摘要：As we know, LTE is the transition between the 3G and 4G and is also the global standard of 3.9G, which has improved and enhanced the air interface technology of 3G. LTE is characterized into two cases: LTE-FDD and LTE-TDD. Since LTE-TDD is researched dominantly in China, all the studies in this paper are discussed under the TD-LTE system. However, in the TDD system, the reciprocity is usually assumed since the uplink and the downlink work at the same frequency, that is to say, the estimated channel in uplink can be used to guide some downlink transmission, such as power allocation and so on. In order to estimate the uplink channel precisely, an appropriate estimation scheme with good performance is needed. In this paper, we have studied various channel estimation algorithms based on the characteristic pilot structure in uplink. And then an improved channel estimation method based on the jointly preprocessing in time-frequency domain is proposed. This method is mainly used in the following cases: the uplink channel is not estimated accurately via the successive pilot due to the interference and noise; the data processing will introduce delay and the user moves quickly, which will cause the estimated channel is not the real downlink channel. We further process the estimated channel both in time domain and in frequency domain. The final channel is used to design the beam forming vector, thus the performance of the system will be improved. Simulation results show that, the proposed method has improved the system performance in terms of bit error rate.
