Apakah rangkaian selular?
"Sel" dalam selular merujuk kepada kawasan liputan geografi yang masing-masing dilayani oleh sebuah menara atau stesen pangkalan. 4G dan 5G ialah generasi teknologi rangkaian selular. SIM fizikal dan eSIM kedua-duanya bersambung ke rangkaian selular dengan cara yang sama.
How a cellular network works
The service area is divided into cells, each served by a base station whose antennas exchange radio signals with phones. As you move, the network hands your connection from one cell to the next without dropping the call or data session. Cells vary in size: in dense cities they are small and close together, in the countryside they are large and spread out, which is why signal on mountains or remote highways is weaker than in town.
Behind the base stations sits the core network, which checks that your SIM is allowed on, handles charging and passes your data out to the internet. A physical SIM and an eSIM do the same job here: they hold the identity the network uses to authorise you.
Who defines 4G and 5G
Most of the world's mobile network specifications are written by 3GPP, the Third Generation Partnership Project. The ITU, the UN agency for telecoms, sets the requirements each generation must meet. IMT-2020 is the set commonly called 5G, and the ITU lists 3GPP's 5G radio technologies among those approved as meeting it. The ITU also explains that legacy 3G and 4G networks struggle to support some newer services, which is part of why 5G was developed.
| Generasi | Main use | What a traveller should know |
|---|---|---|
| 2G / 3G | Calls, texts, slow data | Many countries have switched these off or are doing so; an old phone that can only call over 3G may not be able to call |
| 4G (LTE) | Fast data, and voice over VoLTE | The baseline that works almost everywhere with service |
| 5G | Faster data, lower latency | Works only when the phone, the network and the plan all support it |
Home network, visited network and roaming
Every SIM has a home network, the operator that issued it. When the phone attaches to another operator that has an agreement with the issuer, that is roaming. Many travel eSIMs work this way: the phone joins a local partner operator, so the network name on screen may be the local brand, and data roaming has to be on for that eSIM profile.
Getting 5G while roaming depends on the agreement between operators, not just on whether the city has 5G masts. That is why the plan pages on this site list the partner networks and supported technology, such as 4G or 5G, for you to check before buying.
Full bars but slow data: why
- Signal bars show radio strength, not how crowded the cell is; at a stadium or concert data can crawl at full bars.
- Some plans slow down after a set amount of data; check the plan notes.
- The phone must support the frequency bands the local network uses; most recent phones cover a wide range, but models built for one region may lack some bands.
Soalan lazim
Does an eSIM use a different network from a physical SIM?+
No. Both connect to the same cellular networks; the only difference is whether the identity is stored on a chip built into the phone or on a removable card.
Why does the network name on screen differ from the eSIM seller?+
Because many travel eSIMs roam onto a local partner operator, so the screen shows that operator's name. That is normal.
My phone supports 5G, so why do I only get 4G abroad?+
5G needs the phone, the local network and the plan to support it together. If the plan lists only 4G, or the roaming agreement does not include 5G, the phone stays on 4G.
Can I make calls on a data-only travel eSIM?+
Not over the mobile network, as there is no number, but internet calling apps work. A Thai number kept in Dual SIM can still take calls and texts under its own operator's roaming terms.
Sumber
- IMT-2020 (a.k.a. "5G") — International Telecommunication Union, 10 Oktober 2026
- 5G networks — International Telecommunication Union, 10 Oktober 2026
- Use eSIM while traveling internationally with your iPhone — Apple, 10 Oktober 2026