Research And Design Of LTE Protocol Stack Based On Open Source Software

Currently LTE(Long Term Evolution) 4G wireless network technology is applied in large scale applicatioins, as the main evolution trends for 3GPP standardization draft, the technology has become the most mature solution for wireless network communication after 3G network. Most of the LTE system is implemented with traditional embedded devices and RF front-end and these equipments have to face the difficulties and challenges in upgrading and maintaining devices with the development in LTE technology. At the same time, when the technology develops to a certain level that the traditional hardware have to be replaced completely, the carrieroperator’s development and maintenance costs will be greatly increased, and its defects is obvious.Eurecom organization developed an open source LTE software named OAI(Open Air Interface). The software platform is based on x86 hardware and is used to provide ecosystem for open source software/hardware development for the core network(EPC) and access-network(EUTRAN) of 3GPP cellular networks. Now this software has been able to access standardized commercial terminals on PC platform.This paper deeply studied the OAI software architecture and describes the shortcomings of it. The author then put forward a RTAI isolation layer sheme in order to restructure OAI software. This design on one hand help the LTE base station software platform to achieve high reliability and real-time property, and on the other hand it also provides an underlying software support for the redesign of LTE layer2 in the future. In this paper, the author designs a new LTE RLC software based on the RTAI isolation layer, and then give a module design and test of RLC in linux operating system.Finally the author transplants the new RLC software to OAI software platform and make sure that the new RLC interface is compatible with current OAI interface, but change the internal message delivery mechanism completely. By constructing an actual software and hardware testing environment, we debugged the RLC code in online environment and test the mobile access process in order to finish the development of RLC software based on RTAI isolation layer.