Requirements

1. GSM device
GSM for “Global System for Mobile Communications” is a standard used all over the world for wireless communication. It is the only system used practically everywhere and at many places exclusively, but is competing with different systems (like CDMA) in America and Asia.

GSM-based devices identify the user by a detachable smartcard called SIM (for “Subscriber Identity Module”). This can be taken out of the device and be replaced by a different SIM card issued by another provider. As only GSM-technology gives worldwide coverage and the choice of different SIM cards, this WIKI is based solely on GSM and all providers listed are GSM providers.

Progress has come in generations with GSM. It started with voice transmission, was later added by text (SMS), pictures (MMS) and data (GPRS).



2G (GPRS, EDGE)
Modern GSM-technology started with 2G for 2nd generation in the 1990s. It has data rates with a max. of 50 kbit/s  called GPRS, later to be accelerated to about 500 kbit/s which is called EDGE.

This is sufficient for the most basic data requirements like messaging, WAP or mobile websites, but too slow for “surfing” desktop websites. Nevertheless, it’s still the backbone of data transmission in rural areas or developing countries where networks are not that advanced.



3G (UMTS, HSPA, HSPA+, HSDPA, HSUPS, DC-HSPA+)
The 3rd generation or UMTS started with the new millennium and higher data rates. This was soon to be added by technologies like HSPA, HSPA+, HSDPA, HSUPA and dual-carriers (DC-) for even more speed. Thus theoretical speeds of some hundred Mbit/s can be reached coming down to some Mbit/s in practice.

These speeds are fine for “surfing” all kinds of websites and many data needs, but there is growing congestion slowing down the speed and high-volume data like downloads take time or are impossible like video streaming. Not using that, you may feel fine on 2G and 3G which are still the only mobile options in many areas.



4G (LTE, FDD-LTE, TDD-LTE)
4G has arrived before it was really here. Some operators called their “3.5G” or “3.99G” networks “4G”. In this WIK

I only LTE is called 4G not to confuse any further. With the arrival of LTE some years ago, unprecedented speeds of double or even triple digit Mbit/s can be reached in practice.

LTE is the state of art of wireless data transmission right now. High-volume data can be sent or received very fast even topping many landline ADSL-providers. The establishment of LTE networks is under way worldwide, but cost a lot of money and time. So LTE is only sold so far in technically advanced countries, within limited areas, sometimes for a surcharge and not so often on prepaid.

2. Unlocked device
A SIM lock or net lock is the capability built into GSM mobile devices by providers to restrict the use to specific countries and network providers. A device sold without a SIM lock is called unlocked and the purchaser can insert any SIM card.

It is not uncommon that a phone purchased together with a plan is SIM-locked to that particular provider. This means that when you go abroad and try to use a foreign SIM card it will not work.

There are many ways to unlock your device, which can't be specified here. Generally, an unlock code from your provider is available after the initial time of youur contract has run out. So take a look around the net or ask your provider or an mobile shop if your device can be unlocked.

Internationally, there are very different laws concerning SIM-locks and unlocking. In some countries SIM-locks are prohibited at all, in other countries unlocking of devices (within a certain time) is iilegal. For a survey of the legal situation refer to this: []

3. Frequencies
Unfortunately, different frequencies are used all over the world for 2G, 3G and 4G GSM-transmissions. To avoid blackouts, check the available frequency bands of the devices you want to take with you while travelling and compare it with the frequencies available in your destination countrie(s). They are given in the introduction of each chapter. This is especially important if you come from or go to America.

For specifc phone models, their frequencies are listed here:Network Compatibility of common phones. If you can't find your device, check its manual or device specification sites on the internet.

Basically, most of the countries within a region agreed on using certain frequency bands. This doesn't mean that no country differs from its neighbors. But it enables us to make a general survey of the frequencies used worldwide in Mhz. Remarks:

+ = other frequencies are in use in some countries by specific providers, for LTE see: []


 * 1) = very different LTE-frequencies are in use in Asia and Oceania, see: []

(!) = no 2G GSM provider in Japan and South Korea

For more info about the specific frequency bands used in your destination countries, check the Basics chapter at the beginning of every country.