The SNR Margin per subcarrier group, expressing the ratio between the received signal power and received noise power per subscriber group. It is an array of 512 octets, designed for supporting up to 512 (downstream) subcarrier groups and can be retrieved in a single segment. The number of utilized octets in the downstream direction depends on NSds; in the upstream direction, it depends on NSus. This value is referred to here as NS. Octet i (0 <= i <= NS) is set to a value in the range 0 to 254 to indicate that the respective downstream or upstream subcarrier group i has an SNR of: (-32 + xdsl2SCStatusSegmentSnr(i)/2) in dB (i.e., -32 to 95 dB). The special value 255 means that no measurement could be done for the subcarrier group because it is out of the PSD mask passband or that the noise PSD is out of range to be represented. Each value in this array is 8 bits wide.