I recently moved and use a ZTE cellular router with a SIM card because fixed-line internet is not available in my current situation. My plan advertises speeds up to 250 Mbps, and since May my PC—connected directly to the router with a LAN cable—usually received around 150–250 Mbps, which was fine for online FPS games.
About a week ago, the speed suddenly fell to 1–4 Mbps for most of the day. Occasionally it jumps to 20–100 Mbps for a few minutes, but the connection keeps fluctuating. The same poor performance happens over Wi-Fi on my phone, so it does not seem limited to my PC or Ethernet cable. My plan supposedly includes unlimited data without a stated high-speed cap.
I have restarted and reset the router, tried different locations, adjusted the Wi-Fi settings and channels, and tested the connection with several speed-test services. My ISP's status page reports no outage, and support mostly suggested the same basic steps before trying to sell me an upgraded plan. Is there anything else I can check—such as signal measurements, LTE/5G bands, or possible throttling—to restore the previous performance?
3 Answers
With a cellular router, the LAN cable only provides a wired link from your computer to the router; it does not make the cellular connection faster. A sudden drop that affects both wired and wireless devices usually points to the mobile network, signal conditions, tower congestion, or account-level traffic management.
Open the router’s administration page and look for RSRP, RSRQ, and SINR values, along with the connected LTE or 5G band. If the router supports band selection, testing another band may help. Also reread the contract for fair-use, deprioritization, or data-management terms, even if the plan is described as unlimited.
First, compare the connection on several devices, including your phone over Wi-Fi. Since the phone is also slow, the problem is probably not your PC, Ethernet cable, or network drivers. Run tests at different times and record the results so you can show the ISP that the issue is persistent.
Call the ISP again and ask them to open a formal technical service case rather than just walking through basic restart steps or discussing an upgrade. Ask them to check the SIM, tower serving your address, network congestion, and whether your account has been deprioritized. Keep the case number and your speed-test results. If they cannot restore the contracted service, ask what cancellation or fault-resolution options are available under the contract.
The first support call only covered general troubleshooting and steered toward an upgrade, so I’ll call back and specifically request a documented technical investigation.
I’ll check the signal statistics and band information. I’ve already confirmed that the same slowdown happens on my phone, and the plan says there is no speed cap after a certain amount of data.