The Algorithm And Realization Of Detecting A Wcdma System

In the study of Wireless Broadband Network, the random access process is very important and indispensable. The main research content of the random access procedure is multi-user randomly selectes the available access slots and sends datas to the base station. There may be some collisions when sending datas. If so, the user improves transmit power and automatically sends datas again until sending successfully or timeout. The random access process needs to send preamble code and datas. Only when the preamble code sends successfully and is detected by base station can datas be sent.The preamble detection is a part of the random access process. What it needs to do is to detect the preamble code at the appointed time. For example, in the range of 0 to 10-km cell, the appointed time is 7680 chips. The preamble code is scrambled by the prefix sequence. The purpose of this thesis is to extract the prefix sequence from the preamble code through the way of a combination of software and hardware. Preamble detector first discrambles the receiving datas, followed by phase rotation and frequency offset compensation. At that time, we can get a FHT matrix. Then we need to process the matrix and the processing methods are cut-off bits law, coherent accumulation, non-coherent accumulation and fast Hadamard transform. After the series of data processing, we can derive some amplitude values and we need to find the offset corresponds to the largest amplitude value. That offset is the serial number. This article implements the algorithm with DSP and CPU. The CPU is 8548 and the DSP is 6488. There are three cores in the DSP and two Rake Search Accelerators per core. This article first uses single-core to run the algorithm, and then uses three-core to run the algorithm. At last it proves it can greatly improved the efficiency of the preamble detecion because of the parallel processing capability of three-core.