Research On Capacity Of CDMA System And MUD Technology

Now CDMA has been the standards adopted by Third Generation Mobile Communication (3G) for its remarkable communication performance. This paper mostly researches the up-link capacity of CDMA system,and Multi-User Detection (MUD)which can efficaciously increase capacity of CDMA system. Firstly, this paper introduces the characteristics of CDMA system in a nutshell. And points out that the capacity of CDMA has the soft-characteristic,Then it gives the pole point of capacity of the up-link under ideal power control . Thereafter,this paper describes the relationship between the Erlang capacity and block probability and pole point of capacity. In a CDMA system,incomplete orthogonality of the code makes other users act as a disturbance source relative to the intended user. The interference thus formed is called Multiple Access Interference (MAI). Multi-User Detection (MUD) is one of the key technologies to eliminate MAI, and it not only improves the capacity of the system,the performance,but mitigates the strict requirement of power control And so,it remains as the research hot pot since then and,was promoted to be one of the key technologies for 3G. This paper introduce and compare all kinds of Multi-User Detection methods, do some theoretical research along with some algorithm improvement on certain detection method-Parallel Interference. This paper uses PCF to improve PIC, and gives the formula of PCF, which is give by experimentation commonly. And it reduces the complication at the same time.