Based Mobile Communications System Study Of The Random Access Procedure

Currently widely-used mobile communication system is second-generation mobile communication system. With the increasing of data service demand and multimedia service's application, the 3^rd generation system appears and becomes a hot research topic.This thesis mainly analyses and realizes slotted-aloha protocol used in random access procedure in the third generation mobile communication system. Random access procedure is very important in mobile communication system. The performance and capacity chiefly affect the whole system. MS (Mobile Station) establishes connection with BS (Base Station) by access channel. MS employ slotted-ALOHA random access protocol on access channel and transmits preamble one after another. Lots of access will produce big uplink interference, which result in received power's increasing and uplink capacity's reducing. In order to ensure the capacity of the voice service, we should restrict the use of access channel. Because preamble is limited, when multiple users want to access, collision happens and the performance of access deteriorates. So how to optimize the access performance in the condition of limited resource is hot research topic.This thesis analyses different multiple access protocol; describes random access procedure in mobile communication system; compares random access procedure in different communication system; compares the different preamble transmission power ramp step's influence on access performance such as delay successful access ratio and interference, obtains the most suitable parameters; compares fixed step, linear step and exponential step algorithm's performance and find that linear step algorithm's performance is better than fixed step.