Channel Prediction for Link Adaptation in LTE Uplink

Link adaptation is the process of selecting Modulation and Coding Scheme (MCS) and Precoder Matrix Index (PMI) based on channel quality measures. Here a Signal to Interference and Noise Ratio (SINR) estimate is used as quality measure, which is calculated from channel and noise covariance estimates. An SINR expression is derived within the current paper which is designed for a Minimum Mean Square Error (MMSE) equalizer with a single tap channel model, which is an equalizer suitable for uplink Long Term Evolution (LTE). Channel estimates from Sounding Reference Signal (SRS) are used for this link adaptation. Illustrations are given in the current paper of the performance impact of the time delay between transmissions of SRS to the time instant when the result of the link adaptation is used. Furthermore, a channel predictor is proposed in order to reduce the impact of this delay. Simulations results indicate the benefits of using the proposed channel predictor, in terms of link level throughput.