Asian operators have led the world in the adoption of RUIMs. China Unicom was the first CDMA operator using the RUIM. A RUIM card would make CDMA more attractive to consumers and would also open the door to better roaming contracts between CDMA and GSM networks, allowing the best possible global coverage for all cellular customers.
The RUIM card provides flexibility to switch phones by simply removing the RUIM card and slipping it into another card-enabled hone. The new phone would then be able to make and receive calls on the user's account without having to go through the carrier for activation. With the appropriate roaming agreement in place, a user could have several phones and switch from a CDMA phone to a GSM one by inserting the dual-mode RUIM card, thus making it available for user to borrow a friend's phone but call with his RUIM card, or even switch to another carrier and keep his or her old phone. The new carrier would simply issue the customer a new RUIM card to use in his or her existing phone. The only requirements are that the phone is unlocked and compatible with the frequency band of the new carrier. People enjoyed the convenience associated with the simplified access.
The benefit of having an RUIM for both GSM and CDMA is that the subscriber can have on phone book, one number, as well as the same interfaces and menus. No matter what technology the subscriber is using, convenience and ease-of-use are crucial to customer satisfaction and to avoid churn.
Smart cards represent security for business and mobile users alike. CDMA subscriber can easily pay their bills with their mobile phones if the CDMA operator guarantees security for their personal data and creates the right partnership with the smart card provider and the bank.
While the subscriber can change handsets at will, the RUIM remains the only element in the network that is completely controlled by the operator.
