Design requirements of adaptive pilot-symbol patterns

Adaptive pilot patterns offer high throughput gains. However, their application requires additional feedback. In this paper, we investigate the feedback requirements for adaptive pilot patterns applied in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing systems. The main goal is to support a wide range of Doppler spreads and Root Mean Square (RMS) delay spreads while keeping the number of allowed pilot patterns at a minimum. Based on our simulation results, we show that only four bits of additional wide-band feedback per user are required in order to optimally support RMS delay spreads up to 800 ns and Doppler frequencies up to 1200 Hz.