NHK has been studying transmission technologies that contribute to increasing spectral efficiency and developing large capacity wireless transmissions. An effective technology is dual-polarized multiple-input multiple-output (MIMO), which uses both horizontal and vertical waves. We are currently developing an advanced Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) system to provide simultaneously a 4K8K broadcasting service for fixed reception and 2K service for mobile reception.

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... The advanced ISDB-T adopts not only single-input single-output (SISO) but also MIMO for the expansion of the transmission capacity. However, a difference of radio propagation or that of a transmitter antenna's radiation pattern can easily cause an imbalance of received power between each polarization even if the transmitted power of each polarization is the same. A broadcasting network usually consists of multiple transmitter stations to cover target broadcasting areas across cities. In this case, a single frequency network (SFN) is considered for an efficient usage of frequency. The transmission performance in an SFN environment depends on the desired-to-undesired power ratio (DUR) of a main station and relay station because of the interference between received signals from them. In the case of MIMO-SFN, both power imbalance between each polarization and the DUR of each polarization need to be considered to analyze the transmission characteristics. In this paper, the transmission performance of dual-polarized MIMO in an SFN environment considering the imbalance of received power is evaluated by computer simulation, laboratory experiment, and field experiment. Furthermore, the distribution of the imbalance of received power is obtained by a large-scale field experiment.