Application Of Embedded Linux In The Acess Subsystem Of TD-SCDMA Radio Network Controller

The TD-SCDMA 3rd Generation Mobile System is composed of User Equipments (UEs), Radio Access Network (RAN) and Core Network (CN). RAN includes NodeB and Radio Network Controller(RNC).The RNC system designed by Datang Mobile Ltd. is fully compliant with 3GPP R99/R4 specifications. The hardware implementation is based on ATM technology . The core exchanging module uses ATM switch platform. The access subsyetem is the interface unit of RNC syetem.IMA (Inverse Multiplexing for ATM) technology provides a method to transmit high speed ATM cell stream in the low speed physical links. ATM queue scheduling algorithm schedules the queue in the transmitting port accordig to the key parameters of each channel. Because embedded Linux has many advantages such as open source, relatively small footprint, customizable, and no royalty or licensing costs, it has been more and more popular in embedded applications.PMC company's PM7341 is selected to achieve the high speed ATM cell transmission in the low speed physical links. And ATM transmitting queue's scheduling is in the charge of the ATM controller of MPC8260 communication processor from Freescale company. The paper implement the generation of BootLoader, the reduction of kernel and the customization of root file system through the U-Boot, ELDK and Busybox development tools in the RNC access subsystem channelizing STM-1 optical interface board . The paper deeply analyzes the following key technologies and important items: the techonolgy of IMA group trafic control, handling method when link clock asynchronours in one group, solution on asynchronization of the different link's transmitting delay, Queue scheduling technology on ATM transferring port, Migration for embedded linux. Meanwhile, the paper delivers the detailed feasible method and summarize the problem and solution during the debugging.In the end of this paper we examined the performance of chanelized STM-1 optical interface board in a stability test, and found the design aims are fully meeted. The research results of this paper have been successfully applied to communication equipment and used in the TD-SCDMA testing network built by China Mobile.