Time dispersion parameters of outdoor cross-polar self-interference radio channels in sub-8-GHz bands

Indeed, self-interference cancellation has been proven to be the key-enabling technique for realizing a full-duplex duplexing scheme. However, a self-interference canceller must possess an up-to-date knowledge about its sensed self-interference wireless channel. In wireless communication systems, these channels usually possess multi-path and time-invariant properties. Moreover, they are very environment dependant. Therefore, in this paper we chose to investigate outdoors experienced channels, more specifically, ones are encountered in a street-level deployment scenario. Furthermore, we narrowed down the focus to concentrate on cross-polar self-interference channels. These channels are observed in dually polarized antenna's configurations among transmitter and receiver ones. In nutshell, we have dedicated this paper to study the multi-path propagation characteristics of outdoor cross-polar self-interference radio channels. By means of an empirical method, time dispersion behavior of our measured self-interference channel was analzyed. To measure a cross-polar self-interference channel, a channel sounding experiment equipped with a dually-polarized ridged horn antenna was performed. For that purpose, we assembled a channel sounding setup, which is composed of a vector network analyzer connected to the dually polarized antenna. The measurement antenna was placed at 3.5 m height, where measurement data were captured at 26 different locations - on a route parallel to the street. Additionally, for the sake of investigating the frequency dependancy on a cross-polar self-interference channel, two broad frequency bands were measured: A band between 2.9 GHz and 4.1 GHz, and a band between 5.9 GHz and 7.1 GHz. Finally, we derive - from measurement data - empirical probability distributions of channels' time dispersion parameters, such as the maximum peak of the self-interference backscatter (SIBS) channel gain, channel delay spread, and maximum excess delay.