Polarized MIMO Channel Sounding In Ionospheric Scatter Environment

Channel measurement is a necessary means to realize effective communication. Effective channel measurement is a theoretical support for the realization of communication. In the specific channel parameters, the design of different sounding code can improve the channel capacity and increase the reliability of communication. Because of its important role in the emergency communication, long-distance communication and radar communication, ionospheric scatter communication has special status. However, because that the ionosphere channel is in the high level of the atmosphere, it has the characteristics of time varying, low SNR, and rich scattering, because of which the channel environment is very poor. To get higher rate of sending, it is necessary to build the specific channel model. The MIMO system is a hot spot in recent years. However, considering of the special case in the ionosphere environment, the normal array antenna cannot be used, so we take the polarization MIMO into consideration.Firstly, the main characteristics of the scatter channel are introduced. Channel characteristic parameters including losses and extensions, which are the important factors affecting the quality of communication, so the experiment of which is very important for all kinds of channel measurement process. Then, as the background of this paper the ionosphere scattering channel is put forward, and the characteristics of which includes large transmission loss, multipath effect and Doppler expansion. The large scale parameters channel characteristics such as the median level, the fading threshold, and the small scale parameters such as delay power spectrum, Doppler expansion is discussed.Because the channel is non-linear and time-varying, the sounding sequence must be a constant envelope sequence in order to let the channel measurement and communication system possible. Therefore, in the polarization MIMO channel measurement, the CAZAC sequence and the Chirp sequence is used the envelope of which is constant to acquire both low in correlation and constant in envelope. Two kind of frame structure is putting forward, one of which is based on time, and the other is based on different kind of code. The time structure works just as SIMO system, and this kind of scheme is used in XPD measuring, so it is of great importance. The scheme of Code division has more diversity gain but has high correlation requirement between codes. Three different kind of channel impulseresponse extraction algorithm is studied and the difference of different algorithm is compared. Because of the high performance, the SAGE algorithm is selected. A detailed analysis and theoretical derivation of the channel matrix of the polarization MIMO channel is carried out.