An array of up to 512 real Quiet Line Noise values in dBm/Hz for the respective transmission direction. It is designed for up to 512 (downstream) subcarrier groups and can be retrieved in a single segment. The number of utilized values in the downstream direction depends on NSds; in the upstream direction, it depends on NSus. This value is referred to here as NS. Each array entry represents the QLN(f = i*Df) value for a particular subcarrier index i, (0 <= i <= NS). The QLN(f) is represented as ( -23-n(i)/2), with n(i) in the range 0 to 254. A special value n(i)=255 indicates that no measurement could be done for the subcarrier group because it is out of the passband or that the noise PSD is out of range to be represented. This parameter is applicable in loop diagnostic procedure and initialization. Each value in this array is 8 bits wide.