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The intelligent reflective surface (RIS) used low-cost passive reflective elements to control the phase of incident signal, which could enhance wireless coverage range and improve channel capacity in the sixth-generation mobile communication system. Since the dispersion environment of the RIS-assisted millimeter wave multiple input multiple output (MIMO) cascaded channel only had a few paths with corresponding spatial angles and loss, the non-grid atomic norm minimization method was proposed to estimate the angle of departure at base station and the angle of arrival at user equipment on downlink in this paper. The angle estimation problem was converted into convex optimization models for solution. Simulation results showed that accurate angles could be obtained only with a small number of snapshots.

In this paper,considering time-frequency doubly selective channel,we utilize the channel's time correlation that the channel coefficientscorresponding tothe neighboring instants have a strong correlation.And we present a linear approximation method,which effectively reduces the number of unknown parameters.Considering the sparseness of the wireless channel in the delay domain,this paper reconstructs unknown channel parameters of the proposed model based on compressed sensing (CS) theory.In the simulations,we observe the system performance of the linear approximation model and the non-linear approximation model,respectively,and present the normalized mean squared error (NMSE) curves based on the least square (LS),orthogonal matching pursuit (OMP) and sparse Bayesian learning (SBL) algorithms.Simulation results show that the linear approximation method can effectively model the time-frequency doubly-selective channels.For the proposed linear approximation model,SBL algorithm can accurately recover the channel response,and overcome the Doppler effecteffectively.

In this paper,short frame was introduced to transmit data in the long term evolution (LTE) system downlink to reduce communication delay.Since the reduction of the frame length would degrade system performance,a new cell-specific reference signal (CRS) mapping pattern was proposed in order to balance the relationship between the system throughput and the channel estimation quality.Link-level simulation results showed that the proposed method could satisfy system throughput requirement while improving the channel estimation quality and reducing system error rate.

Compared with orthogonal frequency division multiplexing technology (OFDM),filter bank multicarrier (FBMC) technique has higher spectrum using rate and easier achieved pulse shaping.It was seen as a potential replacement for OFDM as future 5G physical layer of alternative technical solutions.However,in practical applications of the estimation of the channelFBMC with offset quadrature amplitude modulation (FBMC/OQAM) system,the FBMC/OQAM system in the filter only orthogonal in the real domain satisfies,there is a natural interference in the imaginary domain,so the classical orthogonal frequency divided multiplex channel estimation methods cannot be directly applied.Aiming at this problem,this paper proposes a new discrete pilot based channel estimation method,in which will be the pilot caused by interference of the data block partition domain processing,in different regions use different interference cancellation scheme,stepwise elimination the imaginary part of interference.The simulation shows that this scheme makes channel estimation performance has been significantly improved,and improve the performance of FBMC/OQAM system.

The paper studies the downlink of GGE and related single antenna interference cancellation (SAIC) technology.A LMS adaptive channel estimation algorithm is proposed to improve the performance of linear filtering and enhance the capability of interference cancellation.For suppressing the multicell asynchronous interference,an adaptive judgment mechanism is designed in LMS adaptive channel estimations to extend the applicative range of LMS and improve the performance of channel estimation in asynchronous multicell scenarios.