This parameter defines the UPBO reference PSD used to compute the upstream power back-off for each upstream band except US0. A UPBOPSD defined for each band ahsll consist of two parameters [a, b]. Parameter a shall be coded as an unsigned 12-bit number from 40 dBm/Hz (coded as 0) to 80.95 dBm/Hz (coded as 4095) in steps of 0.01 dBm/Hz; and b shall be coded as an unsigned 12 bit number from 0 (coded as 0) to 40.95 dBm/Hz (coded as 4095) in steps of 0.01 dBm/Hz. The UPBO reference PSD at the frequency f expressed in MHz shall be equal to '-a-b(SQRT(f))'. The set of parameter values a = 40 dBm/Hz, b = 0 dBm/Hz is a special configuration to disable UPBO in the respective upstream band. Octets 0+1 - a[0] Octets 2+3 - b[0] Octets 4+5 - a[1] Octets 6+7 - b[1] Octets 8+9 - a[2] Octets 10+11 - b[2] Octets 12+13 - a[3] Octets 14+15 - b[3]