The Research Of Channel Estimation Technology In The Next Generation WLAN System

WLAN has permeated every aspect of social life, this broadband wireless access technology has become a essential part of daily work and daily life. The rapid growth of large-scale WLAN networks and terminal equipments make the problem of WLAN interference so prominent that both the coverage of WLAN network, but the quality of service and users’experience are worse. In May2013, IEEE presented the next generation of wireless LAN-HEW, the overall goal is to improve performance in WLAN networking environment, improve service quality and practical WLAN user experience, and HEW considered high-speed mobile environment outdoors. This paper studies the channel estimation technique, according to the HEW need to adapt to the next generation WLAN system.The article first introduces the evolution of IEEE802.11family of standards, focusing on the IEEE802.11n standard,which includes the technology features and six kinds of TGn channel models. Next section is the focus of this paper, which is divided into three parts:the channel estimation techniques of SISO-OFDM system, the channel estimation techniques of MIMO-OFDM system, and the estimation algorithm design of the next-generation WLAN system.The part of SISO-OFDM introduces several common channel estimation algorithms and several interpolation algorithms. The estimation algorithms includes LS, LMMSE, LMMSE-SVD and DFT algorithms. This paper focuses on the DFT channel estimation algorithm, analyze the three factors causing the diffusion of channel energy in time domain, that is:the mismatch of Sample rate, the exist of virtual sub-carrier, high ratio of signal to noise.In the section of MIMO-OFDM, the paper describes the case of pilot designs in case of multi-antenna, time domain channel estimation algorithm in MIMO-OFDM system, and common channel estimation algorithm in frequency domain.The third part is the main part of this paper, which studies the traditional WLAN channel estimation algorithm from three aspects, one is use a bulk pilot instead of the massive pilot; second, introduces a optimal training sequence channel estimation scheme; finally, after the study of a DFT algorithm with Hamming window,the paper designs an improved bulk pilot program, and simulate its performance.