Research On Channel Estimation Technology In Vehicular Network Environment

With the proposal and rapid development of intelligent transportation system,planning and research of corresponding vehicular communications standards are more sufficient.Especially,IEEE 802.11 p and C-V2 X standards represent the two development directions of Vehicular Ad-hoc Network(VANET).How to guarantee reliable information transmission in VANET becomes one of core researches.Moreover,a good performance of channel estimation in VANET sets a premise for subsequent correct signal detection.Hence,research on channel estimation in VANET shows a very important meaning.Due to the physical layer similarity between IEEE 802.11 p and C-V2 X,we focus on the research of channel estimation aiming at IEEE 802.11 p VANET in order to enhance the channel estimation accuracy.The main works of this thesis are as follows.Firstly,related theories on channel estimation in VANET are illustrated.Characteristics of VANET channels are analyzed from the points of views of wireless channel theoretical models and time-frequency double selective perspective.Typical channel models and corresponding statistical description are also given.Key parameters in physical layer,data frame structure and OFDM techniques in IEEE 802.11 p standard are further introduced in detail.Secondly,the theoretical model of pilot-based OFDM channel estimation is analyzed.The pilot structure and corresponding channel estimation algorithms of an OFDM system are discussed respectively.Based on simulations,performances of different pilot patterns in given channel conditions are analyzed and a proper pilot structure is proposed.Due to the disadvantage of the current DFT-based channel estimation scheme,we put forward an improved DFT-based channel estimation method,which compares its performance with the current counterpart.Simulations show that the performance of the proposed improved algorithm outperforms that of the former one.Finally,various channel estimation techniques developed for IEEE 802.11 p standard are studied.Advantages and disadvantages of several practical channel estimation techniques are compared via simulations.Moreover,an improved channel estimation technique based on constructed data pilots is proposed,whose performances outperform those of available channel estimation schemes.