Research And Implementation On LTE TDD System Random Access Channel And Detection Algorithm

As the latest communication technology today, LTE also need to resolve the performance of random access. As a communication system aimed at providing data service for mobile users, the requirements for the performance of LTE random access is higher than former mobile communication systems. So the research of LTE random access has a very important significance. In this paper a brief introduction to the development of the mobile communication system and LTE system. After this, the article researched the multiple access protocol of random access and random access system and back-off algorithm of random access system. After the research of multiple access protocol and back-off algorithm, we will analyze the random access of TD-LTE system, including the role of random access and the classification of the random access and the selection of random access preamble sequence. After the introduction of the entire TD-LTE system, we will focus on LTE uplink physical layer link, and we will focus on the structure of LTE physical uplink random preamble. After this we will research the implementation PARCH preamble, as well as the detecting of it. In this paper, a method is proposed to implement ZC sequence based on the look-up table and accumulator. This method calculates the index portion of exponential function with the accumulator, and the values of exponential function are stored in a ROM. When needed we can get the value by look up the table by the index. For intermediate calculations such as the division, it can be done by multiple with the reciprocal of the. division number. While in order to get accurate result, we should change the length of decimals and the length of integer with the change of the data. This method was validated, and met the design requirements very well. Also it can achieve a good clock as well as variable sequence length.In this paper a, method to implement the random access channel preamble is proposed, this method is to get frequency-domain sequence of the preamble directly. This implementation requires the DFT transform of the preamble sequence in the cell calculated in advance, and stored in the ROM, when sending preamble, according to the configuration information such as the root ID (u), the cyclic shift value to obtain the frequency-domain sequence directly. This implementation avoids performing a DFT operation, and effectively improves the efficiency of the module.Also the detection of the preamble sequence was done,which uses the frequency domain detect algorithm, while the generation of local frequency-domain preamble sequence uses the method proposed former, and do point multiplication with the received data, and then take IFFT transform then search for the peak and obtain the final result.After the design of modules, the validation and simulation was done, and the result showed the design in this paper meet the requirements very well.