  Ultra-massive multiple-input-multiple-output (UM-MIMO) is promising to meet
the high rate requirements for future 6G. However, due to the large number of
antennas and high path loss, the hardware power consumption and computing power
consumption of UM-MIMO will be unaffordable. To address this problem, we
implement a low-power communication system based on reconfigurable intelligent
surface (RIS) and artificial intelligence (AI) for 6G. For hardware design, we
employ a 256-element RIS at the base station to replace the traditional phased
array. Moreover, a 2304-element RIS is developed as a relay to assist
communication with much reduced transmit power. For software implementation, we
develop an AI-based transmission design to reduce computing power consumption.
By jointly designing the hardware and software, this prototype can realize
real-time 4K video transmission with much reduced power consumption.
