Channel Sounding Technology Based On The LTE Signal

Channel sounding is one basic work of research for wireless communication systems. Channel sounding can obtain channel parameters in time domain, frequency domain and spatial domain. With these parameters, we can build accurate communication channel model. Traditional channel sounding methods use transceiver test equipment to sounding the fixed scene. These methods include periodic pulse test method, PN sequence sounding method and sounding method of frequency domain. The advantage of these methods is to have high sounding accuracy, but the equipment is expensive and the efficiency is very low. In the context of broadband mobile communications evolving to next-generation networks, it has important practical significance to research more effective channel sounding technology.First, this paper studies the LTE (Long Term Evolution) downlink physical layer and OFDM (Orthogonal Frequency Division Multiplexing), MIMO (Multiple In Multiple Out) technologies. Then it analyzes the radio channel characteristics, the traditional channel sounding methods and the existing channel model. The existing channel sounding methods have expensive equipment, low efficiency, and bad scalability and do not apply to a specific scene that can’t send sounding signals. In order to solve these problems, this paper proposes the channel sounding method based on LTE signals. This method uses LTE base station signals as the excitation signal, only receiving equipment, high efficiency, high scalability, effectively compensates for the lack of traditional channel sounding method. This paper gives the block diagram of the principle of the method. It uses software radio platform to achieve LTE signal acquisition. After the completion of data acquisition, it analysis and offline processing the acquired data to obtain channel characteristic parameters. First, it detect primary synchronization signal and the secondary synchronization signal to get time and frequency synchronization, and obtain the UE (User Equipment) physical layer cell ID, the length of the CP (Cyclic Prefix) and the duplex type. Then, it removes CP and FFT transform to extract the CRS (Cell-specific Reference Signals); uses the least squares channel estimation method to obtain the channel frequency response matrix; gets the channel impulse response matrix after the IFFT. Finally, it uses the channel impulse response matrix to extract the time domain, frequency domain and spatial domain channel characteristic parameters. It simulates the proposed method with three standard channel model, ITU model, Extended-ITU model and SCM model. According to the simulation results, the default channel parameters match the sounding channel parameters. It suggests that the channel sounding method proposed in this paper is feasible and effective, applicable to the radio channel sounding.