LTE/FDD Downlink System Level And Link Level Interface Study

Future communication system must support high speed data transfer and ensure low latency in different mobile environment. With the merits of high spectral efficiency and resistance to ISI, OFDM modulation and access technology will be widely used in B3G and 4G systems. In order to evaluate the performance of OFDM system, link level need to do vast of simulation to meet the demand of system level simulation, and it is also time consuming. However, separate system and link level simulation and establish system and link level mapping interface can improve the computing efficiency. Therefore, study system and link level interface become particularly important for LTE/FDD downlink for which used OFDMA as the access technology. Based on 3GPP LTE physical layer protocol long term following and learning, author designed the LTE/FDD downlink physical layer simulation platform and made highlight of the receiver key algorithm study. Specially, soft demodulation algorithm, Turbo decoding algorithm and multi-path channel models are derived from a large number of foreign references. Based on the built link level simulation platform, this paper did lots of research emphasis on system and link level interface algorithm on the condition of HARQ, made the algorithm low complexity and easy to implementation.The first chapter of this paper introduced the development trend of mobile communications,3GPP LTE system and the work of paper briefly. The second chapter described the related technologies of LTE/FDD downlink system and link level simulation platform, including OFDMA, MIMO, HARQ, adaptive transmission and cell interference coordination technologies. In chapter three, LTE/FDD downlink processing was introduced in detail at the beginning; then, the receiving part key algorithms, which including frequency domain channel estimation, frequency domain equalization, soft demodulation, Turbo decoding and HARQ algorithms, and wireless channel modeling were studied in depth; at the ending, link level simulation configuration and results were gave. The fourth chapter was focused on LTE/FDD downlink system and link level interface study, which gave the derivation of EESM algorithm, advanced the EESM algorithms under HARQ, implemented EESM algorithm for LTE/FDD downlink, and put forward the adaptive transmission scheme for LTE/FDD downlink. The last chapter summarized the work, analyzed the shortcomings, pointed out the next targets, and brought forward some issues need to be considered for LTE evolution to IMT-Advanced.