A method for a mmWave user terminal (102A, 102B, 102C, 102D) capable of analog beamforming and digital beamforming, the method comprising: receiving, from an access node (114A, 114B), a downlink reference signal using an analog beamforming setting; measuring, using the received downlink reference signal, an effective channel based on the analog beamforming setting, whereas the effective channel follows by applying an analog precoder at the access node and an analog combiner at the user terminal and without applying digital precoding; receiving, from the access node, an assistance parameter indicating a target performance threshold; determining a minimum digital precoder codebook size that satisfies the performance threshold, indicated by the assistance parameter received from the access node, using the measured effective channel; sending the determined minimum digital precoder codebook size to the access node; wherein the at least one assistance parameter comprises a performance improvement threshold PIT, wherein the PIT comprises a threshold that corresponds to a difference in performance for a given performance metric when the given performance metric is used without digital precoding and with digital precoding; and wherein determining the minimum digital precoder codebook size comprises: calculating a channel capacity C NO_DP of the effective channel and the channel capacity of each of the channels resulting from the effective channel under different digital precoder codebook resolution index values i, C DP, i, whereas each digital precoder codebook resolution index value i corresponds to a different codebook size; and determining the smallest codebook size that achieves C DP, i - C NO_DP > PIT as the minimum digital precoder codebook size. receiving, from an access node (114A, 114B), a downlink reference signal using an analog beamforming setting; measuring, using the received downlink reference signal, an effective channel based on the analog beamforming setting, whereas the effective channel follows by applying an analog precoder at the access node and an analog combiner at the user terminal and without applying digital precoding; receiving, from the access node, an assistance parameter indicating a target performance threshold; determining a minimum digital precoder codebook size that satisfies the performance threshold, indicated by the assistance parameter received from the access node, using the measured effective channel; sending the determined minimum digital precoder codebook size to the access node; wherein the at least one assistance parameter comprises a performance improvement threshold PIT, wherein the PIT comprises a threshold that corresponds to a difference in performance for a given performance metric when the given performance metric is used without digital precoding and with digital precoding; and wherein determining the minimum digital precoder codebook size comprises: calculating a channel capacity C NO_DP of the effective channel and the channel capacity of each of the channels resulting from the effective channel under different digital precoder codebook resolution index values i, C DP, i, whereas each digital precoder codebook resolution index value i corresponds to a different codebook size; and determining the smallest codebook size that achieves C DP, i - C NO_DP > PIT as the minimum digital precoder codebook size. calculating a channel capacity C NO_DP of the effective channel and the channel capacity of each of the channels resulting from the effective channel under different digital precoder codebook resolution index values i, C DP, i, whereas each digital precoder codebook resolution index value i corresponds to a different codebook size; and determining the smallest codebook size that achieves C DP, i - C NO_DP > PIT as the minimum digital precoder codebook size.