthy amount of time to connect to Notehub, inconsistently syncs with the cloud, and/or is completely unable to establish a cellular connection, this guide will help you troubleshoot and resolve the most commonly seen connectivity issues.

note

This guide assumes you can communicate with the Notecard locally over serial, USB, or I2C but cannot get the Notecard to consistently communicate with Notehub via a cellular connection.

If you're unable to communicate with a Notecard locally over USB, be sure you are using a Micro USB data cable and not a charge-only cable.

Verify Antenna Usage and Placement
Check Cellular Signal Quality
Check Country Compatibility
Other Issues and Solutions

Verify Antenna Usage and Placement

The vast majority of issues we see regarding connectivity stem from improper antenna usage and placement of the Notecard and Notecarrier.

Check the Antenna Connection

Verify that the U.FL connector from the antenna to the Notecard is seated properly. Ensure the connector labeled MAIN (and DIV if using a wideband Notecard) is properly seated on both ends of the connection (i.e. on the Notecard and the antenna). When seated properly, you will feel it "click" into place. If the U.FL connector is not fully secured, this will prevent any signal from getting through.

Notecard MAIN antenna U.FL

Ensure No Antenna Signal Interference

Antennas that are touching/too close to metal objects or other devices that produce electro-magnetic interference (EMI) may prevent the establishment of a cellular connection. This is most often an issue when using a Notecarrier with onboard antennas, like the Notecarrier A.

Notecarrier A keep out zones

If using the Notecarrier A (or any previously-sold Notecarrier with onboard antennas), ensure that there are no metal objects within the regions labelled "Keep-Out Zones". These regions represent an 11 mm cylinder around the cellular and GPS antennas mounted on the board. You should also consider elevating the Notecarrier from the table surface and moving it away from your laptop computer and other metal objects.

Ensure the Antenna is Not Damaged

Flexible antennas that are cut, or board-mounted antennas that have broken free, have been sources of connectivity issues for some of our customers.

Verify the Type of Antenna

If using an external LTE antenna with your Notecard, be sure it supports a broad frequency range of 698 MHz to 3.8 GHz.

This forum thread is actively maintained and provides a breakdown of which antenna types are supported by the Notecard (for both cellular and GPS).

Try a Different Physical Location

Weak and non-existent cellular signals can be caused by your Notecard's physical location.

If the Notecard is located inside a large building, deep underground, inside a shipping container, or otherwise effectively in a Faraday cage (i.e. a structure designed to block wireless signals), you may need to physically move the Notecard closer to an external window or a different location outdoors.

Likewise, if no cellular connection whatsoever can be established, be sure to confirm Notecard compatibility with your country and double-check the antenna type and placement.

Check Cellular Signal Quality

When you have validated that your antenna is seated properly and positioned away from any possible areas of interference, it is then a good idea to measure the strength and quality of your cellular connection.

A weak connection can turn into myriad issues with data syncing which do not always present themselves explicitly as connection issues.

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Even with a weak signal, a Notecard can connect to Notehub given enough time. Most notably if using a narrowband Notecard on NB-IoT specifically, it can take a few minutes to establish a connection.

Using the card.wireless API

The card.wireless API allows you to examine the last known network state of the cellular modem and the quality of its connection.

JSON

{
  "req": "card.wireless"
}

Examining the response of a card.wireless request can provide additional data to help diagnose the quality of the cellular connection (see "Measuring the Quality of the Cellular Collection" below).

JSON

{
  "status": "{modem-off}",
  "count": 1,
  "net": {
    "iccid": "00000000000000000000",
    "imsi": "000000000000000",
    "imei": "000000000000000",
    "modem": "EG91NAXGAR07A03M1G_BETA0415_01.001.01.001",
    "band": "LTE BAND 2",
    "rat": "lte",
    "rssir": -69,
    "rssi": -70,
    "rsrp": -105,
    "sinr": 86,
    "rsrq": -17,
    "bars": 1,
    "mcc": 310,
    "mnc": 410,
    "lac": 28681,
    "cid": 211150856,
    "updated": 1599225076
  }
}

Using Network Information from a Notehub Session

In Notehub, a _session.qo Notefile is created for each newly established session. By inspecting the JSON of this Notefile, you will find much of the same connectivity data that is provided by a card.wireless request.

Instructions for navigating to session data in Notehub can be found in the Fleet Admin Guide.

JSON

{
    "event": "4bf80f08-8ebe-4db1-835f-ede95f4c8521",
    "session": "a2fdc05f-93jf-45ac-je83-46437fu4e04",
    "tls": true,
    "best_id": "dev:868050040240000",
    "device": "dev:868050040240000",
    "product": "product:com.blues.demo:demo",
    "app": "app:3733f429-0393-40b2-83i3-c397j3864301",
    "received": 1667323216.257653,
    "req": "session.begin",
    "when": 1667323216,
    "file": "_session.qo",
    "body": {
        "why": "first sync; continuous connection mode (TLS)"
    },
    "best_location_type": "tower",
    "best_location_when": 1667323216,
    "best_lat": 43.0742625,
    "best_lon": -89.44239062499999,
    "best_location": "Shorewood Hills WI",
    "best_country": "US",
    "best_timezone": "America/Chicago",
    "tower_when": 1667323216,
    "tower_lat": 43.0742625,
    "tower_lon": -89.44239062499999,
    "tower_country": "US",
    "tower_location": "Shorewood Hills WI",
    "tower_timezone": "America/Chicago",
    "tower_id": "310,410,17169,77315594",
    "moved": 1667323180,
    "orientation": "face-up",
    "rssi": -58,
    "sinr": 181,
    "rsrp": -89,
    "rsrq": -14,
    "rat": "lte",
    "bars": 3,
    "voltage": 4.17,
    "temp": 25.625,
    "status": "success"
}

Measuring the Quality of the Cellular Collection

The data elements to look at most closely in the responses from the previous two methods include:

bars - The number of "bars" of cellular signal quality (0-4).
rat - The "Radio Access Technology" in use.
band - The LTE band in use (useful for matching up with the appropriate LTE antenna - this data is not available in _session.qo).
rssi - The "Received Signal Strength Indicator" is a measure of cellular signal strength. The value is a negative number, where the higher the value (a.k.a. the closer to 0), the stronger the signal.
rsrp - The "Reference Signal Received Power". The value is a negative number, where the higher the value (a.k.a. the closer to 0), the stronger the power.
sinr - The "Signal to Interference and Noise Ratio". The higher the value, the better the signal strength.
rsrq - The "Reference Signal Received Quality" value. The value is a negative number, where the higher the value (a.k.a. the closer to 0), the better the signal quality.

As a rough guide, use the following table to measure the quality of your cellular connection:

Quality	RSSI (dB)	RSRP (dB)	SINR (dB/5)	RSRQ (dB)
Excellent	> -65	> -84	> 162	> -5
Good	-75 to -65	-102 to -85	150 to 162	-9 to -5
Fair	-85 to -75	-111 to -103	135 to 150	-12 to -9
Poor	< -85	< -111	< 135	< -12

Check Country Compatibility

Each Notecard model operates only in certain countries based on band and carrier support. Be sure to verify that the Notecard model in use matches the list of supported countries.

Consult the Notecard datasheets for specific information on country support by Notecard SKU.

Wideband vs Narrowband Notecards

Using a wideband (WB*) Notecard has two distinct advantages over a narrowband (NB*) Notecard.

The wideband antennas provide for the usage of an additional diversity (DIV) antenna.
The cellular radio used on the wideband Notecards generally allows for improved signal strength and quality.