6 Core Causes of IoT SIM Card Disconnection

For businesses relying on Internet of Things (IoT) devices—whether smart meters, logistics trackers, or industrial sensors—sudden IoT SIM card disconnection is far from a trivial issue. It can directly lead to operational disruptions, loss of critical data, and even cascading financial losses. As the scale of IoT deployments expands, "why does my IoT SIM card lose network" has become a frequent question in enterprise operations and maintenance. This article details the 6 core causes of IoT SIM card disconnection, helping you quickly identify problems and minimize downtime.

This is the most common cause of IoT SIM card disconnection, rooted in the fact that IoT devices often operate in scenarios beyond the signal coverage of consumer-grade mobile phones. On one hand, many devices need to run in remote areas where the density of cellular base stations is low. Signal transmission is easily blocked by terrain, resulting in weak or even no signal. On the other hand, some devices are deployed in enclosed spaces—concrete walls and metal structures severely weaken signal penetration. Even if the base station is not far away, it is difficult to establish a stable connection. Additionally, electromagnetic interference exacerbates the problem: large motors in factories, for example, emit electromagnetic signals that interfere with cellular network frequency bands, causing frequent interruptions in communication between the IoT SIM card and the base station.

The Access Point Name (APN) is the "bridge" connecting IoT devices to the carrier’s data network. It defines the path, protocol type, and authentication method for the device to access the network. Once there is an issue with APN settings, the IoT SIM card cannot establish an effective data connection even with full signal. Common error scenarios include: first, typos during manual entry, which prevent the system from recognizing the correct path; second, using the wrong type of APN—for instance, replacing the APN dedicated to industrial-grade IoT with a general APN for regular mobile phones. The two differ in network permissions and data transmission priority, leading to rejection of access by the carrier; third, outdated APN parameters. Some carriers adjust APN configurations due to network upgrades. If the device fails to update synchronously, the old parameters become invalid, resulting in connection failure.

IoT SIM cards are prone to hardware failure if exposed to harsh environments or improper operation for a long time. Failures mainly fall into three categories: first, physical damage—deformation of the device’s SIM card slot or scratches on the SIM card chip; second, environmental erosion—rainwater seepage in outdoor environments causing chip corrosion, or oil stains in industrial settings adhering to the SIM card surface, hindering contact with the slot; third, extreme temperature impact. In environments below -40°C or above 85°C, the chip material of the SIM card fails due to thermal expansion and contraction, making it impossible to read data normally. Additionally, some low-cost SIM cards have quality defects that may cause poor contact.

Even if the IoT SIM card and the device itself are in good condition, fluctuations in the external network environment can cause disconnection. Network congestion mostly occurs in high-density scenarios. During peak hours, a large number of devices send data simultaneously, leading to saturation of the carrier’s base station bandwidth. Some devices lose network because they "cannot compete" for network resources. Carrier outages are uncontrollable factors, which may result from base station hardware failures, network upgrade and maintenance, or interruptions caused by force majeure (such as heavy rain or earthquakes). The characteristic of this type of disconnection is "regional"—multiple devices under the same carrier’s coverage experience issues at the same time, and the disconnection duration matches the outage duration.

The firmware and supporting software of IoT devices are the "invisible support" for ensuring the normal network connection of IoT SIM cards. Once vulnerabilities occur, they directly affect connection stability. You can troubleshoot technical issues one by one, such as compatibility of firmware versions, configuration conflicts in software, and whether security vulnerabilities have been attacked. Additionally, if the device’s firmware is not updated for a long time, old vulnerabilities will accumulate, and the probability of disconnection will increase with usage time.

To access the carrier’s network, an IoT SIM card must undergo strict identity authentication. This process relies on core credentials built into the SIM card—International Mobile Subscriber Identity (IMSI) and Authentication Key (Ki). Once there is a problem in the authentication process, the connection will be directly rejected by the carrier. It is also necessary to continuously monitor the validity period of the credentials to avoid being deemed invalid due to expiration. Furthermore, the use of the SIM card must comply with the carrier’s regulations. If the carrier detects "abnormal usage" of the SIM card, it will temporarily block the SIM card to prevent risks, prohibiting it from accessing the network.

Metrix Aero Core, ranking among the Top 10 in the IoT industry, has close strategic cooperation with carriers in multiple countries and regions. It offers a variety of solutions to cope with dynamic changes of carriers, providing round-the-clock protection for the stability of customers’ IoT networks.

If you are looking for reliable IoT SIM card solutions to reduce disconnection risks, or need professional support for IoT network maintenance, Metrix Aero Core can be your trusted partner.