Uplink Random Access Scheme with Variable Collision Protection for Ofdma Csi Feedback

The optimization of the Downlink (DL) scheduling in wireless systems that utilize Orthogonal Frequency Division Multiple Access (OFDMA) requires knowledge of the Channel State Information (CSI) for each user and subchannel at the Base Station (BS). This requires a prohibitively high amount of channel resources in Uplink (UL). We focus on the problem of CSI feedback by UL Random Access (RA). Our method relies on the proposed concept of variable collision protection, where the probability that a certain feedback information experiences a collision depends on the importance of that CSI. In the proposed scheme, 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.