Uplink Random Access Scheme with Prioritized Orthogonal Layers for OFDMA CSI Feedback

The optimization of the Downlink (DL) performance in wireless systems that utilize Orthogonal Frequency Division Multiple Access (OFDMA) requires knowledge of the Channel State Information (CSI) for each user over each subchannel at the Base Station (BS), which requires a high amount of Uplink (UL) radio resources. In this work, we focus on the problem of CSI feedback by UL Random Access (RA). We introduce the concept of variable collision protection, where the probability that a feedback information experiences a collision depends on its importance. By partitioning the CSI into orthogonal layers of priority, and by allocating different numbers of RA slots to each layer, this scheme ensures that the feedback success probability is higher for the CSI with better quality, as it is more likely to be used by the scheduler. Analytical and simulation results show that our proposed scheme provides an excellent trade-off between system performance and the amount of feedback overhead.