Citycell RIM Cards

Citycell is one of the well known mobile phone services in Bangladesh. Everyone here knows that the Citycell service is somewhat different from the other mobile services. The Citycell mobile phones do not contain a regular SIM card, and instead they contain something called a RIM card. The matter was quite confusing to me. What is this RIM card after all? So yesterday I carried out a small research sitting on the Internet.

Mobile phones that contain a SIM card are called GSM devices, and the mobile networks on which they work are GSM networks. In contrast, mobile phones that contain a RIM card are called CDMA devices, and the mobile networks on which they work are CDMA networks. All the mobile services available in Bangladesh are GSM networks, except Citycell. The Citycell network is CDMA, and Citycell is the only CDMA mobile service available in the country.

A SIM card and a RIM card are physically the same thing. It means that from a mobile handset, you can take out the SIM card, and easily insert a RIM card in its place. But for the mobile phone to work properly with a RIM card inside, the handset must be CDMA-compatible. Therefore, if you want to use the Citycell service, your handset must be CDMA compatible; a simple GSM handset will not serve your purpose. If you are currently using a GSM handset, you can check back its documentation to see if the handset also supports CDMA.

Normally, a GSM user can easily change the SIM card in his handset. In Bangladesh, for example, a Banglalink user can easily switch over to Grameenphone simply by changing his SIM. He does not need to buy a new handset for it. But CDMA users did not have this facility previously. The concept of RIM card is relatively new, and today it allows CDMA users to enjoy the same facility. Today, a Citycell user can easily change his phone number, simply by replacing the RIM card in his handset.

Finally, note that there is actually nothing called a "RIM" card. Its actual name is "R-UIM" card, where R-UIM stands for Removable User Identity Module. It is only the Citycell company which calls it a "RIM" card.

Derivations:
SIM - Subscriber Identity Module
R-UIM - Removable User Identity Module
RIM - Removable User Identity Module (according to Citycell)
GSM - Global System for Mobile Communications, originally Groupe Spécial Mobile
CDMA - code division multiple access