Research On Channel Estimation For Outdoor Scenes Of 802.11

With the development of science and technology, wireless communication technology changes the human life upside down. The popularity of intelligent terminals make people more and more to rely on the wireless network, especially wireless local area network. One of the key technologies of wireless communication technology is the channel estimation. Current WLAN channel estimation generally applies to the quasi static channel models, in order to realize communication at any time, any place, channel estimate scheme which is suitable for mobile scenarios is necessary.In wireless communication standards, generally block pilot structure is employed for channel estimation, but it is not suitable for time-varying channel.802.11ah adopts the scattered pilot structure which is named traveling pilot. It can effectively track and update CSI. So, it is reasonable to design the pilot scheme for next generation WLAN by referring to the traveling pilot structure. But the sub-carrier spacing is relatively large in existing WiFi standard, only 1-2 spatial streams are defined so that multi-antenna case does not directly reference 802.11ah. This thesis uses orthogonal position in time domain to distinguish between multiple antennas, and compares with time domain sequence orthogonal scheme. The simulation results show that the position of orthogonal traveling pilot is well suited for time-varying channel.In order to improve the channel estimation performance, and realize to track and update in the fast time-varying channel, on the basis of existing literature, this thesis presents a grouping optimal position orthogonal pilot design. In the data part we periodically insert grouping pilots which are equal amplitude. When each group pilot has uniform distribution, channel estimation of the LS mean square error is minimized. For multi-antennas case, due to sub-carrier spacing is relatively large in the existing standard, the method of orthogonal position is used to distinguish between multiple antennas. The simulation results show that the proposed pilot scheme in this thesis is correct and efficient.