Feedback Interval Optimization for MISO LiFi Systems

Utilizing the densely deployed light-emitting diodes (LEDs) as transmitters, multiple-input-single-output (MISO) becomes an attractive technique to improve the transmission throughput of light-fidelity (LiFi) systems. To fully exploit the benefits of joint transmission of multiple LEDs, beamforming techniques are usually employed to improve the downlink throughput, which requires the knowledge of channel state information (CSI) at transmitter. Since frequent CSI feedback leads to heavy overhead, the optimization of feedback interval, defined as the time period between two adjacent feedbacks, is investigated in this paper, which aims at maximizing the weighted bidirectional transmission throughput. Additionally, a quasi-optimal solution is calculated as a well approximation of the exact optimal solution in order to reduce the computational complexity. Simulation results show that, the proposed feedback interval optimization is capable of improving the weighted bidirectional throughput considerably thanks to the reduced CSI feedback overhead, compared with its conventional counterparts using classical feedback mechanisms. Besides, by employing the obtained quasi-optimal feedback interval, the weighted bidirectional throughput approaches that of the optimal interval with much lower computational complexity.