Optimizing Feedback User Selection for Standalone U-LTE Networks With Randomly Delayed CSI

Accurate channel state information (CSI) plays a critical role in channel-aware transmissions. However, in standalone long-term evolution networks in unlicensed spectrum, it is challenging to obtain accurate CSI timely via intermittent and random channel access. In this letter, we propose an optimization framework to achieve the maximum user utility with appropriate user selection for CSI feedback. Specifically, in the proposed framework, the selection of CSI feedback users is optimized together with subchannel pre-allocation for maximizing the proportional fairness utility of users’ expected throughput of future channel access, considering the impact of randomly delayed CSI due to channel contentions. Simulation results show the effectiveness of the proposed optimization framework.