Experimental Investigation of MIMO Relay Transmission Based on Wideband Outdoor Measurements at 2.35 GHz

In order to obtain a more accurate assessment of relay performance in real-world outdoor propagation environment and to provide guidelines for the relay-based system deployment in the IMT-Advanced frequency band, the performance of a variety of relay schemes is investigated based on wideband measurements. The measurements were conducted at 2.35 GHz with 50 MHz bandwidth, which is within the frequency bands allocated to the IMT-Advanced system. We pay attention to two aspects: 1) the performance evaluation of a variety of transmission schemes in real propagation environment, and 2) the impact of propagation environment on the relay performance. Based on the measured channel transfer matrix, the achieved signal-to-noise ratio (SNR), spatial diversity and capacity of different transmission schemes are analyzed and compared. The measurement results reveal that in the NLOS region of the base station (BS) or in the region far away from the BS, the decode-and-forward (DF) relaying can significantly enhance the system performance. When the quality of the link between the BS and the relay station (RS) is good, the DF can provide larger performance improvement than the amplify-and-forward relaying. It is also found that propagation condition in the link between the RS and MS has major impact on the SNR, but minor impact on the spatial diversity.