The rapid advances in mobile communication systems. especially in Global Svstem communications (GSM), have led to a wide range of developments in design, simulation. controlling mechanism, management protocols, and performance analyzing techniques of such systems Several software simulator systems are designed and implemented in this work. The designed systems have simulated the real GSM cellular network with all related topics conceming the control on calling mechanism, mobility managements, and others. In this concern, simulators for the GSM Cellular Network, Mobile Station, Base Transceiver Station, Base Station Controller, and Mobile Switching Center are all designed and implemented in this work. Moreover, several Graphical User Interfaces (GUls) are built to analyze and evaluate the performance of the designed cellular network systems at different operating conditions. This has been base on a comprehensive investigation to the mathematical analyzing approaches such as calculating the call blocking probability, the handoff dropping probability and network performance optinization after adopting the guard channel principle.