Real-time experiments on channel adaptive transmission in the multi-user up-link at very high data rates using MIMO-OFDM

In this paper we focus on channel adaptive transmission in the multi-user OFDM Uplink where the base station uses multiple antennas. The additional degree of freedom in space requires extra signal processing effort which becomes challenging especially for a high data rate implementation in real-time. Our MIMO-OFDM experimental system which is capable to transmit data rates beyond 1 Gbit/s, was enhanced by adaptive resource allocation, where the modulation on each antenna and each sub-carrier was controlled by a narrow-band feed-back channel. We present experimental results for the total rate achieved at the base station and the individual rates per user terminal in line-of-sight and non-line-of-sight scenarios. We compare the rates expected from theory on the measured indoor channels with rates achieved in the experiments.