Field trial results on multi-user MIMO downlink OFDMA in typical outdoor scenario using proportional fair scheduling

In this paper we present rest real-time outdoor multi-user multi-antenna measurements based on system parameters close to 3GPP-long term evolution. We demonstrate switching between various transmission modes in the downlink steered by a quantized feedback channel. Real time results show that an OFDMA proportional fair scheduler based on the quantized feedback achieves significant performance gains over axed OFDM-TDMA system. However, the proportional fair scheduler results in user starvation periods in the event of correlated feedbacks. To this end, we formulate a downlink scheduling problem with zero-starvation as a short term fairness in Kulkami, S.S., et al (2003) objective. This is an integer programming (IP) problem. In this paper, we present a simple heuristic algorithm for this problem for K = 2 users. Significant system sum rate gains are shown while still fulfilling the fairness objective.