Performance Evaluation Of Precoding With Channel Estimation Error In Massive MIMO System

The application of massive Multi-Input Multi-Output(MIMO)technology has greatly improved the system capacity,spectrum utilization and energy efficiency of mobile communication systems.Through channel estimation and prediction,the massive MIMO system can obtain real-time channel state information,and on this basis,the precoding matrix at the base station can be designed.Precoding can effectively weaken the effects of multi-user interference(MUI)and noise,thereby giving play to the advantages of massive MIMO.Existing research usually adopts ideal assumptions,ignoring many non-ideal factors in real communication scenarios.This dissertation takes the digital precoding scheme of the narrow-band massive MIMO system and the hybrid precoding scheme of the millimeterwave massive MIMO system as the research objects to investigate the influence of channel estimation errors on the system performance.Moreover,when studying the precoding scheme of millimeter-wave massive MIMO,the beam squint problem caused by the spatial wideband effect is also considered,and the influence of the channel estimation error on the beam squint compensation precoding is investigated.The main work is as follows:First,the digital precoding scheme of the narrow-band massive MIMO system is studied.Since the performance of linear precoding in massive MIMO systems is close to nonlinear precoding with higher computational complexity,this paper chooses more practical linear precoding as the research object.Take the more typical Zero Forcing(ZF)algorithm and Minimum Mean Square Error(MMSE)algorithm as examples to analyze the performance of the precoding scheme.Secondly,research the hybrid precoding scheme of millimeter wave massive MIMO system.In the millimeter wave massive MIMO system,because the signal bandwidth and the number of antennas are huge,the propagation delay of the signal cannot be ignored.This time delay brings about the Spatial-Wideband Effect,which in turn causes the direction shift of the precoding beam in the frequency domain(Beam Squint).This paper analyzes the influence of beam squint on system performance,and adopts a wide-band modified channel model,and adds a compensation algorithm for beam squint in the precoding scheme.However,the hybrid precoding scheme cannot perform independent compensation for each subcarrier.Therefore,this paper studies a hybrid precoding scheme based on phase-shifting zero force(PZF)beam squint compensation.The analog precoding matrix in hybrid precoding is generated by constructing an equivalent channel independent of frequency.Finally,according to the channel estimation error model of the massive MIMO system,the channel estimation error is simulated under different signal-to-noise ratio conditions,and this error is introduced into the system performance simulation to evaluate the performance of the massive MIMO precoding scheme described above.