Patent ID: 7633999

Claim:
A Digital Subscriber Line (DSL) communications system comprising: a central office Asynchronous Digital Subscriber Line (ADSL) transceiver unit (ATU-C) in discrete multitone (DMT) communication with a remote ADSL transceiver unit (ATU-R), wherein the ATU-C comprises a central office (CO) operator configured to perform spectral shaping of a dual bit map (DBM) mode downstream transmission based on a power spectral density (PSD) mask represented by the following equation: PSD DBMsOL = K ADSL_OL × C f 0 × [ sin ⁡ ( π ⁢ f f 0 ) ] 2 ( π ⁢ f f 0 ) 2 × 1 1 + ( f f LP3dB ) 12 × 1 1 + ( f HP3dB f ) 6 , 0 ≺ f ≺ ∞ where PSD DBMsOL represents the PSD mask, K ADSL — OL represents a constant value, C represents a constant value, f represents a frequency of the downstream transmission, f 0 represents a constant value, f LP3dB represents a 3 decibel (dB) low pass frequency and f HP3dB represents a 3 dB high pass frequency.