Abstract
In this thesis, we introduce number portability and its call routing mechanisms, DR and IR. We establish a number portability database to record these ported numbers. DR must consume much cost to establish a very huge database. IR must communicate with NRH network to obtain the information of ported users. We propose DR-RRD to improve the above two drawbacks by using replacement algorithms. DR-RRD only record ported users with high call arrival rate. Because of unknowing the distribution of call arrival rates of ported users, we propose four replacement algorithms in order to achieve the above purpose. Through the simulation, we compare these replacement algorithms and discuss their advantages and disadvantages. DR-RRD can save more memory for database without depending on NRH network. We mention short message service and signaling protocol for number portability with DR-RRD. We will discuss cost, database memory and signaling routing cost, between DR, IR, and DR-RRD. At last, we will analyze all parameters to find a bound, which let DR-RRD be best mechanism with the least cost.