NimbeLink Embedded Modem FAQs

This page lists some of the most Frequently Asked Questions (FAQs) about our NimbeLink Skywire End-Device Certified Cellular Modems.


How do I ask a provider if our modem will work on their network?
  1. Present them with the datasheet for the modem and the frequencies on which it operates, and compare it to what the provider’s network uses
  2. Ask what requirements the provider has for modems to operate on their network.
  3. If the provider has any questions, they can email NimbeLink product support.

Cellular Technology

What is the difference between LTE-M and NB-IoT?

The primary differences between LTE Cat M1 (AKA LTE-M) and NB-IoT comes down to power, speed, and mobility. The price for the hardware and for the data use is the same. LTE CAT-M1 supports higher data rates and is better suited for applications that require firmware over-the-air updates. NB-IoT data rates may be too low for large file transfers. NB-IoT is great for stationary use when very small amounts of data are being sent infrequently.

Why does my phone say I have signal but my modem doesn't?

Consumer devices like phones, tablets, etc. are built quite differently from most IoT devices. Phones often use multiple cellular radios which equates to more LTE bands than application specific IoT devices do, as well as different types of antennas. Generally this should not result in different coverage, but in certain uncommon situations there may be a difference in the networks each one is able to pick up. Most often we see modems able to connect in places that phones can’t!


Do I really need two antennas?
Yes. Any Skywire modem that provides two antenna connectors (primary and diversity) should be used with two antennas. There are some modems that do not require two antennas, such as 2G and 3G modems, or Cat M1 and NB-IoT, but all others are designed to use both antennas to ensure that the device is able to distinguish the useable signal from the background radio noise. Additionally, these modems are certified with a two-antenna configuration. Using it with a different configuration voids the certification. The second antenna typically provides 3dB of additional gain, which will improve the range at which the device can hear signals from the cellular tower.  
How do diversity antennas work?
At a basic level, the second/diversity antenna is used to help compare the signal to what the primary antenna is picking up. As long as there is sufficient physical (distance) separation between the primary and diversity antenna, the modem will be able to cancel out the background radio noise and significantly improve its ability to pick out the useable signal.
How to I determine the signal situation on the modem?
There are multiple commands for different providers. Telit modems use AT+CSQ and AT#MONI. Sierra Wireless Modems use AT+CSQ and AT+CESQ. Quectel uses AT+QCSQ. Refer to the AT command manuals for more help with this. Ideally you should rely on the RSRP and RSRQ values and not the RSSI values.


Which SIM card do I use, and what APN?

Some of our Skywire modems include a soldered-down chip SIM, which is locked to a specific carrier. These, and all of our other modems, also include a removable SIM slot. The appropriate size of SIM card for these slots is “3FF.” The APN will be determined by the carrier/MVNO whose SIM card you are using. You can typically obtain this is information at the time of your SIM card purchase.

Where do I buy SIM cards and data plans?

In our quest to make integrating cellular connectivity into your custom IoT device as simple as possible, NimbeLink offers data service and SIMs for most carriers throughout North America, as well as some international locations. However, it is not necessary to use a NimbeLink SIM or data plan. You can work with the carrier/MVNO of your choice to obtain an IoT SIM and data plan. Just make sure that you get a “3FF” size SIM card and you’ll be fine!

Activate Data Plan

Does the Skywire support eSIM/eUICC?

Yes, all Skywire modems support using removable eSIM/eUICC that are available in 3FF form factor. Some Skywire modems include a soldered down SIM with carrier-specific profiles.

Does the modem need a SIM card?

Yes, all of our current Skywire modems require a SIM card. Some Skywire modems utilize an onboard soldered-down chip SIM, which can be used in place of a removable 3FF SIM card. This chip SIM is specific to one carrier, so it should only be used when activating on that carrier.

The QBG96 chip SIM - how does it work and how do I know which one I'm using?

The chip SIM found on some of our Skywire modems is dedicated to a specific carrier. In these modems the user has the ability to select between the chip SIM and the 3FF removable SIM slot via AT Commands. To find out how to do this, please refer to the datasheet found in the Documentation section of the product’s webpage. For example, for the NL-SW-LTE-QBG96 refer to Section 3.8 in the Datasheet.

How can I test if my SIM card is active? How do I test basic connectivity?

The most basic test that we do to determine connectivity with our modems is a Socket Dial to a test point, such as or If the modem is able to send an HTTP post request using a TCP socket dial to a website and get a response, even an ERROR 404 message from the remote server, this is an indication that a SIM is able to pass traffic. In some cases, the SIM card may have limited access to the internet and be redirected to, for example, a Verizon portal asking for credentials. This can usually be seen in the response the modem receives from the network.

Development Kits

Which development kit do you recommend as a starting point?

NimbeLink highly recommends starting with the Skywire Development Kit (NL-SWDK) for all new Skywire development projects. This enables an easy-to-use platform to connect to a PC or dev board with a known good hardware configuration, eliminating any potential issues related to incorrect custom hardware. It has the added advantage of being referenced in most Skywire documentation, and design files are available for reference as well, further simplifying the development process.

We also offer other shields, capes, and adapters that may provide a more compact or specialized hardware connection to the development board of your choice, but these are typically meant as a second step or for proof-of-concepts that can be used for testing.


How do i pick the right development kit for my project?

NimbeLink highly recommends starting with the Skywire Development Kit (NL-SWDK) for all new Skywire development projects. This allows for an easy-to-use platform to connect to a PC or dev board with a known good hardware configuration, eliminating any potential issues related to incorrect custom hardware. It has the added advantage of being referenced in most Skywire documentation, and design files are available for reference as well, further simplifying the development process.

We also offer other shields, capes, and adapters that may provide a more compact or specialized hardware connection to the development board of your choice, but these are typically meant as a second step, or for proof-of-concepts that can be used for testing.

If you are using a BeagleBone, Raspberry Pi, Mini-PCI Express, or Arduino header compatible product, NimbeLink sells adapter boards specifically for these products.


SIM cards, which one do I use, what APN?

Each hardware device supports specific RF bands that determine which carrier the hardware is compatible with. The compatible carriers’ SIM cards are the ones to use. Sometimes they are technology specific, for example Verizon has LTE SIMs for CAT1-CAT4 technologies, and separate SIMs for LTE-M1 & NB-IoT SIMs. The APN is dependent on how the data plan was provisioned on a specific SIM.

As an example, Verizon provides customer specific APNs for private network IPs, and a regional specific APN for public static IPs.

How do I find and set the APN for my device?

The cellular network provider will be able to provide you with the APN you need to use to access their network. If you’re using NimbeLink for cellular network data plans, you can either refer to our User Manual or contact for details on which APN to use.

For most modems, the command to set the APN for your device is AT+CGDCONT=1,”IPV4V6″,”APN”. If you’re using a Verizon modem with NimbeLink data plans, it will normally be AT+CGDCONT=3,”IPV4V6″,”NIMBLINK.GW12.VZWENTP”.

What is an APN, and where do I get it? What is a PDP context?

An APN is an Access Point Name. You can think of it as the “address” to which your modem connects to register and to pass TCP/UDP data traffic on the network. Your cellular provider will be able to provide this to you. On NimbeLink modems, you’ll need to insert your APN into a “PDP Context.” A PDP context is a container that tells the modem how to connect to the cellular network. It includes the IP mode – meaning IPv4 or IPv6 or both – and the APN given to you by the cellular provider.


What are the power numbers for each modem?

Cellular modems are typically very power hungry while active and transmitting, but low power while in listening and idle states. Skywire modem Datasheets provide detailed power numbers for each product in multiple states.



Got my modem and Skywire Dev. Kit. What are my next steps?

Look at the User Manual for the NL-SWDK development kit and learn how to activate a cellular data plan and test the functionality of the modem.


How do I pick the right modem for my application?
First start with the geography. Each country has different cellular carriers that provide cellular data plans. Find the cellular carrier that meets your geographic coverage needs, then learn which RF bands they support. You can then down select devices that support the same RF frequency bands. Second, consider the supported cellular technology level. Higher speed technologies are typically more expensive from a hardware perspective than lower speed technologies.  
What is the correct modem for "xyz" carrier?
Determine which RF bands and technology types the carrier supports, and compare those to available modem solutions.
What is the correct modem for "xyz" country?

Determine which RF bands and technologies are supported by cellular carriers in that country, and compare that to available modem solutions.

Do you have a modem that supports voice? VoLTE?

We support voice via TCP/UDP traffic, but not VoLTE.

What antennas are certified on your modems?

Because cellular carriers operate in licensed bands, you can use any antenna that is below the max gain listed in the datasheet for a specific Skywire modem.


What drivers do I need for Skywire modems?

Each operating system has different driver needs. Generally speaking, we provide Windows, Windows Embedded, Android, and Linux drivers for multiple versions depending on the product. At a minimum we provide an OS-agnostic path for raw socket dials.

Does the modem need a SIM card?

All GSM and LTE modems require a SIM card. Some NimbeLink products like the NL-SW-LTE-QBG96 include a soldered-down SIM card for Verizon’s network so you do not need to insert an external SIM.

How do I move from one Skywire modem to another?

Skywire modems conform to a mechanical and electrical standard. Moving from one modem to another mechanically and electrically should be a painless activity. The AT commands do differ between modems, so customers should review the AT command manuals and any OS driver-specific or PPPd documentation differences between products.


What is the difference between a module and an "embedded modem?"

Cellular carriers and 3rd party organizations such as PTCRB and GCF establish two levels of certification: “Module Certifications” and “End-Device Certifications.” Module Certifications require designers to go through additional testing to achieve “End-Device Certifications.” Skywire modem products are “End-Device Certified” so you can embed a Skywire modem into your product and qualify as an “End-Device” without any additional certifications.


How do I initiate a cellular connection to a Skywire modem? (Mobile terminated connection)

In order to accept inbound connections, the modem must have an IP address from the carrier in the same Private Network or a Public IP address accessible from the outside world. Second, the system must be put into a mode to be a socket listener. This is accomplished different ways depending on how the data transport is implemented in your environment. If you are using PPP or a native device driver to communicate with the modem, the Operating System on your device would contain firewall settings and listener settings that need to be configured to allow inbound connections. If you want to use the modem to accept and terminate inbound connections directly, you’ll use AT commands to configure the modem’s firewall settings and enable a socket listener stack.

How does the modem communicate?
Skywire modems support both USB & UART for physical connections. Customers can use one or both in their products. Each of these paths provide a serial port for sending raw AT commands, and the USB path provides an additional means for an OS native cellular driver like MBIM, NDIS, QMI, NCM, and other types depending on the specific modem.  

Yes. NL-SW-LTE-QB96 is a worldwide single SKU option that supports LTE-M1, NB-IoT, and 2G GSM. NL-SW-HSPA is a worldwide SKU that supports HSPA, UMTS, and 2G GSM technologies.


What SKUs work in Latin America?
Does the Skywire support eSIM/eUICC?

Yes, using a removable eSIM/eUICC in 3FF (Micro-SIM) form factor.

Can I solder the pins on the Skywire to my board?
Yes. Rework is difficult when the modem is soldered into a PCB, so ensure there is a path to USB and/or UART for manual physical connection in case a firmware update is needed during the manufacturing or debug process.  
How do I connect the serial output of my device to the Skywire modem’s serial interface?

The Skywire modem supports both a USB and 4-wire UART interface. For best results, use one of the Skywire development kits like the NL-SWDK for a convenient user-accessible USB port, UART converted to USB, or UART at TTL levels at a debug connector is available for engineers to easily wire into other MCU development platforms.


Will the Skywire automatically send my serial data without AT Commands?
No, at a minimum the host board must send commands to register on the network, open a socket, send data, shut down socket, and de-register from the network.  
Can I use the Skywire as a USB dongle?

Yes, with limitations. All Skywire modems support USB for data transport, however, not all USB ports support the extreme current demands required for cellular communication. To prevent the modems from browning out, the host USB port must be able to supply up to 2 Amps of current in short bursts .

How much does data service cost for Cat M1 versus Cat 4?

Currently, cellular data carriers sell data by the byte, independent of the type of technology used to transport the byte. Therefor, an LTE-M (CAT M1) device sending 1 Kilobyte of data would cost the same per month as an LTE CAT 4 device sending the same amount of data.

I need to send SMS - which product do you recommend?
All Skywire modems are capable of sending and receiving SMS, however each carrier treats sending and receiving SMS differently. For example, Verizon allows device-to-device SMS on LTE-M, but does not currently allow device-to-mobile phone and vice versa for LTE-M devices.  
I want to be able to switch between carriers, which product do you recommend?

Start by looking at the products that support multiple carriers with a single SKU, and follow up with a family of SKUs depending on technology requirements. Currently low-speed solutions support multiple carriers with a single SKU (like the NL-SW-LTE- QBG96). For higher speed solutions, multiple SKUs are required to support multiple carriers, such as the NL-SW-LTE-TSVG and NL-SW-LTE-TNAG or NL-SW-LTE-S7648 and NL-SW-LTE-S7618RD families.

Is there a processor/microcontroller on board?

No. All Skywire products are bare modules with the minimum amount of hardware and software needed to achieve carrier “End-Device Certifications.”

Does it work with Linux?

Yes, all Skywire modems are compatible with Linux over USB and UART using either a native Linux driver like MBIM, NCM, ECM, or a more universal driver like PPPd.

What do you mean when you say a modem is Global?
When we say “Global” we mean a modem that supports many RF bands so there is at least 1 band that is supported in every country.  

Basic Troubleshooting Steps

When should I ask for an RMA?

Requesting an RMA is appropriate when a Skywire modem does not perform to the expectations of the User Manual when used in an NL-SWDK development kit.

What do I consider with regards to Power Supplies and LDO?

Cellular modems require current in very short bursts, and switching power supplies can typically react to current demand changes faster than LDO power supplies. However, switching power supplies creates both conducted and radiated noise that can desense the cellular radio receivers in cellular products. Therefore, proper RF design techniques should be used to mitigate conducted and radiated noise from the power supplies.


Common Troubleshooting Commands

How do I see my PDP context configuration?

A PDP context configuration is a container in which you place the APN and IP mode that you wish to connect to the network with. You will configure this with your APN and then activate it to connect to the network.

What commands do I use to determine cellular network registration status?"

AT+CREG? , AT+CGREG? , AT+CEREG? – tells you if the cell tower recognizes your IMEI and ICCID pair as able to register on the carrier network. These commands can be specific to each modem depending on the type of cellular capabilities that the modem has. Please consult the AT command manual for details on which command is suitable for your modem.

We recommend relying on the RSRP and the RSRQ values that the modem provides, instead of the commonly used RSSI. Use these commands to retrieve the RSRP and RSRQ values from the modem.

Telit modems – AT#MONI
Quectel modems – AT+QCSQ
All others – AT+CESQ or AT+CSQ


How do I check if my PDP context is activated?

Accessing the PDP context is different for each modem AND different modems use different contexts and syntax, so we recommend referring to the AT command manual and UserManual for the modem you are using to determine the best way to query the state.

What are the querries for the current network operator of the cell tower on which I am registered?

For Sierra Wireless and most other modems, AT+CGACT? to query the current PDP activation status. For Telit modems, use AT#SGACT? As always, please consult the AT command manual for more details on these commands.

What is the command to configure my modem to automatically activate the PDP context?

The command is AT+CGATT=1 for enable, AT+CGATT=0 for disable. You can check the status with AT+CGATT?

Connecting to the Cloud

How do I connect to the SAP / Azure / AWS / Google cloud?

NimbeLink publishes Applications Notes specific to each cloud platform. If you don’t see your cloud provider posted, please contact and request an example.

Data Plans

Yes, quick and easy! Visit, select your plan and subscribe.


Can't you just shut off my data plan service once I've reached the max amount on my plan?

No. Unfortunately we do not have this level of control over data plan usage.



How do I connect to SAP / Azure / AWS / Google…?

NimbeLink publishes Applications Notes specific to each cloud platform. If you don’t see your cloud provider posted, please contact and request an example.


Raw Socket Dials are recommended for low-end MCU based devices that do not implement formal operating systems. PPP is a universal protocol that is supported by most operating systems and is a highly flexible protocol supporting many different modems and operating system versions, but is less efficient in data usage than native OS drivers. Native OS drivers are more efficient than PPP, allowing them to create lower latency and lower over-all data usage in high usage applications, but these are typically modem and OS-specific implementations that must be re-implemented if the modem or OS software is updated.

Do I need a connection watchdog, or why should I log modem commands and responses?

Our experience from working with dozens of modem module suppliers, technologies and carriers shows that every modem fails eventually and system designers should develop hardware and software safeguards to recover cellular modems that have become unresponsive or failed in some way. In order to debug and diagnose issues in the field, designers should record the modem command and response sequence and preserve this data either through physical storage on the device or by periodically sending data to the cloud for remote access during the discovery and debug process when issues are discovered. Without comprehensive logs, NimbeLink and the underlying module vendors cannot help.

Design Services

I would like to do a custom design, can you help me or point me to a third party that can?
Yes, please contact

Certifications / Approvals

What else do I need to do to get my device fully approved?
Nothing! NimbeLink’s Skywire and Asset Tracking products are all fully end-device certified on the relevant government, regulatory, and carrier certifications. As long as there are no changes to these devices and they are used as outlined in the product datasheets they can be used without additional certifications. The best way to see if a specific carrier/geography you wish to use is supported is to go to the product page for that device and check the Certifications heading in the Documentation section. If you don’t see it there, then reach out to and inquire about products for your carrier of choice.  


What information should I provide to support when submitting a ticket?
The Model Number of the device, modem IMEI, SIM ICCID, description of problem, AT command logs, photo of device setup including a photo of the modem’s label, and a photo of the development kit, host device, power supply, antenna, and any connectors attached to the modem.

Contact Airgain Today

Have questions about which Airgain products and services are best for your application?
Contact us today.