The recent explosion of mobile Internet usage results in the need for higher data rate in future mobile communication systems. One of the key technologies to satisfy this requirement is the multilink transmission technique which utilizes the cooperative signal processing among spatially distributed multiple users and/or base stations, thus it is considered as more robust in ensuring the degree of freedom in spatial domain over the conventional single-link multiple-input-multiple-output (MIMO) systems [1]. However for the proper design and development of multi-link transmission systems, the level of inter-link channel correlation needs to be accurately modeled. Moreover since each user terminal and base station will also be equipped with multiple antennas, characterization of directional property at transmitter (Tx) and receiver (Rx) is also important for the design of array antennas. Previously, a lot of field measurement results reported focused on the characterization of multi-link propagation channel as summarized in [2]. However in the earlier works, channel stationarity is often assumed due to the limitations of channel sounder capabilities. Recently in [3], geometry-based multi-link channel modeling approach is proposed based on the measurement by dual-link MIMO channel sounder [4], and the propagation mechanisms which cause the correlation among two links are reported. Nevertheless, the existing results are still limited to specific frequency bands (below 2 GHz or 5 GHz) and environments, thus further evaluation based on the multi-link measurements is desired.
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