MU-MIMO Channel Emulator with Automatic Channel Sounding Feedback for IEEE 802.11ac

This paper proposes a 4x4 MU-MIMO channel emulator with automatic channel sounding feedback used for beamforming and MU-MIMO precoding features of IEEE 802.11ac. The main contribution of this paper is the design of a MU-MIMO channel emulator capable of sending channel feedback automatically to the AP from the generated channel coefficients after a programmable time duration. This function helps to evaluate the precoding algorithms without channel estimation error and uses very minimal MAC features. The second contribution is the design of single path implementation with serial processing which plays an important role on reducing the hardware complexity. The design choice makes it possible to generate channel coefficients for very high sampling rate systems with little increase in complexity. In addition, single path implementation allows the addition of the feedback channel output with only few additional non sequential elements which would otherwise double in a parallel implementation. To demonstrate the functionality of our MU-MIMO channel emulator, we present actual hardware emulator results of precoded receive signal constellation on oscilloscope.