Research And Implementation Of Wireless Motion Detection Platform Based On OFDM System With USRP

Seeing Through Walls is always a hot point in detecting motions in a closed room in resent years. For the advantages of high spectral efficiency, bandwidth scalability and anti-multipath, we can use OFDM in detecting systems. In this paper we introduce and realize the motion sense platform in the closed environment based on OFDM using USRPs as sending and receiving equipment.Firstly, the article introduce the necessary knowledge of motion sense platform.It introduces the basic principle of OFDM, characteristic and relative techniques, including synchronization, channel estimation and equalization, coding and interweaving et.al. As the detecting equipment, the software and hardware of USRP is introduced also. And then we find the main problem in motion detection in a closed room including static interference cancellation and detecting algorithm.Secondly, the article raise the way to solve the two main problems to detect motions.At first before sloving the main problem, we need to get the value of channel.So we deduce and analysis the algorithm of channel estimation including. We simulate and vertificate the LS,DFT,MMSE algorithm performance of mean square error increasing. We use the ZF algorithm in MIMO detecting to clear up the signal interference.Then,we use the ISAR technique that make people simulate array antenna and use MUSIC algorithms to detect motion.Finally, we complete the entire motion sensing platform and gives test results.At first,we set up the OFDM system link with C++ and use UHD driving USRP to construct a whole sending and receiving platform in real channel.And then, we construct a two sending-one receiving MIMO platform. Using the signal recived by the platform, after cancelling static interference, we simulate standard array antenna to detect people and image the motion trajectory.