TD-LTE In OFDM And Radio Downlink Simulation

The wireless communication industry is growing rapidly in recent years. With the increasing connections with traditional IT industry and mobile communication demands, Long Term Evolution (LTE) mobile communication standard comes into being. As a part of standard of LTE R8, LTE TDD is named TD-LTE by the Ministry of industry and information technology. On the occasion that4G technology is in the ascendant and mobile business increases dramatically, discussion and study on the structure and key technologies of TD-LTE is necessary.LTE network uses a single-layer structure composed by eNode B, which makes the network structure tend to flatten, that is a revolutionary change for terms of3GPP system. Meanwhile, many new technologies have been introduced in the LTE system, such as Orthogonal Frequency Division Multiplexing (OFDM), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Retransmission Request (HARQ), Adaptive Modulation and Coding (AMC), scheduling algorithm in MAC layer and Inter-cell interference cancellation (ICIC). OFDM is a quadrature carrier technology and uses SC-FDMA in the LTE uplink, while uses OFDMA in downlink.In this paper, before detailing the principles of OFDM and relevant knowledge, we do some relevant research and analysis on the important modulation technique of OFDM.named M-level Quadrature Amplitude Modulation (M-QAM), which clear the advantages of M-QAM. Simulation results show that, when the order of M-QAM increases, the bit error rate raises too. The noise power has a direct influence on the performance of M-QAM and standard normal distribution noise has the maximum degree of interference. In order to ensure a higher quality of communication, the random channel can be selected, and if the channel has impulse noise in it. the differentiator may be added for processing. Then we make a presentation on OFDMA and SC-FDMA, which give a subtle analysis between them. Later, we simulate the OFDM system using different modulation. After investigating MIMO space-time coding, we give the simulation of MIMO system. Simulation results show that the MIMO system can significantly improve system performance which can effectively combat fading. Finally we simulate the MIMO-OFDM system. In the last, we show the simulation of PDSCH channel in radio downlink of LTE.