Channel Assignment Scheme Analyzing In Downlink In WCDMA

The 1st and 2nd generation wireless telecommunication system provide voice traffic and limited data traffic. The target of 3G is providing a wide-scale service. Except a little information about mobility, the rest are the expanding of the ISDN in the wireless network.The CDMA protocol and technical improvement make 3G to be true, by using 3G techniques; users can get high speed data access, internet browsing, mobile video phone, multi-media, and global roaming. Users also can get the services based on the location, pilot, and other advanced technology.WCDMA was brought forward by the ETSI, is one of the three mainstream standards in IMT-2000 family. As a DS-SS (direct sequence spreading system), the DCH (dedicated channel) assignment scheme is an important part in the system design. In recent years, it's a hot topic. This paper is dedicated in several typical DCH assignment schemes' analyzing, discussing, and comparing.In the first part, I depict some research background of WCDMA, including the origin, the standardization of 3G, and some base knowledge of WCDMA.In the second part, I discuss some technologies related with the DCH assignment in WCDMA, including the MAC layer, the PHY layer, the principle spreading frequencies, and the base knowledge of OVSF tree.In the third part, I discuss the main guidelines and principles of the DCH assignment scheme (the bandwidth utility, the rate of code-blocking) and some main code select schemes (left-most, random and crowd-first), I also analyze several typical DCH assignment schemes (single-code OVSF, multi-code, FEX), for the further research, I construct a series simulation model by using OPNET, and get the simulation data.In the forth part, based on the above result, I provide a new DCH assignment schemes, it is more difficult but more efficient. I quote all its advantages in this part. And I get a conclusion, the scheme is the best one among all the above, but it has...