Research On Measurement Scheme Of Scattering Channel

Channel, to a great degree, determines the performance of the communication system, resulting that the channel measurements are indispensable in the system designs. And because of its unpredictable, scattering channel also has the features of serious path loss, existing of time-varying multipath and the Doppler frequency shift owing to the movement of the scatters, etc. Thus the environment of scattering channel is much worse that the existing measurements cannot meet the measurement requirements.Firstly, the properties of the scattering channel were analyzed and an effective mathematical model was introduced utilizing the tapped delay line model. Many channel measurements were designed based on this model, which has strong generality and good practicality. At the same time, the characteristics of the large and small scale parameters of scattering channel were described. The former mainly expresses the path loss of scattering channel, and helps understanding the process of the received power attenuation. The latter includes the time delay parameters and Doppler parameters describing in detail for the power delay distribution and Doppler effects of the channel respectively. Considering the possibility existence of a strong diameter, the rice factor and its common extraction method were studied.Secondly, the channel measurement theory and the basic requirements were discussed synoptically and the existing channel measurement methods were introduced, including the time domain channel measurement methods and frequency domain measurement methods. The popular methods of sliding correlation measurements were emphasized. Because of the special distribution of the multipath of the scattering channel, the SAGE algorithm is extracted and simplified, and then applied in the sliding correlation method to improve the measurement performance. Next, so as to further improving the measurement reliability and looking for more efficient measurement methods, the pulse compression system was explored. By comparing the existing matching compression algorithm and heterodyne algorithm, the pulse compression measurement scheme based on chirp signals has been adopted with its relative factors discussed. According to the expected measurement indicators of scattering channel, the frame structure of the scheme was designed and the technology of frame synchronization was given. And using the continuous feature of the chirp signals, a new data processing method was crea-tively proposed. In this process, not one but several samples of channel impulse responses can be obtained from a single measuring chirp frame, thus a more detail of the time-varying characteristics of scattering channel were resulted.Finally, the proposed and improved measurement methods including sliding correlation of SAGE treatment process and chirp based pulse compression channel measurement method were carried on either the simulation or the field measurement experiment. Among them, the simulation with SAGE algorithm, compared the performance of different settings on the number of multipath and also with the correlation method. The results showed its perfect capacity on estimating the channel impulse response with smaller MSE, especially under the very low SNR. For the design of the pulse compression channel measurement scheme, the field measurement experiment was carried out. In the experiment, the large scale and small scale characteristics were extracted in the order of the given processing, resulting a detail description of the measured scattering channel. From simulation and field experiment results, the feasibility and effectiveness of the proposed parameters extracted method and the pulse compression measurement based on chirp signal have been verified.