Research & Implementation Of The Key Technologies In LTE Downlink

The LTE (Long Term Evolution) scheme was proposed by 3GPP, which is compatible with current 3G telecommunications system. Channel estimation plays a quite important role in the LTE system which requires high data rate, high quality and high mobility. Besides, Multiple-input multiple-output (MIMO) technology can breakthrough the constraint of limited radio frequency resource and significantly increase the spectral efficiency of wireless systems. Hence, MIMO is also adopted by 3GPP as an important method to enhance the overall transmission rate.All of above key technologies for LTE downlink are investigated in this thesis. Firstly, the basic knowledge of Physical Layer in LTE system is introduced. We mainly investigate the baseband process, including cyclic redundancy check, tail biting convolutional coding, scrambling, rate matching, modulation, layer mapping and precoding. Then, a LTE downlink baseband process implementation scheme is proposed, which is realized on DSP platform. Secondly, we study the LTE downlink channel estimation and interpolation technology, and then analyze the LS channel estimation, MMSE channel estimation algorithm, two-dimensional linear interpolation, as well as Gaussian interpolation algorithm. Considering the simulation conclusion and the complexity of hardware implementation, a scheme for designing the LTE downlink channel estimator is presented, which is also implemented on DSP platform. Finally, the LTE downlink MIMO transmit diversity techniques is researched. We investigate the MRC receive diversity technique and SFTD transmit diversity technique, and then simulate them in the Matlab platform. According to the simulation conclusion, a scheme for LTE MIMO transmit diversity in downlink is put forward, which is also implemented on the DSP platform.