Wcdma System Capacity Analysis And Simulation

This dissertation has discussed the link characteristics and cell capacity of WCDMA system. The WCDMA can provide a way for GSM to transfer to 3G system smoothly, so it is a competitive 3G scheme for our country.This dissertation first will describe the link characteristics of WCDMA system:its coding and modulating technology. Then we will compute the for different bit rate services under required BER for unplink and downlink respectively. Through simulation we can see that WCDMA system has a good performace under high bit rate service because of the advanced coding technology, we can also see that this performance is better in downtlink than uplink.Secondly, this dissertation will discuss how to choose and compute some important parameters for WCDMA dimentioning purposes. On the basis of these parameters we will provide the cell capacity for different services through simulation. Then we conclude that the cell capacity decrease dramatically under the high bit rate service; the interference factor of ajacent cells and the orthorgonal factor are also important parameters to influence the cell capacity; The downlink can accept more users than uplink, so the capacity of WCDMA system will be limited in uplink.This dissertation will discuss the cell capacity under the admixture of various services in detail. For this purpose, we will establish a multi-services model for voice, background and streaming classes users. We will compute the block possibility of the system in different traffic load, the result is that this possibility increase fast when there are more and more data users. In order to improve the cell capacity, we will introduce a admission control algorithm based on time delay sensitivity, the essential idea for this algorithm is when the capacity of the cell reaches its limit, block the users who are not very sensitive to the time delay, thus, the system could accept more new users. When the system release resource, theblocked user can get into the system again, otherweise, if its waiting time has exceed the maximal value, it will be discarded. After this algorithm is applied, we will use block possibility and interrupt possibility to evaluate the improvement of the system. As a result, we will see that the block and interrupt possibility are two contradictory issues, and the simulation will also help us to choose the appropriate parameters for this algorithm.