Lte Downlink Adaptive Technology Research And Implementation,

For the reason of market competition with WiMax standard and the integration of wireless mobile communication and broadband wireless access technology, 3GPP has started LTE (Long Term Evolution) project. These are both driven by people's growing demand for wireless mobile communication, because people want more, faster and better services. Wireless mobile communication, the selection of appropriate modul- ation and multiple access technology has been essential to achieve good system perfor- mance. In the development of LTE standard, 3GPP chose the orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) as its multiple access method finally, owing to the OFDM has the advantages of spectral efficiency, strong bandwidth expandability, powerful capability of anti-multipath fading and be capable of frequency-domain scheduling and adaptive. The research of adaptive OFDM technology can enhance its spectrum utilization, and then improve the whole system's performance.This paper first outlines the development of mobile communication, key techno- logy of LTE standard, adaptive OFDM technology's development and current status, and the significance of OFDM technology studying. Then the paper introduces the LTE downlink physical channel, the basic principles of OFDM system, and the application of OFDM technology in LTE. The basic principle of OFDM is that the actual radio channel is divided into several sub-channel to transmit data by utilizing sub-carriers orthogonal nature. One of the benefits of doing so is that each sub-channel can dynami- cally allocate bits of information and transmit power according to the instantaneous transmission.This paper focuses on the adaptive allocation algorithm of the OFDM system. It presents the multi-path fading channel characteristic and adaptive OFDM system, studies the Huahes-Hanogs greedy algorithm, Chow algorithm, Fischer algorithm, simple bit-loading algorithm(SBLA), and simulate these four algorithms to analyze their performance in the system. On this basis, LTE downlink adaptive system is complete by the application of the SBLA algorithm, the advantage of this system using the adaptive algorithm is also verified.This paper also presents a solution of the adaptive algorithm applies to MSC8156 DSP which is provided by Freescale Corporate. The solution is tested and verified by corresponding with given environment and parameters. By comparing the result which is obtained from the adaptive algorithm work in the DSP with the Matlab simulation, the correctness of the algorithm is verified. In addition, in order to improve the effici- ency of the programs, the programs about data storage allocation and complex operation are optimized according to the structural characteristics of MSC8156 multi-core DSP processor. The result obtained from DSP which is running adaptive algorithm shows that running time meets the system requirements, and the engineered practicability of adaptive technology is verified.