The number portability (NP) solution enables to provide number portability service to end-users. The number portability service allows the user to retain his/her telephone communication number when the services provider is replaced. Decentralized and centralized number portability solutions, are used in different countries of the world.

The choice of solutions of this nature prevailed 10-15 years ago when each operator owned separate databases which described allocation of telephone numbers. The NP process was extremely complicated, hard to administer and required large technological and human resources.

The incumbent operators used to limit by various measures the small alternative operators' possibilities to access the number portability databases. The operators used to exchange information by fax, and later by electronic means; often the data was simply lost, while the number portability process itself took anywhere from 10 to 30 days. Because of all the aforementioned circumstances, number portability was not attractive to the user at that time and few decided to undergo the long and complicated process.

Decentralized number portability solutions are potentially cheap to implement but there is one very big disadvantage to them: provision of the NP service is expensive and complicated to administer. Due to all the aforementioned circumstances, centralized number portability solutions have been receiving increasingly more attention during the last 8 years; although their implementation was more expensive than that of decentralized ones, provision of the NP service and administration was much smoother and cheaper.

Centralized number portability solution is a solution with a unified database which is used by all operators in the country without exceptions and, if needed, by the institutions regulating the telecommunication market. More