Lower the transmit power from 28dBm to 17dBm on both devices to increase the throughput. There was no need to set the transmit power to high, because the distance is only 150ft. The high transmit power may have caused receiver overload, and thus the low throughput.
To enable the Transmit Power setting, click Operation Mode and uncheck the box beside "Green". Select the Country/Region then click Save/Apply