CAT-M vs NB-IoT for IoT SIM Cards | the Differences

By Rony Cohen | floLIVE 

Choosing Between NB-IoT and Cat-M for IoT Deployments

As the number, scope, and sophistication of IoT deployments expand, selecting the appropriate connectivity technology for your business needs becomes increasingly critical. This article explores NB-IoT and Cat-M in detail, helping you make an informed decision for your specific IoT deployment.

Who is Choosing Between Cat-M and NB-IoT?

Cat-M and NB-IoT are both standardised technologies under 3GPP (3rd Generation Partnership Project) guidelines. These options are crucial for operators and enterprises seeking benefits from low-power wide area networks (LPWANs), a versatile alternative to WiFi and traditional cellular networks like 2G-4G. Unlike conventional solutions tailored for mobile phone subscribers, LPWANs support wide-area networking with smaller data transfers, making them ideal for IoT applications that require expansive geographical coverage and involve low Average Revenue Per Unit (ARPU) devices, such as sensors in logistics, asset tracking, fleet management, smart cities, or agriculture.

LPWANs represent a significant advancement for IoT by offering power-efficient networking options that can operate on either licensed or unlicensed spectrums, tailoring to specific location and business needs concerning availability or latency.

Cat-M vs NB-IoT: Understanding the Similarities

Both NB-IoT and Cat-M feature a Power Saving Mode (PSM), which allows devices to hibernate when not actively transmitting data, significantly extending battery life. This is particularly beneficial for IoT devices that do not require constant connectivity but need to activate periodically, for instance, to transmit data on rainfall, location, or speed. Devices typically remain dormant until such data needs to be sent or when actions like manual checks on smart meters are performed, reducing power usage considerably.

Another shared feature is the Extended Discontinuous Reception (eDRX), which allows devices to remain reachable for messages from operators or enterprises, such as Over-The-Air (OTA) updates or configuration changes. While mobile subscribers typically check for messages every few seconds, NB-IoT and Cat-M devices can extend this interval up to 40 minutes, enhancing battery conservation while maintaining coverage.

Cat-M vs NB-IoT: Delineating the Differences

Choosing the right connectivity technology depends on specific needs:

  • Bandwidth and Data Rate: NB-IoT is optimal for applications requiring low data rates, supporting a narrow bandwidth of 200 kHz and a data rate ceiling of about 250 Kbps. This makes it suitable for environments with challenging radio conditions. In contrast, Cat-M supports higher data rates up to 1 Mbps due to its wider 1.4 MHz bandwidth, enabling lower latency and more precise device positioning. This could, however, result in higher costs compared to NB-IoT.
  • Functionality: Cat-M additionally supports voice calls and mobility, which are beneficial if required by the deployment but may add unnecessary costs if not utilised.

Understanding NB-IoT Spectrum Use

NB-IoT’s use of narrow bandwidth allows for more devices within the same spectrum allocation, a significant advantage given the limited radio frequency spectrum available. It also utilizes guard bands—the spectrum between the radio bands—to accommodate more connections without interference.

Making Your Choice

NB-IoT is designed specifically for massive IoT deployments, where large numbers of sensors and devices connect to a single base station. It’s less suitable for mission-critical applications due to potential latencies up to 10 seconds. In contrast, Cat-M is generally more power-efficient and is better suited for areas without established roaming agreements for NB-IoT, where managing multiple mobile operator relationships may be necessary.

Both NB-IoT and Cat-M offer considerable benefits and can work complementarily for certain business needs. Ensuring you have a robust plan for disaster recovery and redundancy to maintain connectivity is crucial, as is flexibility for handovers and OTA switching to keep your devices always connected.

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