Research And Implementation Of TD-SCDMA Soft Baseband Key Technologies

With the advent of the mobile internet era, network constructing, the maintaining and upgrading costs under traditional wireless access network architecture continue growing. In view of this, China Mobile proposes a new wireless access network architecture C-RAN. By changing the way of network construction and deployment, C-RAN can effectively reduce the costs of network construction and maintenance, and provide users with flexible and efficient services.This paper refers to C-RAN architecture and 3GPP standard protocol. Architecture of general purpose processor plus analog RRU is adopted. In addition, receiver structure, transmitter structure and key technology of TD-SCDMA baseband signal processing are researched. Finally, real-time processing of the baseband signal is achieved on an Intel processor.Firstly, TD-SCDMA physical layer standard protocol is analyzed. Meanwhile, time synchronization algorithm based on match filtering is researched and joint detection algorithm based on matrix inversion is discussed. According to orthogonality of PN code, algorithms are simplified.Secondly, A baseband signal processing scheme is designed and realized in the paper. In this part, tasks are assigned according to correlation of algorithms. Processor resources are rationally allocated among tasks. Communication mechanism between tasks and detailed process flow of tasks are designed. Module interface is defined and calling relationship between modules is given. Meanwhile, real-time processing of baseband signal is realized on the Linux system with Xenomai kernel.Finally, the system performance is evaluated. Access probability of synchronization algorithm can reach 0.98 at-10 dB. Accuracy of frequency estimation algorithm can reach 3Hz at-3dB. On the condition of additive Gaussian white noise channel, performance gap of bit error rate between test and fixed-point simulation with MATLAB is 1dB.The paper achieves real-time processing of TD-SCDMA baseband signal on a general purpose processor. The feasibility of a general purpose processor for signal processing is verified. That provides a reference for design of virtual baseband pool under C-RAN architecture.