In cellular service there are two main competing network technologies: Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA). According CDG.org, CDMA networks support over 270 million subscribers worldwide and have been the dominant network standard for North America and parts of Asia.

GSM.org tallies up their score at over 1 billion people in over 130 countries.

The number of mobile subscribers in the EU is enormous and 81% of EU citizens now have a mobile telephone. In a number of Member States the mobile subscription rate is close to 90%. Also, Europeans who are frequent travellers are using their cell phones abroad almost as often as they do in their own home country. But the high level of the international roaming prices has made this very expensive. This high cost contrast sharply with the much lower tariffs applied for domestic calls.

So what are the alternatives?

When travelling, remember you may be able to influence the level of roaming charges by selecting the most suitable network upon which you are roaming. Typically, your home operator will automatically guide you to roam on a specified partner network – but this may not necessarily be the cheapest option for you. Always try to use off-peak rates, which can be considerably cheaper. Off-peak rates apply on weekends and on weekdays in the evening, typically after 7 p.m.

If you need to make calls to other countries, a GSM carrier can offer international roaming, as GSM networks dominate the world market. If you travel to other countries you can even use your GSM cell phone abroad. To really use a cell phone abroad like you do at home and not need the salary of an investment banker, you will want to rent a local prepaid SIM. By renting a SIM card with minutes and a local number in the country you are visiting, you can make calls against the card to save yourself international roaming charges from your carrier back home. CDMA phones that are not card-enabled do not have this capability.

Unlike typical cellular phones in the US, GSM world cell phones do not come with phone numbers programmed into them and the actual service is not even tied to the phone itself. Instead customers activate their mobile phones by popping in so-called SIM cards, little thumbnail sized devices that determine your cell phone number and any additional services like voicemail.

A pre-paid SIM card for each country you visit, gives you a local phone number and local calling rates are usually a low 25 cents/minute. It is easy, convenient, and relatively inexpensive for you to call other people in the country you’re visiting. It will also save money for the people phoning you within the country. Your number will change while you are away but you will only pay local rates for your outgoing calls. This will be significantly cheaper if you need to make calls within the country you are visiting. But be aware that phoning your home country in such a way will be charged at international rates. Best of all, Incoming calls are FREE regardless of where they originate. One of the most unpleasant elements of roaming is the charge for receiving calls. Operators make extremely high margins and the end result for consumers is that they have to pay excessive prices for receiving a call. High prices for incoming calls are an important limitation to consumer and business mobile communications. For many consumers, this is a primary reason for changing a number and renting a SIM card of the foreign operator.

There is always the option of buying a SIM card for each country, however this will be very costly compared to international cell phone renting and SIM rentals.