Iterative Detection Technology Of 4×4 IEEE802.11ac

The fifth-generation WiFi standard,the IEEE802.11ac wireless standard,is known as the wireless local area network highway to meet the fast demand of high data rate of 5GHz channel,achieving very high throughput communication.The core technology is MIMO-OFDM technology.In MIMO-OFDM systems,in addition to inter-symbol interference and inter-subcarrier interference,there are inter-antenna interference.Finding an effective multi-antenna detection algorithm is the key to MIMO-OFDM technology.The commonly used linear detection is applied to the 802.11ac system with poor performance.Therefore,the paper studies the iterative detection technology applicable to IEEE802.11ac.The main work includes:First,combined with the principle of least squares estimation,the channel estimation of the DATA field of the 802.11ac system is performed.First,according to the structure of the VHT_LTF field,the channel estimation value of the field is obtained;then the residual phase tracking and compensation is performed by using the pilot of the DATA field to obtain the channel estimation value of the DATA field.Secondly,the BI-GDFE detection algorithm of decision feedback is studied.It focuses on how to select the input decision correlation coefficient(IDC)of the previous iteration decision to design the feedforward equalizer and the feedback equalizer to maximize the SINR of the detected output.Firstly,the IDC curve corresponding to the different decision output SNR of the 4th and 4th 802.11ac systems is simulated.Secondly,the BI-GDFE detection algorithm is simulated according to the IDC curve.The simulation results show that under the condition of selecting dynamic IDC coefficients,the system error rate can be reduced by continuous iteration.Near the BER,the BI-GDFE iteration is about 3.5 dB higher than the MMSE,and the iteration is increased by about 4.5 dB twice.Thirdly,the Turbo iterative detection algorithm based on MAP criterion and MMSE Gaussian approximation criterion is studied.For Turbo-MAP,the calculation formulas of posterior probability information and external information are deduced.For Turbo-MMSE,the MMSE detector with the output of the decoder as the prior information is studied.The Gaussian distribution is used to approximate the filtered noise.Interference,calculate the LLR of the soft decision output.The simulation results show that the performance of the Turbo-MAP is approximately 2.2 dB higher than that of the iteration in the vicinity of the BER,and the performance of the iteration is 3 dB over the iteration of the iteration.The performance of the Turbo-MMSE detection is 2 times.2 dB higher than iteration of iteration;Turbo-MAP overall is 2.5 dB better than Turbo-MMSE.Based on the iterative detection algorithm of Turbo iterative detection and decision feedback,the iterative detection scheme of IEEE802.11ac MIMO-OFDM system is designed,which provides a reference for the research of IEEE802.11ac standard in the next generation wireless LAN.